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Sample records for aromatic radical anions

  1. The benzene radical anion: A computationally demanding prototype for aromatic anions

    International Nuclear Information System (INIS)

    The benzene radical anion is studied with ab initio coupled-cluster theory in large basis sets. Unlike the usual assumption, we find that, at the level of theory investigated, the minimum energy geometry is non-planar with tetrahedral distortion at two opposite carbon atoms. The anion is well known for its instability to auto-ionization which poses computational challenges to determine its properties. Despite the importance of the benzene radical anion, the considerable attention it has received in the literature so far has failed to address the details of its structure and shape-resonance character at a high level of theory. Here, we examine the dynamic Jahn-Teller effect and its impact on the anion potential energy surface. We find that a minimum energy geometry of C2 symmetry is located below one D2h stationary point on a C2h pseudo-rotation surface. The applicability of standard wave function methods to an unbound anion is assessed with the stabilization method. The isotropic hyperfine splitting constants (Aiso) are computed and compared to data obtained from experimental electron spin resonance experiments. Satisfactory agreement with experiment is obtained with coupled-cluster theory and large basis sets such as cc-pCVQZ

  2. Long-range intramolecular electron transfer in aromatic radical anions and binuclear transition metal complexes

    DEFF Research Database (Denmark)

    Kuznetsov, A. M.; Ulstrup, Jens

    1981-01-01

    Intramolecular electron transfer (ET) over distances up to about 10 Å between states in which the electron is localized on donor and acceptor groups by interaction with molecular or external solvent nuclear motion occurs, in particular, in two classes of systems. The excess electron in anionic ra...

  3. Anion photoelectron spectroscopy of radicals and clusters

    Energy Technology Data Exchange (ETDEWEB)

    Travis, Taylor R.

    1999-12-16

    Anion photoelectron spectroscopy is used to study free radicals and clusters. The low-lying {sup 2}{Sigma} and {sup 2}{Pi} states of C{sub 2n}H (n = 1--4) have been studied. The anion photoelectron spectra yielded electron affinities, term values, and vibrational frequencies for these combustion and astrophysically relevant species. Photoelectron angular distributions allowed the author to correctly assign the electronic symmetry of the ground and first excited states and to assess the degree of vibronic coupling in C{sub 2}H and C{sub 4}H. Other radicals studied include NCN and I{sub 3}. The author was able to observe the low-lying singlet and triplet states of NCN for the first time. Measurement of the electron affinity of I{sub 3} revealed that it has a bound ground state and attachment of an argon atom to this moiety enabled him to resolve the symmetric stretching progression.

  4. Radiation chemistry of aromatic dimer radical cations

    International Nuclear Information System (INIS)

    π-π Interactions of aromatic molecules are paid attention much in many fields, especially biology, chemistry, and applied physics, represented as protein, DNA, electron donor-accepter complexes, charge transfers, and self assembly molecules. Aromatic molecules including benzene rings are the simplest case to study the π-π interactions. To interpret the charge resonance (CR) structure in the dimer radical cations, spectroscopic and ESR methods have been carried out. The spectroscopic study on the dimer radical ion of molecules with two chromophores would be profitable to identify the electronic and configurational properties. In this article, dynamics of the dimer radical cation of benzenes, polystyrenes, and resist polymers is described on the basis of direct observation of CR band by the nanosecond pulse radiolysis and low temperature γ-radiolysis methods. (author)

  5. Aromatic-radical oxidation chemistry

    Energy Technology Data Exchange (ETDEWEB)

    Glassman, I.; Brezinsky, K. [Princeton Univ., NJ (United States)

    1993-12-01

    The research effort has focussed on discovering an explanation for the anomalously high CO{sub 2} concentrations observed early in the reaction sequence of the oxidation of cyclopentadiene. To explain this observation, a number of plausible mechanisms have been developed which now await experimental verification. One experimental technique for verifying mechanisms is to probe the reacting system by perturbing the radical concentrations. Two forms of chemical perturbation of the oxidation of cyclopentadiene were begun during this past year--the addition of NO{sub 2} and CO to the reacting mixture.

  6. Protonation Reaction of Benzonitrile Radical Anion and Absorption of Product

    DEFF Research Database (Denmark)

    Holcman, Jerzy; Sehested, Knud

    1975-01-01

    The rate constant for the protonation of benzonitrile radical anions formed in pulse radiolysis of aqueous benzonitrile solutions is (3.5 ± 0.5)× 1010 dm3 mol–1 s–1. A new 270 nm absorption band is attributed to the protonated benzonitrile anion. The pK of the protonation reaction is determined to...

  7. Inhibitory effects of chitosan on superoxide anion radicals and lipid free radicals

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    With the electron spin resonance (ESR) technique, the inhibitory effects of chitosan on superoxide anion radicals and linoleic acid lipid radicals were found. The inhibitory ratio E for these two kinds of radicals is in proportion to the concentration of chitosan. It was also observed that E for linoleic acid lipid radicals increased with the increase of the degree of deacetylation and decreased with the increase of the molecular weight of chitosan.

  8. Isoprene, sulphoxy radical-anions and acidity

    Directory of Open Access Journals (Sweden)

    K. J. Rudziński

    2008-12-01

    Full Text Available Transformation of isoprene coupled with autoxidation of SIV in aqueous solutions was studied experimentally and by chemical-kinetic modelling over broad range of solution acidities (pH=3–9 to complement the research on aqueous-phase and heterogeneous transformation of isoprene reported recently by many laboratories. Isoprene significantly slowed down the autoxidation in acidic and basic solutions, and accelerated it slightly in neutral solutions. Simultaneously, production of sulphate ions and formation of solution acidity were significantly reduced. Formation of sulphite and sulphate derivatives of isoprene – sulphurous acid mono-(2-methyl-4-oxo-but-2-enyl ester (m/z=162.9, sulphurous acid mono-(4-hydroxy-2-methyl-but-2-enyl ester (m/z=164.9, sulphuric acid mono-(2-methyl-4-oxo-but-2-enyl ester (m/z=178.9, sulphuric acid mono-(4-hydroxy-2-methyl-but-2-enyl ester (m/z=180.9 – was indicated by mass spectroscopic analysis of post-reaction mixtures. The results of experiments were explained by changes in a subtle quantitative balance of three superimposed processes whose rates depended in different manner on the acidity of reacting solutions – the scavenging of sulphoxy radicals by isoprene, the formation of sulphoxy radicals during further reactions of isoprene radicals, and the autoxidation of SIV itself. A chemical mechanism based on this idea was explored numerically to show good agreement with experimental data. Interaction of isoprene with sulphur(IV species and oxygen can possibly result in formation of new organosulphate components of atmospheric aerosols and waters, and influence distribution of reactive sulphur and oxygen species in isoprene-emitting organisms exposed to SIV pollutants.

  9. Electronic structure calculations of acetonitrile cluster anions: Stabilization mechanism of molecular radical anions by solvation

    International Nuclear Information System (INIS)

    Systematic electronic structure calculations have been performed for (CH3CN)n-(n=2-10) anion clusters with the hybrid B3LYP and non-hybrid PW91 density-functional methods in order to understand the stabilization mechanism of an acetonitrile dimer radical anion core by solvent molecules. Since the excess negative charge is mainly localized on N atoms in the dimer anion core, solvent acetonitrile molecules are bound to the N atoms by C-H...Nδ- hydrogen-bond-like attractive interaction with the binding energy per bond being about 10-13kcal/mol. Due to this stabilization mechanism, the anion cluster for n>=4-6 is stable with respect to the electron autodetachment. Geometry optimization was also carried out for the (CH3CN)6- anion cluster where an excess electron was internally trapped. The size dependence of the stabilization energy and vertical detachment energy for the (CH3CN)n- anion clusters is discussed

  10. Oxidation of silicon surface with atomic oxygen radical anions

    Institute of Scientific and Technical Information of China (English)

    Wang Lian; Song Chong-Fu; Sun Jian-Qiu; Hou Ying; Li Xiao-Guang; Li Quan-Xin

    2008-01-01

    The surface oxidation of silicon (Si) wafers by atomic oxygen radical anions (O- anions) and the preparation of metal-oxide-semiconductor (MOS) capacitors on the O--oxidized Si substrates have been examined for the first time. The O- anions are generated from a recently developed O- storage-emission material of [Ca24Al28O64]4+.4O- (C12A7-O- for short). After it has been irradiated by an O- anion beam (0.5 μA/cm2) at 300℃ for 1-10 hours, the Si wafer achieves an oxide layer with a thickness ranging from 8 to 32 nm. X-ray photoelectron spectroscopy (XPS) results reveal that the oxide layer is of a mixture of SiO2, Si2O3, and Si2O distributed in different oxidation depths. The features of the MOS capacitor of are investigated by measuring capacitance-voltage (C - V) and current-voltage (Ⅰ - Ⅴ) curves. The oxide charge density is about 6.0×1011 cm-2 derived from the C - V curves. The leakage current density is in the order of 10-6 A/cm2 below 4 MV/cm, obtained from the Ⅰ - Ⅴ curves. The Oanions formed by present method would have potential applications to the oxidation and the surface-modification of materials together with the preparation of semiconductor devices.

  11. Solvation of benzophenone anion radical in ethanol and ethanol/2-methyltetrahydrofuran mixture

    International Nuclear Information System (INIS)

    The electron spin-echo modulations and the absoprtion spectra of benzophenone anion radicals generated by γ-irradiation in the glassy matrices of ethanol and ethanol2-methyltetrahydrofuran mixtures have been measured for elucidating the mechanism of spectral shift observed during the solvation of the anion radicals in alcohols. The anion radical generated at 4.2 K in the ethanol matrix maintains the same solvation structure as that of neutral benzophenone. At 77 K ethanol molecules solvate the anion radical by orienting the O-H dipoles toward the anion radical. The anion radical is hydrogen-bonded by two ethanol molecules through the p/sub z/ orbital on the benzophenone oxygen which composes the π orbitals of anion radical. Three kinds of anion radicals are observed in the mixed matrix at 77 K. Two of them are essentially the same as those observed in the ethanol matrix at 4.2 and 77 K. The third has the absorption maximum at 700 nm and is attributed to the anion radical hydrogen-bonded by one ethanol molecule through the p/sub z/ orbital. It is concluded that the spectral shift observed in alcohols is caused by the stabilization of a SOMO π* orbital induced by the hydrogen bonding with the (RO)H--O--H(OR) angle perpendicular to the molecular plane of the anion radical

  12. Pulse radiolysis study of the formation and the reactivity of baicalin radical anion, and in comparison with rutin, quercetin and acyrlate ester radical anions in ethanol

    Energy Technology Data Exchange (ETDEWEB)

    Sun Gang [Department of Applied Chemistry, College of Chemical and Molecular Engineering, Peking University, Beijing 100871 (China) and Department of Internal Medicine, Division of Bioorganic Chemistry and Molecular Pharmacology, Washington University School of Medicine, St Louis, MO 63110 (United States)]. E-mail: gangsun@wustl.edu; Wang Wenfeng [Shanghai Institute of Applied Physics, Academic Sinica, P.O. Box 800-204, Shanghai 201800 (China); Wu Jilan [Department of Applied Chemistry, College of Chemical and Molecular Engineering, Peking University, Beijing 100871 (China)]. E-mail: wangwqchem@pku.edu.cn

    2007-06-15

    The reaction of solvated electrons with baicalin in N{sub 2}-saturated ethanol has been studied by pulse radiolysis. The results show that a solvated electron can add to baicalin and generate a baicalin radical anion with a maximum UV absorbance peak at 360 nm. Its molar extinction coefficient at this wavelength is 1.3x10{sup 4} M{sup -1} cm{sup -1}. The rate constant for the build-up of the baicalin radical anion is 1.3({+-}0.4)x10{sup 10} M{sup -1} s{sup -1}. Decay of the radical anion is induced by a proton transfer reaction and a recombination reaction, which involves a pseudo-first-order reaction with rate constant 2.6({+-}0.4)x10{sup 3} s{sup -1} and a second-order reaction with rate constant 1.3({+-}0.2)x10{sup 9} M{sup -1} s{sup -1}. The effect of acetaldehyde on the decay of the baicalin radical anion was also investigated. Electron transfer between the baicalin radical anion and acetaldehyde was not observed, probably due to the low rate of electron transfer between the baicalin radical anion and acetaldehyde. Reactivity of the rutin, quercetin, baicalin and ethyl acrylate radical anions are also compared.

  13. Spectroscopy of free-base N-confused tetraphenylporphyrin radical anion and radical cation.

    Science.gov (United States)

    Alemán, Elvin A; Manríquez Rocha, Juan; Wongwitwichote, Wongwit; Godínez Mora-Tovar, Luis Arturo; Modarelli, David A

    2011-06-23

    The radical anions and radical cations of the two tautomers (1e and 1i) of 5,10,15,20-tetraphenyl N-confused free-base porphyrin have been studied using a combination of cyclic voltammetry, steady state absorption spectroscopy, and computational chemistry. N-Confused porphyrins (NCPs), alternatively called 2-aza-21-carba-5,10,15,20-tetraphenylporphyrins or inverted porphyrins, are of great interest for their potential as building blocks in assemblies designed for artificial photosynthesis, and understanding the absorption spectra of the corresponding radical ions is paramount to future studies in multicomponent arrays where electron-transfer reactions are involved. NCP 1e was shown to oxidize at a potential of E(ox) 0.65 V vs Fc(+)|Fc in DMF and reduce at E(red) -1.42 V, while the corresponding values for 1i in toluene were E(ox) 0.60 V and E(red) -1.64 V. The geometries of these radical ions were computed at the B3LYP/6-31+G(d)//B3LYP/6-31G(d) level in the gas phase and in solution using the polarizable continuum model (PCM). From these structures and that of H(2)TPP and its corresponding radical ions, the computed redox potentials for 1e and 1i were calculated using the Born-Haber cycle. While the computed reduction potentials and electron affinities were in excellent agreement with the experimental reduction potentials, the calculated oxidation potentials displayed a somewhat less ideal relationship with experiment. The absorption spectra of the four radical ions were also measured experimentally, with radical cations 1e(•+) and 1i(•+) displaying significant changes in the Soret and Q-band regions as well as new low energy absorption bands in the near-IR region. The changes in the absorption spectra of radical anions 1e(•-) and 1i(•-) were not as dramatic, with the changes occurring only in the Soret and Q-band regions. These results were favorably modeled using time-dependent density functional calculations at the TD-B3LYP/6-31+G(d)//B3LYP/6-31G

  14. The nature of the CO2- radical anion in water

    Science.gov (United States)

    Janik, Ireneusz; Tripathi, G. N. R.

    2016-04-01

    The reductive conversion of CO2 into industrial products (e.g., oxalic acid, formic acid, methanol) can occur via aqueous CO2- as a transient intermediate. While the formation, structure, and reaction pathways of this radical anion have been modelled for decades using various spectroscopic and theoretical approaches, we present here, for the first time, a vibrational spectroscopic investigation in liquid water, using pulse radiolysis time-resolved resonance Raman spectroscopy for its preparation and observation. Excitation of the radical in resonance with its 235 nm absorption displays a transient Raman band at 1298 cm-1, attributed to the symmetric CO stretch, which is at ˜45 cm-1 higher frequency than in inert matrices. Isotopic substitution at C (13CO2-) shifts the frequency downwards by 22 cm-1, which confirms its origin and the assignment. A Raman band of moderate intensity compared to the stronger 1298 cm-1 band also appears at 742 cm-1 and is assignable to the OCO bending mode. A reasonable resonance enhancement of this mode is possible only in a bent CO2-(C2v/Cs) geometry. These resonance Raman features suggest a strong solute-solvent interaction, the water molecules acting as constituents of the radical structure, rather than exerting a minor solvent perturbation. However, there is no evidence of the non-equivalence (Cs) of the two CO bonds. A surprising resonance Raman feature is the lack of overtones of the symmetric CO stretch, which we interpret due to the detachment of the electron from the CO2- moiety towards the solvation shell. Electron detachment occurs at the energies of 0.28 ± 0.03 eV or higher with respect to the zero point energy of the ground electronic state. The issue of acid-base equilibrium of the radical, which has been in contention for decades, as reflected in a wide variation in the reported pKa (-0.2 to 3.9), has been resolved. A value of 3.4 ± 0.2 measured in this work is consistent with the vibrational properties, bond structure

  15. Structure and Reactivity of the N-Acetyl-Cysteine Radical Cation and Anion: Does Radical Migration Occur?

    NARCIS (Netherlands)

    Osburn, S.; G. Berden,; Oomens, J.; O' Hair, R. A. J.; Ryzhov, V.

    2011-01-01

    The structure and reactivity of the N-acetyl-cysteine radical cation and anion were studied using ion-molecule reactions, infrared multi-photon dissociation (IRMPD) spectroscopy, and density functional theory (DFT) calculations. The radical cation was generated by first nitrosylating the thiol of N-

  16. Inactivation of Bacillus Subtilis by Atomic Oxygen Radical Anion

    Institute of Scientific and Technical Information of China (English)

    LI Longchun; WANG Lian; YU Zhou; LV Xuanzhong; LI Quanxin

    2007-01-01

    UAtomic oxygen radical anion (O- ) is one of the most active oxygen species, and has extremely high oxidation ability toward small-molecules of hydrocarbons. However, to our knowledge, little is known about the effects of O- on cells of micro-organisms. This work showed that O- could quickly react with the Bacillus subtilis cells and seriously damage the cell walls a s well as their other contents, leading to a fast and irreversible inactivation. SEM micrographs revealed that the cell structures were dramatically destroyed by their exposure to O-. The inactivation efficiencies of B. subtilis depend on the O-- intensity, the initial population of cells and the treatment temperature, but not on the pH in the range of our investigation. For a cell concentration of 106 cfu/ml, the number of survived cells dropped from 106 cfu/ml to 103 cfu/ml after about five-minute irradiation by an O- flux in an intensity of 233 nA/cm2 under a dry argon environment (30 ℃, 1 atm, exposed size: 1.8 cm2). The inactivation mechanism of micro-organisms induced by O- is also discussed.

  17. Radical intermediates involved in the bleaching of the carotenoid crocin. Hydroxyl radicals, superoxide anions and hydrated electrons

    Energy Technology Data Exchange (ETDEWEB)

    Bors, W.; Saran, M.; Michel, C. (Gesellschaft fuer Strahlen- und Umweltforschung m.b.H. Muenchen, Neuherberg (Germany, F.R.). Abt. Strahlenbiologie)

    1982-05-01

    The participation of the primary radicals in the bleaching of aqueous solutions of the carotenoid crocin by ionizing radiation was investigated, employing both X-radiolysis and pulse radiolysis. The pulse-radiolytic data demonstrated a very rapid diffusion-controlled attack by both hydroxyl radicals (radicalsOH) and hydrated electrons (e/sup -/sub(aq)), while superoxide anions (O/sub 2//sup -/) did not react at all. The site of the initial reaction of these radicals was not limited to the polyene chromophore. Slower secondary reactions involving crocin alkyl or peroxy radicals contribute mainly to the overall bleaching, in particular during steady-state irradiation.

  18. Radical intermediates involved in the bleaching of the carotenoid crocin. Hydroxyl radicals, superoxide anions and hydrated electrons

    International Nuclear Information System (INIS)

    The participation of the primary radicals in the bleaching of aqueous solutions of the carotenoid crocin by ionizing radiation was investigated, employing both X-radiolysis and pulse radiolysis. The pulse-radiolytic data demonstrated a very rapid diffusion-controlled attack by both hydroxyl radicals (radicalsOH) and hydrated electrons (e-sub(aq)), while superoxide anions (O2-) did not react at all. The site of the initial reaction of these radicals was not limited to the polyene chromophore. Slower secondary reactions involving crocin alkyl or peroxy radicals contribute mainly to the overall bleaching, in particular during steady-state irradiation. (author)

  19. Effect of temperature on O anion radical reactions and equilibria: a pulse radiolysis study

    International Nuclear Information System (INIS)

    The pKa of the hydroxyl radical was measured over the 20-800C temperature range. At 200C, the pKa was 11.84 and fell to 10.81 at 800C. The dissociation constant for the ozonide anion (O2-anion radical ↔ O2 + O anion radical) was found to be 5.5 x 10-7 mol dm-3 at 200C and 46.2 x 10-7 mol dm-3 at 700C. The rate constants and activation energies for the reaction of O anion radical and OH with 2-propanol, methanol and 3-hexene-1,6-dicarboxylate ions have also been measured. (author)

  20. Optical properties of the radical anion derived from {alpha}-alanine by deamination

    Energy Technology Data Exchange (ETDEWEB)

    Zagorski, Z.P.; Przybytniak, G.K. [Institute of Nuclear Chemistry and Technology, Warsaw (Poland)

    1997-12-31

    The free radical anion CH{sub 3}CHCOO derived during high energy irradiation from {alpha}-alanine by deamination has been investigated until now by EPR, in irradiated single crystals, for basic research or in completely randomized polycrystalline material for {gamma}-dosimetric purposes. It has been found by spectrophotometry of irradiated single crystals that the free radical absorbs light at {lambda}{sub max}=350 nm. The same radical anion is observed by pulse radiolysis of {alpha}-chloropropionic or propionic anion in aqueous solutions by Cl resp. {alpha}-H abstraction.Basic and applied aspects of the identity of the radical anion obtained in different ways are discussed, as well as consequences for dosimetric techniques. (author). 11 refs, 4 figs.

  1. Membrane Separator for Redox Flow Batteries that Utilize Anion Radical Mediators.

    Energy Technology Data Exchange (ETDEWEB)

    Delnick, Frank M.

    2014-10-01

    A Na + ion conducting polyethylene oxide membrane is developed for an organic electrolyte redox flow battery that utilizes anion radical mediators. To achieve high specific ionic conductivity, tetraethyleneglycol dimethylether (TEGDME) is used as a plasticizer to reduce crystallinity and increase the free volume of the gel film. This membrane is physically and chemically stable in TEGDME electrolyte that contains highly reactive biphenyl anion radical mediators.

  2. Generation of radical anions from metronidazole, misonidazole and azathioprine by photoreduction in the presence of EDTA

    International Nuclear Information System (INIS)

    Ultraviolet irradiation of the nitroimidazole derivatives metronidazole, misonidazole, azathioprine and 1-methyl-4-nitroimidazole in aqueous solution with various reductants produced the respective nitro radical anions, as detected by electron spin resonance spectroscopy. The most effective reductant, yielding high concentrations of the radical anions, was EDTA at pH 10. NADH, NADPH, formaldehyde glutathione and methanol were also tested but were less efficient as reductants. (author)

  3. Generation of radical anions from metronidazole, misonidazole and azathioprine by photoreduction in the presence of EDTA

    Energy Technology Data Exchange (ETDEWEB)

    Moore, D.E.; Chignell, C.F.; Sik, R.H.; Motten, A.G.

    1986-11-01

    Ultraviolet irradiation of the nitroimidazole derivatives metronidazole, misonidazole, azathioprine and 1-methyl-4-nitroimidazole in aqueous solution with various reductants produced the respective nitro radical anions, as detected by electron spin resonance spectroscopy. The most effective reductant, yielding high concentrations of the radical anions, was EDTA at pH 10. NADH, NADPH, formaldehyde glutathione and methanol were also tested but were less efficient as reductants.

  4. Sensitization of microorganisms and enzymes by radiation-induced selective inorganic radical anions

    International Nuclear Information System (INIS)

    Bacterial survival and enzymatic inactivation were examined following exposure to radiolytically-generated radical anions, X-2, where X=Cl, Br, I or CNS-. Depending on pH, radical anions react selectively or specifically with cysteine, tryptophan, tyrosine and histidine. Consequently, when one or more of these amino acids is crucial for enzymatic activity or bacterial survival and is attacked by a radical anion, a high degree or radiosensitization may be realized. Halide radical anions can form free chlorine, bromine or iodine. However, these bactericidal halogens are destroyed by reaction with the hydrated electron, e-sub(aq), or at pHs>9, as occurs, for example, when a medium saturated with nitrous oxide, N2O, and e-sub(aq) scavenger, is replaced by nitrogen or oxygen. Increasing concentration of other e-sub(aq) scavengers, such as phosphate buffer, promotes formation of halogen from halides. The conditions producing formation and elimination of halogens in irradiated media must be appreciated to avoid confusing radiosensitization by X2 to X-2. Radiosensitization by radical anions of several microorganisms: S. faecalis, S. typhimurium, E. coli, and M. radiodurens is described. A crucial amino acid for survival of S. faecalis appears to be tyrosine, while both tyrosine and tryptophan seem essential for recovery of S. typhimurium from effects of ionizing radiation. It is postulated that the radiosensitizing action of radical anions involves inhibition of DNA repair of strand-breaks by depriving the cells of energy. In view of the high OH scavenging power of foods, it is concluded that the radiosensitization of bacteria and enzymes in foods by radical anions, except for special cases, is not practical. Rather, radical anions serve to identify crucial amino acids to radiosensitization mechanisms in model systems, and possibly in radiotherapy. (author)

  5. Sensitization of Microorganisms and Enzymes by Radiation-Induced Selective Inorganic Radical Anions

    International Nuclear Information System (INIS)

    Bacterial survival and enzymatic inactivation were examined following exposure to radiolytically-generated radical anions, X-2 , where X = Cl, Br, I, or CNS. Depending on pH, radical anions react selectively or specifically with cysteine, tryptophan, tyrosine and histidine. Consequently, when one or more of these amino acids is crucial for enzymatic activity or bacterial survival and is attacked by a radical anion, a high degree or radiosensitization may be realized. Halide radical anions can form free chlorine, bromine or iodine. However, these bactericidal halogens are destroyed by reaction with the hydrated electron, e-aq, or at pHs > 9, as occurs, for example, when a medium saturated with nitrous oxide, N2O , and e-aq scavenger, is replaced by nitrogen or oxygen. Increasing concentration of other e-aq scavengers, such as phosphate buffer, promotes formation of halogen from halides. The conditions producing formation and élimination o f halogens in irradiated media m ust be appreciated to avoid confusing radiosensitization by X2 to X-2. Radiosensitization by radical anions o f several microorganisms: S. faecalis, S. typhimurium, E. coli, and M. radiodurens is described. A crucial amino acid for survival of S. faecalis appears to be tyrosine, while both tyrosine and tryptophan seem essential for recovery of S. typhimurium from effects of ionizing radiation. It is postulated that the radiosensitizing action o f radical anions involves inhibition of DNA repair of strand-breaks by depriving the cells of energy. In view of the high OH scavenging power of foods, it is concluded that the radiosensitization of bacteria and enzymes in foods by radical anions, except for special cases, is not practical. Rather, radical anions serve to identify crucial amino acids to radiosensitization mechanisms in model systems, and possibly in radiotherapy. (author)

  6. Kinetics and mechanism of protection of thymine from sulphate radical anion under anoxic conditions

    Indian Academy of Sciences (India)

    M Sudha Swaraga; M Adinarayana

    2003-04-01

    The rates of photooxidation of thymine in presence of peroxydisulphate (PDS) have been determined by measuring the absorbance of thymine at 264 nm spectrophotometrically. The rates and the quantum yields () of oxidation of thymine by sulphate radical anion have been determined in the presence of different concentrations of caffeic acid. Increase in [caffeic acid] is found to decrease the rate of oxidation of thymine suggesting that caffeic acid acts as an efficient scavenger of SO$^{\\bullet -}_{4}$ and protects thymine from it. Sulphate radical anion competes for thymine as well as for caffeic acid. The rate constant of sulphate radical anion with caffeic acid has been calculated to be 1.24 × 1010 dm3 mol-1 s-1. The quantum yields of photooxidation of thymine have been calculated from the rates of oxidation of thymine and the light intensity absorbed by PDS at 254 nm, the wavelength at which PDS is activated to sulphate radical anion. From the results of experimentally determined quantum yields (exptl) and the quantum yields calculated (cl) assuming caffeic acid acting only as a scavenger of SO$^{\\bullet -}_{4}$ radicals show that exptl values are lower than cl values. The ' values, which are experimentally found quantum yield values at each caffeic acid concentration and corrected for SO$^{\\bullet-}_{4}$ scavenging by caffeic acid, are also found to be greater than exptl values. These observations suggest that the thymine radicals are repaired by caffeic acid in addition to scavenging of sulphate radical anions.

  7. Mechanism of protection of adenosine from sulphate radical anion and repair of adenosine radicals by caffeic acid in aqueous solution

    Indian Academy of Sciences (India)

    M Sudha Swaraga; L Charitha; M Adinarayana

    2005-07-01

    The photooxidation of adenosine in presence of peroxydisulphate (PDS) has been studied by spectrophotometrically measuring the absorbance of adenosine at 260 nm. The rates of oxidation of adenosine by sulphate radical anion have been determined in the presence of different concentrations of caffeic acid. Increase in [caffeic acid] is found to decrease the rate of oxidation of adenosine suggesting that caffeic acid acts as an efficient scavenger of $SO_{4}^{\\bullet-}$ and protects adenosine from it. Sulphate radical anion competes for adenosine as well as for caffeic acid. The quantum yields of photooxidation of adenosine have been calculated from the rates of oxidation of adenosine and the light intensity absorbed by PDS at 254 nm, the wavelength at which PDS is activated to sulphate radical anion. From the results of experimentally determined quantum yields (exptl) and the quantum yields calculated (cal) assuming caffeic acid acting only as a scavenger of $SO_{4}^{\\bullet-}$ show that exptl values are lower than cal values. The ' values, which are experimentally found quantum yield values at each caffeic acid concentration and corrected for $SO_{4}^{\\bullet-}$ scavenging by caffeic acid, are also found to be greater than exptl values. These observations suggest that the transient adenosine radicals are repaired by caffeic acid in addition to scavenging of sulphate radical anions.

  8. Fluorinated and trifluoromethylated CB11 carborane anions and radicals

    Czech Academy of Sciences Publication Activity Database

    Higelin, Alexander; Šembera, Filip; Tamadon, F.; Wahab, Abdul; Janoušek, Zbyněk; Ludvík, Jiří; Klíma, Jiří; Crespo, R.; Piqueras, M. C.; Michl, Josef

    San Francisco: American Chemical Society, 2014. 37FLUO. [ACS National Meeting & Exposition /248./. 10.08.2014-14.08.2014, San Francisco] Institutional support: RVO:61388963 Keywords : carborane anions Subject RIV: CC - Organic Chemistry

  9. Efficient production of aromatic cation radicals by irradiation with visible light. Utilization of 60C as photocatalyst

    International Nuclear Information System (INIS)

    Complete text of publication follows. Photoinduced electron transfer reactions of fullerenes have of widespread interest because of their potential application in the initiation of chemical processes. The high stability, broad range of visible absorption of 60C as well as the efficient formation and long lifetime of the triplet excited state facilitate its implementation as light harvester. The remarkable ability of the 60C to accept electron have stimulated a number of studies, however, the data concerning the participation of the triplet 60C as electron donor are scarce and formation of 60C+ cation radical has not been detected in photoinduced reactions with strong electron acceptors such as tetracyanoethylene tetracyanoquinodimethane or chloranil. We now report a laser flash photolysis study of triplet 60C quenching by chloranil and demonstrate that addition of trifluoroacetic acid (TFA) results in several orders of magnitude increase in reaction rate. The large rate enhancement is attributed to development of a local polar environment by the preferential solvation of chloranil with TFA. 60C+ cation radical and semiquinone radical are clearly identified as reaction products. The quantum yield of radical formation is found to be as high as 0.80 in the presence of 0.5 M TFA indicating that the efficient protonation of the chloranil radical anion, formed in the primary electron transfer, competes effectively with the back electron transfer process. Because of its high oxidation potential (1.76 V vs. SCE in benzonitrile) 60C+ cation radical readily oxidizes aromatic compounds e.g. fluoranthene, naphthalene derivatives in secondary electron transfer process. Therefore, 60C is a very efficient photocatalyst for production of aromatic cation radicals by irradiation with visible light

  10. Screening of radical scavenging activity of some medicinal and aromatic plant extracts

    NARCIS (Netherlands)

    Miliauskas, G.; Venskutonis, R.P.; Beek, van T.A.

    2004-01-01

    Extracts of 12 medicinal and aromatic plants were investigated for their radical scavenging activity using DPPH and ABTS assays: Salvia sclarea, Salvia glutinosa, Salvia pratensis, Lavandula angustifolia, Calendula officinalis, Matricaria recutita, Echinacea purpurea, Rhaponticum carthamoides, Jugla

  11. Electrochemical examination of the ascorbic acid radical anion in non-aqueous electrolytes

    Energy Technology Data Exchange (ETDEWEB)

    Yoshimura, M.; Honda, K.; Kondo, T.; Rao, T.N.; Tryk, D.A.; Fujishima, A

    2002-10-15

    A quasi-reversible redox reaction involving ascorbic acid was observed in non-aqueous electrolytes at conductive diamond electrode. The chemical reversibility of these reactions is consistent with ascorbic acid being reduced to the ascorbic acid radical anion in a one-electron process, with subsequent reoxidation to ascorbic acid. This is the first report on the electrochemical production of the ascorbic acid radical anion in non-aqueous electrolytes. Ascorbyl 6-stearate and 4-hydroxy 2(5H)-furanone, which have somewhat similar structures as ascorbic acid, also showed one-electron transfer reduction reaction producing radicals with a single negative charge, suggesting that these compounds follow the same electrochemical behavior as ascorbic acid. The double bond and hydroxyl substituent on the five-membered ring are shown to be necessary for the stabilization of the radical anions. It was confirmed by the calculation of the total energy using molecular orbital methods that resonance structures involving the double-bond and hydroxyl group provide significant stabilization of the radical anions. Electrochemical preparation may be a useful method for the detailed study of radicals, their molecular structure and reactivity.

  12. Electrochemical examination of the ascorbic acid radical anion in non-aqueous electrolytes

    International Nuclear Information System (INIS)

    A quasi-reversible redox reaction involving ascorbic acid was observed in non-aqueous electrolytes at conductive diamond electrode. The chemical reversibility of these reactions is consistent with ascorbic acid being reduced to the ascorbic acid radical anion in a one-electron process, with subsequent reoxidation to ascorbic acid. This is the first report on the electrochemical production of the ascorbic acid radical anion in non-aqueous electrolytes. Ascorbyl 6-stearate and 4-hydroxy 2(5H)-furanone, which have somewhat similar structures as ascorbic acid, also showed one-electron transfer reduction reaction producing radicals with a single negative charge, suggesting that these compounds follow the same electrochemical behavior as ascorbic acid. The double bond and hydroxyl substituent on the five-membered ring are shown to be necessary for the stabilization of the radical anions. It was confirmed by the calculation of the total energy using molecular orbital methods that resonance structures involving the double-bond and hydroxyl group provide significant stabilization of the radical anions. Electrochemical preparation may be a useful method for the detailed study of radicals, their molecular structure and reactivity

  13. The AHA Moment: Assessment of the Redox Stability of Ionic Liquids Based on Aromatic Heterocyclic Anions (AHAs) for Nuclear Separations and Electric Energy Storage.

    Science.gov (United States)

    Shkrob, Ilya A; Marin, Timothy W

    2015-11-19

    Because of their extended conjugated bond network, aromatic compounds generally have higher redox stability than less saturated compounds. We conjectured that ionic liquids (ILs) consisting of aromatic heterocyclic anions (AHAs) may exhibit improved radiation and electrochemical stability. Such properties are important in applications of these ILs as diluents in radionuclide separations and electrolytes in the electric energy storage devices. In this study, we systematically examine the redox chemistry of the AHAs. Three classes of these anions have been studied: (i) simple 5-atom ring AHAs, such as the pyrazolide and triazolides, (ii) AHAs containing an adjacent benzene ring, and (iii) AHAs containing electron-withdrawing groups that were introduced to reduce their basicity and interaction with metal ions. It is shown that fragmentation in the reduced and oxidized states of these AHAs does not generally occur, and the two main products, respectively, are the H atom adduct and the imidyl radical. The latter species occurs either as an N σ-radical or as an N π-radical, depending on the length of the N-N bond, and the state that is stabilized in the solid matrix is frequently different from that having the lowest energy in the gas phase. In some instances, the formation of the sandwich π-stack dimer radical anions has been observed. For trifluoromethylated anions, H adduct formation did not occur; instead, there was facile loss of fluoride from their fluorinated groups. The latter can be problematic in nuclear separations, but beneficial in batteries. Overall, our study suggests that AHA-based ILs are viable candidates for use as radiation-exposed diluents and electrolytes. PMID:26506410

  14. Production of the carbonate radical anion during xanthine oxidase turnover in the presence of bicarbonate.

    Science.gov (United States)

    Bonini, Marcelo G; Miyamoto, Sayuri; Di Mascio, Paolo; Augusto, Ohara

    2004-12-10

    Xanthine oxidase is generally recognized as a key enzyme in purine catabolism, but its structural complexity, low substrate specificity, and specialized tissue distribution suggest other functions that remain to be fully identified. The potential of xanthine oxidase to generate superoxide radical anion, hydrogen peroxide, and peroxynitrite has been extensively explored in pathophysiological contexts. Here we demonstrate that xanthine oxidase turnover at physiological pH produces a strong one-electron oxidant, the carbonate radical anion. The radical was shown to be produced from acetaldehyde oxidation by xanthine oxidase in the presence of catalase and bicarbonate on the basis of several lines of evidence such as oxidation of both dihydrorhodamine 123 and 5,5-dimethyl-1-pyrroline-N-oxide and chemiluminescence and isotope labeling/mass spectrometry studies. In the case of xanthine oxidase acting upon xanthine and hypoxanthine as substrates, carbonate radical anion production was also evidenced by the oxidation of 5,5-dimethyl-1-pyrroline-N-oxide and of dihydrorhodamine 123 in the presence of uricase. The results indicated that Fenton chemistry occurring in the bulk solution is not necessary for carbonate radical anion production. Under the conditions employed, the radical was likely to be produced at the enzyme active site by reduction of a peroxymonocarbonate intermediate whose formation and reduction is facilitated by the many xanthine oxidase redox centers. In addition to indicating that the carbonate radical anion may be an important mediator of the pathophysiological effects of xanthine oxidase, the results emphasize the potential of the bicarbonate-carbon dioxide pair as a source of biological oxidants. PMID:15448145

  15. The strong influence of the solvent on the electron spin resonance spectra of semiquinone radical anions

    DEFF Research Database (Denmark)

    Spanget-Larsen, Jens

    2013-01-01

    proton hyperfine constants predicted for the chrysazin semiquinone radical anion were highly sensitive to the assumed dielectric constant ε of the solvent continuum, inverting the relative magnitudes of the hyperfine constants and thereby leading to agreement with the observed data published by Stegmann...

  16. Kinetic observation of rapid electron transfer between thymine and thymidine anion radicals and caffeic acid: a pulse radiolysis study

    International Nuclear Information System (INIS)

    Rapid electron transfer from thymine or thymidine anion radicals to caffeic acid with rate constant of 1 x 109 M-1s-1 was observed by pulse radiolysis, leading to the formation of anion radicals of caffeic acid which is characterized with absorption maximum at 360nm. Caffeic acid has a higher one-electron reduction potential than the target molecule (thymine or thymidine) and acts as a electrophilic protector which prevent the target anion radical from its irreversible protonation at C6 leading to its 5-yl radical via fast electron transfer. The kinetic demonstrations have provided dynamic evidence of charge transfer protection mechanism. (author)

  17. Formation of semiquinone radical anion and free radical scavenging reactions of plumbagin. A pulse radiolysis study

    International Nuclear Information System (INIS)

    Kinetics and mechanism of scavenging of reducing free radicals by plumbagin (5-hydroxy-2-methyl-1,4-naphthoquinone) are studied using pulse radiolysis technique. It scavenged superoxide radical, hydroxyethyl radical and hydrated electron with bimolecular rate constants of 8.9 × 107, 2.3 × 109 and 1.6 × 1010 M-1 s-1, respectively in aqueous-alcohol medium. Plumbagin also scavenged linoleic acid peroxyl radical and tyrosyl radical with bimolecular rate constants of 1.0 × 108 and 7.0 × 106 M-1 s-1, respectively. Further, redox properties of plumbagin and its transients are studied using standard redox couples and cyclic voltammetry. (author)

  18. Oxidation of caffeine by phosphate radical anion in aqueous solution under anoxic conditions

    Indian Academy of Sciences (India)

    Maram Ravi Kumar; Mundra Adinarayana

    2000-10-01

    The photooxidation of caffeine in presence of peroxydiphosphate (PDP) in aqueous solution at natural H (∼7 5) has been carried out in a quantum yield reactor using a high-pressure mercury lamp. The reactions were followed spectrophotometrically by measuring the absorbance of caffeine at max (272 nm). The rates of reaction were calculated under different experimental conditions. The quantum yields were calculated from the rates of oxidation of caffeine and the intensity of light at 254 nm which was measured by using peroxydisulphate solution as a standard chemical actinometer. The reaction rates of oxidation of caffeine by PDP increase with increase in [PDP] as well as with increase in light intensity, while they are independent of [caffeine]. The quantum yields of oxidation of caffeine by PDP are independent of [PDP] as well as light intensity. However, quantum yields of oxidation of caffeine by PDP increase with increase in caffeine concentration. On the basis of these experimental results and product analysis, a probable mechanism has been suggested in which PDP is activated to phosphate radical anions (PO$_{4}^{\\bullet 2-}$) by direct photolysis of PDP and also by the sensitizing effect of caffeine. The phosphate radical anions thus produced react with caffeine by electron transfer reaction, resulting in the formation of caffeine radical cation, which deprotonates in a fast step to produce C8OH adduct radicals. These radicals might react with PDP to give final product 1,3,7-trimethyluric acid and PO$_{4}^{\\bullet 2-}$ radicals, the latter propagates the chain reaction.

  19. Formation of radical anions of radiosensitizers and related model compounds via electrospray ionization

    DEFF Research Database (Denmark)

    Feketeová, Linda; Albright, Abigail L; Sørensen, Brita Singers;

    2014-01-01

    Radiosensitizers are used in radiotherapy to enhance tumour control of radioresistant hypoxic tumours. While the detailed mechanism of radiosensitization is still unknown, the formation of radical anions is believed to be a key step. Thus understanding the ionization reactions of radiosensitizers...... is crucial in evaluating the radiosensitization potential and in developing new and more effective drugs. The present work investigates the negative and positive electrospray ionization and subsequent collision-induced dissociation and electron-induced dissociation reactions of ions derived from...... nimorazole, misonidazole and related compounds using a hybrid linear ion trap – Fourier Transform Ion Cyclotron Resonance mass spectrometer (Finnigan-LTQ-FT). A key finding is that negative electrospray ionization of these radiosensitizers leads to the formation of radical anions, allowing their...

  20. Bioactive Metabolites from Propolis Inhibit Superoxide Anion Radical, Acetylcholinesterase and Phosphodiesterase (PDE4)

    OpenAIRE

    Abd El-Hady, Faten K.; Shaker, Kamel H.; Imhoff, Johannes F.; Zinecker, Heidi; Salah, Nesma M.; Ibrahim, Amal M.

    2013-01-01

    Cycloartane-triterpenes (cycloartenol, 3α-cycloartenol-26-oic acid and 3β-cycloartenol-26-oic acid) together with α-amyrin acetate and flavonoids (pinostrobin, tectochrysin and chrysin) were isolated from Egyptian propolis for the first time. Their antioxidant activity was evaluated with DPPH and superoxide anion radical (O2 .-). All compounds possessed both (O2 .-) scavenging as well as XOD inhibitory activity in the range of 50 – 75 %. With DPPH, only the flavonoids showed sc...

  1. Electrochemical investigations of antioxidant interactions with radical anion and dianion of 1,3-dinitrobenzene

    Energy Technology Data Exchange (ETDEWEB)

    Arshad, Nasima [Department of Chemistry, Allama Iqbal Open University, Islamabad (Pakistan); Janjua, Naveed Kausar [Department of Chemistry, Quaid-i-Azam University, Islamabad (Pakistan)], E-mail: nkausarjanjua@yahoo.com; Ahmed, Safeer [Department of Chemistry, Quaid-i-Azam University, Islamabad (Pakistan); Khan, Athar Yaseen [Department of Chemistry, Allama Iqbal Open University, Islamabad (Pakistan); Skibsted, Leif H. [Food Chemistry, Department of Food Science, University of Copenhagen (Denmark)

    2009-11-01

    Interactions of five antioxidants (AO), quercetin (Q), morin (M), rutin (R), ascorbic acid (AA) and {beta}-carotene ({beta}-C) with anion radical and dianion of 1,3-dinitrobenzene (1,3-DNB) in two aprotic solvents - dimethyl formamide (DMF) and dimethyl sulfoxide (DMSO) - have been studied by cyclic voltammetry using glassy carbon electrode. Electrochemical parameters - peak potential (E{sub p}), half-wave potential (E{sub 1/2}), and peak current (i{sub p}) - for the reduction of 1,3-DNB before and after the addition of various concentrations of antioxidants, were evaluated. A gradual decrease in the oxidation peak current and finally irreversibility in 1,3-DNB radical anion and dianion systems upon the addition of antioxidant, reveals their interactions. The homogeneous bi-molecular rate constant (k{sub 2}) was determined from electrochemical data. In comparison to all other antioxidants used, enhanced homogeneous second order rate constant for the interaction of morin with 1,3-DNB anion radical and dianion, was observed. This aspect is attributable to protonation initiated by hydrogen bonding and greater acidic nature of morin.

  2. Polymorphism and Metallic Behavior in BEDT-TTF Radical Salts with Polycyano Anions

    Directory of Open Access Journals (Sweden)

    Carlos J. Gómez-García

    2012-04-01

    Full Text Available Up to five different crystalline radical salts have been prepared with the organic donor BEDT-TTF and three different polynitrile anions. With the polynitrile dianion tcpd2− (=C[C(CN2]32−, two closely related radical salts: α'-(ET4tcpd·THF (1 (THF = tetrahydrofurane and α'-(ET4tcpd·H2O (2 have been prepared, depending on the solvent used in the synthesis. With the mono-anion tcnoetOH− (=[(NC2CC(OCH2CH2OHC(CN2]− two polymorphs with similar physical properties but different crystal packings have been synthesized: θ-(ET2(tcnoetOH (3 and β''-(ET2(tcnoetOH (4. Finally, with the mono-anion tcnoprOH− (=[(NC2CC(OCH2CH2CH2OHC(CN2]− we have prepared a metallic radical salt: β''-(ET2(tcnoprOH(CH2Cl2CH3Cl0.5 (5. Salts 1‑4 are semiconductors with high room temperature conductivities and activation energies in the range 0.1–0.5 eV, whereas salt 5 is metallic down to 0.4 K although it does not show any superconducting transition above this temperature.

  3. Electrochemical investigations of antioxidant interactions with radical anion and dianion of 1,3-dinitrobenzene

    International Nuclear Information System (INIS)

    Interactions of five antioxidants (AO), quercetin (Q), morin (M), rutin (R), ascorbic acid (AA) and β-carotene (β-C) with anion radical and dianion of 1,3-dinitrobenzene (1,3-DNB) in two aprotic solvents - dimethyl formamide (DMF) and dimethyl sulfoxide (DMSO) - have been studied by cyclic voltammetry using glassy carbon electrode. Electrochemical parameters - peak potential (Ep), half-wave potential (E1/2), and peak current (ip) - for the reduction of 1,3-DNB before and after the addition of various concentrations of antioxidants, were evaluated. A gradual decrease in the oxidation peak current and finally irreversibility in 1,3-DNB radical anion and dianion systems upon the addition of antioxidant, reveals their interactions. The homogeneous bi-molecular rate constant (k2) was determined from electrochemical data. In comparison to all other antioxidants used, enhanced homogeneous second order rate constant for the interaction of morin with 1,3-DNB anion radical and dianion, was observed. This aspect is attributable to protonation initiated by hydrogen bonding and greater acidic nature of morin.

  4. Effect of the Structure of Cations and Anions of Ionic Liquids on Separation of Aromatics from Hydrocarbon Mixtures

    Institute of Scientific and Technical Information of China (English)

    Liu Yansheng; Zhang Zhongxin; Zhang Guofu; Liu Zhichang; Hu Yufeng; Shi Quan; Ji Dejun

    2006-01-01

    The effects of the structure of typical cations and anions of ionic liquids on the separation of benzene and toluene from aromatic/paraffin mixtures were studied. The results showed that the corresponding separation factors were considerably larger than those of the traditional solvents (Benzene+Hexane+sulfolane), and that the ionic liquids could be used as novel solvents for the separation of aromatics from hydrocarbon mixtures. The key parameters governing the ability of ionic liquids for separating aromatics from hydrocarbon sources were investigated. It was found that the effectiveness of the ionic liquids, based on the same anion, changed in the cation order of [BIqu]+< [BPy]+< [BMIM]+. The selectivity of the ionic liquid toward aromatics decreased apparently with the increasing length of the substituted alkyl chain of its cationic head ring. The separation factors, based on the same cation, changed in the anion order of [Tf2N]-<[PF6]-<[BF4]-<[C2H5SO4]-. The solubilities of the aromatics were greater in the ionic liquids based on the former three anions than that in the ionic liquids involving [C2H5SO4]-.

  5. Formation of environmentally persistent free radicals from the heterogeneous reaction of ozone and polycyclic aromatic compounds.

    Science.gov (United States)

    Borrowman, Cuyler K; Zhou, Shouming; Burrow, Timothy E; Abbatt, Jonathan P D

    2016-01-01

    In the 1980s long-lived radical species were identified in cigarette tar. Since then, environmentally persistent free radicals (EPFRs) have been observed in ambient particulate matter, and have been generated in particulate matter generated from internal combustion engines. For the first time, we measure in situ the formation and decay of EPFRs through the heterogeneous reaction of ozone and several polycyclic aromatic compounds (PAC). Solid anthracene (ANT), pyrene (PY), benzo[a]pyrene (BAP), benzo[ghi]perylene (BGHIP), 1,4-naphthoquinone (1,4NQ), and 9,10-anthraquinone (AQ) were reacted with gas-phase ozone in a flow system placed in the active cavity of an electron paramagnetic resonance (EPR) spectrometer, and the formation of radicals was measured on the timescale of tens of minutes at ambient levels of ozone down to 30 ppb. For most substrates the net radical production is initially rapid, slows at intermediate times, and is followed by a slow decay. For oxidized solid BAP, radical signal persists for many days in the absence of ozone. To evaluate the effect of substrate phase, the solid PAHs were also dissolved in squalane, an organic oil inert to ozone, which yielded a much higher maximum radical concentration and faster radical decay when exposed to ozone. With higher mobility, reactants were apparently able to more easily diffuse and react with each other, yielding the higher radical concentrations. The EPR spectra exhibit three radicals types, two of which have been assigned to semiquinone species and one to a PAH-derived, carbon-centered radical. Although our system uses levels of PAC not typically found in the environment it is worth noting that the amounts of radical formed, on the order of 10(18) radicals per g, are comparable to those observed in ambient particulate matter. PMID:26603953

  6. Chemistry of Secondary Organic Aerosol Formation From the Reaction of Hydroxyl Radicals With Aromatic Compounds

    OpenAIRE

    Strollo Gordon, Christen Michelle

    2013-01-01

    ABSTRACT OF THE DISSERTATIONChemistry of Secondary Organic Aerosol Formation From the Reaction of Hydroxyl Radicals With Aromatic CompoundsbyChristen Michelle Strollo GordonDoctor of Philosophy, Graduate Program in Chemistry University of California, Riverside, August 2013Dr. Paul J. Ziemann, ChairpersonSecondary Organic Aerosol (SOA) can have significant impacts on visibility, human health, and global climate, and a more detailed understanding of the roles of both gas-phase and heterogeneous...

  7. Polycyclic aromatic hydrocarbon (PAH) formation from benzyl radicals: a reaction kinetics study.

    Science.gov (United States)

    Sinha, Sourab; Raj, Abhijeet

    2016-03-01

    The role of resonantly stabilized radicals such as propargyl, cyclopentadienyl and benzyl in the formation of aromatic hydrocarbons such as benzene and naphthalene in the high temperature environments has been long known. In this work, the possibility of benzyl recombination to form three-ring aromatics, phenanthrene and anthracene, is explored. A reaction mechanism for it is developed, where reaction energetics are calculated using density functional theory (B3LYP functional with 6-311++G(d,p) basis set) and CBS-QB3, while temperature-dependent reaction kinetics are evaluated using transition state theory. The mechanism begins with barrierless formation of bibenzyl from two benzyl radicals with the release of 283.2 kJ mol(-1) of reaction energy. The further reactions involve H-abstraction by a H atom, H-desorption, H-migration, and ring closure to gain aromaticity. Through mechanism and rate of production analyses, the important reactions leading to phenanthrene and anthracene formation are determined. Phenanthrene is found to be the major product at high temperatures. Premixed laminar flame simulations are carried out by including the proposed reactions for phenanthrene formation from benzyl radicals and compared to experimentally observed species profiles to understand their effects on species concentrations. PMID:26923612

  8. Electrochemical reduction of aromatic ketones in 1-butyl-3-methylimidazolium-based ionic liquids in the presence of carbon dioxide: the influence of the ketone substituent and the ionic liquid anion on bulk electrolysis product distribution.

    Science.gov (United States)

    Zhao, Shu-Feng; Horne, Mike; Bond, Alan M; Zhang, Jie

    2015-07-15

    Electrochemical reduction of aromatic ketones, including acetophenone, benzophenone and 4-phenylbenzophenone, has been undertaken in 1-butyl-3-methylimidazolium-based ionic liquids containing tetrafluoroborate ([BF4](-)), trifluoromethanesulfonate ([TfO](-)) and tris(pentafluoroethyl)trifluorophosphate ([FAP](-)) anions in the presence of carbon dioxide in order to investigate the ketone substituent effect and the influence of the acidic proton on the imidazolium cation (C2-H) on bulk electrolysis product distribution. For acetophenone, the minor products were dimers (50%) derived from proton coupled electron transfer reactions involving the electrogenerated radical anions and C2-H. In the cases of both acetophenone and benzophenone, the product distribution is essentially independent of the ionic liquid anion. By contrast, 4-phenylbenzophenone shows a product distribution that is dependent on the ionic liquid anion. Higher yields of carboxylic acids (∼40%) are obtained with [TfO](-) and [FAP](-) anions because in these ionic liquids the C2-H is less acidic, making the formation of alcohol less favourable. In comparison with benzophenone, a higher yield of carboxylic acid (>30% versus ∼15%) was obtained with 4-phenylbenzophenone in all ionic liquids due to the weaker basicity of 4-phenylbenzophenone radical anion. PMID:26136079

  9. Ab initio study of long-range electron transfer between biphenyl anion radical and naphthalene

    Institute of Scientific and Technical Information of China (English)

    李象远; 肖顺清; 何福城

    1999-01-01

    After the separation of the donor, the aeceptor, and the σ-type bridge from the π-σ-π system, the geometries of biphenyl, biphenyl anion radical, naphthalene, and naphthalene anion radical are optimized, and then the reorganization energy for the intermolecular electron transfer (ET) at the levels of HF/4-31G and HF/DZP is calculated. The ET matrix elements of the self-exchange reactions of the π-σ-π systems have been calculated by means of both the direct calculation based on the variational principle, and the transition energy between the molecular orbitals at the linear coordinate R=0.5. For the cross reactions, the ET matrix element and the geometry of the transition state are determined by searching the minimum energy splitting △min along the reaction coordinate. In the evaluation of the solvent reorganization energy of the ET in solution, the Marcus’ two-sphere model has been invoked. A few of ET rate constants for the intramolecular ET reactions for the π-σ-π systems, which contain

  10. Insights in the radical scavenging mechanism of syringaldehyde and generation of its anion

    Science.gov (United States)

    Yancheva, D.; Velcheva, E.; Glavcheva, Z.; Stamboliyska, B.; Smelcerovic, A.

    2016-03-01

    The ability of syringaldehyde, a naturally occurring phenolic antioxidant and medicinally important compound, to scavenge free radicals according different mechanisms was elucidated by computing the respective reaction enthalpies at DFT B3LYP/6-311++G** level. Bond dissociation enthalpy, ionization potentials and proton affinities were calculated in gas phase, benzene, water and DMSO in order to account for different environment (nonpolar lipid membranes and polar physiological liquids) where the antioxidant action in the living organism could take place and various experimental in vitro conditions. Molecular and electronic properties influencing the reactivity of syringaldehyde according to the different mechanisms were discussed in the light of the reported radical scavenging activities in crocin bleaching, oxidation potential of the first anodic peak and DPPH test. According to the calculated reaction enthalpies, in polar environment the syringaldehyde reacts preferably by sequential proton loss electron transfer which is related to the formation of a phenoxy anion. Such phenoxy anion was generated in DMSO solution and the changes in the force field, steric and electronic structure, resulting from the conversion, were described in detail based on the IR spectral data and DFT computations.

  11. Pulse radiolysis study of salt effects on reactions of aromatic radical cations with Cl-

    International Nuclear Information System (INIS)

    The effect of quaternary ammonium salts on the decays of the radical cations of biphenyl, trans-stilbene, anthracene and pyrene generated by pulse radiolysis in chlorohydrocarbons has been investigated. The decays, which are due to neutralization reactions with Cl-, are retarded by the addition of salts having non-nucleophilic PF6-, BF4- and ClO4-, whereas the radical cations are rapidly quenched by salts having I- and BPh4-. The retarding effect of the salts is attributed to the formation of ion pairs between the reacting ions and the counter-ions from the salts. The rate constants for the neutralization reactions in 1,2-dichloroethane have been determined for the free-ion and ion-paired states; the latter state is attained by the addition of Bu4NPF6. The rate constant determined in the absence of the salt for Pysup(radical)+ is one order of magnitude smaller than those for the others. The salt effect is also smallest on the reaction of Pysup(radical)+. The charge delocalisation of the large aromatic radical cation may be responsible for the exceptional results for Pysup(radical)+. The largest salt effect was observed on the reaction of Ph2CH+, a charge-localized carbenium ion investigated for comparison. The solvent effect on the neutralization reactions is also discussed. (author)

  12. First observation of alkyne radical anions by electron spin resonance spectroscopy: Hexyne/n-hexane mixed crystals

    International Nuclear Information System (INIS)

    The radical anions of alkynes have been first observed by electron spin resonance spectroscopy following alkene anions previously studied. Hexyne radical anions were formed in 1-, 2-, or 3-hexyne/n--hexane mixed crystals irradiated at 4.2 or 77 K. The characters of the anions were as follows; (a) the α-proton hyperfine coupling is very large (∼4.5 mT for the 1-hexyne anion), (b) the β-proton couplings are very small (∼1.0 mT for C--Hβ proton with the conformational angle of 0 degree), and (c) the radicals show a negative g shift (2.0014). From these observations, it was found that the anions have a nonlinear(bent) molecule structure in the anticonfiguration (trans C--C≡C--C) with the bend angle ∼60 degree, and that the unpaired electron orbital is approximately composed of the anticombination of the sp2 hybrid orbitals of the C≡C carbon atoms. A discussion based on complete neglect of differential overlap (CNDO) molecular orbital (MO) calculations was given for the observed negative g shift, which was shown to be characteristic of the alkyne anions which have a high-lying unpaired electron orbital and an antibonding 2p--2p π carbon orbital just above it on the upper energy side

  13. The first BETS radical cation salts with dicyanamide anion: Crystal growth, structure and conductivity study

    International Nuclear Information System (INIS)

    Electrochemical oxidation of bis(ethylenedithio)tetraselenafulvalene (BETS) has been investigated. Simple and complex dicyanamides of transition metals (Mn2+, Ni2+ and Fe2+) were used as electrolytes. The correlation between composition of prepared radical cation salts and metal nature in electrolytes was established. Manganese dicyanamides provide the formation of BETS salts with the {Mn[N(CN)2]3}- and [N(CN)2]-XH2O anions. When Ni- or Fe-containing electrolytes were used only metalless BETS salts, α''-BETS2[N(CN)2].2H2O (I) and θ-BETS2[N(CN)2].3.6H2O (II), formed. Structures and conducting properties of these salts were analyzed. Both salts exhibit layered structure. Conducting radical cation layers have α'' (I)- or θ-type (II). Anion sheets appear as two-dimensional polymer networks of different types. These networks are formed by [N(CN)]2- anions and water molecules interlinked by hydrogen bonds. Salt I is a semiconductor and II demonstrates resistance drop down to150 K at normal pressure and down to 72 K at ∼0.4 kbar pressure. - Graphical abstract: We studied electrochemical oxidation of BETS donor in the presence of simple and/or complex dicyanamides of transition metals (Ni, Fe, Mn) as electrolytes. New conducting salts α''-BETS2[N(CN)2].2H2O and θ-BETS2[N(CN)2].3.8H2O have been synthesized and characterized. Highlights: → We studied electrochemical oxidation of BETS donor. → Dicyanamides of transition metals (Ni, Fe, Mn) were used as electrolytes. → We found a well-reproducible synthesis of magnetic superconductor BETS2Mn[N(CN)2]3. → Two new metalless BETS salts form when Ni and Fe electrolytes were used. → Their structure and conductivity were investigated.

  14. Study of radicals, clusters and transition state species by anion photoelectron spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Arnold, D.W.

    1994-08-01

    Free radicals, elemental and van der Waals clusters and transition state species for bimolecular chemical reactions are investigated using anion photoelectron spectroscopy. Several low-lying electronic states of ozone have been identified via photoelectron spectroscopy of O{sub 3}{sup {minus}}. A characterization of these states is important to models for atmospheric ozone reaction kinetics. The fluoroformyloxyl radical, FCO{sub 2}, has been investigated, providing vibrational frequencies and energies for two electronic states. The technique has also been employed to make the first direct observation and characterization of the NNO{sub 2} molecule. Several electronic states are observed for this species which is believed to play a role as a reactive intermediate in the N + NO{sub 2} reaction. The experimental results for all three of these radicals are supplemented by ab initio investigations of their molecular properties. The clusters investigations include studies of elemental carbon clusters (C{sub 2}{sup {minus}} {minus} C{sub 11}{sup {minus}}), and van der Waals clusters (X{sup {minus}}(CO{sub 2}){sub n}, X = I, Br, Cl; n {le} 13 and I{sup {minus}} (N{sub 2}O){sub n=1--11}). Primarily linear clusters are observed for the smaller carbon clusters, while the spectra of the larger clusters contain contribution from cyclic anion photodetachment. Very interesting ion-solvent interactions are observed in the X{sup {minus}}(CO{sub 2})n clusters. The transition state regions for several bimolecular chemical reactions have also been investigated by photodetachment of a negative ion precursor possessing a geometry similar to that of the transition state species. These spectra show features which are assigned to motions of the unstable neutral complex existing between reactants and products.

  15. Study of radicals, clusters and transition state species by anion photoelectron spectroscopy

    International Nuclear Information System (INIS)

    Free radicals, elemental and van der Waals clusters and transition state species for bimolecular chemical reactions are investigated using anion photoelectron spectroscopy. Several low-lying electronic states of ozone have been identified via photoelectron spectroscopy of O3-. A characterization of these states is important to models for atmospheric ozone reaction kinetics. The fluoroformyloxyl radical, FCO2, has been investigated, providing vibrational frequencies and energies for two electronic states. The technique has also been employed to make the first direct observation and characterization of the NNO2 molecule. Several electronic states are observed for this species which is believed to play a role as a reactive intermediate in the N + NO2 reaction. The experimental results for all three of these radicals are supplemented by ab initio investigations of their molecular properties. The clusters investigations include studies of elemental carbon clusters (C2- - C11-), and van der Waals clusters (X-(CO2)n, X = I, Br, Cl; n ≤ 13 and I- (N2O)n=1--11). Primarily linear clusters are observed for the smaller carbon clusters, while the spectra of the larger clusters contain contribution from cyclic anion photodetachment. Very interesting ion-solvent interactions are observed in the X-(CO2)n clusters. The transition state regions for several bimolecular chemical reactions have also been investigated by photodetachment of a negative ion precursor possessing a geometry similar to that of the transition state species. These spectra show features which are assigned to motions of the unstable neutral complex existing between reactants and products

  16. Concerted effects of substituents in the reaction of •OH radicals with aromatics: The hydroxybenzaldehydes

    Science.gov (United States)

    Albarran, Guadalupe; Mendoza, Edith; Schuler, Robert H.

    2016-07-01

    In the present work, we have examined the distribution of products in the radiolytic hydroxylation of 2-, 3- and 4-hydroxybenzaldehyde to obtain information on the concerted effect of the -CHO and -OH groups at the addition site of •OH radicals. The •OH radical was found to selectively add to the free positions of the aromatic ring. Furthermore, the •OH radical reacts by substitution at the ipso position followed by elimination of the substituent, producing dihydroxybenzene compounds. Additionally, the formation of carboxylic acids as an initial product has been conclusively identified by retention times and UV and mass spectra. These acids are formed as a result of the radiolytic oxidation of the initial radical formed by the addition reaction of the •OH radicals to the meso position (exocyclic carbon). The identification of the products, dihydroxybenzaldehydes, dihydroxybenzenes and hydroxybenzoic acids and calculation of their yields were achieved through HPLC. The G values of each product are given, which reflect the charge distributions in the hydroxybenzaldehydes, such that the formyl group modifies the ortho-para directing effect of the -OH substituent. The 3 and 5 positions in 2- and 4-hydroxybenzaldehyde showed increased the electronic density compared to that of phenol, indicating that the formyl group has a significant effect on the electronic structure of those hydroxybenzaldehydes. In 3-hydroxybenzaldehyde, the -OH substituent had a dominant ortho-directing effect similar to that observed for phenol.

  17. Conjugation between σ- and π-Aromaticity in 1-C-Arylated Monocarba-closo-dodecaborate Anions.

    Science.gov (United States)

    Otsuka, Mai; Takita, Ryo; Kanazawa, Junichiro; Miyamoto, Kazunori; Muranaka, Atsuya; Uchiyama, Masanobu

    2015-12-01

    Conjugation between σ- and π-aromatic moieties in 1-C-arylated monocarba-closo-dodecaborate anion derivatives 2 has been identified by means of kinetic experimental studies combined with theoretical calculations. We found that the reaction rate of iodination at the 12-B vertex of the carborane anion cage was affected by distal substituents on the benzene ring connected at the antipodal carbon vertex. Hammett and Yukawa-Tsuno plots indicated that substantial resonance effects are involved. Density functional theory calculations enabled detailed interpretation of the electronic interaction. PMID:26584675

  18. Ab initio and DFT study of the geometric structures and static dipole (hyper)polarizabilities of aromatic anions.

    Science.gov (United States)

    Castellano, O; Bermúdez, Y; Giffard, M; Mabon, G; Cubillan, N; Sylla, M; Nguyen-Phu, X; Hinchliffe, A; Soscún, H

    2005-11-17

    The geometries and the static dipole (hyper)polarizabilities (alpha, beta, gamma) of a series of aromatic anions were investigated at the ab initio (HF, MP2, and MP4) and density functional theory DFT (B3LYP) levels of theory. The anions chosen for the present study are the benzenethiolate (Ph-S-), benzenecarboxylate (Ph-CO2-), benzenesulfinate (Ph-SO2-), benzenesulfonate (Ph-SO3-), and 1,3-benzenedicarboxylate (1,3-Ph-(CO2)2(2-)). For benzenethiolate anion, additional alpha, beta, and gamma calculations were performed at the coupled cluster CCSD level with MP2 optimized geometries. The standard diffuse and polarized 6-31+G(d,p) basis set was employed in conjunction to the ab initio and DFT methods. Additional HF calculations were performed with the 6-311++G(3d,3p) basis set for all the anions. The correlated electric properties were evaluated numerically within the formalism of finite field. The optimized geometries were analyzed in terms of the few reports about the phenolate and sulfonate ions. The results show that electron correlation effects on the polarizabilities are very important in all the anion series. Was found that Ph-SO2- is highly polarizable in terms of alpha and beta, and the Ph-S- is the highest second hyperpolarizable in the series. The results of alpha were rationalized in terms of the analysis of the polarization of charge based in Mulliken atomic population and the structural features of the optimized geometries of anions, whereas the large differences in the beta and gamma values in the series were respectively interpreted in terms of the bond length alternation BLA and the separation of charge in the aromatic ring by effects of the substitution. These results allowed us to suggest the benzenesulfinate and benzenethiolate anions as promising candidates that should be incorporated in ionic materials for second and third-order nonlinear optical devices. PMID:16833334

  19. THERMODYNAMIC STUDY ON ADSORPTION OF AROMATIC SULFONIC ACIDS ONTO MACROPOROUS WEAK BASE ANION EXCHANGER FROM AQUEOUS SOLUTIONS

    Institute of Scientific and Technical Information of China (English)

    Chao Long; Quan-xing Zhang; Ai-min Li; Jin-long Chen

    2004-01-01

    The adsorption equilibrium isotherms of three aromatic sulfonic acid compounds, 2-naphthalenesulfonic acid, ptoluenesulfonic acid and p-chlorobenzenesulfonic acid, from aqueous solutions by macroporous weak base anion exchanger within the temperature range of 293 K-313 K were obtained. Several isotherm equations were correlated with the equilibrium data, and the experimental data was found to fit the three-parameter Redlich-Peterson equation best within the entire range of concentrations. The study showed that the hydrophobicity of solute has distinct influence on adsorption capacity of the anion exchanger for the aromatic sulfonic acid. Moreover, estimations of the isosteric enthalpy, free energy,and entropy change of adsorption were also reported. The positive isosteric enthalpy and entropy change for adsorption indicate an endothermic and entropy driven process in the present study.

  20. Charge transfer from the n-hexadecane radical cation to cycloalkanes, alkenes and aromatics

    International Nuclear Information System (INIS)

    Charge transfer from n-hexadecane radical cations C16H34+ to solutes as cycloalkanes, alkenes and aromatics was studied by pulse radiolysis. Using ion-pair kinetics the rate constants ksub(s) of the electron transfer reactions C16H34+ + S ->sup(ks) S+ + C16H34 were determined. The electron transfer rate constants ksub(s) increase from low values for slightly exothermic reactions to a limiting value of 9 . 109 dm3 mol-1 s-1 when the electron transfer reaction is more exothermic than -0.4 eV. (orig.)

  1. A study on scavenging effects of Chinese medicine on superoxide anion radicals by pulse radiolysis

    Science.gov (United States)

    Fengmei, Li; Andong, Liu; Hongchun, Gu; Shaojie, Di

    1993-10-01

    A study on scavenging and dismutation effects on superoxide anion radical (·O -2) by using two Chinese antiaging medicine-Salvia Miltiorrhiza injection (S.M.) and Sulekang capsule (S.C.) were performed by pulse radiolysis. The absorption spectra of ·O -2 have been redetermined in radiolysis of aqueous solution of sodium format. The absorption maximum is at about 250nm. The results suggested that S.M. and S.C. can dismutate and scavenge ·O -2. The experimental scavenging rate of S.M. (150μg/ml) and S.C. (250μg/ml) were 89.6% and 69.5% respectively.

  2. A study on scavenging effects of Chinese medicine on superoxide anion radicals by pulse radiolysis

    Energy Technology Data Exchange (ETDEWEB)

    Li Fengmei; Liu Andong; Gu Hongchun; Di Shaojie (Beijing Normal Univ., BJ (China). Inst. of Low Energy Nuclear Physics)

    A study on scavenging and dismutation effects on superoxide anion radical ([center dot]O[sub 2][sup -]) using two Chinese antiaging medicines - Salvia miltiorrhiza injection (S.M.) and Sulekang capsule (S.C.) was carried out using pulse radiolysis. The absorption spectra of [center dot] OH[sub 2][sup -] was redetermined by radiolysis of an aqueous solution of sodium format. The absorption maximum is at about 250 nm. The results suggested that S.M. and S.C. can dismutate and scavenge [center dot]O[sub 2][sup -]. The experimental scavenging rates of S.M. (150[mu]g/ml) and S.C. (250[mu]g/ml) were 89.6% and 69.5% respectively. (author).

  3. A study on scavenging effects of Chinese medicine on superoxide anion radicals by pulse radiolysis

    International Nuclear Information System (INIS)

    A study on scavenging and dismutation effects on superoxide anion radical (·O2-) using two Chinese antiaging medicines - Salvia miltiorrhiza injection (S.M.) and Sulekang capsule (S.C.) was carried out using pulse radiolysis. The absorption spectra of · OH2- was redetermined by radiolysis of an aqueous solution of sodium format. The absorption maximum is at about 250 nm. The results suggested that S.M. and S.C. can dismutate and scavenge ·O2-. The experimental scavenging rates of S.M. (150μg/ml) and S.C. (250μg/ml) were 89.6% and 69.5% respectively. (author)

  4. Electron transfer reactions of singlet and triplet pyrene in micelles with various radical anions in aqueous solution

    International Nuclear Information System (INIS)

    The radicals CO-2, CH2O-, CH3CHO-, and CH3COCH-3 were pulse radiolytically produced in aqueous solutions of pH 13 containing 5.5 x 10-5 to 1 x 10-3 M pyrene in cationic micelles. The pyrene reacted in either its singlet ground state or its lowest triplet state, the latter being produced by UV pre-irradiation before formation of the radicals. The electron transfer reactions were monitored by measuring either the optical absorption of the pyrene anion at 495 nm or that of triplet pyrene at 414 nm. The triplet state of pyrene was found to be reduced by these radicals, the rate becoming larger with increasing redox potential of the system aldehyde (or ketone)/radical anion, although the reduction power of these radicals increases in the reverse order. These results are explained in terms of elctron tunneling through the electrical double layer separating the lipoidic part of the micelle where the pyrene molecule resides and the aqueous phase where the hydrophilic radical anions exist. The rate of tunneling is dependent on the relative positions of occupied and unoccupied electronic redox levels of the redox systems involved in the two phases. (orig./HK)

  5. Pulse radiolysis study of salt effects on reactions of aromatic radical cations with Cl-

    International Nuclear Information System (INIS)

    Pulse radiolysis of all-trans diphenyl-substituted polyenes, such as 1,4-diphenylbuta-1,3-diene, 1,6-diphenylhexa-1,3,5-triene and 1,8-diphenyl-octa-1,3,5,7-tetraene, in 1,2-dichloroethane solution has been undertaken in the absence and presence of Bu4NPF6. The absorption maxima of the diphenylpolyene radical cations are shifted to shorter wavelengths in the presence of the salt. This is evidence for the formation of the contact ion pairs between the radical cations and PF6-. The decays of the radical cations, which are due to neutralization reactions with Cl-, are retarded by the addition of the salt. The rate constants for the neutralization reactions have been determined for the free-ion and ion-paired states. The pulse radiolysis results are compared with those for other aromatic compounds such as triphenylethylene, tetraphenylethylene and perylene. The appreciable spectral shift is characteristic of the diphenylpolyene radical cations. (author)

  6. Anion-π Catalysis of Enolate Chemistry: Rigidified Leonard Turns as a General Motif to Run Reactions on Aromatic Surfaces.

    Science.gov (United States)

    Cotelle, Yoann; Benz, Sebastian; Avestro, Alyssa-Jennifer; Ward, Thomas R; Sakai, Naomi; Matile, Stefan

    2016-03-18

    To integrate anion-π, cation-π, and ion pair-π interactions in catalysis, the fundamental challenge is to run reactions reliably on aromatic surfaces. Addressing a specific question concerning enolate addition to nitroolefins, this study elaborates on Leonard turns to tackle this problem in a general manner. Increasingly refined turns are constructed to position malonate half thioesters as close as possible on π-acidic surfaces. The resulting preorganization of reactive intermediates is shown to support the disfavored addition to enolate acceptors to an absolutely unexpected extent. This decisive impact on anion-π catalysis increases with the rigidity of the turns. The new, rigidified Leonard turns are most effective with weak anion-π interactions, whereas stronger interactions do not require such ideal substrate positioning to operate well. The stunning simplicity of the motif and its surprisingly strong relevance for function should render the introduced approach generally useful. PMID:26916316

  7. A study of quasi reversible nitro radical anion from -nitrostyrene at wax-impregnated carbon paste electrode

    Indian Academy of Sciences (India)

    Ronald J Mascarenhas; Irishi N Namboothiri; B S Sherigara; Vijayakumar K Reddy

    2006-05-01

    A comprehensive study of the electrochemical reduction of -nitrostyrene and the corresponding heterocyclic analogue has been carried out in aprotic media using wax-impregnated carbon paste electrodes. Nitrostyrene exhibits quasi-reversible reduction process in aprotic medium at the waximpregnated carbon paste electrodes as compared to other electrodes reported in the literature. The nitroradical anion couple detected in the presence of tetrabutyl ammonium perchlorate is found to be stable only in aprotic media. Though, as reported, the pharmacological activity related to this nitro radical anion and its therapeutic value are related to the stability of the nitro radical anion, the stability itself depends on the electrode system employed. Added benzoic acid is found to bring about a positive shift in cathodic peak potential.

  8. Ferrous Ion Chelating, Superoxide Anion Radical Scavenging and Tyrosinase Inhibitory Properties of Pure and Commercial Essential Oils of Anetrhum Graveolens

    Directory of Open Access Journals (Sweden)

    Sh Darvish Alipour Astaneh

    2013-04-01

    Full Text Available Introduction: Despite slight toxicities of essential oils, they are not under strict control in many countries. Anethum graveolens is widely consumed and its essential oils are at public reach. This study was designed to study essential oils of Anethum graveolens. Methods: The biological properties of pure and commercial essential oils of Anethum graveolens were investigated. In fact, Ferrous ion chelating activity, superoxide anion radical scavenging property, tyrosinase inhibition and total flavonoids of the oils were determined. Results: Chelating activity of 7.8 µg of EDTA was equivalent to 2 µg of the pure oil. The oils had superoxide anion radical scavenging activities which may be related to their total phenol and flavonoid contents. IC50 of ferrous ion chelating, antityrosiase and superoxide anion radical scavenging activities of pure and commercial oils were 1.3, 1.4, 1 and (171.6, 589, 132 µg respectively. Antityrosiase activity of 6.4 µg pure oil was equal to 1000 µg of the commercial oil. Conclusion: Anethum possesses antioxidative and free radical scavenging properties. This oil chelates ferrous ions and superoxide radicals. It is effective in formation of reactive toxic products. Anethum has good potentials regarding its applications in food and drug industries.

  9. ESR spectra of anion-radicals of (π-cyclopentadienyl)(nitrosyl)dicarbonyls of chromium and molybdenum and of (σ-methyl)(π-cyclopentadienyl)tricarbonylmolybdenum photolysis products

    International Nuclear Information System (INIS)

    ESR spectra of anion-radicals of Mo (π-cyclopentadienyl) (nitrosyl) dicarbonyl and of molybdenum (σ-methyl) (π-cyclopentadienyl) tricarbonyl photolysis products are studied. Anion-radicals have the structure of aminyl radicals with localization of unpaired electron on nitrogen atom. Photolysis of cyclopentadienyl methyltricarbonyl molybdenum and its derivatives containing trivalent phosphorus compounds as ligands results in paramagnetic compounds due to oxidation processes

  10. Study on the Retention Behavior of Aromatic Carboxylic and Sulfonic acid on a New Anion Exchange Column

    Institute of Scientific and Technical Information of China (English)

    SHI,Ya-Li; CAI,Ya-Qi; MOU,Shi-Fen

    2008-01-01

    Ion chromatography (IC) has gradually developed into a preferred method for the determination of inorganic anions. And in recent years some low molecular aliphatic acid can be also separated in the ion exchange column with the development of stationary phase. But for the determination of aromatic ionic compounds there are some problems. The aromatic anions show enhanced retention due to interaction with the π electrons of the aromatic backbone. Although the addition of an organic modifier can alleviate the difficulty, it is not the ultimate solution.IonPac AS20 column was developed using a unique polymer bonding technology and its substrate coating is aliphatic backbone. The polymer is completely free of any π electron-containing substituents in the AS20 column. In this paper, the retention behavior of aromatic carboxylic and sulfonic acid on two hydroxide-selective columns,IonPac AS11-HC, AS16, and the new column AS20 was also studied. The result showed that the retentions of ten compounds on three columns were different with each other because of their different column characteristics.Among them 4-chlorobenzene sulfonic acid, 3,5-dihydric benzoic acid and salicylic acid obviously exhibited the weakest retention on the IonPac AS20. It was showed that π-π bond function between anion and stationary phases was weakened in AS20 column because its polymer was completely free of any π electron-containing substituents.So in this paper the AS20 was selected as an analytical column to separate ten aromatic ionic compounds, fumaric acid with conjugate bond included. The retention behavior, separation of the ten compounds and effect of temperature on their retention in the anion-exchange column AS20 (2 mm) were studied. The result showed that those compounds could be separated with each other when running in gradient program and the organic modifier was unnecessary during the separation. So it is showed that AS20 column can be used as a separating column because its

  11. Aqueous oxidation of sulfonamide antibiotics: aromatic nucleophilic substitution of an aniline radical cation.

    Science.gov (United States)

    Tentscher, Peter R; Eustis, Soren N; McNeill, Kristopher; Arey, J Samuel

    2013-08-19

    Sulfonamide antibiotics are an important class of organic micropollutants in the aquatic environment. For several, sulfur dioxide extrusion products have been previously reported upon photochemical or dark oxidation. Using quantum chemical modeling calculations and transient absorption spectroscopy, it is shown that single-electron oxidation from sulfadiazine produces the corresponding aniline radical cation. Density functional theory calculations indicate that this intermediate can exist in four protonation states. One species exhibits a low barrier for an intramolecular nucleophilic attack at the para position of the oxidized aniline ring, in which a pyrimidine nitrogen acts as a nucleophile. This attack can lead to a rearranged structure, which exhibits the same connectivity as the SO2 -extruded oxidation product that was previously observed in the aquatic environment and characterized by NMR spectroscopy. We report a detailed reaction mechanism for this intramolecular aromatic nucleophilic substitution, and we discuss the possibility of this reaction pathway for other sulfonamide drugs. PMID:23828254

  12. Electrocatalytic analysis of superoxide anion radical using nitrogen-doped graphene supported Prussian Blue as a biomimetic superoxide dismutase

    International Nuclear Information System (INIS)

    Graphical abstract: Prussian Blue (PB) cubes supported on nitrogen-doped graphene sheets (NGS) were synthesized using a simple and scalable method, and the utilization of the PB-NGS hybrid as an efficient superoxide dismutase mimic in the electrochemical sensing of O2·− was demonstrated. - Highlights: • Facile and scalable synthesis of Prussian Blue cubes supported on nitrogen-doped graphene; • Nitrogen-doped graphene supported Prussian Blue as an efficient biomimetic superoxide dismutase for the electrocatalytic sensing of superoxide anion; • Good sensitivity, excellent selectivity and attractive long-term stability for superoxide anion sensing. - Abstract: Considering the double-sided roles of superoxide anion radical, monitoring of its track in living systems is attracting increasing academic and practical interest. Here we synthesized Prussian Blue (PB) cubes that were supported on nitrogen-doped graphene sheets (NGS) using a facile and scalable method, and explored their potential utilization in the electrochemical sensing of superoxide anion. As an efficient superoxide dismutase mimic, direct electron transfer of the prepared PB-NGS hybrid immobilized on a screen-printed gold electrode was harvested in physiological media. With the bifunctional activities, the synthetic mimic could catalyze the dismutation of superoxide anion via the redox cycle of active iron. By capturing the electro-reduction amperometric responses of superoxide anion radical to hydrogen peroxide in the cathodic polarization, highly sensitive determination (a sensitivity of as high as 0.32 μA cm−2 μM−1) of the target was achieved, with no interference from common coexisting species including ascorbic acid, dopamine, and uric acid observed. Compared to natural superoxide dismutases, the artificial enzyme mimic exhibited favorable activity stability, indicating its promising applications in the in vivo long-term monitoring of superoxide anion

  13. Structure dependence of the rate coefficients of hydroxyl radical+aromatic molecule reaction

    International Nuclear Information System (INIS)

    The rate coefficients of hydroxyl radical addition to the rings of simple aromatic molecules (kOH) were evaluated based on the literature data. By analyzing the methods of kOH determination and the data obtained the most probable values were selected for the kOH's of individual compounds and thereby the most reliable dataset was created for monosubstituted aromatics and p-substituted phenols. For these compounds the rate coefficients fall in a narrow range between 2×109 mol−1 dm3 s−1 and 1×1010 mol−1 dm3 s−1. Although the values show some regular trend with the electron donating/withdrawing nature of the substituent, the log kOH−σp Hammett substituent constant plots do not give straight lines because these high kOH's are controlled by both, the chemical reactivity and the diffusion. However, the logarithms of the rate coefficients of the chemical reactivity controlled reactions (kchem), are calculated by the equation 1/kOH=1/kchem+1/kdiff, and accepting for the diffusion controlled rate coefficient kdiff=1.1×1010 mol−1 dm3 s−1, show good linear correlation with σp. - Highlights: ► OH·+aromatic molecule rate coefficients are in the range 2×109–1×1010 mol−1 dm3 s−1. ► The logarithms of rate coefficients as a function of Hammett constants do not give straight lines. ► Logarithms rate coefficients of chemically activated reaction linearly depend on Hammett constants. ► Liquid phase chemically activated reaction rate coefficients and gas phase values are correlated

  14. Photoinduced oxidation of sea salt halides by aromatic ketones: a source of halogenated radicals

    Directory of Open Access Journals (Sweden)

    A. Jammoul

    2009-07-01

    Full Text Available The interactions between triplet state benzophenone and halide anion species (Cl, Br and I have been studied by laser flash photolysis (at 355 nm in aqueous solutions at room temperature. The decay of the triplet state of benzophenone was followed at 525 nm. Triplet lifetime measurements gave rate constants, kq (M−1 s, close to diffusion controlled limit for iodide (~8×109 M−1 s, somewhat less for bromide (~3×108 M−1 s and much lower for chloride (<106 M−1 s. The halide (X quenches the triplet state; the resulting product has a transient absorption at 355 nm and a lifetime much longer than that of the benzophenone triplet state, is formed. This transient absorption feature matches those of the corresponding radical anion (X2. We therefore suggest that such reactive quenching is a photosensitized source of halogen in the atmosphere or the driving force for the chemical oxidation of the oceanic surface micro layer.

  15. Evidence for the involvement of loosely bound plastosemiquinones in superoxide anion radical production in photosystem II.

    Directory of Open Access Journals (Sweden)

    Deepak Kumar Yadav

    Full Text Available Recent evidence has indicated the presence of novel plastoquinone-binding sites, QC and QD, in photosystem II (PSII. Here, we investigated the potential involvement of loosely bound plastosemiquinones in superoxide anion radical (O2- formation in spinach PSII membranes using electron paramagnetic resonance (EPR spin-trapping spectroscopy. Illumination of PSII membranes in the presence of the spin trap EMPO (5-(ethoxycarbonyl-5-methyl-1-pyrroline N-oxide resulted in the formation of O2-, which was monitored by the appearance of EMPO-OOH adduct EPR signal. Addition of exogenous short-chain plastoquinone to PSII membranes markedly enhanced the EMPO-OOH adduct EPR signal. Both in the unsupplemented and plastoquinone-supplemented PSII membranes, the EMPO-OOH adduct EPR signal was suppressed by 50% when the urea-type herbicide DCMU (3-(3,4-dichlorophenyl-1,1-dimethylurea was bound at the QB site. However, the EMPO-OOH adduct EPR signal was enhanced by binding of the phenolic-type herbicide dinoseb (2,4-dinitro-6-sec-butylphenol at the QD site. Both in the unsupplemented and plastoquinone-supplemented PSII membranes, DCMU and dinoseb inhibited photoreduction of the high-potential form of cytochrome b559 (cyt b559. Based on these results, we propose that O2- is formed via the reduction of molecular oxygen by plastosemiquinones formed through one-electron reduction of plastoquinone at the QB site and one-electron oxidation of plastoquinol by cyt b559 at the QC site. On the contrary, the involvement of a plastosemiquinone formed via the one-electron oxidation of plastoquinol by cyt b559 at the QD site seems to be ambiguous. In spite of the fact that the existence of QC and QD sites is not generally accepted yet, the present study provided more spectroscopic data on the potential functional role of these new plastoquinone-binding sites.

  16. A Molecular Precursor to Phosphaethyne and Its Application in Synthesis of the Aromatic 1,2,3,4-Phosphatriazolate Anion.

    Science.gov (United States)

    Transue, Wesley J; Velian, Alexandra; Nava, Matthew; Martin-Drumel, Marie-Aline; Womack, Caroline C; Jiang, Jun; Hou, Gao-Lei; Wang, Xue-Bin; McCarthy, Michael C; Field, Robert W; Cummins, Christopher C

    2016-06-01

    Dibenzo-7-phosphanorbornadiene Ph3PC(H)PA (1, A = C14H10, anthracene) is reported here as a molecular precursor to phosphaethyne (HC≡P), produced together with anthracene and triphenylphosphine. HCP generated by thermolysis of 1 has been observed by molecular beam mass spectrometry, laser-induced fluorescence, microwave spectroscopy, and nuclear magnetic resonance (NMR) spectroscopy. In toluene, fragmentation of 1 has been found to proceed with activation parameters of ΔH(⧧) = 25.5 kcal/mol and ΔS(⧧) = -2.43 eu and is accompanied by formation of an orange insoluble precipitate. Results from computational studies of the mechanism of HCP generation are in good agreement with experimental data. This high-temperature method of HCP generation has pointed to new reaction chemistry with azide anion to produce the 1,2,3,4-phosphatriazolate anion, HCPN3(-), for which structural data have been obtained in a single-crystal X-ray diffraction study. Negative-ion photoelectron spectroscopy has shown the adiabatic detachment energy for this anion to be 3.555(10) eV. The aromaticity of HCPN3(-) has been assessed using nucleus-independent chemical shift, quantum theory of atoms in molecules, and natural bond orbital methods. PMID:27171847

  17. Concerted effects in the reaction of ·OH radicals with aromatics: radiolytic oxidation of salicylic acid

    International Nuclear Information System (INIS)

    Liquid chromatographic and capillary electrophoretic studies have been used to resolve the products produced in the radiolytic oxidation of salicylic acid in aqueous solution. These studies have shown that, as in the case of phenol, ·OH radicals preferentially add to the positions ortho and para to the OH substituent. However, in contrast to its reaction with phenol, addition at the ortho position is favored over addition at the para position. Because ·OH radical is a strong electrophile this difference suggests that the electron population at the ortho position in the salicylate anion is enhanced as a result of the hydrogen bonding in salicylic acid

  18. Al4(2-); the anion-π interactions and aromaticity in the presence of counter ions.

    Science.gov (United States)

    Foroutan-Nejad, Cina

    2012-07-21

    The influence of presence of counter ions and π-complexation with benzene on the bonding and magnetic properties of Al(4)(2-), the most studied all-metal cluster, is studied here. It is shown that complexation by either counter ions or benzene decreases the delocalization index between Al atoms and the magnitude of bond magnetizability, that is a Quantum Theory of Atoms in Molecules, QTAIM, -based magnetic index of aromaticity. Benzene forms two types of π-complexes with the Al(4) framework; CH-π (T-shaped) complexes and parallel π-π stacking (PPS) complexes. It is shown that variation in the π-charge of the Al(4) framework affects the relative stability of the T-shaped/PPS complexes. Free Al(4)(2-) forms a stable T-shaped anion-π complex with benzene but in the presence of cations, formation of PPS complexes is more favourable, energetically. It is suggested that this property could be used for designing molecular switches and tuneable anion sensors. PMID:22684037

  19. Aqueous-Phase Reactions of Isoprene with Sulfoxy Radical Anions as a way of Wet Aerosol Formation in the Atmosphere

    Science.gov (United States)

    Kuznietsova, I.; Rudzinski, K. J.; Szmigielski, R.; Laboratory of the Environmental Chemistry

    2011-12-01

    Atmospheric aerosols exhibit an important role in the environment. They have implications on human health and life, and - in the larger scale - on climate, the Earth's radiative balance and the cloud's formation. Organic matter makes up a significant fraction of atmospheric aerosols (~35% to ~90%) and may originate from direct emissions (primary organic aerosol, POA) or result from complex physico-chemical processes of volatile organic compounds (secondary organic aerosol, SOA). Isoprene (2-methyl-buta-1,3-diene) is one of the relevant volatile precursor of ambient SOA in the atmosphere. It is the most abundant non-methane hydrocarbon emitted to the atmosphere as a result of living vegetation. According to the recent data, the isoprene emission rate is estimated to be at the level of 500 TgC per year. While heterogeneous transformations of isoprene have been well documented, aqueous-phase reactions of this hydrocarbon with radical species that lead to the production of new class of wet SOA components such as polyols and their sulfate esters (organosulfates), are still poorly recognized. The chain reactions of isoprene with sulfoxy radical-anions (SRA) are one of the recently researched route leading to the formation of organosulfates in the aqueous phase. The letter radical species originate from the auto-oxidation of sulfur dioxide in the aqueous phase and are behind the phenomenon of atmospheric acid rain formation. This is a complicated chain reaction that is catalyzed by transition metal ions, such as manganese(II), iron(III) and propagated by sulfoxy radical anions . The presented work addresses the chemical interaction of isoprene with sulfoxy radical-anions in the water solution in the presence of nitrite ions and nitrous acid, which are important trace components of the atmosphere. We showed that nitrite ions and nitrous acid significantly altered the kinetics of the auto-oxidation of SO2 in the presence of isoprene at different solution acidity from 2 to 8

  20. DNA-strand breaks induced by dimethylarsinic acid, a metabolite of inorganic arsenics, are strongly enhanced by superoxide anion radicals.

    Science.gov (United States)

    Rin, K; Kawaguchi, K; Yamanaka, K; Tezuka, M; Oku, N; Okada, S

    1995-01-01

    We previously reported that dimethylarsinic acid (DMAA), a major metabolite of inorganic arsenics, induced DNA single-strand breaks (ssb) both in vivo and in cultured alveolar type II (L-132) cells in vitro, possibly via the production of dimethylarsenic peroxyl radicals. Here, the interaction of superoxide anion radicals (O2-) in the induction of ssb in L-132 cells was investigated using paraquat, an O2(-)-producing agent. A significant enhancement of ssb formation was observed in the DMAA-exposed cells when coexposed to paraquat. This enhancement occurred even when post-exposed to DMAA after washing, suggesting that the DMAA exposure caused some modification of DNA such as DNA-adducts, which was recognized by active oxygens to form ssb. An experiment with UV-irradiation, which was likely to induce ssb at the modified region, supported the possibility of DNA modification by DMAA exposure. An ESR study indicated that O2- produced by paraquat in DMAA-exposed cells was more consumed than in non-exposed cells, assumingly through the reaction with the dimethylarsenic-modified region of DNA. The species of active oxygens were estimated by using diethyldithiocarbamate, aminotriazole, diethylmaleate, hydrogen peroxide (H2O2), gamma-irradiation and ethanol. O2- but neither H2O2 nor hydroxyl radicals was very likely to contribute to the ssb-enhancing action of paraquat. PMID:7735248

  1. Role of Kekul\\'e and Non-Kekul\\'e Structures in the Radical Character of Alternant Polycyclic Aromatic Hydrocarbons: A TAO-DFT Study

    CERN Document Server

    Yeh, Chia-Nan

    2016-01-01

    We investigate the role of Kekul\\'e and non-Kekul\\'e structures in the radical character of alternant polycyclic aromatic hydrocarbons (PAHs) using thermally-assisted-occupation density functional theory (TAO-DFT), an efficient electronic structure method for the study of large ground-state systems with strong static correlation effects. Our results reveal that the studies of Kekul\\'e and non-Kekul\\'e structures qualitatively describe the radical character of alternant PAHs, which could be useful when electronic structure calculations are infeasible due to the expensive computational cost. In addition, our results support previous findings on the increase in radical character with increasing system size. For alternant PAHs with the same number of aromatic rings, the geometrical arrangements of aromatic rings are responsible for their radical character.

  2. Polyimido sulphur anions S(NR)$^{m-}_{n}$: Free radicals and coordination behaviour

    Indian Academy of Sciences (India)

    Dietmar Stalke

    2000-06-01

    In a reaction sequence of amide addition followed by halogen oxidation the triazasulphite S(NR)$^{2-}_{3}$ and the tetrazasulphate S(NR)$^{2-}_{4}$ are readily accessible from sulphur diimide S(NR)2 via sulphur triimide S(NR)3. Addition of lithium organics to sulphur triimide provides a general route to triazasulphonates RS(NR)$^{2-}_{3}$. All these anions resemble potential tripodal coordination behaviour because of their nitrogen donor centres. Furthermore, the sulphur polyimido ligands are capable of responding to the various requirements of different metals (even in mixed metal species) by charge (de)localization. This paper deals with the synthetic routes of the sulphur nitrogen anions and their coordination behaviour. Their reactivity, mainly towards main group metal synthons, is also discussed.

  3. Proton transfer from 1,4-pentadiene to superoxide radical anion: a QTAIM analysis

    Directory of Open Access Journals (Sweden)

    Angela Rodríguez-Serrano

    2014-04-01

    Full Text Available We studied the bis-allylic proton transferreaction from 1,4-pentadiene to superoxideradical anion (O2·־. Minima andtransition state geometries, as well asthermochemical parameters were computedat the B3LYP/6-311+G(3df,2plevel of theory. The electronic wavefunctions of reactants, intermediates,and products were analyzed within theframework of the Quantum Theory ofAtoms in Molecules. The results showthe formation of strongly hydrogen bondedcomplexes between the 1,4-pentadien-3-yl anion and the hydroperoxylradical as the reaction products. Theseproduct complexes (PCs are more stablethan the isolated reactants and muchmore stable than the isolated products.This reaction occurs via pre-reactivecomplexes which are more stable thanthe PCs and the transition states. This isin agreement with the fact that the netproton transfer reaction that leads to freeproducts is an endothermic and nonspontaneousprocess.

  4. Impendance Study of Hypoxic Cells Radiosensitizer Etanidazole Radical Anion in Water

    Czech Academy of Sciences Publication Activity Database

    Gál, Miroslav; Híveš, J.; Sokolová, Romana; Hromadová, Magdaléna; Kolivoška, Viliam; Pospíšil, Lubomír

    2009-01-01

    Roč. 74, 11-12 (2009), s. 1571-1581. ISSN 0010-0765 R&D Projects: GA ČR GP203/09/P502; GA ČR GA203/09/0705; GA MŠk LC510; GA MŠk OC 140 Institutional research plan: CEZ:AV0Z40400503 Keywords : electrochemistry * electrochemical characteristics * aromatic nitro-compounds Subject RIV: CG - Electrochemistry Impact factor: 0.856, year: 2009

  5. Generation of superoxide anion radicals and platelet glutathione peroxidase activity in patients with schizophrenia

    OpenAIRE

    Dietrich-Muszalska A; Kwiatkowska A.

    2014-01-01

    Anna Dietrich-Muszalska, Anna KwiatkowskaDepartment of Biological Psychiatry of the Chair of Experimental and Clinical Physiology, Medical University of Lodz, Lodz, PolandAbstract: Blood platelets are considered to be a peripheral marker in schizophrenia and other psychiatric disorders. Oxidative stress in schizophrenia may be responsible for changes in platelet metabolism and function; therefore, the aim of this study was to examine and compare the generation of superoxide anions and activit...

  6. Non-enzymatic superoxide anion radical sensor based on Pt nanoparticles covalently bonded to thiolated MWCNTs

    International Nuclear Information System (INIS)

    Highlights: ► Synthesis of MWCNTs–Pt nanoparticles and characterization by TEM and X-ray photoelectron spectroscopy. ► Fabrication of modified electrode PDDA/MWCNTs–Pt for electrochemical determination of O2·− without enzyme. ► The modified electrode exhibited high conductivity, biocompatibility and stability. ► This modified electrode provided higher sensitivity, wide linear range, low detection limit, good reproducibility. ► This proposed electrode displayed better electrocatalytic activity than other modified electrodes toward superoxide. - Abstract: In this study, we developed a superoxide anion biosensor based on Pt nanoparticles covalently bonded to the multi-walled carbon nanotubes (MWCNTs–Pt) and poly-diallyldimethylammonium chloride (PDDA) on a glassy carbon electrode (GCE) without enzyme. The MWCNTs–Pt film was characterized with transmission electron microscopy and X-ray photoelectron spectroscopy. The mechanism of the reduction of superoxide anion at PDDA/MWCNTs–Pt/GCE was determined to be an irreversible diffusion-controlled electrode process. The electrocatalytic properties of the MWCNTs–Pt catalyst for superoxide anion reduction were investigated by cyclic voltammetry and chronoamperometry. Good sensitivity, wide linear range, low detection limit, good reproducibility and excellent storage stability were obtained by using the amperometric response. In the study results, the proposed electrode displayed better electrocatalytic activity than the previously reported electrodes toward the dismutation of superoxide.

  7. METRONIDAZOLE RADICAL ANION FORMATION STUDIED BY MEANS OF ELECTROCHEMICAL IMPEDANCE SPECTROSCOPY

    Czech Academy of Sciences Publication Activity Database

    Gál, Miroslav; Sokolová, Romana; Kolivoška, Viliam; Morovská Turoňová, A.; Ambrová, M.; Híveš, J.

    2011-01-01

    Roč. 76, č. 12 (2011), s. 1607-1617. ISSN 0010-0765 R&D Projects: GA ČR GP203/09/P502; GA MŠk LC510 Institutional research plan: CEZ:AV0Z40400503 Keywords : radicals * radiopharmaceuticals * electron transfer Subject RIV: CG - Electrochemistry Impact factor: 1.283, year: 2011

  8. Umbrella motion of the methyl cation, radical, and anion molecules. I. Potentials, energy levels and partition functions

    Science.gov (United States)

    Ragni, Mirco; Bitencourt, Ana Carla P.; Prudente, Frederico V.; Barreto, Patricia R. P.; Posati, Tamara

    2016-03-01

    A study of the umbrella motion of the methyl cation, radical, and anion molecules is presented. This is the floppiest mode of vibration of all three species and its characterization is of fundamental importance for understanding their reactivity. Minimum Energy Paths of the umbrella motions according to the hyperspherical treatment were obtained, by single point calculations, at the CCSD(T)/aug-cc-pVQT level of theory in the Born-Oppenheimer approximation. These energy profiles permit us to calculate the vibrational levels through the Hyperquantization algorithm, which is shown appropriated for the description of the umbrella motion of these three molecules. The adiabatic electron affinity and ionization potentials were estimated to good accuracy. Partition functions are also calculated in order to obtain information on the reaction rates involving these groups.

  9. Identification of essential amino-acid residues in Azotobacter vinelandii isocitrate dehydrogenase by radical anions and H atoms

    International Nuclear Information System (INIS)

    Pure TPN+-specific isocitrate dehydrogenase from Azotobacter vinelandii was irradiated with H atoms generated in a γ-irradiated solution at pH 6.5. A G(-activity) = 0.12 +- 0.01 was found. At the same time no corresponding loss in free sulfhydryls was observed. These results confirmed the essentiality of methionine for the enzymatic activity as known from previous studies. Irradiation with the radical anions, (CNS)2- and Br2- generated in γ-irradiated solutions at pH 6.5, strongly inactivated isocitrate dehydrogenase with yields of G(-activity) of 2.1 and 3.9, respectively. Part of the inactivating effect, however, is due to oxidation of sulfhydryl groups. These results lead to the conclusion that tryptophan is an essential amino-acid residue to isocitrate dehydrogenase from A. vinelandii. The presence of tryptophan in the enzyme was demonstrated by pulse radiolysis

  10. A 1,2,3-dithiazolyl-o-naphthoquinone: a neutral radical with isolable cation and anion oxidation states.

    Science.gov (United States)

    Smithson, Chad S; MacDonald, Daniel J; Matt Letvenuk, T; Carello, Christian E; Jennings, Michael; Lough, Alan J; Britten, James; Decken, Andreas; Preuss, Kathryn E

    2016-06-21

    Under aprotic conditions, the reaction of 4-amino-1,2-naphthoquinone with excess S2Cl2 generates 4,5-dioxo-naphtho[1,2-d][1,2,3]dithiazol-2-ium chloride in a typical Herz condensation. By contrast, prior literature reports an imine (NH) product, 4,5-dioxo-1H-naphtho[1,2-d][1,2,3]dithiazole, for the same reaction performed in acetic acid. Herein, the cation product is isolated with four different counter-anions (Cl(-), GaCl4(-), FeCl4(-) and OTf(-)). Reduction of the cation generates a neutral radical 1,2,3-dithiazolyl-o-naphthoquinone, with potential ligand properties. Further reduction generates a closed shell anion, isolated as a water-stable Li(+) complex and exhibiting O,O-bidentate chelation. The hydroxy (OH) isomer of the original imine (NH) product is reported, and this can be readily deprotonated and acylated (OAc). All species are structurally characterized. Solution redox behaviour and EPR are discussed where appropriate. PMID:27216412

  11. The role of neutral and radical anionic organozinc complexes in the alkylation reactions of 1,4-diaza-1,3-butadienes with diorganozinc compounds

    OpenAIRE

    van Koten, G; Rijnberg, E.; Boersma, J.; Jastrzebski, J.T.B.H.; Lakin, M.T.; Spek, A.L.

    1997-01-01

    We have earlier postulated the intermediacy of organozinc radical species in the regioselective alkylation reactions of 1,4-di-tert-butyl-1,4-diaza-1,3-butadiene (t-BuNCHCHN-t-Bu) with diorganozinc compounds (ZnR2). To verify these postulates, we have prepared and studied the neutral organozinc radical complex MeO(CH2)3Zn(t-BuNCHCHN-t-Bu) (A) and two diorganozinc radical-anionic complexes, K[R2Zn(t-BuNCHCHN-t-Bu)] (R = Me (8a), Et (8b)). A was prepared in situ by the reaction of t-BuNCHCHN-t-...

  12. Formation of stable anion-radical of C,C'-dipyridyl-carborane in the reaction of lithium and sodium alumohydrides, lithium isopropylate and lithium n-butylmercaptide with 1,2-diphenyl-o-carborane in tetrahydrofurane solution

    International Nuclear Information System (INIS)

    On the interaction of lithium and sodium alumohydrides, lithium isopropylate and n-butylmercaptide with 1,2-diphenyl-o-carborane in a tetrahydrofuran solution, a transfer of one electron to the carborane polyhedron occurs to form a stable anion-radical of C,C'-diphenylcarborane. This is a reversible reaction, and under the action of oxidizers the anion-radical of C,C'-diphenylcarborane transforms into the starting 1,2-diphenyl-0-carborane. On treatment with water the anion-radical decomposes affording the anion of 7,8-diphenyl-7,8-dicarboundecaborate

  13. Sonochemiluminescence of lucigenin: Evidence of superoxide radical anion formation by ultrasonic irradiation

    Science.gov (United States)

    Matsuoka, Masanori; Takahashi, Fumiki; Asakura, Yoshiyuki; Jin, Jiye

    2016-07-01

    The sonochemiluminescence (SCL) behavior of lucigenin (Luc2+) has been studied in aqueous solutions irradiated with 500 kHz ultrasound. Compared with the SCL of a luminol system, a tremendously increased SCL intensity is observed from 50 µM Luc2+ aqueous solution (pH =11) when small amounts of coreactants such as 2-propanol coexist. It is shown that SCL intensity strongly depends on the presence of dissolved gases such as air, O2, N2, and Ar. The highest SCL intensity is obtained in an O2-saturated solution, indicating that molecular oxygen is required to generate SCL. Since SCL intensity is quenched completely in the presence of superoxide dismutase (SOD), an enzyme that can catalyze the disproportionation of O2 •‑, the generation of O2 •‑ in the ultrasonic reaction field is important in the SCL of Luc2+. In this work, the evidence of O2 •‑ production is examined by a spectrofluorometric method using 2-(2-pyridyl)benzothiazoline as the fluorescent probe. The results indicate that the yield of O2 •‑ is markedly increased in the O2-saturated solutions when a small amount of 2-propanol coexists, which is consistent with the results of SCL measurements. 2-Propanol in the interfacial region of a cavitation bubble reacts with a hydroxyl radical (•OH) to form a 2-propanol radical, CH3C•(OH)CH3, which can subsequently react with dissolved oxygen to generate O2 •‑. The most likely pathways for SCL as well as the spatial distribution of SCL in a microreactor are discussed in this study.

  14. EPR characterization of ascorbyl and sulfur dioxide anion radicals trapped during the reaction of bovine Cytochrome c Oxidase with molecular oxygen

    Science.gov (United States)

    Yu, Michelle A.; Egawa, Tsuyoshi; Yeh, Syun-Ru; Rousseau, Denis L.; Gerfen, Gary J.

    2010-04-01

    The reaction intermediates of reduced bovine Cytochrome c Oxidase (C cO) were trapped following its reaction with oxygen at 50 μs-6 ms by innovative freeze-quenching methods and studied by EPR. When the enzyme was reduced with either ascorbate or dithionite, distinct radicals were generated; X-band (9 GHz) and D-band (130 GHz) CW-EPR measurements support the assignments of these radicals to ascorbyl and sulfur dioxide anion radical ( SO2-rad ), respectively. The X-band spectra show a linewidth of 12 G for the ascorbyl radical and 11 G for the SO2-rad radical and an isotropic g-value of 2.005 for both species. The D-band spectra reveal clear distinctions in the g-tensors and powder patterns of the two species. The ascorbyl radical spectrum displays approximate axial symmetry with g-values of g x = 2.0068, g y = 2.0066, and g z = 2.0023. The SO2-rad radical has rhombic symmetry with g-values of g x = 2.0089, g y = 2.0052, and g z = 2.0017. When the contributions from the ascorbyl and SO2-rad radicals were removed, no protein-based radical on C cO could be identified in the EPR spectra.

  15. Directing effects of phenyl substitution in the reaction of OH radical with aromatics: The radiolytic hydroxylation of biphenyl

    International Nuclear Information System (INIS)

    The initial yields for formation of 2-, 3- and 4- hydroxybiphenyl following the radiolytic oxidation of biphenyl in the presence of ferricyanide are, respectively, 2.19, 1.13 and 1.55 molecules/100eV. These yields reflect relative rates of 0.71:0.37:1 for sm-bulletOH radical attack on each of the ortho, meta, and para positions of biphenyl. Comparison of the corresponding partial rate constants to that for benzene shows that phenyl substitution has a significant effect in directing sm-bulletOH addition to the ortho and para positions of aromatic systems. Comparison with phenol shows that a phenyl substitution has only a slightly smaller effect than does OH in increasing the partial rate constant at the ortho and para positions but is substantially less effective in decreasing the rate of sm-bulletOH reaction at the meta position. 15 refs., 9 figs

  16. Aromatic hydroxylation. 8. A radiation chemical study of the oxidation of hydroxycyclohexadienyl radicals

    International Nuclear Information System (INIS)

    Substituted hydroxycyclohexadienyl radicals have been generated by pulse radiolysis of N2O-saturated aqueous solutions of monosubstituted benzene derivatives. Their rates of disproportionation/dimerization and of oxidation by Fe(CN)63- and by IrCl62- have been measured by optical and conductimetric methods. For the fluoro- and chlorohydroxycyclohexadienyl radicals disproportionation is shown to involve hydrogen atom abstraction rather than electron transfer. However, the Fe(CN)63- oxidation of the substituted hydroxycyclohexadienyl radicals occurs by a rate-determining electron transfer followed by a fast proton loss rather than by hydrogen atom abstraction or synchronous removal of an electron and a proton. A plot of the log of the rate constants for oxidation against Hammett σ+ constants gives a good linear relationship with a rho value of -3.0 +/- 0.1. With the more powerful oxidant IrCl6-, the electron-transfer oxidation of all but the least reactive hydroxycyclohexadienyl radicals is diffusion controlled

  17. Aromatic hydroxylation. 8. A radiation chemical study of the oxidation of hydroxycyclohexadienyl radicals

    Energy Technology Data Exchange (ETDEWEB)

    Buxton, G.V.; Langan, J.R.; Smith, J.R.L.

    1986-11-06

    Substituted hydroxycyclohexadienyl radicals have been generated by pulse radiolysis of N/sub 2/O-saturated aqueous solutions of monosubstituted benzene derivatives. Their rates of disproportionation/dimerization and of oxidation by Fe(CN)/sub 6//sup 3 -/ and by IrCl/sub 6//sup 2 -/ have been measured by optical and conductimetric methods. For the fluoro- and chlorohydroxycyclohexadienyl radicals disproportionation is shown to involve hydrogen atom abstraction rather than electron transfer. However, the Fe(CN)/sub 6//sup 3 -/ oxidation of the substituted hydroxycyclohexadienyl radicals occurs by a rate-determining electron transfer followed by a fast proton loss rather than by hydrogen atom abstraction or synchronous removal of an electron and a proton. A plot of the log of the rate constants for oxidation against Hammett sigma/sup +/ constants gives a good linear relationship with a rho value of -3.0 +/- 0.1. With the more powerful oxidant IrCl/sub 6//sup -/, the electron-transfer oxidation of all but the least reactive hydroxycyclohexadienyl radicals is diffusion controlled.

  18. Acyl Radicals from Aromatic Carboxylic Acids by Means of Visible-Light Photoredox Catalysis

    OpenAIRE

    Bergonzini, Giulia; Cassani, Carlo; Wallentin, Carl-Johan

    2015-01-01

    Simple and abundant carboxylic acids have been used as acyl radical precursor by means of visible-light photoredox catalysis. By the transient generation of a reactive anhydride intermediate, this redox-neutral approach offers a mild and rapid entry to high-value heterocyclic compounds without the need of UV irradiation, high temperature, high CO pressure, tin reagents, or peroxides.

  19. The activity of 3- and 7-hydroxyflavones as scavengers of superoxide radical anion generated from photo-excited riboflavin

    International Nuclear Information System (INIS)

    The visible-light irradiation of the system Riboflavin plus 3-hydroxyflavone or plus 7-hydroxyflavone, under aerobic conditions, produces a series of competitive processes that depend on the relative concentrations of the pigment and the flavones. The picture comprises photochemical mechanisms that potentially operate in nature. They mainly include the quenching of Rf singlet (1Rf*) and triplet (3Rf*) excited states (with bimolecular rate constants in the order of 109 M-1 s-1) and superoxide radical anion-mediated reactions. The participation of the oxidative species singlet molecular oxygen was not detected. The overall result shows chemical transformations in both Rf and 3-hydroxyflavone. No experimental evidence was found indicating any chemical reaction involving 7-hydroxyflavone. The fate of the pigment also depends on the amount of the dissolved flavonoid. At 50 mM concentrations of these compounds or higher, practically no photochemistry occurs, owing to the extensive quenching of (1Rf*) When the concentration of the flavones is in the mM range or lower, (3Rf*) is photogenerated. Then, the excited triplet species can be quenched mainly by the flavones through an electron-transfer process, yielding the semireduced pigment. The latter interacts with dissolved oxygen producing O2.-, which reacts with both the pigment and 3-hydroxyflavone. In summary, 3-hydroxyflavone and 7-hydroxyflavone participate in the generation of superoxide ion in an Rf-sensitized process, and simultaneously 3-hydroxyflavone constitutes a degradable quencher of the oxidative species. (author)

  20. Induction of strand breaks in polyribonucleotides and DNA by the sulphate radical anion: role of electron loss centres as precursors of strand breakage

    International Nuclear Information System (INIS)

    The interaction of the sulphate radical anion, SO4.-, with the polyribonucleotides, poly U and poly C, in deaerated, aqueous solutions at pH 7.5 results in strand breakage (sb) with efficiencies of 57 and 23%, respectively, determined by time resolved laser light scattering (TRLS). Most sb are produced within 70 μs, the risetime of the detection system. Oxygen inhibits the induction of sb in poly U and poly C by SO4.-through its interaction with a radical precursor to sb. In contrast, the interaction of SO4.- with poly A and single stranded DNA does not lead to significant strand breakage (≤ 5% efficiency). From optical studies, the interaction of poly A and poly G with SO4.- radicals yields predominantly the corresponding one electron oxidized base radicals. (author)

  1. Efficient, "tin-free" radical cyclization to aromatic systems. synthesis of 5,6,8,9,10,11-hexahydroindolo[2,1-a]isoquinolines.

    Science.gov (United States)

    Menes-Arzate, Martha; Martínez, Roberto; Cruz-Almanza, Raymundo; Muchowski, Joseph M; Osornio, Yazmin M; Miranda, Luis D

    2004-05-28

    Efficient radical cyclization of alkyl iodides to various aromatic systems including pyrrole, indole, isoquinolone, pyridone, and benzene, mediated by dicumyl peroxide, is described. The methodology was used to provide access to 5,6,8,9,10,11-hexahydroindolo[2,1-a]isoquinoline derivatives. PMID:15153044

  2. Fluorescence quenching of aromatic hydrocarbons by nitroxide radicals: a mechanismatic study

    Directory of Open Access Journals (Sweden)

    Stephan Landgraf

    1999-01-01

    Full Text Available The fluorescence quenching of phenanthrene (Phen, 9-cyanophenanthrene (CPhen, 9-cyanoanthracene (CA, perylene (Per, 9,10-dicyanoanthracene (DCA, and 9,10-diphenylanthracene (DPA using stable nitroxide radicals as quenchers has been studied by steady state and flash photolysis measurements. Both linearity and deviation from linearity in the Stern-Volmer plots have been observed. The active sphere model was used to discuss the upward curvature of the Stern-Volmer plots in case of Per, DCA, and DPA. The bimolecular quenching rate constant (kq of Phen, CPhen and CA was found to be diffusion controlled while in other cases it is lower than the diffusion limit. On the basis of flash photolysis measurements as well as the overlap between the emission spectra of hydrocarbons and the absorption spectra of radicals, a resonance energy transfer mechanism is taken place in case of Per, DPA, DCA, and CA. For Phen and CPhen where the energy gap between the first excited singlet and the nearest lower triplet state is small, an induced intersystem crossing was suggested. Finally, the quenching process was discussed in terms of the free energy dependence (ΔG of the electron transfer from nitroxide radicals to the excited hydrocarbons.

  3. Free radical inactivation of trypsin

    International Nuclear Information System (INIS)

    Reactivities of free radical oxidants, radical OH, Br2-anion radical and Cl3COO radical and a reductant, CO2-anion radical, with trypsin and reactive protein components were determined by pulse radiolysis of aqueous solutions at pH 7, 200C. Highly reactive free radicals, radical OH, Br2-anion radical and CO2-anion radical, react with trypsin at diffusion controlled rates. Moderately reactive trichloroperoxy radical, k(Cl3COO radical + trypsin) preferentially oxidizes histidine residues. The efficiency of inactivation of trypsin by free radicals is inversely proportional to their reactivity. The yields of inactivation of trypsin by radical OH, Br2-anion radical and CO2-anion radical are low, G(inactivation) = 0.6-0.8, which corresponds to ∼ 10% of the initially produced radicals. In contrast, Cl3COO radical inactivates trypsin with ∼ 50% efficiency, i.e. G(inactivation) = 3.2. (author)

  4. Enhanced generation of hydroxyl radical and sulfur trioxide anion radical from oxidation of sodium sulfite, nickel(II) sulfite, and nickel subsulfide in the presence of nickel(II) complexes.

    OpenAIRE

    Shi, X.; Dalal, N.; Kasprzak, K S

    1994-01-01

    Electron spin resonance (ESR) spin trapping was utilized to investigate the generation of free radicals from oxidation of sodium sulfite, nickel(II) sulfite, and nickel subsulfide (Ni3S2) by ambient oxygen or H2O2 at pH 7.4. The spin trap used was 5,5-dimethyl-1-pyrroline-N-oxide (DMPO). Under ambient oxygen, a solution of sodium sulfite alone generated predominantly sulfur trioxide anion radical (.SO3-) due to the autoxidation of sulfite. Addition of nickel(II) chloride [Ni(II)] enhanced the...

  5. Reactivity of atomic oxygen radical anions bound to titania and zirconia nanoparticles in the gas phase: low-temperature oxidation of carbon monoxide.

    Science.gov (United States)

    Ma, Jia-Bi; Xu, Bo; Meng, Jing-Heng; Wu, Xiao-Nan; Ding, Xun-Lei; Li, Xiao-Na; He, Sheng-Gui

    2013-02-27

    Titanium and zirconium oxide cluster anions with dimensions up to nanosize are prepared by laser ablation and reacted with carbon monoxide in a fast low reactor. The cluster reactions are characterized by time-of-flight mass spectrometry and density functional theory calculations. The oxygen atom transfers from (TiO(2))(n)O(-) (n = 3-25) to CO and formations of (TiO(2))(n)(-) are observed, whereas the reactions of (ZrO(2))(n)O(-) (n = 3-25) with CO generate the CO addition products (ZrO(2))(n)OCO(-), which lose CO(2) upon the collisions (studied for n = 3-9) with a crossed helium beam. The computational study indicates that the (MO(2))(n)O(-) (M = Ti, Zr; n = 3-8) clusters are atomic radical anion (O(-)) bonded systems, and the energetics for CO oxidation by the O(-) radicals to form CO(2) is strongly dependent on the metals as well as the cluster size for the titanium system. Atomic oxygen radical anions are important reactive intermediates, while it is difficult to capture and characterize them for condensed phase systems. The reactivity pattern of the O(-)-bonded (TiO(2))(n)O(-) and (ZrO(2))(n)O(-) correlates very well with different behaviors of titania and zirconia supports in the low-temperature catalytic CO oxidation. PMID:23368886

  6. DNA damage by the sulfate radical anion: hydrogen abstraction from the sugar moiety versus one-electron oxidation of guanine.

    Science.gov (United States)

    Roginskaya, Marina; Mohseni, Reza; Ampadu-Boateng, Derrick; Razskazovskiy, Yuriy

    2016-07-01

    The products of oxidative damage to double-stranded (ds) DNA initiated by photolytically generated sulfate radical anions SO4(•-) were analyzed using reverse-phase (RP) high-performance liquid chromatography (HPLC). Relative efficiencies of two major pathways were compared: production of 8-oxoguanine (8oxoG) and hydrogen abstraction from the DNA 2-deoxyribose moiety (dR) at C1,' C4,' and C5' positions. The formation of 8oxoG was found to account for 87% of all quantified lesions at low illumination doses. The concentration of 8oxoG quickly reaches a steady state at about one 8oxoG per 100 base pairs due to further oxidation of its products. It was found that another guanine oxidation product identified as 2-amino-5-(2'-alkylamino)-4H-imidazol-4-one (X) was released in significant quantities from its tentative precursor 2-amino-5-[(2'-deoxy-β-d-erythro-pentofuranosyl)amino]-4H-imidazol-4-one (dIz) upon treatment with primary amines in neutral solutions. The linear dose dependence of X release points to the formation of dIz directly from guanine and not through oxidation of 8oxoG. The damage to dR was found to account for about 13% of the total damage, with majority of lesions (33%) originating from the C4' oxidation. The contribution of C1' oxidation also turned out to be significant (17% of all dR damages) despite of the steric problems associated with the abstraction of the C1'-hydrogen. However, no evidence of base-to-sugar free valence transfer as a possible alternative to direct hydrogen abstraction at C1' was found. PMID:27043476

  7. Radicals

    Czech Academy of Sciences Publication Activity Database

    Jahn, Ullrich; Cornils, B.

    Weinheim: Wiley-VCH, 2013 - (Cornils, B.; Herrmann, W.; Wong, C.; Zanthoff, H.), s. 1897-1898 ISBN 978-3-527-33307-3 Institutional support: RVO:61388963 Keywords : radicals * enzymatic catalysis * coenzyme B12 * ribonucleotide reductase * mutases Subject RIV: CC - Organic Chemistry

  8. The reactions of hydroxyl radicals with aromatic rings in lignins, studied with creosol and 4-methylveratrol

    International Nuclear Information System (INIS)

    Creosol and its methyl ether (4-methylveratrol), two simple model compounds representing phenolic and non-phenolic nuclei in lignins, were reacted in aqueous solution ai ambient temperature and pressure with hydroxyl radicals generated by gamma-radiolysis. The reactions were conducted at different pH levels (2-12) and in the presence and absence of oxygen. After fractionation of the reaction mixtures, more than 40 products from each model compound were identified by HPLC-UV. GC-MS and/or NMR analyses. In some cases the data were compared with those of corresponding authentic samples. On the basis of the composition of the reaction mixtures. the most important reaction modes were identified as oxidative coupling, demethoxylation, hydroxylation and oxidation of the methyl group. Surprisingly, only small yields of ring opening products were found, even when the reactions were run in the presence of oxygen. The mechanisms of the observed types of reaction are discussed and the influence of pH and of oxygen on the product pattern and on the rate of substrate consumption is tentatively interpreted. (author)

  9. Superoxide anion radical (O2(-)) degrades methylmercury to inorganic mercury in human astrocytoma cell line (CCF-STTG1).

    Science.gov (United States)

    Mailloux, Ryan J; Yumvihoze, Emmanuel; Chan, Hing Man

    2015-09-01

    Methylmercury (MeHg) is a global pollutant that is affecting the health of millions of people worldwide. However, the mechanism of MeHg toxicity still remains somewhat elusive and there is no treatment. It has been known for some time that MeHg can be progressively converted to inorganic mercury (iHg) in various tissues including the brain. Recent work has suggested that cleavage of the carbon-metal bond in MeHg in a biological environment is facilitated by reactive oxygen species (ROS). However, the oxyradical species that actually mediates this process has not been identified. Here, we provide evidence that superoxide anion radical (O2(-)) can convert MeHg to iHg. The calculated second-order rate constant for the degradation of 1μM MeHg by O2(-) generated by xanthine/xanthine oxidase was calculated to be 2×10(5)M(-1)s(-1). We were also able to show that this bioconversion can proceed in intact CCF-STTG1 human astrocytoma cells exposed to paraquat (PQ), a O2(-) generating viologen. Notably, exposure of cells to increasing amounts of PQ led to a dose dependent increase in both MeHg and iHg. Indeed, a 24h exposure to 500μM PQ induced a ∼13-fold and ∼18-fold increase in intracellular MeHg and iHg respectively. These effects were inhibited by superoxide dismutase mimetic MnTBAP. In addition, we also observed that a 24h exposure to a biologically relevant concentration of MeHg (1μM) did not induce cell death, oxidative stress, or even changes in cellular O2(-) and H2O2. However, co-exposure to PQ enhanced MeHg toxicity which was associated with a robust increase in cell death and oxidative stress. Collectively our results show that O2(-) can bioconvert MeHg to iHg in vitro and in intact cells exposed to conditions that simulate high intracellular O2(-) production. In addition, we show for the first time that O2(-) mediated degradation of MeHg to iHg enhances the toxicity of MeHg by facilitating an accumulation of both MeHg and iHg in the intracellular

  10. Fluorinated Dodecaphenylporphyrins: Synthetic and Electrochemical Studies Including the First Evidence of Intramolecular Electron Transfer Between an Fe(II) Porphyrin -Anion Radical and an Fe(I) Porphyrin

    Energy Technology Data Exchange (ETDEWEB)

    D' Souza, F.; Forsyth, T.P.; Fukuzumi, S.; Kadish, K.M.; Krattinger, B.; Lin, M.; Medforth, C.J.; Nakanishi, I.; Nurco, D.J.; Shelnutt, J.A.; Smith, K.M.; Van Caemelbecke, E.

    1998-10-19

    Dodecaphenylporphyrins with varying degrees of fluorination of the peripheral phenyl rings (FXDPPS) were synthesized as model compounds for studying electronic effects in nonplan~ porphyrins, and detailed electrochemical studies of the chloroiron(HI) complexes of these compounds were undertaken. The series of porphyrins, represented as FeDPPCl and as FeFXDPPCl where x = 4, 8 (two isomers), 12, 20,28 or 36, could be reversibly oxidized by two electrons in dichloromethane to give n-cation radicals and n-dications. All of the compounds investigated could also be reduced by three electrons in benzonitrile or pyridine. In benzonitrile, three reversible reductions were observed for the unfluorinated compound FeDPPC1, whereas the FeFXDPPCl complexes generally exhibited irreversible first and second reductions which were coupled to chemical reactions. The chemical reaction associated with the first reduction involved a loss of the chloride ion after generation of Fe FXDPPC1. The second chemical reaction involved a novel intramolecular electron transfer between the initially generated Fe(H) porphyrin n-anion radical and the final Fe(I) porphyrin reduction product. In pyridine, three reversible one electron reductions were observed with the second reduction affording stable Fe(II) porphyrin o - anion radicals for ail of the complexes investigated.

  11. Preparation of high-capacity, weak anion-exchange membranes by surface-initiated atom transfer radical polymerization of poly(glycidyl methacrylate) and subsequent derivatization with diethylamine

    Science.gov (United States)

    Qian, Xiaolei; Fan, Hua; Wang, Chaozhan; Wei, Yinmao

    2013-04-01

    Ion-exchange membrane is of importance for the development of membrane chromatography. In this work, a high-capacity anion-exchange membrane was prepared by grafting of glycidyl methacrylate (GMA) onto the surface of regenerated cellulose (RC) membranes via surface-initiated atom transfer radical polymerization (SI-ATRP) and subsequent derivatization with diethylamine. Attenuated total reflectance Fourier-transform infrared (ATR-FTIR), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) were used to characterize changes in the chemical functionality, surface topography and pore morphology of the modified membranes. The static capacity of the prepared anion-exchange membrane was evaluated with bovine serum albumin (BSA) as a model protein. The results indicated that the anion-exchange membrane which could reach a maximum capacity of 96 mg/mL for static adsorption possesses a higher adsorption capacity, and the adsorption capacity increases with the polymerization time. The effect of pH and salt concentration confirmed that the adsorption of BSA followed ion-exchange mechanism. The established method would have potential application in the preparation of anion-exchange membrane.

  12. Double-layer effects and distance dependence of electron transfer in reduction of nitro aromatic radical anions

    Czech Academy of Sciences Publication Activity Database

    Mořkovská, Petra; Hromadová, Magdaléna; Pospíšil, Lubomír; Giannarelli, S.

    2006-01-01

    Roč. 22, č. 4 (2006), s. 1896-1902. ISSN 0743-7463 R&D Projects: GA ČR GA203/03/0821; GA AV ČR IAA400400505; GA MŠk LC510 Institutional research plan: CEZ:AV0Z40400503 Keywords : mercury-acetonitrile interface * aprotic-solvents * transfer kinetics Subject RIV: CG - Electrochemistry Impact factor: 3.902, year: 2006

  13. Reduction of aromatic nitro radical anion in acetonitrile. Dougle-layer effect on the second electron transfer

    Czech Academy of Sciences Publication Activity Database

    Mořkovská, Petra; Hromadová, Magdaléna; Pospíšil, Lubomír; Giannarelli, S.

    2006. Roč. 601, - (2006), s. 996. ISSN 1091-8213. [ECS Meeting Denver Colorado /209./. 07.05.06-11.05.06, Denver] R&D Projects: GA AV ČR IAA400400505; GA MŠk LC510 Grant ostatní: MURST(XE) COFIN2000 Institutional research plan: CEZ:AV0Z40400503 Keywords : electrochemistry * acetonitrile * double-layer structure Subject RIV: CG - Electrochemistry

  14. Orientational preference of long, multicenter bonds in radical anion dimers: a case study of π-[TCNB]2 (2-) and π-[TCNP]2 (2.).

    Science.gov (United States)

    Capdevila-Cortada, Marçal; Miller, Joel S; Novoa, Juan J

    2015-04-20

    The similar shape and electronic structure of the radical anions of 1,2,4,5-tetracyanopyrazine (TCNP) and 1,2,4,5-tetracyanobenzene (TCNB) suggest a similar relative orientation for their long, multicenter carbon-carbon bond in π-[TCNP]2 (2-) and in π-[TCNB]2 (2-) , in good accord with the Maximin Principle predictions. Instead, the two known structures of π-[TCNP]2 (2-) have a D2h (θ=0°) and a C2 (θ=30°) orientation (θ being the dihedral angle that determines the rotation of one radical anion relative to the other along the axis that passes through center of the two six-membered rings). The only known π-[TCNB]2 (2-) structure has a C2 (θ=60°) orientation. The origin of these preferences was investigated for both dimers by computing (at the RASPT2/RASSCF(30,28) level) the variation with θ of the interaction energy (Eint ) and the variation of the Eint components. It was found that: 1) a long, multicenter bond exists for all orientations; 2) the Eint (θ) angular dependence is similar in both dimers; 3) for all orientations the electrostatic component dominates the value of Eint (θ), although the dispersion and bonding components also play a relevant role; and 4) the Maximin Principle curve reproduces well the shape of the Eint (θ) curve for isolated dimers, although none of them reproduce the experimental preferences. Only after the (radical anion)(.-) ⋅⋅⋅cation(+) interactions are also included in the model aggregate are the experimental data reproduced computationally. PMID:25727499

  15. Ion distribution in quaternary-ammonium-functionalized aromatic polymers: effects on the ionic clustering and conductivity of anion-exchange membranes.

    Science.gov (United States)

    Weiber, E Annika; Jannasch, Patric

    2014-09-01

    A series of copoly(arylene ether sulfone)s that have precisely two, three, or four quaternary ammonium (QA) groups clustered directly on single phenylene rings along the backbone are studied as anion-exchange membranes. The copolymers are synthesized by condensation polymerizations that involve either di-, tri-, or tetramethylhydroquinone followed by virtually complete benzylic bromination using N-bromosuccinimide and quaternization with trimethylamine. This synthetic strategy allows excellent control and systematic variation of the local density and distribution of QA groups along the backbone. Small-angle X-ray scattering of these copolymers shows extensive ionic clustering, promoted by an increasing density of QA on the single phenylene rings. At an ion-exchange capacity (IEC) of 2.1 meq g(-1), the water uptake decreases with the increasing local density of QA groups. Moreover, at moderate IECs at 20 °C, the Br(-) conductivity of the densely functionalized copolymers is higher than a corresponding randomly functionalized polymer, despite the significantly higher water uptake of the latter. Thus, the location of multiple cations on single aromatic rings in the polymers facilitates the formation of a distinct percolating hydrophilic phase domain with a high ionic concentration to promote efficient anion transport, despite probable limitations by reduced ion dissociation. These findings imply a viable strategy to improve the performance of alkaline membrane fuel cells. PMID:25044778

  16. Spectroscopic Properties of Novel Aromatic Metal Clusters: NaM4 (M=Al, Ga, In) and their Cations and Anions

    Energy Technology Data Exchange (ETDEWEB)

    Balasubramanian, K; Zhao, C

    2004-03-17

    The ground and several excited states of metal aromatic clusters, namely NaM4 and NaM{sub 4}{sup {+-}} (M=Al, Ga, In) clusters have been investigated by employing complete activespace self-consistent-field (CASSCF) followed by Multi-reference singles and doubles configuration interaction (MRSDCI) computations that included up to 10 million configurations and other methods. The ground states NaM{sub 4}{sup -} of aromatic anions are found to be symmetric C{sub 4v} ({sup 1}A{sub 1}) electronic states with ideal square pyramid geometries. While the ground state of NaIn4 is also predicted to be a symmetric C{sub 4v} ({sup 2}A{sub 1}) square pyramid, the ground state of the NaAl4 cluster is found to have a C{sub 2v} ({sup 2}A{sub 1}) pyramid with a rhombus base and the ground state of NaGa{sub 4} possesses a C{sub 2v} ({sup 2}A{sub 1}) pyramid with a rectangle base. In general these structures exhibit 2 competing geometries, viz., an ideal C{sub 4v} structure and a distorted rhomboidal or rectangular pyramid structure (C{sub 2v}). All of the ground states of the NaM{sub 4}{sup +} (M= Al, Ga, In) cations are computed to be C{sub 2v} ({sup 3}A{sub 2}) pyramids with rhombus bases. The equilibrium geometries, vibrational frequencies, dissociation energies, adiabatic ionization potentials, adiabatic electron affinities for the electronic states of NaM{sub 4} (M=Al, Ga, In) and their ions are computed and compared with experimental results and other theoretical calculations. On the basis of our computed excited states energy separations, we have tentatively suggested assignments to the observed X and A states in the anion photoelectron spectra of Al{sub 4}Na{sup -} reported by Li et al. The X state can be assigned to a C{sub 2v} ({sup 2}A{sub 1}) rhomboidal pyramid. The A state observed in the anion spectrum is assigned to the first excited state ({sup 2}B{sub 1}) of the neutral NaAl{sub 4} with the C{sub 4v} symmetry. The assignments of the excited states are consistent with

  17. 'Chemical repair' in irradiated DNA solutions containing thiols and/or disulphides. Further evidence for disulphide radical anions acting as electron donors

    International Nuclear Information System (INIS)

    The ring-closed disulphide radical anion D/SS.-, formed radiolytically either by hydrogen abstraction from dithiothreitol (D(SH)2), or by one-electron reduction of the corresponding cyclic dithiane (DS2), is proposed to engage efficiently in 'chemical repair' of .OH-induced DNA intermediates (DNA.) under gamma-irradiation of aqueous DNA solutions, DNA. + D/SS.- → DNA + DS2. Evidence for this derives from observations that radioprotection of DNA by DS2 or D(SH)2 is enhanced in anoxic N2O-saturated solution by addition of formate, at a constant total .OH scavenger capacity: carbon dioxide radical anions (CO2.-) actually promote generation of D/SS.-, by interacting both with DS2 and D(SH)2. Oxygen enhancement of radiation-induced DNA damage in systems containing DS2 and/or D(SH)2 can be explained by the concept. Further support of the mechanism proposed is shown by the protection efficiency under anoxia, and concomitantly oxygen enhancement, increase with dose rate and with salt concentration, when DNA is irradiated in presence of DS2. (author)

  18. Interaction of 1,2,5-chalcogenadiazole derivatives with thiophenolate: hypercoordination with formation of interchalcogen bond versus reduction to radical anion.

    Science.gov (United States)

    Suturina, Elizaveta A; Semenov, Nikolay A; Lonchakov, Anton V; Bagryanskaya, Irina Yu; Gatilov, Yuri V; Irtegova, Irina G; Vasilieva, Nadezhda V; Lork, Enno; Mews, Rüdiger; Gritsan, Nina P; Zibarev, Andrey V

    2011-05-12

    According to the DFT calculations, [1,2,5]thiadiazolo[3,4-c][1,2,5]thiadiazole (4), [1,2,5]selenadiazolo[3,4-c][1,2,5]thiadiazole (5), 3,4-dicyano-1,2,5-thiadiazole (6), and 3,4-dicyano-1,2,5-selenadiazole (7) have nearly the same positive electron affinity (EA). Under the CV conditions they readily produce long-lived π-delocalized radical anions (π-RAs) characterized by EPR. Whereas 4 and 5 were chemically reduced into the π-RAs with thiophenolate (PhS(-)), 6 did not react and 7 formed a product of hypercoordination at the Se center (9) isolated in the form of the thermally stable salt [K(18-crown-6)][9] (10). The latter type of reactivity has never been observed previously for any 1,2,5-chalcogenadiazole derivatives. The X-ray structure of salt 10 revealed that the Se-S distance in the anion 9 (2.722 Å) is ca. 0.5 Å longer than the sum of the covalent radii of these atoms but ca. 1 Å shorter than the sum of their van der Waals radii. According to the QTAIM and NBO analysis, the Se-S bond in 9 can be considered a donor-acceptor bond whose formation leads to transfer of ca. 40% of negative charge from PhS(-) onto the heterocycle. For various PhS(-)/1,2,5-chalcogenadiazole reaction systems, thermodynamics and kinetics were theoretically studied to rationalize the interchalcogen hypercoordination vs reduction to π-RA dichotomy. It is predicted that interaction between PhS(-) and 3,4-dicyano-1,2,5-telluradiazole (12), whose EA slightly exceeds that of 6 and 7, will lead to hypercoordinate anion (17) with the interchalcogen Te-S bond being stronger than the Se-S bond observed in anion 9. PMID:21500829

  19. Competitive Deprotonation and Superoxide [O2 (-•)] Radical-Anion Adduct Formation Reactions of Carboxamides under Negative-Ion Atmospheric-Pressure Helium-Plasma Ionization (HePI) Conditions.

    Science.gov (United States)

    Hassan, Isra; Pinto, Spencer; Weisbecker, Carl; Attygalle, Athula B

    2016-03-01

    Carboxamides bearing an N-H functionality are known to undergo deprotonation under negative-ion-generating mass spectrometric conditions. Herein, we report that N-H bearing carboxamides with acidities lower than that of the hydroperoxyl radical (HO-O(•)) preferentially form superoxide radical-anion (O2 (-•)) adducts, rather than deprotonate, when they are exposed to the glow discharge of a helium-plasma ionization source. For example, the spectra of N-alkylacetamides show peaks for superoxide radical-anion (O2 (-•)) adducts. Conversely, more acidic amides, such as N-alkyltrifluoroacetamides, preferentially undergo deprotonation under similar experimental conditions. Upon collisional activation, the O2 (-•) adducts of N-alkylacetamides either lose the neutral amide or the hydroperoxyl radical (HO-O(•)) to generate the superoxide radical-anion (m/z 32) or the deprotonated amide [m/z (M - H)(-)], respectively. For somewhat acidic carboxamides, the association between the two entities is weak. Thus, upon mildest collisional activation, the adduct dissociates to eject the superoxide anion. Superoxide-adduct formation results are useful for structure determination purposes because carboxamides devoid of a N-H functionality undergo neither deprotonation nor adduct formation under HePI conditions. Graphical Abstract ᅟ. PMID:26545766

  20. Competitive Deprotonation and Superoxide [O2 -•] Radical-Anion Adduct Formation Reactions of Carboxamides under Negative-Ion Atmospheric-Pressure Helium-Plasma Ionization (HePI) Conditions

    Science.gov (United States)

    Hassan, Isra; Pinto, Spencer; Weisbecker, Carl; Attygalle, Athula B.

    2016-03-01

    Carboxamides bearing an N-H functionality are known to undergo deprotonation under negative-ion-generating mass spectrometric conditions. Herein, we report that N-H bearing carboxamides with acidities lower than that of the hydroperoxyl radical (HO-O•) preferentially form superoxide radical-anion (O2 -•) adducts, rather than deprotonate, when they are exposed to the glow discharge of a helium-plasma ionization source. For example, the spectra of N-alkylacetamides show peaks for superoxide radical-anion (O2 -•) adducts. Conversely, more acidic amides, such as N-alkyltrifluoroacetamides, preferentially undergo deprotonation under similar experimental conditions. Upon collisional activation, the O2 -• adducts of N-alkylacetamides either lose the neutral amide or the hydroperoxyl radical (HO-O•) to generate the superoxide radical-anion ( m/z 32) or the deprotonated amide [ m/z (M - H)-], respectively. For somewhat acidic carboxamides, the association between the two entities is weak. Thus, upon mildest collisional activation, the adduct dissociates to eject the superoxide anion. Superoxide-adduct formation results are useful for structure determination purposes because carboxamides devoid of a N-H functionality undergo neither deprotonation nor adduct formation under HePI conditions.

  1. Time-dependent density functional study on the electronic excitation energies of polycyclic aromatic hydrocarbon radical cations of naphthalene, anthracene, pyrene, and perylene

    International Nuclear Information System (INIS)

    Time-dependent density functional theory (TDDFT) and its modification, the Tamm - Dancoff approximation to TDDFT, are employed to calculate the electronic excitation energies and oscillator strengths for a series of polycyclic aromatic hydrocarbon radical cations. For the radical cations of naphthalene and anthracene, TDDFT using the Becke - Lee - Yang - Parr functional and the 6-31G** basis set provides the excitation energies that are roughly within 0.3 eV of the experimental data. The assignments of the electron transitions proposed by TDDFT accord with the previous assignments made by accurate ab initio calculations, except that TDDFT indicates the existence of a few additional transitions of π*left-arrow σ character among the several low-lying transitions. The calculated energies for these π*left-arrow σ transitions are found to be consistent with the onset of a σ electron ionization manifold in the photoelectron spectra. For the pyrene radical cation, TDDFT supports the previous assignments made by semiempirical calculations, whereas for the perylene radical cation, TDDFT suggests the energy ordering of the three lowest-lying excited states be changed from those of the semiempirical results. copyright 1999 American Institute of Physics

  2. Prion-derived copper-binding peptide fragments catalyze the generation of superoxide anion in the presence of aromatic monoamines

    Directory of Open Access Journals (Sweden)

    Tomonori Kawano

    2007-01-01

    Full Text Available Objectives: Studies have proposed two opposing roles for copper-bound forms of prion protein (PrP as an anti-oxidant supporting the neuronal functions and as a pro-oxidant leading to neurodegenerative process involving the generation of reactive oxygen species. The aim of this study is to test the hypothesis in which putative copper-binding peptides derived from PrP function as possible catalysts for monoamine-dependent conversion of hydrogen peroxide to superoxide in vitro. Materials and methods: Four peptides corresponding to the copper (II-binding motifs in PrP were synthesized and used for analysis of peptide-catalyzed generation of superoxide in the presence of Cu (II and other factors naturally present in the neuronal tissues. Results: Among the Cu-binding peptides tested, the amino acid sequence corresponding to the Cu-binding site in the helical region was shown to be the most active for superoxide generation in the presence of Cu(II, hydrogen peroxide and aromatic monoamines, known precursors or intermediates of neurotransmitters. Among monoamines tested, three compounds namely phenylethylamine, tyramine and benzylamine were shown to be good substrates for superoxide-generating reactions by the Cu-bound helical peptide. Conclusions: Possible roles for these reactions in development of prion disease were suggested.

  3. Aggregation behavior of 1-dodecyl-3-methylimidazolium bromide in aqueous solution: effect of ionic liquids with aromatic anions.

    Science.gov (United States)

    Gu, Yingqiu; Shi, Lijuan; Cheng, Xiyuan; Lu, Fei; Zheng, Liqiang

    2013-05-28

    The effects of ionic liquids (ILs), 1-butyl-3-methylimidazolium methylsulfonate (bmimMsa), 1-butyl-3-methylimidazolium benzenesulfonate (bmimBsa), and 1-butyl-3-methylimidazolium 2-naphthalenesulfonate (bmimNsa), on the aggregation behavior of 1-dodecyl-3-methylimidazolium bromide (C12mimBr) in aqueous solution were investigated by surface tension, dynamic light scattering measurements, and (1)H NMR spectroscopy. The ability to promote the surfactant aggregation is in the order bmimNsa > bmimBsa > bmimMsa. Nevertheless, only bmimNsa distinctly reduces both the CMC value and the surface tension at CMC. Due to the penetration of C10H7SO3(-)anions into the surfactant aggregate, bmimNsa is found to induce a phase transition from micelles to vesicles, whereas the other ILs only slightly increase the sizes of micelles. The combined effect of intermolecular interactions, such as hydrophobic effect, electrostatic attractions, and π-π stacking interactions, is supposed to be responsible for this structural transformation, in which π-π stacking plays an important role. PMID:23642150

  4. Application of dissolvable layered double hydroxides as sorbent in dispersive solid-phase extraction and extraction by co-precipitation for the determination of aromatic acid anions.

    Science.gov (United States)

    Tang, Sheng; Lee, Hian Kee

    2013-08-01

    Three types of magnesium-aluminum layered double hydroxides were synthesized and employed as solid-phase extraction (SPE) sorbents to extract several aromatic acids (protocatechuic acid, mandelic acid, phthalic acid, benzoic acid, and salicylic acid) from aqueous samples. An interesting feature of these sorbents is that they dissolve when the pH of the solution is lower than 4. Thus, the analyte elution step, as needed in conventional sorbent-based extraction, was obviated by dissolving the sorbent in acid after extraction and separation from the sample solution. The extract was then directly injected into a high-performance liquid chromatography-ultraviolet detection system for analysis. In the key adsorption process, both dispersive SPE and co-precipitation extraction with the sorbents were conducted and experimental parameters such as pH, temperature, and extraction time were optimized. The results showed that both extraction methods provided low limits of detection (0.03-1.47 μg/L) and good linearity (r(2) > 0.9903). The optimized extraction conditions were applied to human urine and sports drink samples. This new and interesting extraction approach was demonstrated to be a fast and efficient procedure for the extraction of organic anions from aqueous samples. PMID:23855757

  5. Evidences of Electron Transfer of a Fullerene Anion Radical (C60(•-)) Prepared under Visible-Light Illumination at a Nitrobenzene/Water Interface.

    Science.gov (United States)

    Watariguchi, Shigeru; Fujimori, Masaaki; Atsumi, Kosuke; Hinoue, Teruo

    2016-01-01

    Fullerene (C60) changes to its anion radical (C60(•-)) in the presence of tetraphenylborate (TPB(-)) under visible-light illumination. Using voltammetry at a liquid/liquid interface, we investigated the electron transfer (ET) between C60(•-), previously prepared based on this photochemical reaction, in a nitrobenzene (NB) solution and hexacyanoferrate(III) ([Fe(CN)6](3-)) or proton in an aqueous solution. We suggest that positive currents appearing in voltammograms are due to the ion transfer of decomposition products of TPB(-) and ET from C60(•-) in the NB phase to [Fe(CN)6](3-), or proton in the W phase. (11)B NMR revealed that TPB(-) decomposed to some borate anions during the photochemical reaction of fullerene. Furthermore, when the NB solution containing C60(•-) was mixed with an aqueous solution containing [Fe(CN)6](3-) or proton, absorption bands of C60(•-) in a visible/near infrared absorption spectrum disappeared. This disappearance supports the ET across the NB/W interface. This finding is significant as both an example of ET at a liquid/liquid interface including photochemical reactions and the photochemistry of C60. PMID:27063721

  6. Free-radical polymerization of some dental and medical materials by pulse radiolysis

    International Nuclear Information System (INIS)

    Complete text of publication follows. The extensive use of N-P-tolylglycine (NPG) analogues in adhesive bonding technologies calls for a better understanding of their role in initiating free-radical polymerization. The fast oxidation and reductions of NTG proceed via the formation of various types of free radicals and radical cation and anion intermediates. These intermediates were identified and their reactivity with oxygen, to produce the corresponding peroxyl radicals, has been measured. Hydroxyl radicals (OH) were used to initiate oxidation reactions of NTG, while the reduction reactions were initiated with hydrated electrons (eaq-). In the presence and absence of oxygen, the oxidation reaction mechanism of NTG by OH proceeded predominately by addition to the aromatic ring followed by OH- elimination reactions to produce NTG+ radical cations. In the presence of oxygen, OH-NTG also reacted with oxygen to produce peroxyl radicals. The reduction reaction of NTG with eaq- proceed via addition to the aromatic ring and amine-elimination, to produce various radicals: addition to the aromatic ring was followed by a fast protonation reaction to produce cyclohexadienyl radicals, and the amine-elimination reaction produced acetic acid free radicals and 4-methylaniline. In addition, it was found that the H-atom reaction with NTG also produced radical cations

  7. Low-temperature pulse radiolysis and γ-irradiated matrix studies of dimer anions of olefin derivatives

    International Nuclear Information System (INIS)

    Intense IR absorptions were found for irradiated methyltetrahydrofuran solutions of various olefin derivatives using low-temperature pulse radiolysis and γ-irradiated matrix techniques. The compounds investigated were fumaronitrile, maleic anhydride, citraconic anhydride, dimethylmaleic anhydride, methyl vinyl ketone, acrolein, crotononitrile, methacrylonitrile, methyl acrylate, methyl methacrylate, and methyl crotonate. The IR absorptions increased gradually with time in pulse radiolysis and also increased by warming solutions via the γ-irradiated matrix method. The growth was always in parallel with the decay of the anion radical of each compound in both experiments. The IR absorptions, therefore, are concluded to be due to dimer anions produced by reactions of anion radicals with neutral parent molecules. Growth rates were determined from the formation curves of dimer anions. In many cases, IR spectra changed in shape by repeated warming and their peaks shifted to shorter wavelengths. These results are attributed to conformational changes of the dimer anions which occur in warmed solutions. Dimer anions were not observed for acrylamide, methacrylamide, 1,3-butadiene, and styrene, although their anion radicals were produced in irradiated solutions. The electron affinity of a functional group seems to be an important factor for dimer anion formation. Aromatic compounds such as phthalonitrile and phthalic anhydride did not form dimer anions under similar conditions

  8. Structural and Mechanistic Analysis through Electronic Spectra: Aqueous Hyponitrite Radical (N2O2-) and Nitrosyl Hyponitrite Anion (N3O3-)

    Energy Technology Data Exchange (ETDEWEB)

    Valiev, Marat; Lymar, Sergei V.

    2011-11-03

    Aqueous hyponitrite radical (N{sub 2}O{sub 2}{sup -}) and nitrosyl hyponitrite anion (N{sub 3}O{sub 3}{sup -}) species are important intermediates in the reductive chemistry of NO. The structures and absorption spectra of various hydrated isomers of these compounds were investigated in this work using high-level quantum mechanical calculations combined with the explicit classical description of the aqueous environment. For N{sub 2}O{sub 2}{sup -}, comparison of the calculated spectra and energetics with the experimental data reveals that: (1) upon the one-electron oxidation of trans-hyponitrite (ON=NO{sub 2}{sup -}), the trans configuration of the resulting ON=NO{sup -} radical is preserved; (2) although cis- and trans-ON=NO{sup -} are energetically nearly equivalent, the barrier for the trans-cis isomerization is prohibitively high due to the partial double character of the NN bond; (3) the UV spectrum of ON=NO{sup -} was misinterpreted in the earlier pulse radiolysis work and its more recent revision has been justified. For the N{sub 3}O{sub 3}{sup -} ion, the symmetric isomer is the dominant observable species, and the asymmetric isomer contributes little to the experimental spectrum. Coherent analysis of the calculated and experimental data suggests a re-interpretation of the N{sub 2}O{sub 2}{sup -} + NO reaction mechanism, according to which the reaction evenly bifurcates to yield both the symmetric and asymmetric isomers of N{sub 3}O{sub 3}{sup -}. While the latter isomer rapidly decomposes to the final NO{sub 2}{sup -} + N{sub 2}O products, the former isomer is stable toward this decomposition but its formation is reversible with the homolysis equilibrium constant Khom = 2.2 - 10{sup -7} M. Collectively, these results demonstrate that advanced theoretical modeling can be of significant benefit in structural and mechanistic analysis of UV spectra.

  9. Transition Metal Complexes and Radical Anion Salts of 1,10-Phenanthroline Derivatives Annulated with a 1,2,5-Tiadiazole and 1,2,5-Tiadiazole 1,1-Dioxide Moiety: Multidimensional Crystal Structures and Various Magnetic Properties

    Directory of Open Access Journals (Sweden)

    Yoshiaki Shuku

    2014-01-01

    Full Text Available Advances in the molecular variety and the elucidation of the physical properties of 1,10-phenanthroline annulated with 1,2,5-thiadiazole and 1,2,5-thiadiazole 1,1-dioxide moieties have been achieved, and are described herein. A 1,2,5-thiadiazole compound, [1,2,5]thiadiazolo[3,4-f][1,10]phenanthroline (tdap, was used as a ligand to create multidimensional network structures based on S•••S and S•••N intermolecular interactions. A 1,2,5-thiadiazole 1,1-dioxide compound, [1,2,5] thiadiazolo[3,4-f][1,10]phenanthroline, 1,1-dioxide (tdapO2, was designed to create a stable radical anion, as well as good network structures. Single crystal X-ray structure analyses revealed that transition metal complexes of tdap, and radical anion salts of tdapO2 formed multidimensional network structures, as expected. Two kinds of tdap iron complexes, namely [Fe(tdap2(NCS2] and [Fe(tdap2(NCS2]•MeCN exhibited spin crossover transitions, and their transition temperatures showed a difference of 150 K, despite their similar molecular structures. Magnetic measurements for the tdapO2 radical anion salts revealed that the magnetic coupling constants between neighboring radical species vary from strongly antiferromagnetic (J = −320 K to ferromagnetic (J = 24 K, reflecting the differences in their π overlap motifs.

  10. Concerted effects in the reaction of ·OH radicals with aromatics. Radiolytic oxidation of salicylic acid

    International Nuclear Information System (INIS)

    Complete text of publication follows. Liquid chromatographic and capillary electrophoretic studies have been used to resolve the products produced in the radiolytic oxidation of salicylic acid in aqueous solution. These studies have shown that, as in the case of phenol, OH radicals preferentially add to the 3- and 5-positions that are, respectively, ortho and para to the OH substituent. However, in contrast to its reaction with phenol, addition at the ortho position is favored over addition to the para position. Because ·OH radical is a strong electrophile this difference suggests that addition of ·OH to the ortho position is enhanced as a result of the hydrogen bonding in salicylic acid. Similarly, addition to the 6-position is discriminated against

  11. Structural and Mechanistic Analysis through Electronic Spectra: Aqueous Hyponitrite Radical (N(2)O(2)(-)) and Nitrosyl Hyponitrite Anion (N(3)O(3)(-))

    Energy Technology Data Exchange (ETDEWEB)

    Lymar S. V.; Valiev M.

    2011-11-03

    Aqueous hyponitrite radical (N{sub 2}O{sub 2}{sup -}) and nitrosyl hyponitrite anion (N{sub 3}O{sub 3}{sup -}) are important intermediates in the reductive chemistry of NO. The structures and absorption spectra of various hydrated isomers of these compounds were investigated in this work using high-level quantum mechanical calculations combined with the explicit classical description of the aqueous environment. For N{sub 2}O{sub 2}{sup -}, comparison of the calculated spectra and energetics with the experimental data reveals that (1) upon the one-electron oxidation of trans-hyponitrite (ON{double_bond}NO{sup 2-}), the trans configuration of the resulting ON{double_bond}NO{sup -} radical is preserved; (2) although cis- and trans-ON{double_bond}NO{sup -} are energetically nearly equivalent, the barrier for the trans-cis isomerization is prohibitively high because of the partial double character of the NN bond; (3) the calculations confirm that the UV spectrum of ONNO{sup -} was misinterpreted in the earlier pulse radiolysis work, and its more recent revision has been justified. For the N{sub 3}O{sub 3}{sup -} ion, the symmetric isomer the dominant observable species, and the asymmetric isomer contributes insignificantly to the experimental spectrum. Coherent analysis of the calculated and experimental data suggests a reinterpretation of the N{sub 2}O{sub 2}{sup -} + NO reaction mechanism according to which the reaction evenly bifurcates to yield both the symmetric and asymmetric isomers of N{sub 3}O{sub 3}{sup -}. While the latter isomer rapidly decomposes to the final NO{sub 2}{sup -} + N{sub 2}O products, the former isomer is stable toward this decomposition, but its formation is reversible with the homolysis equilibrium constant K{sub hom} = 2.2 x 10{sup -7} M. Collectively, these results demonstrate that advanced theoretical modeling can be of significant benefit in structural and mechanistic analysis on the basis of the electronic spectra of aqueous transients.

  12. The negative ion photoelectron spectrum of cyclopropane-1,2,3-trione radical anion, (CO)3(•-)--a joint experimental and computational study.

    Science.gov (United States)

    Chen, Bo; Hrovat, David A; West, Robert; Deng, Shihu H M; Wang, Xue-Bin; Borden, Weston Thatcher

    2014-09-01

    Negative ion photoelectron (NIPE) spectra of the radical anion of cyclopropane-1,2,3-trione, (CO)3(•-), have been obtained at 20 K, using both 355 and 266 nm lasers for electron photodetachment. The spectra show broadened bands, due to the short lifetimes of both the singlet and triplet states of neutral (CO)3 and, to a lesser extent, to the vibrational progressions that accompany the photodetachment process. The smaller intensity of the band with the lower electron binding energy suggests that the singlet is the ground state of (CO)3. From the NIPE spectra, the electron affinity (EA) and the singlet-triplet energy gap of (CO)3 are estimated to be, respectively, EA = 3.1 ± 0.1 eV and ΔEST = -14 ± 3 kcal/mol. High-level, (U)CCSD(T)/aug-cc-pVQZ//(U)CCSD(T)/aug-cc-pVTZ, calculations give EA = 3.04 eV for the (1)A1' ground state of (CO)3 and ΔEST = -13.8 kcal/mol for the energy gap between the (1)A1' and (3)A2 states, in excellent agreement with values from the NIPE spectra. In addition, simulations of the vibrational structures for formation of these states of (CO)3 from the (2)A2″ state of (CO)3(•-) provide a good fit to the shapes of broad bands in the 266 nm NIPE spectrum. The NIPE spectrum of (CO)3(•-) and the analysis of the spectrum by high-quality electronic structure calculations demonstrate that NIPES can not only access and provide information about transition structures but NIPES can also access and provide information about hilltops on potential energy surfaces. PMID:25148567

  13. Aromatic products from reaction of lignin model compounds with UV-alkaline peroxide

    International Nuclear Information System (INIS)

    A series of guaiacyl and syringyl lignin model compounds and their methylated analogues were reacted with alkaline hydrogen peroxide while irradiating with UV light at 254 nm. The aromatic products obtained were investigated by gas chromatography-mass spectrometry (GC-MS). Guaiacol, syringol and veratrol gave no detectable aromatic products. However, syringol methyl ether gave small amounts of aromatic products, resulting from ring substitution and methoxyl displacement by hydroxyl radicals. Reaction of vanillin and syringaldehyde gave the Dakin reaction products, methoxy-1,4-hydroquinones, while reaction of their methyl ethers yielded benzoic acids. Acetoguaiacone, acetosyringone and their methyl ethers afforded several hydroxylated aromatic products, but no aromatic products were identified in the reaction mixtures from guaiacylpropane and syringylpropane. In contrast, veratrylpropane gave a mixture from which 17 aromatic hydroxylated compounds were identified. It is concluded that for phenolic lignin model compounds, particularly those possessing electrondonating aromatic ring substituents, ring-cleavage reactions involving superoxide radical anions are dominant, whereas for non-phenolic lignin models, hydroxylation reactions through attack of hydroxyl radicals prevail

  14. Antioxidant, Anti-5-lipoxygenase and Antiacetylcholinesterase Activities of Essential Oils and Decoction Waters of Some Aromatic Plants

    OpenAIRE

    Sílvia M. Albano; A. Sofia Lima; M. Graça Miguel; Luis G. Pedro; Barroso, José G.; A. Cristina Figueiredo

    2012-01-01

    The scavenging of free radicals and superoxide anion, the inhibition of 5-lipoxygenase and the antiacetylcholinesterase activities of essential oils and decoction waters of eight aromatic plants (Dittrichia viscosa, Foeniculum vulgare, Origanum vulgare, Salvia officinalis, Thymbra capitata, Thymus camphoratus, Thymus carnosus and Thymus mastichina) were studied. The essential oils were dominated by 1,8-cineole in S. officinalis (59%), T. mastichina (49%) and T. camphoratus (21%); borneol (20%...

  15. Intrinsic anion oxidation potentials.

    Science.gov (United States)

    Johansson, Patrik

    2006-11-01

    Anions of lithium battery salts have been investigated by electronic structure calculations with the objective to find a computational measure to correlate with the observed (in)stability of nonaqueous lithium battery electrolytes vs oxidation often encountered in practice. Accurate prediction of intrinsic anion oxidation potentials is here made possible by computing the vertical free energy difference between anion and neutral radical (Delta Gv) and further strengthened by an empirical correction using only the anion volume as a parameter. The 6-311+G(2df,p) basis set, the VSXC functional, and the C-PCM SCRF algorithm were used. The Delta Gv calculations can be performed using any standard computational chemistry software. PMID:17078600

  16. Development of PhSCF2CF2SiMe3 as tetrafluoroethylene radical anion equivalent. Preparation of tetrafluoroethyl substituted alcohols and tetrafluoro-tetrahydro-pyrans

    Czech Academy of Sciences Publication Activity Database

    Beier, Petr; Chernykh, Yana; Klepetářová, Blanka

    2011-01-01

    Roč. 7, č. 13 (2011), s. 206-206. ISSN 1336-7242. [Zjazd Chemikov /63./. 05.09.2011-09.09.2011, Vysoké Tatry ] R&D Projects: GA ČR GAP207/11/0421 Institutional research plan: CEZ:AV0Z40550506 Keywords : tetrafluoroethyl * tetrafluoroethylene * nucleophilic addition * radical addition Subject RIV: CC - Organic Chemistry

  17. Salts of Dodecamethylcarba-closo-dodecaborate(-) Anion, CB11Me12-, and the Radical Dodecamethylcarba-closo-dodecaboranyl, CB11Me12

    Czech Academy of Sciences Publication Activity Database

    Clayton, J. R.; King, B. T.; Zharov, I.; Fete, M. G.; Volkis, V.; Douvris, C.; Valášek, Michal; Michl, Josef

    2010-01-01

    Roč. 35, - (2010), s. 56-63. ISSN 0073-8077 Grant ostatní: NSF(US) CHE0446688; NSF(US) CHE0848477 Institutional research plan: CEZ:AV0Z40550506 Keywords : boron clusters * methylation * stable free radical Subject RIV: CF - Physical ; Theoretical Chemistry

  18. Development of PhSCF2CF2SiMe3 as a Tandem Anion and Radical Tetrafluoroethylene Equivalent: Preparation of Tetrafluoroethyl-Substituted Alcohols and Tetrafluorotetrahydropyrans

    Czech Academy of Sciences Publication Activity Database

    Chernykh, Yana; Hlat-Glembová, Katarina; Klepetářová, Blanka; Beier, Petr

    -, č. 24 (2011), s. 4528-4531. ISSN 1434-193X R&D Projects: GA ČR GAP207/11/0421 Institutional research plan: CEZ:AV0Z40550506 Keywords : fluorine * alkylation * nucleophilic addition * radical reactions * oxygen heterocycles Subject RIV: CC - Organic Chemistry Impact factor: 3.329, year: 2011

  19. Application of PhSCF2CF2SiMe3 as a Tandem Anion and Radical Tetrafluoroethylene Equivalent: Fluoride-Catalyzed Addition to N-Substituted Cyclic Imides Followed by Radical Cyclization

    Czech Academy of Sciences Publication Activity Database

    Chernykh, Yana; Opekar, Stanislav; Klepetářová, Blanka; Beier, Petr

    2012-01-01

    Roč. 23, č. 8 (2012), s. 1187-1190. ISSN 0936-5214 R&D Projects: GA ČR GAP207/11/0421 Institutional research plan: CEZ:AV0Z40550506 Keywords : nucleophilic addition * radical reaction * fluorine * heterocycles * imides Subject RIV: CC - Organic Chemistry Impact factor: 2.655, year: 2012

  20. Fate of the nitro anion radical of pesticide bifenox in nin-aqueros systems. Double-layer effects in tetraalkylammonium solutions

    Czech Academy of Sciences Publication Activity Database

    Mořkovská, Petra; Hromadová, Magdaléna; Pospíšil, Lubomír; Giannarelli, S.

    2005-01-01

    Roč. 1, č. 1 (2005), s. 138-139. ISSN 1336-7242. [Zjazd chemických spoločností /57./. 04.09.2005-08.09.2005, Tatranské Matliare] R&D Projects: GA ČR GA203/03/0821; GA AV ČR IAA400400505; GA MŠk LC510 Institutional research plan: CEZ:AV0Z40400503 Keywords : free radicals * electron transfer kinetics * electrochemistry Subject RIV: CG - Electrochemistry

  1. EPR Study of Radicals in Irradiated Ionic Liquids and Implications for the Radiation Stability of Ionic Liquid-Based Extraction Systems

    CERN Document Server

    Shkrob, I A; Wishart, J F; Chemerisov, Sergey D.; Shkrob, Ilya A.; Wishart, James F.

    2007-01-01

    The radiation- and photo- chemistry of room temperature ionic liquids (ILs) composed of ammonium, phosphonium, pyrrolidinium, and imidazolium cations and bis(triflyl)amide, dicyanamide, and bis(oxalato)borate anions, have been studied using low-temperature Electron Paramagnetic Resonance (EPR). Several classes of radicals have been identified and related to reactions of the primary radiolytically generated electrons and holes. Large yields of terminal and penultimate C-centered radicals are observed in the aliphatic chains of the phosphonium, ammonium and pyrrolidinium cations, but not for imidazolium cation. This pattern can be accounted for by efficient deprotonation of a hole trapped on the cation (the radical dication) that competes with rapid charge transfer to a nearby anion. The latter leads to the formation of stable N- or O-centered radicals. The electrons either react with the protic impurity (for nonaromatic cations) yielding H atoms or the aromatic moiety (for imidazolium cations). Excitation of b...

  2. An aromatic hydroxylation assay for hydroxyl radicals utilizing high-performance liquid chromatography (HPLC). Use to investigate the effect of EDTA on the Fenton reaction.

    Science.gov (United States)

    Grootveld, M; Halliwell, B

    1986-01-01

    A highly sensitive HPLC method for the separation of hydroxylation products derived from the attack of hydroxyl radical upon phenol is described. Catechol and hydroquinone are the major hydroxylation products formed, with little resorcinol. The effect of EDTA upon hydroxyl radical generation from an iron (II)-H2O2 system is shown to depend upon the order of addition of chelator and metal ion to the reaction mixture, the ratio [iron salt]/[chelator] and the presence or absence of a phosphate buffer. Reasons for these different effects are discussed. PMID:2849582

  3. Free Radical Scavenging Fingerprints of Selected Aromatic and Medicinal Tunisian Plants Assessed by Means of TLC-DPPH(•) Test and Image Processing.

    Science.gov (United States)

    El Euch, Salma Kammoun; Cieśla, Łukasz; Bouzouita, Nabiha

    2014-01-01

    Aqueous-methanol extracts prepared from 10 Tunisian plant species were analyzed for the presence of potent direct antioxidants. The analyzed species included: Anacyclus clavatus Desf., Erica multiflora L., Cistus salvifolius L., Centaurium erythraea Rafn., Marrubium vulgare L., Lavandula stoechas L., Artemisia campestris L., Origanum majorana L., Salvia officinalis L., and Pistacia lentiscus L. All the extracts were chromatographed on the RP18 W plates with methanol-water-acetic acid (48 + 47 + 5, v/v/v) mobile phase. Upon completion of the chromatographic development and the drying step, the plates were stained with a chloroform solution of 2, 2-diphenyl-1-picrylhydrazyl radical (DPPH(•)). An image processing protocol, with use of Sorbfil TLC Videodensitometer, was applied to quantitatively measure the activity of polyphenols and to screen complex samples for the presence of free radical scavengers. The activity of the individual compounds was compared with that of rutin, used as a standard. The TLC-DPPH(•) test showed that C. salvifolius had the most potent antioxidant activity, as it possessed the highest activity coefficient (calculated as the sum of the areas under the peaks of all active compounds/area under peak of rutin). The proposed procedure may be used to differentiate potent chain-breaking antioxidants and compounds propagating radical chain reactions. PMID:25902978

  4. A new era for homolytic aromatic substitution: replacing Bu3SnH with efficient light-induced chain reactions.

    Science.gov (United States)

    Gurry, Michael; Aldabbagh, Fawaz

    2016-04-28

    Herein is a pertinent review of recent photochemical homolytic aromatic substitution (HAS) literature. Issues with using the reductant Bu3SnH in an oxidative process where the net loss of a hydrogen atom occurs is discussed. Nowadays more efficient light-induced chain reactions are used resulting in HAS becoming a synthetic mechanism of choice rivaling organometallic, transition-metal and electrophilic aromatic substitution protocols. The review includes aromatic substitution as part of a tandem or cascade reaction, Pschorr reaction, as well as HAS facilitated by ipso-substitution, and Smiles rearrangement. Recently visible-light photoredox catalysis, which is carried out at room temperature has become one of the most important means of aromatic substitution. The main photoredox catalysts used are polypyridine complexes of Ru(ii) and Ir(iii), although eosin Y is an alternative allowing metal-free HAS. Other radical initiator-free aromatic substitutions have used 9-mesityl-10-methylacridinium ion and N,N-bis(2,6-diisopropylphenyl)perylene-3,4,9,10-bis(dicarboximide) as the photoredox catalyst, UV-light, photoinduced electron-transfer, zwitterionic semiquinone radical anions, and Barton ester intermediates. PMID:27056571

  5. A dinuclear [{(p-cym)Ru(II)Cl}2(μ-bpytz˙(-))](+) complex bridged by a radical anion: synthesis, spectroelectrochemical, EPR and theoretical investigation (bpytz = 3,6-bis(3,5-dimethylpyrazolyl)1,2,4,5-tetrazine; p-cym = p-cymene).

    Science.gov (United States)

    Tripathy, Suman Kumar; van der Meer, Margarethe; Sahoo, Anupam; Laha, Paltan; Dehury, Niranjan; Plebst, Sebastian; Sarkar, Biprajit; Samanta, Kousik; Patra, Srikanta

    2016-08-01

    The reaction of the chloro-bridged dimeric precursor [{(p-cym)Ru(II)Cl}(μ-Cl)]2 (p-cym = p-cymene) with the bridging ligand 3,6-bis(3,5-dimethylpyrazolyl)-1,2,4,5-tetrazine (bpytz) in ethanol results in the formation of the dinuclear complex [{(p-cym)Ru(II)Cl}2(μ-bpytz˙(-))](+), [1](+). The bridging tetrazine ligand is reduced to the anion radical (bpytz˙(-)) which connects the two Ru(II) centres. Compound [1](PF6) has been characterised by an array of spectroscopic and electrochemical techniques. The radical anion character has been confirmed by magnetic moment (corresponding to one electron paramagnetism) measurement, EPR spectroscopic investigation (tetrazine radical anion based EPR spectrum) as well as density functional theory based calculations. Complex [1](+) displays two successive one electron oxidation processes at 0.66 and 1.56 V versus Ag/AgCl which can be attributed to [{(p-cym)Ru(II)C}2(μ-bpytz˙(-))](+)/[{(p-cym)Ru(II)Cl}2(μ-bpytz)](2+) and [{(p-cym)Ru(II)Cl}2(μ-bpytz)](+)/[{(p-cym)Ru(III)Cl}2(μ-bpytz)](2+) processes (couples I and II), respectively. The reduction processes (couple III-couple V), which are irreversible, likely involve the successive reduction of the bridging ligand and the metal centres together with loss of the coordinated chloride ligands. UV-Vis-NIR spectroelectrochemical investigation reveals typical tetrazine radical anion containing bands for [1](+) and a strong absorption in the visible region for the oxidized form [1](2+), which can be assigned to a Ru(II) → π* (tetrazine) MLCT transition. The assignment of spectroscopic bands was confirmed by theoretical calculations. PMID:27435992

  6. Ultrafast studies on the photophysics of matrix-isolated radical cations of polycyclic aromatic hydrocarbons: implications for the Diffuse Interstellar Bands (DIB) problem

    CERN Document Server

    Zhao, L; Shkrob, I A; Crowell, R A; Pommeret, S; Chronister, E L; Liu, A D; Trifunac, A D; Zhao, Liang; Lian, Rui; Shkrob, Ilya A.; Crowell, Robert A.; Pommeret, Stanislas; Chronister, Eric L.; Liu, An Dong; Trifunac, Alexander D.

    2004-01-01

    Rapid, efficient deactivation of the photoexcited PAH cations accounts for their remarkable photostability and have important implications for astrochemistry, as these cations are the leading candidates for the species responsible for the diffuse interstellar bands (DIB) observed throughout the Galaxy.Ultrafast relaxation dynamics for photoexcited PAH cations isolated in boric acid glass have been studied using femtosecond and picosecond transient grating spectroscopy. With the exception of perylene+, the recovery kinetics for the ground doublet (D0) states of these radical cations are biexponential, containing a fast (< 200 fs) and a slow (3-20 ps) components. No temperature dependence or isotope effect was observed for the fast component, whereas the slow component exhibits both the H/D isotope effect (1.1-1.3) and strong temperature dependence (15 to 300 K). We suggest that the fast component is due to internal Dn to D0 conversion and the slow component is due to vibrational energy transfer (VET) from a...

  7. Novel pseudo-delocalized anions for lithium battery electrolytes.

    Science.gov (United States)

    Jónsson, Erlendur; Armand, Michel; Johansson, Patrik

    2012-05-01

    A novel anion concept of pseudo-delocalized anions, anions with distinct positive and negative charge regions, has been studied by a computer aided synthesis using DFT calculations. With the aim to find safer and better performing lithium salts for lithium battery electrolytes two factors have been evaluated: the cation-anion interaction strength via the dissociation reaction LiAn ⇌ Li(+) + An(-) and the anion oxidative stability via a vertical ionisation from anion to radical. Based on our computational results some of these anions have shown promise to perform well as lithium salts for modern lithium batteries and should be interesting synthetic targets for future research. PMID:22441354

  8. Some reactions of oxidizing radicals with enzymes in aqueous solution

    International Nuclear Information System (INIS)

    A range of oxidizing radicals including some inorganic radical anions and the superoxide radical, can be generated by radiolysis of aqueous solutions. These radicals are more selective in their reactions with amino acids than the hydroxyl radical. Factors controlling the apparent reactivity of radical anions with proteins, such as free radical equilibria and ion-binding, are described. The superoxide radical inactivates papain by reaction with the cysteine residue. This reaction has been studied in solutions subjected to radiations of varying linear energy transfer. (Auth.)

  9. Electron transfer in dinucleoside phosphate anions

    International Nuclear Information System (INIS)

    The electron transfer reaction within various dinucleoside phosphate radical anions has been investigated by ESR spectroscopy and pulse radiolysis. In the ESR work electrons are produced by photolysis of K4Fe(CN)6 in a 12 M LiCl glass at 770K. Upon photobleaching the electrons react with the dinucleoside phosphate to form the anion radical. The anions of the four DNA nucleosides were also produced and their ESR spectra were appropriately weighted and summed by computer to simulate the spectra found for the dinucleoside phosphate anions. From the analysis the relative amounts of each of the nucleoside anions in the dinucleoside phosphate anion were determined. Evidence suggests the electron affinity of the pyrimidine bases are greater than the purine bases; however, the results are not sufficient to distinguish between the individual purine or pyrimidine. When dinucleoside phosphate anions containing thymidine are warmed, protonation occurs only on thymine to produce the well known ''thymyl'' spectrum. Pulse radiolysis experiments on individual nucleotides (TMP, dAMP), mixtures of these nucleotides and the dinucleoside phosphate, TdA, in aqueous solution at room temperature show that in the TdA anion electron transfer occurs from adenine to thymine, whereas no electron transfer is found for mixtures of individual nucleotides. Protonation is found to occur only on thymine in the TdA anion in agreement with the ESR results

  10. Physiology of free radicals

    Directory of Open Access Journals (Sweden)

    Stevanović Jelka

    2011-01-01

    Full Text Available Free radicals imply that every atom, molecule, ion, group of atoms, or molecules with one or several non-paired electrons in outer orbital. Among these are: nitrogenoxide (NO•, superoxide-anion-radical (O2•-, hydroxyl radical (OH•, peroxyl radical (ROO•, alcoxyl radical (RO• and hydroperoxyl radical (HO2•. However, reactive oxygen species also include components without non-paired electrons in outer orbital (so-called reactive non-radical agents, such as: singlet oxygen (1O2, peroxynitrite (ONOO-, hydrogen-peroxide (H2O2, hypochloric acid (eg. HOCl and ozone (O3. High concentrations of free radicals lead to the development of oxidative stress which is a precondition for numerous pathological effects. However, low and moderate concentrations of these matter, which occur quite normally during cell metabolic activity, play multiple significant roles in many reactions. Some of these are: regulation of signal pathways within the cell and between cells, the role of chemoattractors and leukocyte activators, the role in phagocytosis, participation in maintaining, changes in the position and shape of the cell, assisting the cell during adaption and recovery from damage (e.g.caused by physical effort, the role in normal cell growth, programmed cell death (apoptosis and cell ageing, in the synthesis of essential biological compounds and energy production, as well as the contribution to the regulation of the vascular tone, actually, tissue vascularization.

  11. Electrical and magnetic properties of new compounds of the conductor anion [Ni(dmit2]- and nitronyl nitroxide magnetic radicals Propriedades elétricas e magnéticas de novos compostos com o ânion condutor [Ni(dmit2]- e radicais magnéticos nitronil nitróxido

    Directory of Open Access Journals (Sweden)

    Mauro Cesar Dias

    2007-08-01

    Full Text Available Three compounds have been synthesized with formulae [3-MeRad][Ni(dmit2] (1, [4-MeRad][Ni(dmit2] (2 and [4-PrRad][Ni(dmit2] (3 where [Ni(dmit2]- is an anionic pi-radical (dmit = 1,3-dithiol-2-thione-4,5-dithiolate and [3-MeRad]+ is 3-N-methylpyridinium alpha-nitronyl nitroxide, [4-MeRad]+ is 4-N-methylpyridinium alpha-nitronyl nitroxide and [4-PrRad]+ is 4-N-propylpyridinium alpha-nitronyl nitroxide. The temperature-dependent magnetic susceptibility of 1 revealed that an antiferromagnetic interaction operates between the 3-MeRad+ radical cations with exchange coupling constants of J1 = - 1.72 cm-1 and antiferromagnetism assigned to the spin ladder chains of the Ni(dmit2 radical anions. Compound 1 exhibits semiconducting behavior and 3 presents capacitor behavior in the temperature range studied (4 - 300 K.

  12. Understanding and modeling removal of anionic organic contaminants (AOCs) by anion exchange resins.

    Science.gov (United States)

    Zhang, Huichun; Shields, Anthony J; Jadbabaei, Nastaran; Nelson, Maurice; Pan, Bingjun; Suri, Rominder P S

    2014-07-01

    Ionic organic contaminants (OCs) are a growing concern for water treatment and the environment and are removed inefficiently by many existing technologies. This study examined removal of anionic OCs by anion exchange resins (AXRs) as a promising alternative. Results indicate that two polystyrene AXRs (IRA910 and IRA96) have higher sorption capacities and selectivity than a polyacrylate resin (A860). For the polystyrene resins, selectivity follows: phenolates ≥ aromatic dicarboxylates > aromatic monocarboxylates > benzenesulfonate > aliphatic carboxylates. This trend can be explained based on hydration energy, the number of exchange groups, and aromaticity and hydrophobicity of the nonpolar moiety (NPM) of the anions. For A860, selectivity only varies within a narrow range (0.13-1.64). Despite the importance of the NPM of the anions, neutral solutes were sorbed much less, indicating synergistic combinations of electrostatic and nonelectrostatic interactions in the overall sorption. By conducting multiple linear regression between Abraham's descriptors and nature log of selectivity, induced dipole-related interactions and electrostatic interactions were found to be the most important interaction forces for sorption of the anions, while solute H-bond basicity has a negative effect. A predictive model was then developed for carboxylates and phenolates based on the poly parameter linear free energy relationships established for a diverse range of 16 anions and 5 neutral solutes, and was validated by accurate prediction of sorption of five test solutes within a wide range of equilibrium concentrations and that of benzoate at different pH. PMID:24877792

  13. Structure-property relationships in radical-cation (electron-donor molecule) and anion-based (including fullerides) organic superconductors and their use in the design of new materials

    Energy Technology Data Exchange (ETDEWEB)

    Williams, J.M.; Carlson, K.D.; Kini, A.M. [Argonne National Lab., IL (United States)

    1993-08-01

    The presently known structure-property relations that have been developed for organic superconductors based on the ET molecule (b- phases and k-phases), and the C{sub 60}-anion-based fullerides, and their use in the structural design of new superconducting materials are discussed. 12 refs, 11 figs, 4 tabs.

  14. Free Radical Scavenging Activity of Leaves of Alocasia indica (Linn)

    OpenAIRE

    Mulla, W. A.; Salunkhe, V. R.; Kuchekar, S. B.; Qureshi, M. N.

    2009-01-01

    The free radical scavenging potential of the plant Alocasia indica(Linn.) was studied by using different antioxidant models of screening like scavenging of 1,1-diphenyl-2-picryl hydrazyl radical, nitric oxide radical, superoxide anion radical, hydroxyl radical, iron chelating activity, total antioxidant capacity, non-enzymatic glycosylation of haemoglobin, rapid screening for antioxidant compounds by thin layer chromatography. The hydroalcoholic extract at 1000 μg/ml showed maximum scavenging...

  15. Electron-Exchange Reactions of Aromatic Molecules

    International Nuclear Information System (INIS)

    A large body of information is available on the rates and mechanisms of inorganic electron-exchange processes. In contrast, purely organic systems have received only minor attention. The homogeneous electron-exchange rates (kexc) and the heterogeneous rate constants for the electrode reaction (kel) have been measured only for a few hydrocarbons. We have measured kexc for a variety of aromatic systems including hydrocarbons, quinones and nitro compounds. These measurements have been carried out via electron paramagnetic resonance (EPR) line broadening measurements on mixtures of radical ions and their parent compounds. We have been able to measure kexc with a precision that allows detection of small differences presumably due to molecular structure and environment. Hydrocarbon systems like anthracene/anthracene anion are very rapid with kexc values of ca. 108-109 litres mole-1 sec-1. Some substituted aromatics like quinones and nitriles are also quite rapid. However, when a strong electron acceptor function is present like a nitro group in nitrobenzene, the value of kexc decreases by a factor of 10. It is possible to correlate changes in kexc in the nitrobenzene series with the unpaired electron density in terms of the 14N coupling constants of the EPR spectra. Further, the nitro aromatic series show very large variations in kexc with the solvent system. These changes can be correlated with recent studies of the solvation effect on hyperfine coupling constants. Marcus has reviewed recently chemical and electrochemical electron-transfer theory and suggested correlations between kexc and kel. We have measured kel especially for the nitrobenzene system under conditions which are as nearly identical experimentally to the EPR studies as possible. The electrochemical investigations were carried out by a steady-state d.c. method to eliminate some of the uncertainties inherent in electrochemical relaxation techniques. Rotated disc electrodes at low temperatures were used

  16. Aromatic graphene

    Science.gov (United States)

    Das, D. K.; Sahoo, S.

    2016-04-01

    In recent years graphene attracts the scientific and engineering communities due to its outstanding electronic, thermal, mechanical and optical properties and many potential applications. Recently, Popov et al. [1] have studied the properties of graphene and proved that it is aromatic but without fragrance. In this paper, we present a theory to prepare graphene with fragrance. This can be used as scented pencils, perfumes, room and car fresheners, cosmetics and many other useful household substances.

  17. Core-modified octaphyrins: Syntheses and anion-binding properties

    Indian Academy of Sciences (India)

    Rajneesh Misra; Venkataramanarao G Anand; Harapriya Rath; Tavarekere K Chandrashekar

    2005-03-01

    In this paper, a brief review of the syntheses, characterization and anion-binding properties of core-modified octaphyrins is presented. It has been shown that the core-modified octaphyrins exhibit aromaticity both in solution and in solid state, confirming the validity of the (4 + 2) Huckel rule for larger -electron systems. Solid-state binding characteristics of TFA anions of two core-modified octaphyrins are also described.

  18. Studies of radiation-produced radicals and radical ions. Progress report, June 1, 1981-August 31, 1982

    International Nuclear Information System (INIS)

    The discovery and characterization of novel radical ions produced by the γ irradiation of solids continues to be a fertile field for investigation. This Progress Report describes the generation and ESR identification of several new paramagnetic species, some of which have long been sought as important intermediates in radiation chemistry. We have also contributed to a general theoretical problem in ESR spectroscopy. Solid-state studies of electron attachment reactions, both non-dissociative and dissociative, reveal interesting structural and chemical information about the molecular nature of these processes for simple compounds. In particular, ESR measurements of the spin distribution in the products allow a fairly sharp distinction to be drawn between radical anions and radical-anion pairs or adducts. Dimer radical anion formation can also take place but the crystal structure plays a role in this process, as expected. Some radical anions undergo photolysis to give radical-anion pairs which may then revert back to the original radical anion by a thermal reaction. The chemistry of these reversible processes is made more intricate by a competing reaction in which the radical abstracts a hydrogen atom from a neighboring molecule. However, the unraveling of this complication has also served to extend our knowledge of the role of quantum tunneling in chemical reactions. The results of this investigation testify to the potential of solid-state techniques for the study of novel and frangible radical ions. Progress in this field shows no sign of abating, as witness the recent discovery of perfluorocycloalkane radical anions and alkane radical cations

  19. Matrix ENDOR of the protonated carboxylic anion radical in γ-irradiated l-alanine. Simulation using a general matrix ENDOR line-shape model and single crystal data

    International Nuclear Information System (INIS)

    The matrix ENDOR line from the CH3CH(+NH3)COOOH- radical in γ-irradiated L-alanine powder at 77 K was simulated by using a generalized matrix ENDOR line-shape theory. The input includes hyperfine coupling constants for all protons in the proximity of the radical site as well as the pure dipolar interaction for more distant protons, microwave and radio-frequency magnetic field magnitudes, and nuclear and electron spin-lattice and spin-spin relaxation times. Simulated matrix ENDOR lines were tested against experimental line shapes, line widths, and the intensity of the ENDOR response as a function of the radio-frequency magnetic field. The simulated ENDOR response was found to be very sensitive to the value of the nuclear spin-lattice relaxation time, and a value of 0.15 s satisfactorily reproduces the experimental results. The relevant conclusion from this study is that an angularly independent nuclear relaxation mechanism dominates the ENDOR response

  20. Anion exchange membrane

    Science.gov (United States)

    Verkade, John G; Wadhwa, Kuldeep; Kong, Xueqian; Schmidt-Rohr, Klaus

    2013-05-07

    An anion exchange membrane and fuel cell incorporating the anion exchange membrane are detailed in which proazaphosphatrane and azaphosphatrane cations are covalently bonded to a sulfonated fluoropolymer support along with anionic counterions. A positive charge is dispersed in the aforementioned cations which are buried in the support to reduce the cation-anion interactions and increase the mobility of hydroxide ions, for example, across the membrane. The anion exchange membrane has the ability to operate at high temperatures and in highly alkaline environments with high conductivity and low resistance.

  1. Anions in Cometary Comae

    Science.gov (United States)

    Charnley, Steven B.

    2011-01-01

    The presence of negative ions (anions) in cometary comae is known from Giotto mass spectrometry of IP/Halley. The anions 0-, OH-, C-, CH- and CN- have been detected, as well as unidentified anions with masses 22-65 and 85-110 amu (Chaizy et al. 1991). Organic molecular anions are known to have a significant impact on the charge balance of interstellar clouds and circumstellar envelopes and have been shown to act as catalysts for the gas-phase synthesis of larger hydrocarbon molecules in the ISM, but their importance in cometary comae has not yet been explored. We present details of the first attempt to model the chemistry of anions in cometary comae. Based on the combined chemical and hydro dynamical model of Rodgers & Charnley (2002), we investigate the role of large carbon-chain anions in cometary coma chemistry. We calculate the effects of these anions on coma thermodynamics, charge balance and examine their impact on molecule formation.

  2. Cl-…苯氰…H2O中阴离子氢键协同效应与芳香性理论研究%A theoretical investigation into the cooperativity effect involving anionic hydrogen bond and aromaticity in Cl-…benzonitrile…H2 O ternary complex

    Institute of Scientific and Technical Information of China (English)

    宋慧; 李斌; 赵光明; 武红娟; 龙泽清

    2015-01-01

    本文采用DFT-B3LYP和MP2(full)方法对三聚体Cl–…苯氰…H2O中O/C–H…Cl–阴离子氢键与传统氢键O–H…N和C–H…O之间的协同效应、热力学性质以及芳香性进行了研究.结果表明阴离子氢键O/C–H…Cl–对O–H…N或 C–H…O相互作用的影响更显著.在线性结构中发生正协同效应,熵变是促进热力学协同效应的主要因素,而在环状结构中发生反协同效应,焓变成为主要因素.在三聚体形成过程中,苯氰环的芳香性是减弱的,而苯氰中π→π∗共轭效应是增强的.结果表明,协同效应能Ecoop.分别与 Rc ( NICS (1) ternary/NICS (1) binary ),ΔΔδ(Δδternary -Δδbinary ), Rc′(( NICS (1) ternary - NICS (1)binary)/NICS (1)binary)和RBDE(C–CN)(BDE(C–CN)ternary/BDE(C–CN)binary)均具有良好的线性关系.同时, AIM的分析也佐证了协同效应的存在.%The cooperativity effects between the O/C–H…Cl–anionic H-bonding and O–H…N and C–H…O H-bonding interactions, thermodynamic properties and aromaticities in Cl–…benzonitrile…H2 O comple-xes are investigated using the B3LYP and MP2(full) methods. The result shows that the influence of the O/C–H…Cl–anionic H-bonding interaction on the C–H…O is more pronounced than that on the O–H…N in-teraction. The cooperativity effect appears in the linear conformation while the anti-cooperativity effect is found in the cyclic structure. The enthalpy change is the major factor driving the cooperativity in forming the linear ter-nary complex while entropy change turns into the favorable factor in forming the cyclic system. The aromaticity of the benzonitrile ring is weakened and theπ→π∗conjugative effect between the ring and C≡N bond is strength-ened upon the ternary-complex formation. To our interest, the cooperativity effect correlates well with Rc(NICS (1)ternary/NICS (1)binary),ΔΔδ (Δδternary– Δδbinary), Rc′((NICS (1)ternary– NICS (1

  3. Radical Evil

    Directory of Open Access Journals (Sweden)

    Carlos Manrique

    2007-12-01

    Full Text Available There is an aporia in Kant’s analysis of evil: he defines radical evilas an invisible disposition of the will, but he also demands an inferential connection between visible evil actions and this invisible disposition. This inference,however, undermines the radical invisibility of radical evil according to Kant’s own definition of the latter. Noting how this invisibility of moral worth is a distinctive feature of Kant’s approach to the moral problem, the paper then asks why, in the Groundwork, he nonetheless forecloses a question about evil that seems to be consistent with this approach. It is argued that to account for this aporia and this foreclosure, one has to interrogate the way in which the category of religion orients Kant’s incipient philosophy of history in Die Religion.

  4. Ion-radical intermediates of the radiation-chemical transformations of organic carbonates

    Science.gov (United States)

    Shiryaeva, Ekaterina S.; Sosulin, Ilya S.; Saenko, Elizaveta V.; Feldman, Vladimir I.

    2016-07-01

    The spectral features and reactions of ion-radical intermediates produced from organic carbonates in low-temperature matrices were investigated by EPR spectroscopy and quantum-chemical calculations. It was shown that radical cations of diethyl carbonate and dimethyl carbonate underwent intramolecular hydrogen transfer to yield alkyl-type species, as was suggested previously. Meanwhile, radical cation of EC demonstrates a ring cleavage even at 77 K, while radical cation of PC is probably intrinsically stable and undergo an ion-molecule reaction with a neighboring neutral molecule in dimers or associates. Radical anions were obtained in glassy matrices of diethyl ether or perdeuteroethanol. The radical anions of linear carbonates show photoinduced fragmentation to yield the corresponding alkyl radicals; such process may also occur directly under radiolysis. Radical anions of cyclic carbonates are relatively stable and yield only trace amounts of fragmentation products under similar conditions.

  5. Fast Resonance Raman Spectroscopy of Short-Lived Radicals

    DEFF Research Database (Denmark)

    Pagsberg, Palle Bjørn; Wilbrandt, Robert Walter; Hansen, Karina Benthin;

    1976-01-01

    We report the first application of pulsed resonance Raman spectroscopy to the study of short-lived free radicals produced by pulse radiolysis. A single pulse from a flash-lamp pumped tunable dye laser is used to excite the resonance Raman spectrum of the p-terphenyl anion radical with an initial...

  6. Free-radical chemistry of thiourea in aqueous solution, induced by OH radical, H atom, α-hydroxyalkyl radicals, photoexcited maleimide, and the solvated electron

    International Nuclear Information System (INIS)

    Hydroxyl radicals react with thiourea (and its tetramethyl derivative) yielding dimeric radical cations which are characterized by strong absorptions at 400 nm (450 nm). An analysis of the kinetics of the buildup of these absorptions gives evidence for the intermediacy of OH-adducts and the monomeric radical cations. The dimeric radical cations are also generated in the reactions of triplet-excited maleimide with those thioureas. Moreover, in acidic solutions even reducing radicals such as the H atom and α-hydroxy alkyl radicals give rise to these intermediates in full yields, albeit displaying different kinetics. Potential mechanistic implications are discussed. The dimeric thiourea radical cations are strong oxidants and readily oxidize the anions of phenol and 2'-deoxyguanosine. The solvated electron gives rise to an intermediate which is rapidly protonated by water (pKa > 11). Quantum mechanical calculations support the assignment of the 400 nm (450 nm) absorption to the respective dimeric thiourea radical cation. (author)

  7. Free radical scavenging activity of leaves of Alocasia indica (Linn)

    OpenAIRE

    Mulla W; Salunkhe V; Kuchekar S; Qureshi M

    2009-01-01

    The free radical scavenging potential of the plant Alocasia indica (Linn.) was studied by using different antioxidant models of screening like scavenging of 1,1-diphenyl-2-picryl hydrazyl radical, nitric oxide radical, superoxide anion radical, hydroxyl radical, iron chelating activity, total antioxidant capacity, non-enzymatic glycosylation of haemoglobin, rapid screening for antioxidant compounds by thin layer chromatography. The hydroalcoholic extract at 1000 ΅g/ml showed maximum scav...

  8. SIMULTANEOUS DTERMINATION OF CHROMATE AND AROMATIC HYDROCARBONS IN ENVIRONMENTAL SAMPLES BY CAPILLARY ELECTROPHORESIS

    Science.gov (United States)

    An analytical method was developed to determine simultaneously, the inorganic anion CrO2-4, and organic aromatic compounds including benzoate, 2-Cl-benzoate, phenol, m-cresol and o-/p-cresol by capillary electrophoresis (CE). Chromate and the aromatics were separated in a relativ...

  9. The direct aromatization of methane

    Energy Technology Data Exchange (ETDEWEB)

    Marcelin, G.; Oukaci, R.; Migone, R.A.; Kazi, A.M. [Altamira Instruments, Pittsburgh, PA (United States)

    1995-12-31

    The thermal decomposition of methane shows significant potential as a process for the production of higher unsaturated and aromatic hydrocarbons when the extent of the reaction is limited. Thermodynamic calculations have shown that when the reaction is limited to the formation of C{sub 2} to C{sub 10} products, yields of aromatics can exceed 40% at temperatures of 1200{degrees}C. Preliminary experiments have shown that when the reaction is limited to the formation of C{sub 2} to C{sub 10} products, yields of aromatics can exceed 40% at temperatures of 1200{degrees}C. Preliminary experiments have shown that cooling the product and reacting gases as the reaction proceeds can significantly reduce or eliminate the formation of solid carbon and heavier (C{sub 10+}) materials. Much work remains to be done in optimizing the quenching process and this is one of the goals of this program. Means to lower the temperature of the reaction are being studied as this result in a more feasible commercial process due to savings realized in energy and material of construction costs. The use of free-radical generators and catalysts will be investigated as a means of lowering the reaction temperature thus allowing faster quenching. It is highly likely that such studies will lead to a successful direct methane to higher hydrocarbon process.

  10. Radical Geography

    Directory of Open Access Journals (Sweden)

    H. Hataminezhad

    2012-07-01

    Full Text Available Interdisciplinary sciences emerging and specialization were result of historical conditions. Lack of common and grand theories have caused social sciences such as Geography disintegrated to many courses. The Geography science has been divided two main courses, Physical and Human through the time. Every one used another similar science in theoretical principles and methodologies for their domain development and strengthening of their bases. The Human Geography was influenced by Anthropology during nineteenth century and was affected by nineteenth century and dawn twentieth century by Sociology and from mid twentieth century until present time by Biological sciences, Psychology, Political economics and social theories. Radical Geography was one of the Human Geography branches that was influenced by Political economics and left ideology. Radical Geography emphasizes on investigation about quality of life in different spaces and attempts to change socio-economic and spatial relationships, therefore critical Geography is one of its similar approaches.

  11. Hydration and sorption characteristics of a polyfunctional weak-base anion exchanger after the sorption of vanillin and ethylvanillin

    Science.gov (United States)

    Rodionova, D. O.; Voronyuk, I. V.; Eliseeva, T. V.

    2016-07-01

    Features of the sorption of substituted aromatic aldehydes by a weak-base anion exchanger under equilibrium conditions are investigated using vanillin and ethylvanillin as examples. Analysis of the sorption isotherms of carbonyl compounds at different temperatures allows us to calculate the equilibrium characteristics of their sorption and assess the entropy and enthalpy contributions to the energy of the process. Hydration characteristics of the macroporous weak-base anion exchanger before and after the sorption of aromatic aldehydes are compared.

  12. BENZO[a]PYRENE METABOLITES EXAGGERATE DNA OXIDATIVE DAMAGE UPON THE INVOLVEMENT OF FREE RADICALS%苯并[a]比代谢产物在自由基参与下加速DNA的氧化损伤

    Institute of Scientific and Technical Information of China (English)

    罗云敬; GAO Da-yuan; WEI Hua-chen

    2003-01-01

    @@ Polycyclic aromatic hydrocarbons (PAHs),which constitute a major class of environmental pollu tants are posing a threat to human health. Benzopyrene,an index of PAH levels omnipresent in the everyday environment ,becomes toxic only when being metabolically and/or photo-activated,i. e. ,in the pres ence of UV light. Free radicals such as superoxide anions ('O2),hydrogen peroxide (H2O2),hydroxyl radicals ('OH) and singlet oxygen (1O2) are involved in carcinogenesis. Wei CE etc[1] studied the effects of different scavengers of active oxygen species (superoxide dismutase,catalase,mannitol and dimethyfu ran) on promoting B[a]P mutagenicity. Bryla P ete[2] investigated the roles of several ROS scavengers in the oxidation and binding of B[a]P to calf thymus DNA using the 32p-postlabeling assay.

  13. Functional Block Copolymers via Anionic Polymerization for Electroactive Membranes

    OpenAIRE

    Schultz, Alison

    2013-01-01

           Ion-containing block copolymers blend ionic liquid properties with well-defined polymer architectures. This provides conductive materials with robust mechanical stability, efficient processability, and tunable macromolecular design. Conventional free radical polymerization and anion exchange achieved copolymers containing n-butyl acrylate and phosphonium ionic liquids. These compositions incorporated vinylbenzyl triphenyl phosphonium and vinylbenzyl tricyclohexyl phosphonium cations be...

  14. Aromatics Oxidation and Soot Formation in Flames

    Energy Technology Data Exchange (ETDEWEB)

    Howard, J. B.; Richter, H.

    2005-03-29

    This project is concerned with the kinetics and mechanisms of aromatics oxidation and the growth process to polycyclic aromatic hydrocarbons (PAH) of increasing size, soot and fullerenes formation in flames. The overall objective of the experimental aromatics oxidation work is to extend the set of available data by measuring concentration profiles for decomposition intermediates such as phenyl, cyclopentadienyl, phenoxy or indenyl radicals which could not be measured with molecular-beam mass spectrometry to permit further refinement and testing of benzene oxidation mechanisms. The focus includes PAH radicals which are thought to play a major role in the soot formation process while their concentrations are in many cases too low to permit measurement with conventional mass spectrometry. The radical species measurements are used in critical testing and improvement of a kinetic model describing benzene oxidation and PAH growth. Thermodynamic property data of selected species are determined computationally, for instance using density functional theory (DFT). Potential energy surfaces are explored in order to identify additional reaction pathways. The ultimate goal is to understand the conversion of high molecular weight compounds to nascent soot particles, to assess the roles of planar and curved PAH and relationships between soot and fullerenes formation. The specific aims are to characterize both the high molecular weight compounds involved in the nucleation of soot particles and the structure of soot including internal nanoscale features indicative of contributions of planar and/or curved PAH to particle inception.

  15. Roaming Radicals

    Science.gov (United States)

    Bowman, Joel M.; Shepler, Benjamin C.

    2011-05-01

    Roaming is a recently verified unusual pathway to molecular products from unimolecular dissociation of an energized molecule. Here we present the evidence for this pathway for H2CO and CH3CHO. Theoretical analysis shows that this path visits the plateau region of the potential energy surface near dissociation to radical products. It is not clear whether roaming is a distinct isolated pathway, in addition to the conventional one via the well-known molecular saddle-point transition state. Evidence is presented to suggest that the two pathways may originate from a single, but highly complicated, dividing surface. Other examples of unusual reaction dynamics are also reviewed.

  16. Polycyclic Aromatic Hydrocarbons

    Science.gov (United States)

    Salama, Farid

    2010-01-01

    Carbonaceous materials play an important role in space. Polycyclic Aromatic Hydrocarbons (PAHs) are a ubiquitous component of the carbonaceous materials. PAHs are the best-known candidates to account for the IR emission bands. They are also thought to be among the carriers of the diffuse interstellar absorption bands (DIBs). PAH ionization states reflect the ionization balance of the medium while PAH size, composition, and structure reflect the energetic and chemical history of the medium. A major challenge is to reproduce in the laboratory the physical conditions that exist in the emission and absorption interstellar zones. The harsh physical conditions of the ISM -low temperature, collisionless, strong UV radiation fields- are simulated in the laboratory by associating a molecular beam with an ionizing discharge to generate a cold plasma expansion. PAH ions and radicals are formed from the neutral precursors in an isolated environment at low temperature and probed with high-sensitivity cavity ringdown spectroscopy in the NUV-NIR range. Carbon nanoparticles are also formed during the short residence time of the precursors in the plasma and are characterized with time-offlight mass spectrometry. These experiments provide unique information on the spectra of large carbonaceous molecules and ions in the gas phase that can now be directly compared to interstellar and circumstellar observations (IR emission bands, DIBs, extinction curve). These findings also hold great potential for understanding the formation process of interstellar carbonaceous grains. We will review recent progress in the experimental and theoretical studies of PAHs, compare the laboratory data with astronomical observations and discuss the global implications.

  17. Anion-π catalysis.

    Science.gov (United States)

    Zhao, Yingjie; Beuchat, César; Domoto, Yuya; Gajewy, Jadwiga; Wilson, Adam; Mareda, Jiri; Sakai, Naomi; Matile, Stefan

    2014-02-01

    The introduction of new noncovalent interactions to build functional systems is of fundamental importance. We here report experimental and theoretical evidence that anion-π interactions can contribute to catalysis. The Kemp elimination is used as a classical tool to discover conceptually innovative catalysts for reactions with anionic transition states. For anion-π catalysis, a carboxylate base and a solubilizer are covalently attached to the π-acidic surface of naphthalenediimides. On these π-acidic surfaces, transition-state stabilizations up to ΔΔGTS = 31.8 ± 0.4 kJ mol(-1) are found. This value corresponds to a transition-state recognition of KTS = 2.7 ± 0.5 μM and a catalytic proficiency of 3.8 × 10(5) M(-1). Significantly increasing transition-state stabilization with increasing π-acidity of the catalyst, observed for two separate series, demonstrates the existence of "anion-π catalysis." In sharp contrast, increasing π-acidity of the best naphthalenediimide catalysts does not influence the more than 12 000-times weaker substrate recognition (KM = 34.5 ± 1.6 μM). Together with the disappearance of Michaelis-Menten kinetics on the expanded π-surfaces of perylenediimides, this finding supports that contributions from π-π interactions are not very important for anion-π catalysis. The linker between the π-acidic surface and the carboxylate base strongly influences activity. Insufficient length and flexibility cause incompatibility with saturation kinetics. Moreover, preorganizing linkers do not improve catalysis much, suggesting that the ideal positioning of the carboxylate base on the π-acidic surface is achieved by intramolecular anion-π interactions rather than by an optimized structure of the linker. Computational simulations are in excellent agreement with experimental results. They confirm, inter alia, that the stabilization of the anionic transition states (but not the neutral ground states) increases with the π-acidity of the

  18. Isolation of Hypervalent Group-16 Radicals and Their Application in Organic-Radical Batteries.

    Science.gov (United States)

    Imada, Yasuyuki; Nakano, Hideyuki; Furukawa, Ko; Kishi, Ryohei; Nakano, Masayoshi; Maruyama, Hitoshi; Nakamoto, Masaaki; Sekiguchi, Akira; Ogawa, Masahiro; Ohta, Toshiaki; Yamamoto, Yohsuke

    2016-01-20

    Using a newly prepared tridentate ligand, we isolated hypervalent sulfur and selenium radicals for the first time and characterized their structures. X-ray crystallography, electron spin resonance spectroscopy, and density functional theory calculations revealed a three-coordinate hypervalent structure. Utilizing the reversible redox reactions between hypervalent radicals and the corresponding anions bearing Li(+), we developed organic radical batteries with these compounds as cathode-active materials. Furthermore, an all-radical battery, with these compounds as the cathode and a silyl radical as the anode, was developed that exhibited a practical discharge potential of ∼ 1.8 V and stable cycle performance, demonstrating the potential of these materials for use in metal-free batteries that can replace conventional Li-ion batteries where Li is used in the metal form. PMID:26721786

  19. Free radical scavenging activity of papaya juice

    International Nuclear Information System (INIS)

    Papaya juice is an efficient scavenger of highly reactive hydroxyl radicals (OH radical) formed during 60Co irradiation of water. The OH anion radicals were detected by the electron spin resonance (ESR) technique of spin trapping using DMPO (5,5-dimethyl-1-pyrroline-N-oxide) or by a colorimetric assay in which salicylate is converted into polyhydroxybenzoic acids. Papaya juice is also able to quench the ESR signal of a stable free radical (TEMPOL) and the ESR signal of the DMPO-OH adduct. The active substance(s) in papaya juice are heat-stable, dialyzable, and soluble in water but not in lipid solvents. The active agents do not appear to be ascorbate, tocopherol, or carotenoids. (author)

  20. Decomposition reactions of bifenox anion radical involving intramolecular electron transfer

    Czech Academy of Sciences Publication Activity Database

    Hromadová, Magdaléna; Mořkovská, Petra; Pospíšil, Lubomír; Giannarelli, S.

    2005-01-01

    Roč. 582, 1-2 (2005), s. 156-164. ISSN 0022-0728 R&D Projects: GA MŠk OC D15.10; GA ČR GP203/02/P082; GA ČR GA203/03/0821 Institutional research plan: CEZ:AV0Z40400503 Keywords : bifenox * nitro-group reduction * double-layer effect Subject RIV: CG - Electrochemistry Impact factor: 2.223, year: 2005

  1. Voltammetry of hypoxic cells radiosensitizer etanidazole radical anion in water

    Czech Academy of Sciences Publication Activity Database

    Gál, Miroslav; Hromadová, Magdaléna; Pospíšil, Lubomír; Híveš, J.; Sokolová, Romana; Kolivoška, Viliam; Kocábová, Jana

    2010-01-01

    Roč. 78, č. 2 (2010), s. 118-123. ISSN 1567-5394 R&D Projects: GA ČR GP203/09/P502 Institutional research plan: CEZ:AV0Z40400503 Keywords : etanidazole * radiosensitizer * electron transfer * voltammetry Subject RIV: CG - Electrochemistry Impact factor: 3.520, year: 2010

  2. Zn-Al LAYERED DOUBLE HYDROXIDE PILLARED BY DIFFERENT DICARBOXYLATE ANIONS

    Directory of Open Access Journals (Sweden)

    S. Gago

    2004-12-01

    Full Text Available Zn-Al layered double hydroxides (LDHs intercalated by terephthalate (TPH and biphenyl-4,4'-dicarboxylate (BPH anions have been synthesized by direct co-precipitation from aqueous solution. The Zn/Al ratio in the final materials was 1.8. The products were characterized by powder X-ray diffraction, thermogravimetric analysis, FTIR and FT Raman spectroscopy, and MAS NMR spectroscopy. The basal spacing for the TPH-LDH intercalate was 14.62 Å, indicating that the guest anions stack to form a monolayer with the aromatic rings perpendicular to the host layers. For the LDH intercalate containing BPH anions, a basal spacing of at least 19.2 Å would be expected if the anions adopted an arrangement similar to that for the TPH anions. The observed spacing was 18.24 Å, suggesting that the anions are tilted slightly with respect to the host layers.

  3. Vanadogermanate cluster anions.

    Science.gov (United States)

    Whitfield, T; Wang, X; Jacobson, A J

    2003-06-16

    Three novel vanadogermanate cluster anions have been synthesized by hydrothermal reactions. The cluster anions are derived from the (V(18)O(42)) Keggin cluster shell by substitution of V=O(2+) "caps" by Ge(2)O(OH)(2)(4+) species. In Cs(8)[Ge(4)V(16)O(42)(OH)(4)].4.7H(2)O, 1, (monoclinic, space group C2/c (No. 15), Z = 8, a = 44.513(2) A, b = 12.7632(7) A, c = 22.923(1) A, beta = 101.376(1) degrees ) and (pipH(2))(4)(pipH)(4)[Ge(8)V(14)O(50).(H(2)O)] (pip = C(4)N(2)H(10)), 2 (tetragonal, space group P4(2)/nnm (No. 134), Z = 2, a = 14.9950(7) A, c = 18.408(1) A), two and four VO(2+) caps are replaced, respectively, and each cluster anion encapsulates a water molecule. In K(5)H(8)Ge(8)V(12)SO(52).10H(2)O, 3, (tetragonal, space group I4/m (No. 87), Z = 2, a = 15.573(1) A, c = 10.963(1) A), four VO(2+) caps are replaced by Ge(2)O(OH)(2)(4+) species, and an additional two are omitted. The cluster ion in 3 contains a sulfate anion disordered over two positions. The cluster anions are analogous to the vanadoarsenate anions [V(18)(-)(n)()As(2)(n)()O(42)(X)](m)(-) (X = SO(3), SO(4), Cl; n = 3, 4) previously reported. PMID:12793808

  4. Resonance ionization detection of combustion radicals

    Energy Technology Data Exchange (ETDEWEB)

    Cool, T.A. [Cornell Univ., Ithaca, NY (United States)

    1993-12-01

    Fundamental research on the combustion of halogenated organic compounds with emphasis on reaction pathways leading to the formation of chlorinated aromatic compounds and the development of continuous emission monitoring methods will assist in DOE efforts in the management and disposal of hazardous chemical wastes. Selective laser ionization techniques are used in this laboratory for the measurement of concentration profiles of radical intermediates in the combustion of chlorinated hydrocarbon flames. A new ultrasensitive detection technique, made possible with the advent of tunable VUV laser sources, enables the selective near-threshold photoionization of all radical intermediates in premixed hydrocarbon and chlorinated hydrocarbon flames.

  5. Anion Ordering in Bichalcogenides

    Directory of Open Access Journals (Sweden)

    Martin Valldor

    2016-07-01

    Full Text Available This review contains recent developments and new insights in the research on inorganic, crystalline compounds with two different chalcogenide ions (bichalcogenides. Anion ordering is used as a parameter to form structural dimensionalities as well as local- and global-electric polarities. The reason for the electric polarity is that, in the heterogeneous bichalcogenide lattice, the individual bond-lengths between cations and anions are different from those in a homogeneous anion lattice. It is also shown that heteroleptic tetrahedral and octahedral coordinations offer a multitude of new crystal fields and coordinations for involved cations. This coordination diversity in bichalcogenides seems to be one way to surpass electro-chemical redox potentials: three oxidation states of a single transition metal can be stabilized, e.g., Ba15V12S34O3. A new type of disproportionation, related to coordination, is presented and results from chemical pressure on the bichalcogenide lattices of (La,CeCrS2O, transforming doubly [CrS3/3S2/2O1/1]3− (5+1 into singly [CrS4/2S2/3]7/3− (6+0 and [CrS4/3O2/1]11/3− (4+2 coordinations. Also, magnetic anisotropy is imposed by the anion ordering in BaCoSO, where magnetic interactions via S or O occur along two different crystallographic directions. Further, the potential of the anion lattice is discussed as a parameter for future materials design.

  6. Stability of magnesium ascorbyl phosphate of vitamin C and its dynamics of scavenging superoxide anion radical%维生素C磷酸酯镁的稳定性及其清除超氧离子自由基的动力学

    Institute of Scientific and Technical Information of China (English)

    付思美; 畅芬芬; 车影; 王晓娟; 靳利娥; 阎果兰

    2013-01-01

    维生素C磷酸酯镁(magnesium aseorbyl phosphate,MAP)是维生素C(Vc)的替代品,由于其特有的性质而广泛应用在食品添加剂中.对比测定了MAP和Vc清除超氧阴离子自由基(O2-·)的能力,研究了Vc和MAP在不同温度和不同保存时间后清除O2-·自由基的能力和稳定性;并拟合了不同温度下储存不同时间后MAP的抗氧化能力.结果表明,MAP在20℃下保存20 d对O2-·的清除能力仅减弱20%左右,半衰期为53 d;但Vc在20℃下保存10 d后清除O2-·的能力几乎完全消失.与此同时,不同温度下储存不同时间后MAP清除超氧阴离子自由基的反应为一级反应,采用拟合方程计算的抗氧化能力理论值和实验值基本相符.%Thanks to its peculiar properties, magnesium ascorbyl phosphate (MAP) as a substitute of vitamin C (Vc) is widely used as food additive. This research compares the ability of MAP and Vc to scavenge superoxide anion radical (O2-·). Their ability to scavenge O2- · and their thermal stability were investigated in relation to storage at different temperature for different duration. Furthermore, their anti-oxidation ability was also examined in relation to storage at different temperature for different duration. Results show that the ability of MAP to scavenge O2- · is reduced by only about 20% after it is stored at 20 ℃ for 20 d, and in this case its half-life is 53 d. However, after being stored at 20 ℃ for 10 d, Vc nearly completely loses ability to scavenge O2-·. In the meantime, the reaction for MAP stored at different temperature for different duration to scavenge O2- · can be described with a first order dynamics equation, and its anti oxidation ability calculated based on the simulated equation well conforms to the experimental one.

  7. Perspective: Electrospray photoelectron spectroscopy: From multiply-charged anions to ultracold anions

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Lai-Sheng, E-mail: Lai-Sheng-Wang@brown.edu [Department of Chemistry, Brown University, Providence, Rhode Island 02912 (United States)

    2015-07-28

    Electrospray ionization (ESI) has become an essential tool in chemical physics and physical chemistry for the production of novel molecular ions from solution samples for a variety of spectroscopic experiments. ESI was used to produce free multiply-charged anions (MCAs) for photoelectron spectroscopy (PES) in the late 1990 s, allowing many interesting properties of this class of exotic species to be investigated. Free MCAs are characterized by strong intramolecular Coulomb repulsions, which create a repulsive Coulomb barrier (RCB) for electron emission. The RCB endows many fascinating properties to MCAs, giving rise to meta-stable anions with negative electron binding energies. Recent development in the PES of MCAs includes photoelectron imaging to examine the influence of the RCB on the electron emission dynamics, pump-probe experiments to examine electron tunneling through the RCB, and isomer-specific experiments by coupling PES with ion mobility for biological MCAs. The development of a cryogenically cooled Paul trap has led to much better resolved PE spectra for MCAs by creating vibrationally cold anions from the room temperature ESI source. Recent advances in coupling the cryogenic Paul trap with PE imaging have allowed high-resolution PE spectra to be obtained for singly charged anions produced by ESI. In particular, the observation of dipole-bound excited states has made it possible to conduct vibrational autodetachment spectroscopy and resonant PES, which yield much richer vibrational spectroscopic information for dipolar free radicals than traditional PES.

  8. Perspective: Electrospray photoelectron spectroscopy: From multiply-charged anions to ultracold anions

    International Nuclear Information System (INIS)

    Electrospray ionization (ESI) has become an essential tool in chemical physics and physical chemistry for the production of novel molecular ions from solution samples for a variety of spectroscopic experiments. ESI was used to produce free multiply-charged anions (MCAs) for photoelectron spectroscopy (PES) in the late 1990 s, allowing many interesting properties of this class of exotic species to be investigated. Free MCAs are characterized by strong intramolecular Coulomb repulsions, which create a repulsive Coulomb barrier (RCB) for electron emission. The RCB endows many fascinating properties to MCAs, giving rise to meta-stable anions with negative electron binding energies. Recent development in the PES of MCAs includes photoelectron imaging to examine the influence of the RCB on the electron emission dynamics, pump-probe experiments to examine electron tunneling through the RCB, and isomer-specific experiments by coupling PES with ion mobility for biological MCAs. The development of a cryogenically cooled Paul trap has led to much better resolved PE spectra for MCAs by creating vibrationally cold anions from the room temperature ESI source. Recent advances in coupling the cryogenic Paul trap with PE imaging have allowed high-resolution PE spectra to be obtained for singly charged anions produced by ESI. In particular, the observation of dipole-bound excited states has made it possible to conduct vibrational autodetachment spectroscopy and resonant PES, which yield much richer vibrational spectroscopic information for dipolar free radicals than traditional PES

  9. Antioxidant, Anti-5-lipoxygenase and Antiacetylcholinesterase Activities of Essential Oils and Decoction Waters of Some Aromatic Plants

    Directory of Open Access Journals (Sweden)

    Sílvia M. Albano

    2012-01-01

    Full Text Available The scavenging of free radicals and superoxide anion, the inhibition of 5-lipoxygenase and the antiacetylcholinesterase activities of essential oils and decoction waters of eight aromatic plants (Dittrichia viscosa , Foeniculum vulgare, Origanum vulgare, Salvia officinalis, Thymbra capitata , Thymus camphoratus, Thymus carnosus and Thymus mastichina were studied. The essential oils were dominated by 1,8-cineole in S. officinalis (59%, T. mastichina (49% and T. camphoratus (21%; borneol (20% in T. carnosus; carvacrol in Thymbra capitata (68%; γ -terpinene (49% in O. vulgare; α -pinene (26% in F. vulgare; and trans-nerolidol (8% + β -oplopenone (7% in D. viscosa. O. vulgare decoction waters had the highest amount of phenols (4 5 ± 3 mg GAE/mL while F. vulgare only had 5 ± 0 mg GAE/mL. The decoction waters showed higher radical scavenging activity than the essential oils. O. vulgare decoction water showed the best antioxidant activity (IC 50= 3 ± 0 m g/mL, while the most effective essential oils were those of Thymbra capitata (IC 50=61 ± 2 m g/mL and O. vulgare (IC 50=15 6 ± 5 m g/mL. Thymbra capitata (IC 50= 6 ± 0 m g/mL decoction water showed the best superoxide anion scavenging activity. F. vulgare decoction water and essential oil revealed the best 5-lipoxygenase inhibition capacity (IC 50=2 7 ± 1 m g/mL and IC 50=6 8 ± 2 m g/mL, respectively. T. mastichina (IC 50=4 6 ± 4 m g/mL, S. officinalis (IC 50=5 1 ± 4 m g/mL, Thymbra capitata (IC 50=5 2 ± 1 m g/mL and T. camphoratus (IC 50=13 7 ± 2 m g/mL essential oils showed the best antiacetylcholinesterase activity.

  10. Radicals of DNA and DNA nucleotides generated by ionising radiation

    International Nuclear Information System (INIS)

    A first stage of cell processes leading to DNA damage of initiated by radical reactions. In a model system such transformations were generated by ionising radiation which involves production of electron loss and electron gain centers of the substrate and radical formation. Using cryogenic ESR spectroscopy it was found that the DNA nucleotides, which convert to radical anions upon electron capture undergo the separation of unpaired spin and charge due to protonation. Circular and linear dichroism studies enabled to conclude that iron ions(III) induce strong changes in the DNA helical structure indicating their coordination with nitrogen bases. The repair of DNA radicals produced via radiolytic oxidation, i.e. the guanine radical cation and the allyl type radical of thymine, is possible at elevated temperatures due to the involvement of sulphydryl groups. The influence of the thiol charge is then limited

  11. Radiogenic free radicals as molecular probes in bone

    International Nuclear Information System (INIS)

    Exposure of bone mineral to X-rays generates free radicals. These are usually very labile, but can be stabilized at liquid nitrogen temperatures for study by electron spin resonance spectroscopy. The free radicals thus detected in the present study included one with resonances arising from an electron excess center and 2 species with electron-deficit centers: a phosphate anion radical and a radical associated with carbonate. Each of these radicals seemed to be located chiefly at the mineral surface and was sensitive to the surface environment. Presence of an organic phase, as in whole bone, modified free radical production in a manner that suggests interference with the formation of electron deficit centers. Comparison with other synthetic minerals suggests that precipitated carbonate-apatites are good models for bone mineral. (orig.)

  12. Superconductivity in aromatic hydrocarbons

    International Nuclear Information System (INIS)

    Highlights: • Aromatic superconductor is one of core research subjects in superconductivity. Superconductivity is observed in certain metal-doped aromatic hydrocarbons. Some serious problems to be solved exist for future advancement of the research. This article shows the present status of aromatic superconductors. - Abstract: ‘Aromatic hydrocarbon’ implies an organic molecule that satisfies the (4n + 2) π-electron rule and consists of benzene rings. Doping solid aromatic hydrocarbons with metals provides the superconductivity. The first discovery of such superconductivity was made for K-doped picene (Kxpicene, five benzene rings). Its superconducting transition temperatures (Tc’s) were 7 and 18 K. Recently, we found a new superconducting Kxpicene phase with a Tc as high as 14 K, so we now know that Kxpicene possesses multiple superconducting phases. Besides Kxpicene, we discovered new superconductors such as Rbxpicene and Caxpicene. A most serious problem is that the shielding fraction is ⩽15% for Kxpicene and Rbxpicene, and it is often ∼1% for other superconductors. Such low shielding fractions have made it difficult to determine the crystal structures of superconducting phases. Nevertheless, many research groups have expended a great deal of effort to make high quality hydrocarbon superconductors in the five years since the discovery of hydrocarbon superconductivity. At the present stage, superconductivity is observed in certain metal-doped aromatic hydrocarbons (picene, phenanthrene and dibenzopentacene), but the shielding fraction remains stubbornly low. The highest priority research area is to prepare aromatic superconductors with a high superconducting volume-fraction. Despite these difficulties, aromatic superconductivity is still a core research target and presents interesting and potentially breakthrough challenges, such as the positive pressure dependence of Tc that is clearly observed in some phases of aromatic hydrocarbon superconductors

  13. Isolation, identification and evaluation of natural antioxidants from aromatic herbs cultivated in Lithuania

    OpenAIRE

    Dapkevicius, A.

    2002-01-01

    Oxidative spoilage of lipid-rich foods decreases their shelf-life and leads to undesirable chemical and physical changes. Nowadays natural antioxidants are generally preferred. The major part of industrially used antioxidants consists of radical scavengers, which inhibit the oxidative chain reaction by inactivating free radicals formed during peroxidation of lipids. Aromatic and medicinal herbs are rich sources of natural radical scavenging compounds. The research described in this thesis foc...

  14. An EQCM study for a novel aromatic poly(amine-imide) electrochromic thin film

    Energy Technology Data Exchange (ETDEWEB)

    Yen, Tsui-Ling [Institute of Polymer Science and Engineering, National Taiwan University, Taipei 10617 (China); Lo, Hwa-Chiang [Department of Chemical Engineering, National Taiwan University, Taipei 10617 (China); Material and Chemical Research Laboratories, Industrial Technology Research Institute, Chutung, Hsinchu 310 (China); Liou, Guey-Sheng [Department of Applied Chemistry, National Chi Nan University, Puli, Nantou Hsien 545 (China); Ho, Kuo-Chuan [Institute of Polymer Science and Engineering, National Taiwan University, Taipei 10617 (China); Department of Chemical Engineering, National Taiwan University, Taipei 10617 (China)

    2008-02-15

    A new aromatic poly(amine-imide) electrochromic thin film synthesized with N,N-bis(4-aminophenyl)-N',N'-diphenyl-1,4-phenylenediamine and 3,3',4,4'-benzo-phenonetetra carboxylic dianhydride, abbreviated as poly(PD-BCD), was studied. The poly(PD-BCD) thin-film electrode has been characterized by cyclic voltammetry (CV) and electrochemical quartz crystal microbalance (EQCM). As the polymer chain acquires positive charge during the oxidation of poly(PD-BCD) to its radical cation state or dication state, the anions would insert into the polymer matrix in order to neutralize the charge. However, when the electrodes were cycled in electrolytes containing different cations, including 0.1 M LiClO{sub 4}/acetonitrile (ACN), 0.1 M NaClO{sub 4}/ACN and 0.1 M TBAClO{sub 4}/ACN, the experimental results revealed two mechanisms for the redox reaction. A plot of mass change ({delta}m) vs. accumulated charge (Q) gave a slope, from which the electrochromic mechanism can be extracted. The slopes of {delta}m-Q obtained from the CV-EQCM measurements in three electrolytes were different for the first redox stage, but the slopes were almost the same for the second redox stage. This means that, in addition to the involvement of anions, cations also play an important role in the first redox stage, however, the role of the cations is less in the second stage. Moreover, two reaction mechanisms for the two reaction stages of poly(PD-BCD) are proposed in this study. (author)

  15. Aromatics oxidation and soot formation in flames

    Energy Technology Data Exchange (ETDEWEB)

    Howard, J.B.; Pope, C.J.; Shandross, R.A.; Yadav, T. [Massachusetts Institute of Technology, Cambridge (United States)

    1993-12-01

    This project is concerned with the kinetics and mechanisms of aromatics oxidation and soot and fullerenes formation in flames. The scope includes detailed measurements of profiles of stable and radical species concentrations in low-pressure one-dimensional premixed flames. Intermediate species identifications and mole fractions, fluxes, and net reaction rates calculated from the measured profiles are used to test postulated reaction mechanisms. Particular objectives are to identify and to determine or confirm rate constants for the main benzene oxidation reactions in flames, and to characterize fullerenes and their formation mechanisms and kinetics.

  16. Proton and hydride affinities in excited states: magnitude reversals in proton and hydride affinities between the lowest singlet and triplet states of annulenyl and benzannulenyl anions and cations

    DEFF Research Database (Denmark)

    Rosenberg, Martin; Ottosson, Henrik; Kilså, Kristine

    2010-01-01

    aromatic and those with 4n+2 pi-electrons are antiaromatic, opposite to Huckel's rule for aromaticity in S(0). Our hypothesis is now that the relative magnitudes of proton and hydride affinities of annulenyl anions and cations reverts systematically as one goes from S(0) to T(1) as a result of the opposite...

  17. Block and Graft Copolymers Containing Carboxylate or Phosphonate Anions

    OpenAIRE

    Hu, Nan

    2014-01-01

    This dissertation focuses on synthesis and characterization of graft and block copolymers containing carboxylate or phosphonate anions that are potential candidates for biomedical applications such as drug delivery and dental adhesives. Ammonium bisdiethylphosphonate (meth)acrylate and acrylamide phosphonate monomers were synthesized based on aza-Michael addition reactions. Free radical copolymerizations of these monomers with an acrylate-functional poly(ethylene oxide) (PEO) macromonomer...

  18. Novel Approach for Evaluating Secondary Organic Aerosol from Aromatic Hydrocarbons: SOA Yield and Chemical Composition

    Science.gov (United States)

    Li, Lijie; Tang, Ping; Nakao, Shunsuke; Qi, Li; Kacarab, Mary; Cocker, David

    2016-04-01

    Aromatic hydrocarbons account for 20%-30% of urban atmospheric VOCs and are major contributors to anthropogenic secondary organic aerosol (SOA). However, prediction of SOA from aromatic hydrocarbons as a function of structure, NOx concentration, and OH radical levels remains elusive. Innovative SOA yield and chemical composition evaluation approaches are developed here to investigate SOA formation from aromatic hydrocarbons. SOA yield is redefined in this work by adjusting the molecular weight of all aromatic precursors to the molecular weight of benzene (Yield'= Yieldi×(MWi/MWBenzene); i: aromatic hydrocarbon precursor). Further, SOA elemental ratio is calculated on an aromatic ring basis rather than the classic mole basis. Unified and unique characteristics in SOA formed from aromatic hydrocarbons with different alkyl groups (varying in carbon number and location on aromatic ring) are explored by revisiting fifteen years of UC Riverside/CE-CERT environmental chamber data on 129 experiments from 17 aromatic precursors at urban region relevant low NOx conditions (HC:NO 11.1-171 ppbC:ppb). Traditionally, SOA mass yield of benzene is much greater than that of other aromatic species. However, when adjusting for molecular weight, a similar yield is found across the 17 different aromatic precursors. More importantly, four oxygens per aromatic ring are observed in the resulting SOA regardless of the alkyl substitutes attached to the ring, which majorly affect H/C ratio in SOA. Therefore, resulting SOA bulk composition from aromatic hydrocarbons can be predicted as C6+nH6+2nO4 (n: alkyl substitute carbon number). Further, the dominating role of the aromatic ring carbons is confirmed by studying the chemical composition of SOA formed from the photooxidation of an aromatic hydrocarbon with a 13C isotopically labeled alkyl carbon. Overall, this study unveils the similarity in SOA formation from aromatic hydrocarbons enhancing the understanding of SOA formation from

  19. Muonium addition reactions to aromatic solutes

    International Nuclear Information System (INIS)

    Reaction rate constants of 0.3 to 1.1 x 10sup(10) Msup(-1) ssup(-1) were determined for the reaction of muonium (μsup(+)esup(-),Mu) with seven aromatic solutes in dilute aqueous solution at approximately 295K. The reaction was deduced to be that of addition to the benzene ring to form cyclohexadienyl radicals. On comparison with the analogous H-atom reactions, the kinetic isotope effects were generally about three, equal to the mean thermal velocity ratio of Mu/H. When analyzed through the Hammett equation there were serious discontinuities but a rho value of +0.6 was deduced, not inconsistent with attack by a mildly electron-donating neutral atom forming only free radical intermediates

  20. Electron attachment to fluorocarbon radicals

    Science.gov (United States)

    Shuman, Nicholas

    2014-10-01

    Most plasma environments contain populations of short-lived species such as radicals, the chemistry of which can have significant effects on the overall chemistry of the system. However, few experimental measurements of the kinetics of electron attachment to radicals exist due to the inherent difficulties of working with transient species. Calculations from first principles have been attempted, but are arduous and, because electron attachment is so sensitive to the specifics of the potential surface, their accuracy has not been established. Electron attachment to small fluorocarbon radicals is particularly important, as the data are needed for predictive modeling of plasma etching of semiconductor materials, a key process in the industrial fabrication of microelectronics. We have recently developed a novel flowing afterglow technique to measure several types of otherwise difficult to study plasma processes, including thermal electron attachment to radicals. Variable Electron and Neutral Density Attachment Mass Spectrometry (VENDAMS) exploits dissociative electron attachment in a weakly ionized plasma as a radical source. Here, we apply VENDAMS to a series of halofluorocarbon precursors in order to measure the kinetics of thermal electron attachment to fluorocarbon radicals. Results are presented for CF2, CF3, C2F5,C2F3,1-C3F7, 2-C3F7, and C3F5 from 300 K to 900 K. Both the magnitude and the temperature dependences of rate coefficients as well as product branching between associative and dissociative attachment are highly system specific; however, thermal attachment to all species is inefficient, never exceeding 5% of the collision rate. The data are analyzed using a recently developed kinetic modeling approach, which uses extended Vogt-Wannier theory as a starting point, accounts for dynamic effects such as coupling between the electron and nuclear motions through empirically validated functional forms, and finally uses statistical theory to determine the fate of

  1. Fundamental spectroscopic studies of carbenes and hydrocarbon radicals

    Energy Technology Data Exchange (ETDEWEB)

    Gottlieb, C.A.; Thaddeus, P. [Harvard Univ., Cambridge, MA (United States)

    1993-12-01

    Highly reactive carbenes and carbon-chain radicals are studied at millimeter wavelengths by observing their rotational spectra. The purpose is to provide definitive spectroscopic identification, accurate spectroscopic constants in the lowest vibrational states, and reliable structures of the key intermediates in reactions leading to aromatic hydrocarbons and soot particles in combustion.

  2. Genomic and molecular mechanisms for efficient biodegradation of aromatic dye.

    Science.gov (United States)

    Sun, Su; Xie, Shangxian; Chen, Hu; Cheng, Yanbing; Shi, Yan; Qin, Xing; Dai, Susie Y; Zhang, Xiaoyu; Yuan, Joshua S

    2016-01-25

    Understanding the molecular mechanisms for aromatic compound degradation is crucial for the development of effective bioremediation strategies. We report the discovery of a novel phenomenon for improved degradation of Direct Red 5B azo dye by Irpex lacteus CD2 with lignin as a co-substrate. Transcriptomics analysis was performed to elucidate the molecular mechanisms of aromatic degradation in white rot fungus by comparing dye, lignin, and dye/lignin combined treatments. A full spectrum of lignin degradation peroxidases, oxidases, radical producing enzymes, and other relevant components were up-regulated under DR5B and lignin treatments. Lignin induced genes complemented the DR5B induced genes to provide essential enzymes and redox conditions for aromatic compound degradation. The transcriptomics analysis was further verified by manganese peroxidase (MnP) protein over-expression, as revealed by proteomics, dye decolorization assay by purified MnP and increased hydroxyl radical levels, as indicated by an iron reducing activity assay. Overall, the molecular and genomic mechanisms indicated that effective aromatic polymer degradation requires synergistic enzymes and radical-mediated oxidative reactions to form an effective network of chemical processes. This study will help to guide the development of effective bioremediation and biomass degradation strategies. PMID:26476316

  3. Glutathione--hydroxyl radical interaction: a theoretical study on radical recognition process.

    Directory of Open Access Journals (Sweden)

    Béla Fiser

    Full Text Available Non-reactive, comparative (2 × 1.2 μs molecular dynamics simulations were carried out to characterize the interactions between glutathione (GSH, host molecule and hydroxyl radical (OH(•, guest molecule. From this analysis, two distinct steps were identified in the recognition process of hydroxyl radical by glutathione: catching and steering, based on the interactions between the host-guest molecules. Over 78% of all interactions are related to the catching mechanism via complex formation between anionic carboxyl groups and the OH radical, hence both terminal residues of GSH serve as recognition sites. The glycine residue has an additional role in the recognition of OH radical, namely the steering. The flexibility of the Gly residue enables the formation of further interactions of other parts of glutathione (e.g. thiol, α- and β-carbons with the lone electron pair of the hydroxyl radical. Moreover, quantum chemical calculations were carried out on selected GSH/OH(• complexes and on appropriate GSH conformers to describe the energy profile of the recognition process. The relative enthalpy and the free energy changes of the radical recognition of the strongest complexes varied from -42.4 to -27.8 kJ/mol and from -21.3 to 9.8 kJ/mol, respectively. These complexes, containing two or more intermolecular interactions, would be the starting configurations for the hydrogen atom migration to quench the hydroxyl radical via different reaction channels.

  4. Radical scavenging ability of some compounds isolated from Piper cubeba towards free radicals.

    Science.gov (United States)

    Aboul-Enein, Hassan Y; Kładna, Aleksandra; Kruk, Irena

    2011-01-01

    The purpose of this study was to identify the antioxidant activity of 16 compounds isolated from Piper cubeba (CNCs) through the extent of their capacities to scavenge free radicals, hydroxyl radical (HO(•)), superoxide anion radical O•(2)(-) and 2,2-diphenyl-1-picrylhydrazyl radical (DPPH(•)), in different systems. Electron paramagnetic resonance (EPR) and 5,5-dimethyl-1-pyrroline-N-oxide, DMPO, as the spin trap, and chemiluminescence techniques were applied. Using the Fenton-like reaction [Fe(II) + H(2)O(2)], CNCs were found to inhibit DMPO-OH radical formation ranging from 5 to 57% at 1.25 mmol L(-1) concentration. The examined CNCs also showed a high DPPH antiradical activity (ranging from 15 to 99% at 5 mmol L(-1) concentration). Furthermore, the results indicated that seven of the 16 tested compounds may catalyse the conversion of superoxide radicals generated in the potassium superoxide/18-crown-6 ether system, thus showing superoxide dismutase-like activity. The data obtained suggest that radical scavenging properties of CNCs might have potential application in many plant medicines. PMID:21681910

  5. Resonant spectra of quadrupolar anions

    CERN Document Server

    Fossez, K; Nazarewicz, W; Michel, N; Garrett, W R; Płoszajczak, M

    2016-01-01

    In quadrupole-bound anions, an extra electron is attached at a sufficiently large quadrupole moment of a neutral molecule, which is lacking a permanent dipole moment. The nature of the bound states and low-lying resonances of such anions is of interest for understanding the threshold behavior of open quantum systems in general. In this work, we investigate the properties of quadrupolar anions as extreme halo systems, the formation of rotational bands, and the transition from a subcritical to supercritical electric quadrupole moment. We solve the electron-plus-molecule problem using a non-adiabatic coupled-channel formalism by employing the Berggren ensemble, which explicitly contains bound states, narrow resonances, and the scattering continuum. We demonstrate that binding energies and radii of quadrupolar anions strictly follow the scaling laws for two-body halo systems. Contrary to the case of dipolar anions, ground-state band of quadrupolar anions smoothly extend into the continuum, and many rotational ban...

  6. Aromatic rings in chemical and biological recognition: energetics and structures.

    Science.gov (United States)

    Salonen, Laura M; Ellermann, Manuel; Diederich, François

    2011-05-16

    This review describes a multidimensional treatment of molecular recognition phenomena involving aromatic rings in chemical and biological systems. It summarizes new results reported since the appearance of an earlier review in 2003 in host-guest chemistry, biological affinity assays and biostructural analysis, data base mining in the Cambridge Structural Database (CSD) and the Protein Data Bank (PDB), and advanced computational studies. Topics addressed are arene-arene, perfluoroarene-arene, S⋅⋅⋅aromatic, cation-π, and anion-π interactions, as well as hydrogen bonding to π systems. The generated knowledge benefits, in particular, structure-based hit-to-lead development and lead optimization both in the pharmaceutical and in the crop protection industry. It equally facilitates the development of new advanced materials and supramolecular systems, and should inspire further utilization of interactions with aromatic rings to control the stereochemical outcome of synthetic transformations. PMID:21538733

  7. Bound anionic states of adenine

    OpenAIRE

    Harańczyk, Maciej; Gutowski, Maciej; Li, Xiang; Bowen, Kit H.

    2007-01-01

    Anionic states of nucleic acid bases are involved in DNA damage by low-energy electrons and in charge transfer through DNA. Previous gas phase studies of free, unsolvated nucleic acid base parent anions probed only dipole-bound states, which are not present in condensed phase environments, but did not observe valence anionic states, which for purine bases are thought to be adiabatically unbound. Contrary to this expectation, we have demonstrated that some thus far ignored tautomers of adenine...

  8. Reaction of alcohol radicals with cyclic disulfides. An optical and conductimetric pulse radiolysis study

    Science.gov (United States)

    Anderson, Robert F.; Vojnovic, Borivoj; Patel, Kantilal B.; Michael, Barry D.

    The disulfides lipoamide (LIPA) and oxidized dithiothreitol ( ox-DTT) react with methanol, ethanol, isopropanol and t-butanol radicals in aqueous solution at pH10.8 to form disulfide radical anions. Electron transfer rates range from ca 10 7 dm 3 mol -1s -1 for t-butanol radicals with LIPA to 3.6 × 10 8 dm 3 mol -1s -1 for methanol radicals with LIPA. The formations of the disulfide radical anions were followed by simultaneously monitoring absorption changes at 400 nm and changes in conductance with time. The electron transfer efficiencies are higher for LIPA than for ox-DTT increasing in the series t-butanol ≪isopropanol radical formation on the alcohols.

  9. Reaction of alcohol radicals with cyclic disulfides, an optical and conductimetric pulse radiolysis study

    International Nuclear Information System (INIS)

    The disulfides lipoamide (LIPA) and oxidized dithiothreitol (ox-DTT) react with methanol, ethanol, isopropanol and t-butanol radicals in aqueous solution at pH 10.8 to form disulfide radical anions. Electron transfer rates range from ca 107dm3mol-1s-1 for t-butanol radicals with LIPA to 3.6 x 108 dm3mol-1s-1 for methanol radicals with LIPA. The formations of the disulfide radical anions were followed by simultaneously monitoring absorption changes at 400 nm and changes in conductance with time. The electron transfer efficiencies are higher for LIPA than for ox-DTT increasing in the series t-butanol << isopropanol < ethanol appro. methanol and are less than the proportion of α-carbon radical formation on the alcohols. (author)

  10. Reaction of alcohol radicals with cyclic disulfides, an optical and conductimetric pulse radiolysis study

    Energy Technology Data Exchange (ETDEWEB)

    Anderson, R.F.; Vojnovic, B.; Patel, K.B.; Michael, B.D.

    1986-01-01

    The disulfides lipoamide (LIPA) and oxidized dithiothreitol (ox-DTT) react with methanol, ethanol, isopropanol and t-butanol radicals in aqueous solution at pH 10.8 to form disulfide radical anions. Electron transfer rates range from ca 10/sup 7/dm/sup 3/mol/sup -1/s/sup -1/ for t-butanol radicals with LIPA to 3.6 x 10/sup 8/ dm/sup 3/mol/sup -1/s/sup -1/ for methanol radicals with LIPA. The formations of the disulfide radical anions were followed by simultaneously monitoring absorption changes at 400 nm and changes in conductance with time. The electron transfer efficiencies are higher for LIPA than for ox-DTT increasing in the series t-butanol <radical formation on the alcohols.

  11. Transients and stable radical from the deamination of α-alanine

    International Nuclear Information System (INIS)

    The objects of investigation were single crystals of L-α-alanine, in which radical anion CH3 C·H CO2- has been formed by radiation induced deamination of alanine. Previously, this stable radical has been spectrally identified (λmax=350 nm, ε=1100 M-1 x cm-1), and its characteristics have found to be identical with characteristics of the same radical obtained by pulse radiolysis in aqueous solution. The mechanism of radical formation in the solid state is not known. Time resolved pulse radiolysis of single crystal alanine has shown more complicated way of the formation of the same radical in solid state than in aqueous solution. The electrons abstracted from the solid alanine molecule neutralise positive the charge of zwitter-ion alanine. Ammonia is leaving the reaction-complex in time of milliseconds, leaving the stable radical anion. (author)

  12. Pressure Effects on Product Channels of Hydrocarbon Radical-Radical Reactions; Implications for Modelling of Planetary Atmospheres

    Science.gov (United States)

    Fahr, A.; Halpern, J.; N'doumi, M.

    2011-10-01

    Previously we had studied the kinetics and product channels of small unsaturated hydrocarbon radical (C2 and C3s) reactions relevant to planetary atmospheric modelling. Reactions of C2 radicals (such as vinyl, H2CCH and ethynyl C2H) and C3 radicals (such as propargyl, HCCCH2 and allyl, H2CCCH3) can affect the abundances of a large number of stable observable C3, C4, C5, C6 and larger molecules, including linear, aromatic and even poly aromatic molecules. We have experimentally determined pressuredependent product yields for self- and cross-radical reactions performed at 298 K and at selected pressures between ~4 Torr (0.5 kPa) and 760 Torr (101 kPa). Final products were determined by gas chromatograph with mass spectrometry/flame ionization detection (GC/MS/FID). In some cases complementary computational studies extended the pressure and temperature range of the observations and provided valuable information on complex reaction mechanisms. These studies provide a systematic framework so that important energetic and structural parameters for radical-radical reactions can be assessed. Here we report a compilation of our earlier results relevant to planetary atmospheres in addition to recent ones for allyl radical (H2CCCH3) reactions.

  13. Superconductivity in aromatic hydrocarbons

    Energy Technology Data Exchange (ETDEWEB)

    Kubozono, Yoshihiro, E-mail: kubozono@cc.okayama-u.ac.jp [Research Laboratory for Surface Science, Okayama University, Okayama 700-8530 (Japan); Research Center of New Functional Materials for Energy Production, Storage and Transport, Okayama University, Okayama 700-8530 (Japan); Japan Science and Technology Agency, ACT-C, Kawaguchi 332-0012 (Japan); Goto, Hidenori; Jabuchi, Taihei [Research Laboratory for Surface Science, Okayama University, Okayama 700-8530 (Japan); Yokoya, Takayoshi [Research Laboratory for Surface Science, Okayama University, Okayama 700-8530 (Japan); Research Center of New Functional Materials for Energy Production, Storage and Transport, Okayama University, Okayama 700-8530 (Japan); Kambe, Takashi [Department of Physics, Okayama University, Okayama 700-8530 (Japan); Sakai, Yusuke; Izumi, Masanari; Zheng, Lu; Hamao, Shino; Nguyen, Huyen L.T. [Research Laboratory for Surface Science, Okayama University, Okayama 700-8530 (Japan); Sakata, Masafumi; Kagayama, Tomoko; Shimizu, Katsuya [Center of Science and Technology under Extreme Conditions, Osaka University, Osaka 560-8531 (Japan)

    2015-07-15

    Highlights: • Aromatic superconductor is one of core research subjects in superconductivity. Superconductivity is observed in certain metal-doped aromatic hydrocarbons. Some serious problems to be solved exist for future advancement of the research. This article shows the present status of aromatic superconductors. - Abstract: ‘Aromatic hydrocarbon’ implies an organic molecule that satisfies the (4n + 2) π-electron rule and consists of benzene rings. Doping solid aromatic hydrocarbons with metals provides the superconductivity. The first discovery of such superconductivity was made for K-doped picene (K{sub x}picene, five benzene rings). Its superconducting transition temperatures (T{sub c}’s) were 7 and 18 K. Recently, we found a new superconducting K{sub x}picene phase with a T{sub c} as high as 14 K, so we now know that K{sub x}picene possesses multiple superconducting phases. Besides K{sub x}picene, we discovered new superconductors such as Rb{sub x}picene and Ca{sub x}picene. A most serious problem is that the shielding fraction is ⩽15% for K{sub x}picene and Rb{sub x}picene, and it is often ∼1% for other superconductors. Such low shielding fractions have made it difficult to determine the crystal structures of superconducting phases. Nevertheless, many research groups have expended a great deal of effort to make high quality hydrocarbon superconductors in the five years since the discovery of hydrocarbon superconductivity. At the present stage, superconductivity is observed in certain metal-doped aromatic hydrocarbons (picene, phenanthrene and dibenzopentacene), but the shielding fraction remains stubbornly low. The highest priority research area is to prepare aromatic superconductors with a high superconducting volume-fraction. Despite these difficulties, aromatic superconductivity is still a core research target and presents interesting and potentially breakthrough challenges, such as the positive pressure dependence of T{sub c} that is clearly

  14. Radical prostatectomy - discharge

    Science.gov (United States)

    ... prostatectomy - discharge; Laparoscopic radical prostatectomy - discharge; LRP - discharge; Robotic-assisted laparoscopic prostatectomy - discharge ; RALP - discharge; Pelvic lymphadenectomy - ...

  15. Synthesis of water-soluble cystine C60 derivative with catalyst and its active oxygen radical scavenging ability

    Institute of Scientific and Technical Information of China (English)

    Wen Chao Guan; Xiang Ying Tang; Li Zhen Huang; Hong Xu

    2007-01-01

    A novel water-soluble cystine C60 derivative was synthesized in the presence of the catalyst, tetrabutylammonium hydroxide (TBAH). The product was characterized by FT-IR, UV, 1H NMR, 13C NMR, MS and elemental analysis. Furthermore, the that cystine C60 derivative showed an excellent efficiency in eliminating superoxygen anion radical and hydroxyl radical. The 50%inhibition concentration (IC50) for superoxygen anion radical and hydroxyl radical were 0.167 and 0.008 mg/mL, respectively.

  16. Porating anion-responsive copolymeric gels.

    Science.gov (United States)

    England, Dustin; Yan, Feng; Texter, John

    2013-09-24

    A polymerizable ionic liquid surfactant, 1-(11-acryloyloxyundecyl)-3-methylimidiazolium bromide (ILBr), was copolymerized with methyl methacrylate (MMA) in aqueous microemulsions at 30% (ILBr w/w) and various water to MMA ratios. The ternary phase diagram of the ILBr/MMA/water system was constructed at 25 and 60 °C. Homopolymers and copolymers of ILBr and MMA were produced by thermally initiated chain radical microemulsion polymerization at various compositions in bicontinuous and reverse microemulsion subdomains. Microemulsion polymerization reaction products varied from being gel-like to solid, and these materials were analyzed by thermal and scanning electron microscopy methods. Microemulsion polymerized materials were insoluble in all solvents tested, consistent with light cross-linking. Ion exchange between Br(-) and PF6(-) in these copolymeric materials resulted in the formation of open-cell porous structures in some of these materials, as was confirmed by scanning electron microscopy (SEM). Several compositions illustrate the capture of prepolymerization nanoscale structure by thermally initiated polymerization, expanding the domain of compositions exhibiting this feat and yet to be demonstrated in any other system. Regular cylindrical pores in interpenetrating ILBr-co-MMA and PMMA networks are produced by anion exchange in the absence of templates. A percolating cluster/bicontinuous transition is "captured" by SEM after using anion exchange to visualize the mixed cluster/pore morphology. Some design principles for achieving this capture and for obtaining stimuli responsive solvogels are articulated, and the importance of producing solvogels in capturing the nanoscale is highlighted. PMID:23968242

  17. Radical theory of rings

    CERN Document Server

    Gardner, JW

    2003-01-01

    Radical Theory of Rings distills the most noteworthy present-day theoretical topics, gives a unified account of the classical structure theorems for rings, and deepens understanding of key aspects of ring theory via ring and radical constructions. Assimilating radical theory's evolution in the decades since the last major work on rings and radicals was published, the authors deal with some distinctive features of the radical theory of nonassociative rings, associative rings with involution, and near-rings. Written in clear algebraic terms by globally acknowledged authorities, the presentation

  18. On the Importance of Water Molecules in the Theoretical Study of Polyphenols Reactivity toward Superoxide Anion

    Directory of Open Access Journals (Sweden)

    Laure Lespade

    2014-01-01

    Full Text Available Numerous studies have shown the benefits of a diet rich in fruits and vegetables. These benefits are partly due to the radical scavenging properties of polyphenols contained in fruits and vegetables since polyphenols can fight against an excess of radicals which goes along inflammation in a certain number of diseases. This pathological state, called oxidative stress, results from the aerobic condition of human organism when OH radical, hydrogen peroxide, superoxide anion, or peroxynitrite is produced in excess. If hydrogen peroxide is easily handled by human defense against radicals, the other radicals can cause damage to biological constituents like lipids, cell membranes, and other biomolecules. This paper is devoted to the theoretical study of the interaction of superoxide anion (O2•- with a very potent radical scavenger, 1,2,4,6,8-pentahydroxynaphthalene. The importance of hydration of superoxide radical for the reactivity is analyzed. Potential energy surfaces (PES are calculated for different number of water molecules around the radical and it is shown that the transition barrier vanishes when complete hydration with six water molecules is explicitly handled. The nature of the reactivity is determined by using the natural bond orbital (NBO analysis.

  19. Free radical scavenging abilities of polypeptide from Chlamys farreri

    Institute of Scientific and Technical Information of China (English)

    HAN Zhiwu; CHU Xiao; LIU Chengjuan; WANG Yuejun; SUN Mi; WANG Chunbo

    2006-01-01

    We investigated the radical scavenging effect and antioxidation property of polypeptide extracted from Chlamys farreri (PCF) in vitro using chemiluminescence and electron spin resonance (ESR) methods. We examined the scavenging effects of PCF on superoxide anions (O-2), hydroxyl radicals (OH·), peroxynitrite (ONOO-) and the inhibiting capacity of PCF on peroxidation of linoleic acid. Our experiment suggested that PCF could scavenge oxygen free radicals including superoxide anions (O-2) (IC50 =0.3 mg/ml), hydroxyl radicals (OH·) (IC50 = 0.2 μg/ml) generated from the reaction systems and effectively inhibit the oxidative activity of ONOO- (IC50 = 0.2 mg/ml). At 1.25 mg/ml of PCF, the inhibition ratio on lipid peroxidation of linoleic acid was 43 %. The scavenging effect of PCF on (O-2), OH·and ONOO- free radicals were stronger than those of vitamin C but less on lipid peroxidation of linoleic acid. Thus PCF could scavenge free radicals and inhibit the peroxidation of linoleic acid in vitro. It is an antioxidant from marine products and potential for industrial production in future.

  20. Chemical Modeling of Cometary Anions

    Science.gov (United States)

    Cordiner, Martin; Charnley, S. B.

    2009-09-01

    The presence of negative ions (anions) in cometary comae is known from Giotto mass spectrometry of 1P/Halley. The anions O-, OH-, C-, CH- and CN- have been detected, as well as unidentified anions with masses 22-65 and 85-110 amu (Chaizy et al. 1991). Organic molecular anions are known to have a significant impact on the charge balance of interstellar clouds and circumstellar envelopes and have been shown to act as catalysts for the gas-phase synthesis of larger hydrocarbon molecules in the ISM, but their importance in cometary comae has not previously been explored. We present details of the first attempt to model the chemistry of anions in cometary comae. Based on the combined chemical and hydrodynamical model of Rodgers & Charnley (2002), we investigate the role of the hydrocarbon and nitrile anions Cn-, CnH- and CnN- in the coma. We calculate the effects of these anions on the charge balance and examine their impact on cometary coma chemistry. References: Chaizy, P. et al. 1991, Nature, 349, 393 Rodgers, S.D. & Charnley, S.B. 2002, MNRAS, 330, 660

  1. Supramolecular chemistry: from aromatic foldamers to solution-phase supramolecular organic frameworks.

    Science.gov (United States)

    Li, Zhan-Ting

    2015-01-01

    This mini-review covers the growth, education, career, and research activities of the author. In particular, the developments of various folded, helical and extended secondary structures from aromatic backbones driven by different noncovalent forces (including hydrogen bonding, donor-acceptor, solvophobicity, and dimerization of conjugated radical cations) and solution-phase supramolecular organic frameworks driven by hydrophobically initiated aromatic stacking in the cavity of cucurbit[8]uril (CB[8]) are highlighted. PMID:26664626

  2. Phosphazene-promoted anionic polymerization

    KAUST Repository

    Zhao, Junpeng

    2014-01-01

    In the recent surge of metal-free polymerization techniques, phosphazene bases have shown their remarkable potential as organic promoters/catalysts for the anionic polymerization of various types of monomers. By complexation with the counterion (e.g. proton or lithium cation), phosphazene base significantly improve the nucleophilicity of the initiator/chain-end resulting in rapid and usually controlled anionic/quasi-anionic polymerization. In this review, we will introduce the general mechanism, i.e. in situ activation (of initiating sites) and polymerization, and summarize the applications of such a mechanism on macromolecular engineering toward functionalized polymers, block copolymers and complex macromolecular architectures.

  3. Charge-transfer-directed radical substitution enables para-selective C–H functionalization

    Science.gov (United States)

    Boursalian, Gregory B.; Ham, Won Seok; Mazzotti, Anthony R.; Ritter, Tobias

    2016-08-01

    Efficient C–H functionalization requires selectivity for specific C–H bonds. Progress has been made for directed aromatic substitution reactions to achieve ortho and meta selectivity, but a general strategy for para-selective C–H functionalization has remained elusive. Herein we introduce a previously unappreciated concept that enables nearly complete para selectivity. We propose that radicals with high electron affinity elicit arene-to-radical charge transfer in the transition state of radical addition, which is the factor primarily responsible for high positional selectivity. We demonstrate with a simple theoretical tool that the selectivity is predictable and show the utility of the concept through a direct synthesis of aryl piperazines. Our results contradict the notion, widely held by organic chemists, that radical aromatic substitution reactions are inherently unselective. The concept of radical substitution directed by charge transfer could serve as the basis for the development of new, highly selective C–H functionalization reactions.

  4. Titanium dioxide induced cell damage: A proposed role of the carboxyl radical

    Energy Technology Data Exchange (ETDEWEB)

    Dodd, Nicholas J.F. [Ecotoxicology and Stress Biology Research Centre, School of Biological Sciences, University of Plymouth, Drake Circus, Plymouth PL4 8AA (United Kingdom); Jha, Awadhesh N. [Ecotoxicology and Stress Biology Research Centre, School of Biological Sciences, University of Plymouth, Drake Circus, Plymouth PL4 8AA (United Kingdom)], E-mail: a.jha@plymouth.ac.uk

    2009-01-15

    Titanium dioxide (TiO{sub 2}) nanoparticles have been shown to be genotoxic to cells exposed to ultraviolet A (UVA) radiation. Using the technique of electron spin resonance (ESR) spin trapping, we have confirmed that the primary damaging species produced on irradiation of TiO{sub 2} nanoparticles is the hydroxyl (OH) radical. We have applied this technique to TiO{sub 2}-treated fish and mammalian cells under in vitro conditions and observed the additional formation of carboxyl radical anions (CO{sub 2}{sup -}) and superoxide radical anions (O{sub 2}{sup -}). This novel finding suggests a hitherto unreported pathway for damage, involving primary generation of OH radicals in the cytoplasm, which react to give CO{sub 2}{sup -} radicals. The latter may then react with cellular oxygen to form O{sub 2}{sup -} and genotoxic hydrogen peroxide (H{sub 2}O{sub 2})

  5. Laparoscopic radical cystectomy

    OpenAIRE

    Fergany, Amr

    2012-01-01

    Objective Laparoscopic radical cystectomy (LRC) has emerged as a minimally invasive alternative to open radical cystectomy (ORC). This review focuses on patient selection criteria, technical aspects and postoperative outcomes of LRC. Methods Material for the review was obtained by a PubMed search over the last 10 years, using the keywords ‘laparoscopic radical cystectomy’ and ‘laparoscopic bladder cancer’ in human subjects. Results Twenty-two publications selected for relevance and content we...

  6. Laparoscopic Radical Trachelectomy

    OpenAIRE

    Rendón, Gabriel J.; Ramirez, Pedro T.; Frumovitz, Michael; Schmeler, Kathleen M.; Pareja, Rene

    2012-01-01

    Introduction: The standard treatment for patients with early-stage cervical cancer has been radical hysterectomy. However, for women interested in future fertility, radical trachelectomy is now considered a safe and feasible option. The use of minimally invasive surgical techniques to perform this procedure has recently been reported. Case Description: We report the first case of a laparoscopic radical trachelectomy performed in a developing country. The patient is a nulligravid, 30-y-old fem...

  7. A KINETIC ANAYSIS OF THE DEGRADATION OF GRAFTED ANIONIC POLYACRYLAMIDE GEL UNDER NONISOTHERMAL CONDITION

    OpenAIRE

    AYMAN ABO JABAL; Tan, Isa M.; ZAKARIA MAN; SAIKAT MAITRA

    2009-01-01

    Grafted anionic polyacrylamide gel has been synthesised in the laboratory following radical polymerisation process. Kinetics of thermal degradation of synthesised gel was evaluated under nonisthothermal condition by integral approximation method to determine the thermal stability of the material from thermogavometric study. The activation energy for the thermal degradation was found to be significantly high for the gel material.

  8. Preparation of the Cyclopentazole Anion in the Bulk: A Computational Study.

    Science.gov (United States)

    Geiger, Uzi; Haas, Yehuda

    2016-07-01

    The cyclopentazole anion (cyclo-N5(-)), calculated to be a stable species, was prepared in the gas phase but attempts to synthesize it in the bulk have so far been futile. An aryl pentazole radical anion was suggested as a promising precursor in the gas phase. It is shown computationally that the radical anion (which may be prepared by reduction of the phenyl pentazole neutral) may indeed be used to form the cyclopetazolate anion in the gas phase and in liquid solution, alongside and in competition with the extrusion of N2 to produce the corresponding azide. In the gas phase, the C-N dissociation yields are very low due to much more efficient detachment of an electron. In polar solvents, ionization is suppressed and the primary yields of the two competing reactions are similar. The reaction must be carried out at low temperatures and special measures have to be taken to avoid recombination of the nascent cyclo-N5(-) with the geminate phenyl radical. A possible remedy is to use a solvent that reacts efficiently with the phenyl radical by H atom transfer. PMID:27028051

  9. Anion Transport with Chalcogen Bonds.

    Science.gov (United States)

    Benz, Sebastian; Macchione, Mariano; Verolet, Quentin; Mareda, Jiri; Sakai, Naomi; Matile, Stefan

    2016-07-27

    In this report, we introduce synthetic anion transporters that operate with chalcogen bonds. Electron-deficient dithieno[3,2-b;2',3'-d]thiophenes (DTTs) are identified as ideal to bind anions in the focal point of the σ holes on the cofacial endocyclic sulfur atoms. Anion binding in solution and anion transport across lipid bilayers are found to increase with the depth of the σ holes of the DTT anionophores. These results introduce DTTs and related architectures as a privileged motif to engineer chalcogen bonds into functional systems, complementary in scope to classics such as 2,2'-bipyrroles or 2,2'-bipyridines that operate with hydrogen bonds and lone pairs, respectively. PMID:27433964

  10. Free radical formation in crystals of guanine hydrochloride dihydrate: an ESR and ENDOR study

    International Nuclear Information System (INIS)

    Radiation-induced free radical formation in single crystals of guanine hydrochloride dihydrate has been studied at temperatures between 20 and 300 K using ESR and ENDOR spectroscopy. At low temperatures three radical species are trapped. Two of these are the C8 H-addition radical R1 previously analysed by Alexander and Gordy (1967) and the O6-protonated anion radical R2. The third species (R4) remains unidentified. Upon annealing at 280 K for an extended period the protonated anion R2 transforms into a new radical R3 which exhibits a well-defined hyperfine pattern but still could not be identified unambiguously. Also radical R4 probably transforms into a new radical (R5) upon such treatment. One proton coupling due to R5 was detected. A scheme of radical reactions incorporating these five radicals is proposed. This scheme also suggests that differences in radical formation between the monohydrate and dihydrate crystals of guanine hydrochloride depends upon differences in the hydrogen bonding network. (author)

  11. Properties of the radicals formed by one-electron oxidation of acetaminophen - a pulse radiolysis study

    International Nuclear Information System (INIS)

    The semi-iminoquinone radical of acetaminophen, which has previously been proposed as a possible hepatotoxic intermediate in the cytochrome P-450 catalysed oxidation of acetaminophen, has been generated and studied by pulse radiolysis. In the absence of other reactive solutes, the radical decays rapidly by second order kinetics with a rate constant (2k2) of (2.2 ± 0.4) x 109 M-1 sec-1. In alkaline solutions the radical deprotonates with a pK of 11.1 ± 0.1 to form a radical-anion. The acetaminophen radical-anion reacts with resorcinol at high pH values, leading to the formation of a transient equilibrium from which the one-electron reduction potential of the semi-iminoquinone radical of acetaminophen is estimated to be + 0.707 ± 0.01 V at pH 7. This value predicts that acetaminophen should be oxidised by thiyl radicals. This was confirmed by pulse radiolysis experiments for reaction of the cysteinyl radical, for which rate constants of 7 x 106 M-1 sec-1 at pH7 and 2.7 x 108 M-1 sec-1 at pH 11.3 were obtained. The reaction of O2 with the acetaminophen semi-iminoquinone radical could not be detected by pulse radiolysis, and alternative mechanisms for superoxide radical formation are discussed. (author)

  12. Organic magnetic diradicals (radical-coupler-radical): standardization of couplers for strong ferromagnetism.

    Science.gov (United States)

    Cho, Daeheum; Ko, Kyoung Chul; Lee, Jin Yong

    2014-07-10

    The intramolecular magnetic coupling constant (J) values of sets of diradicals linked to bis-DTDA, OVER, and NN radicals (DTDA, OVER, and NN groups) through an aromatic coupler were studied by unrestricted density functional theory calculations (UB3LYP/6-311++G(d,p)). Among 15 aromatic couplers, 9 compounds with an odd number of carbon atoms along its spin coupling path were found to interact ferromagnetically upon coupling with bisradicals while the other 6 couplers with an even number of carbon atoms along its spin coupling path give rise to antiferromagnetic coupling. The overall trends in the strength of magnetic interactions of aromatic couplers were preserved for DTDA, OVER, and NN groups so that the trend can be utilized as an index for the magnetic strength of a given coupler. It was found that the differences in the nucleus-independent chemical shift (NICS), bond order of connecting bonds, and Mulliken atomic spin density at connected atoms between triplet and BS states are closely related to the intramolecular magnetic behavior. 2,4- and 2,5-phosphole couplers exhibit the strongest intramolecular ferromagnetic and antiferromagnetic interactions among 15 aromatic couplers when linked to diverse bisradicals. PMID:24936749

  13. (Hetero)aromatics from dienynes, enediynes and enyne-allenes.

    Science.gov (United States)

    Raviola, Carlotta; Protti, Stefano; Ravelli, Davide; Fagnoni, Maurizio

    2016-08-01

    The construction of aromatic rings has become a key objective for organic chemists. While several strategies have been developed for the functionalization of pre-formed aromatic rings, the direct construction of an aromatic core starting from polyunsaturated systems is yet a less explored field. The potential of such reactions in the formation of aromatics increased at a regular pace in the last few years. Nowadays, there are reliable and well-established procedures to prepare polyenic derivatives, such as dienynes, enediynes, enyne-allenes and hetero-analogues. This has stimulated their use in the development of innovative cycloaromatizations. Different examples have recently emerged, suggesting large potential of this strategy in the preparation of (hetero)aromatics. Accordingly, this review highlights the recent advancements in this field and describes the different conditions exploited to trigger the process, including thermal and photochemical activation, as well as the use of transition metal catalysis and the addition of electrophiles/nucleophiles or radical species. PMID:27263976

  14. COSMO-RS based predictions for the desulphurization of diesel oil using ionic liquids: Effect of cation and anion combination

    Energy Technology Data Exchange (ETDEWEB)

    Anantharaj, R.; Banerjee, Tamal [Department of Chemical Engineering, Indian Institute of Technology Guwahati, Guwahati, Assam (India)

    2011-01-15

    Ionic Liquids ILs provide an important alternative in removing aromatic sulphur compounds by Liquid-Liquid Extraction (LLE). A total of 28 anions and 6 cations resulting in 168 possible combinations were screened via COSMO-RS (COnductor Like Screening MOdel for Real Solvents). Initially benchmarking was performed to predict the infinite dilution activity coefficients of thiophene in ionic liquids. Comparison with literature values involving 8 ILs with 20 points gave the average root mean square deviation (RMS) to be 11%. Thereafter artificial simulated diesel, aromatic sulphur compound and the cation and anion combination was used to predict the capacity (C) and selectivity (S) at infinite dilution. In general the selectivities were found to decrease in the following order: thiophene (4-24) > benzothiophene (2-12)> dibenzothiophene (1-7). The different hetero atom (N,S,O) and its location in the cation structure strongly influenced the selectivity and capacity at infinite dilution for all the three aromatic sulphur compounds. It was found that the cation without the aromatic ring combined with anions having sterical shielding effect such as [SCN], [CH{sub 3}SO{sub 3}], [CH{sub 3}COO], [Cl], and [Br] proved to be the most favourable IL for desulphurization. [EMMOR][SCN] proved to be the most viable IL for the removal of all the three aromatic sulphur compounds. (author)

  15. Efficient scavenging of β-carotene radical cations by antiinflammatory salicylates

    DEFF Research Database (Denmark)

    Cheng, Hong; Liang, Ran; Han, Rui-Min;

    2014-01-01

    by the anion of salicylic acid with 2.2 × 10 L mol s, but still of possible importance for light-exposed tissue. Surprisingly, acetylsalicylate, the aspirin anion, reacts with an intermediate rate in a reaction assigned to the anion of the mixed acetic-salicylic acid anhydride formed through base induced......The radical cation generated during photobleaching of β-carotene is scavenged efficiently by the anion of methyl salicylate from wintergreen oil in a second-order reaction approaching the diffusion limit with k = 3.2 × 10 L mol s in 9:1 v/v chloroform-methanol at 23 °C, less efficiently...... rearrangements. The relative scavenging rate of the β-carotene radical cation by the three salicylates is supported by DFT-calculations. © 2014 The Royal Society of Chemistry....

  16. Polyimidazoles via aromatic nucleophilic displacement

    Science.gov (United States)

    Connell, John W. (Inventor); Hergenrother, Paul M. (Inventor)

    1992-01-01

    Polyimidazoles (PI) are prepared by the aromatic nucleophilic displacement reaction of di(hydroxyphenyl) imidazole monomers with activated aromatic dihalides or activated aromatic dinitro compounds. The reactions are carried out in polar aprotic solvents such as N,N-dimethyl acetamide, sulfolane, N-methylpyrrolidinone, dimethylsulfoxide, or diphenylsulfone using alkali metal bases such as potassium carbonate at elevated temperatures under nitrogen. The di(hydroxyphenyl) imidazole monomers are prepared by reacting an aromatic aldehyde with a dimethoxybenzil or by reacting an aromatic dialdehyde with a methoxybenzil in the presence of ammonium acetate. The di(methoxyphenyl) imidazole is subsequently treated with aqueous hydrobromic acid to give the di(hydroxphenyl) imidazole monomer. This synthetic route has provided high molecular weight PI of new chemical structure, is economically and synthetically more favorable than other routes, and allows for facile chemical structure variation due to the availability of a large variety of activated aromatic dihalides and dinitro compounds.

  17. Role of the superoxide anion in the oxidative activation of the new antitumor drug BD40: a radiolysis study

    International Nuclear Information System (INIS)

    BD40, a new antitumor drug derived from 9-azaellipticine, is thought to have an oxygen-dependent metabolism in vivo. The one-electron oxidation of this drug was effected by γ radiolysis using OH radical free radicals as oxidants and the reaction of O2anionradical with the BD40 oxidized transient(s). The absorption spectrum of the one-electron oxidized free radical was determined by pulse radiolysis using OH radical or N3radical as reactant. In the absence of O2 and O2anionradical, the initial yield of disappearance of the drug is equal to 2.5 x 10-7 molJ-1 independently of the initial concentration of the drug and of the dose rate. When BD40 is oxidized by OH anion radicals in the presence of O2 and O2anionradical, the yield is the same. This yield is halved if superoxide dismutase is present during irradiation. Superoxide anions do not react directly with the drug. Thus it is suggested that these radicals oxidize the BD40 free radical produced by oxidation with OH radical. Biological implications are discussed. (author)

  18. Competitive reactions of organophosphorus radicals on coke surfaces.

    Science.gov (United States)

    Catak, Saron; Hemelsoet, Karen; Hermosilla, Laura; Waroquier, Michel; Van Speybroeck, Veronique

    2011-10-17

    The efficacy of organophosphorus radicals as anticoking agents was subjected to a computational study in which a representative set of radicals derived from industrially relevant organophosphorus additives was used to explore competitive reaction pathways on the graphene-like coke surface formed during thermal cracking. The aim was to investigate the nature of the competing reactions of different organophosphorus radicals on coke surfaces, and elucidate their mode of attack and inhibiting effect on the forming coke layer by use of contemporary computational methods. Density functional calculations on benzene and a larger polyaromatic hydrocarbon, namely, ovalene, showed that organophosphorus radicals have a high propensity to add to the periphery of the coke surface, inhibiting methyl radical induced hydrogen abstraction, which is known to be a key step in coke growth. Low addition barriers reported for a phosphatidyl radical suggest competitive aptitude against coke formation. Moreover, organophosphorus additives bearing aromatic substituents, which were shown to interact with the coke surface through dispersive π-π stacking interactions, are suggested to play a nontrivial role in hindering further stacking among coke surfaces. This may be the underlying rationale behind experimental observation of softer coke in the presence of organophosphorus radicals. The ultimate goal is to provide information that will be useful in building single-event microkinetic models. This study presents pertinent information on potential reactions that could be taken up in these models. PMID:21956815

  19. Aromatic molecules as spintronic devices

    International Nuclear Information System (INIS)

    In this paper, we study the spin-dependent electron transport through aromatic molecular chains attached to two semi-infinite leads. We model this system taking into account different geometrical configurations which are all characterized by a tight binding Hamiltonian. Based on the Green's function approach with a Landauer formalism, we find spin-dependent transport in short aromatic molecules by applying external magnetic fields. Additionally, we find that the magnetoresistance of aromatic molecules can reach different values, which are dependent on the variations in the applied magnetic field, length of the molecules, and the interactions between the contacts and the aromatic molecule

  20. Radical attached aluminum nanoclusters: an alternative way of cluster stabilization.

    Science.gov (United States)

    Sengupta, Turbasu; Pal, Sourav

    2016-08-21

    The stability and electronic structure of radical attached aluminum nanoclusters are investigated using density functional theory (DFT). A detailed investigation shows good correlation between the thermodynamic stability of radical attached clusters and the stability of the attached radical anions. All other calculated parameters like HOMO-LUMO gap and charge transfer are also found to be consistent with the observed thermodynamic stabilities of the complexes. Investigation of the electronic structure of radical attached complexes further shows the presence of jellium structures within the core similar to the ligated clusters. Comparison with available experimental and theoretical data also proves the validity of superatomic complex theory for the radical attached clusters as well. Based on the evaluated thermodynamic parameters, selected radical attached clusters are observed to be more thermodynamically stable in comparison with experimentally synthesized ligated clusters. Stabilization of small metal clusters is one of the greatest challenges in current cluster science and the present investigation confirms the fact that radical attached clusters can provide a viable alternative to ligated clusters in the future. PMID:27435912

  1. Radical chemistry of artemisinin

    Energy Technology Data Exchange (ETDEWEB)

    Denisov, Evgenii T; Solodova, S L; Denisova, Taisa G [Institute of Problems of Chemical Physics, Russian Academy of Sciences, Chernogolovka, Moscow Region (Russian Federation)

    2010-12-29

    The review summarizes physicochemical characteristics of the natural sesquiterpene peroxide artemisinin. The kinetic schemes of transformations of artemisinin radicals under anaerobic conditions are presented and analyzed. The sequence of radical reactions of artemisinin in the presence of oxygen is considered in detail. Special emphasis is given to the intramolecular chain oxidation resulting in the transformation of artemisinin into polyatomic hydroperoxide. The kinetic characteristics of elementary reaction steps involving alkyl, alkoxyl, and peroxyl radicals generated from artemisinin are discussed. The results of testing of artemisinin and its derivatives for the antimalarial activity and the scheme of the biochemical synthesis of artemisinin in nature are considered.

  2. Pu Anion Exchange Process Intensification

    Energy Technology Data Exchange (ETDEWEB)

    Taylor-Pashow, K. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)

    2015-10-08

    This project seeks to improve the efficiency of the plutonium anion-exchange process for purifying Pu through the development of alternate ion-exchange media. The objective of the project in FY15 was to develop and test a porous foam monolith material that could serve as a replacement for the current anion-exchange resin, Reillex® HPQ, used at the Savannah River Site (SRS) for purifying Pu. The new material provides advantages in efficiency over the current resin by the elimination of diffusive mass transport through large granular resin beads. By replacing the large resin beads with a porous foam there is much more efficient contact between the Pu solution and the anion-exchange sites present on the material. Several samples of a polystyrene based foam grafted with poly(4-vinylpyridine) were prepared and the Pu sorption was tested in batch contact tests.

  3. Development of imidazolium-type alkaline anion exchange membranes for fuel cell application

    OpenAIRE

    Ran, J; Wu, L.; XU, T; Varcoe, JR; Ong, AL; Poynton, SD

    2012-01-01

    This study reports the development of imidazolium-type alkaline anion exchange membranes (Im-AAEMs) based on the functionalization of bromomethylated poly(2,6-dimethyl-1,4-phenylene oxide) (BPPO) using 1-methylimdazole. Aromatic polymers bearing bromomethyl, instead of chloromethyl, functional groups were employed as base materials to avoid complicated chloromethylation which require toxic reagents. H NMR and FT-IR spectroscopic data indicated the synthesis of a series of membranes with contr...

  4. Anion-π interactions in complexes of proteins and halogen-containing amino acids.

    Science.gov (United States)

    Borozan, Sunčica Z; Zlatović, Mario V; Stojanović, Srđan Đ

    2016-06-01

    We analyzed the potential influence of anion-π interactions on the stability of complexes of proteins and halogen-containing non-natural amino acids. Anion-π interactions are distance and orientation dependent and our ab initio calculations showed that their energy can be lower than -8 kcal mol(-1), while most of their interaction energies lie in the range from -1 to -4 kcal mol(-1). About 20 % of these interactions were found to be repulsive. We have observed that Tyr has the highest occurrence among the aromatic residues involved in anion-π interactions, while His made the least contribution. Furthermore, our study showed that 67 % of total interactions in the dataset are multiple anion-π interactions. Most of the amino acid residues involved in anion-π interactions tend to be buried in the solvent-excluded environment. The majority of the anion-π interacting residues are located in regions with helical secondary structure. Analysis of stabilization centers for these complexes showed that all of the six residues capable of anion-π interactions are important in locating one or more of such centers. We found that anion-π interacting residues are sometimes involved in simultaneous interactions with halogens as well. With all that in mind, we can conclude that the anion-π interactions can show significant influence on molecular organization and on the structural stability of the complexes of proteins and halogen-containing non-natural amino acids. Their influence should not be neglected in supramolecular chemistry and crystal engineering fields as well. PMID:26910415

  5. Cellular electron transfer and radical mechanisms for drug metabolism

    International Nuclear Information System (INIS)

    Aerobic and anaerobic reductions of various nitroaromatic compounds by mammalian cells result in the production of reactive intermediates. Drug reduction is dependent upon glucose, nonprotein thiols, endogenous enzyme levels, and drug electron affinity. Drugs with electron affinities approaching that of oxygen are reduced, in the presence of oxygen, beyond a one-electron radical anion. Nitroaromatic radical anion inactivation occurs by reaction with cellular ferricytochrome c, endogenous thiols, and with oxygen. In the latter case the reaction results in the production of peroxide. Drugs that are substrates for the enzyme glutathione-S-transferase remove endogeneous thiols and demonstrate peroxide production without prior thiol removal. Less electron affinic drugs such as misonidazole require thiol removal as well as the presence of cyanide or azide for maximal peroxide production. Under anaerobic conditions radical anion and nitroso intermediates are reactive with glutathione. Removal of endogenous thiols by hypoxic preincubation with misonidazole may be related to the enhanced radiation response and cytotoxicity of this drug. Reduction of nitro compounds in the presence of DNA and chemicals such as dithionite, zinc dust, or polarographic techniques causes binding to macromolecules and DNA breaks. Chemical-reduction of nitro compounds by ascorbate in the presence of cells enhances drug cytotoxic effects

  6. Tar Balls from Deep Water Horizon Oil Spill: Environmentally Persistent Free Radicals (EPFR) Formation During Crude Weathering

    Science.gov (United States)

    Kiruri, Lucy W.; Dellinger, Barry; Lomnicki, Slawo

    2014-01-01

    Tar balls collected from the Gulf of Mexico shores of Louisiana and Florida after the BP oil spill have shown the presence of electron paramagnetic resonance (EPR) spectra characteristic of organic free radicals as well as transition metal ions, predominantly iron(III) and manganese(II). Two types of organic radicals were distinguished: an asphaltene radical species typically found in crude oil (g = 2.0035) and a new type of radical resulting from the environmental transformations of crude (g = 2.0041−47). Pure asphaltene radicals are resonance stabilized over a polyaromatic structure and are stable in air and unreactive. The new radicals were identified as products of partial oxidation of crude components and result from the interaction of the oxidized aromatics with metal ion centers. These radicals are similar to semiquinone-type, environmentally persistent free radicals (EPFRs) previously observed in combustion-generated particulate and contaminated soils. PMID:23510127

  7. "Carbo-aromaticity" and novel carbo-aromatic compounds.

    Science.gov (United States)

    Cocq, Kévin; Lepetit, Christine; Maraval, Valérie; Chauvin, Remi

    2015-09-21

    While the concept of aromaticity is being more and more precisely delineated, the category of "aromatic compounds" is being more and more expanded. This is illustrated by an introductory highlight of the various types of "aromaticity" previously invoked, and by a focus on the recently proposed "aromatic character" of the "two-membered rings" of the acetylene and butatriene molecules. This serves as a general foundation for the definition of "carbo-aromaticity", the relevance of which is surveyed through recent results in the synthetic, physical, and theoretical chemistry of carbo-mers and in particular macrocyclic-polycyclic representatives constituting a natural family of "novel aromatic compounds". With respect to their parent molecules, carbo-mers are constitutionally defined as "carbon-enriched", and can also be functionally regarded as "π-electron-enriched". This is exemplified by recent experimental and theoretical results on functional, aromatic, rigid, σ,π-macrocyclic carbo-benzene archetypes of various substitution patterns, with emphasis on the quadrupolar pattern. For the purpose of comparison, several types of non-aromatic references of carbo-benzenes are then considered, i.e. freely rotating σ,π-acyclic carbo-n-butadienes and flexible σ-cyclic, π-acyclic carbo-cyclohexadienes, and to "pro-aromatic" congeners, i.e. rigid σ,π-macrocyclic carbo-quinoids. It is shown that functional carbo-mers are entering the field of "molecular materials" for properties such as linear or nonlinear optical properties (e.g. dichromism and two-photon absorption) and single molecule conductivity. Since total or partial carbo-mers of aromatic carbon-allotropes of infinite size such as graphene (graphynes and graphdiynes) and graphite ("graphitynes") have long been addressed at the theoretical or conceptual level, recent predictive advances on the electrical, optical and mechanical properties of such carbo-materials are surveyed. Very preliminary experimental results

  8. Radical cystectomy in eldery

    OpenAIRE

    Bančević Vladimir; Aleksić Predrag; Milović Novak; Spasić Aleksandar; Kovačević Božidar; Toševski Perica; Čampara Zoran; Milošević Radovan; Cerović Snežana

    2015-01-01

    Background/Aim. Radical cystectomy is the method of choice for the treatment of muscle invasive bladder cancer. This major surgery is associated with many complications, especially in older patients. The aim of this study was to analyze preoperative comorbidity, and intraoperative and postoperative complicatons in patients older than 75 years. Methods. This clinical, retrospective study included 46 patients over 75 years, who underwent radical cystectomy. I...

  9. Energetics, structure, and rovibrational spectroscopic properties of the sulfurous anions SNO− and OSN−

    International Nuclear Information System (INIS)

    The SNO− and OSN− anions are shown in this work to be very stable negatively charged species in line with other recent work [T. Trabelsi et al., J. Chem. Phys. 143, 164301 (2015)]. Utilizing established quartic force field techniques, the structural and rovibrational data for these anions are produced. The SNO− anion is less linear and has weaker bonds than the corresponding neutral radical giving much smaller rotational constants. OSN− is largely unchanged in these regards with inclusion of the additional electron. The S–N bond is actually stronger, and the rotational constants of OSN− versus OSN are similar. The vibrational frequencies of SNO− are red-shifted from the radical while those in OSN− are mixed. OSN− has mixing of the stretching modes while the S–N and N–S stretches of SNO− are largely independent of one another. The ω3 stretches are much brighter in these anions than they are in the radicals, but the ω1 stretches are still the brightest

  10. The many ways of making anionic clays

    Indian Academy of Sciences (India)

    Michael Rajamathi; Grace S Thomas; P Vishnu Kamath

    2001-10-01

    Together with hydrotalcite-like layered double hydroxides, bivalent and trivalent metal hydroxides and their hydroxy salts are actually anionic clays consisting of positively charged hydroxide layers with anions intercalated in the interlayer region. The anionic clays exhibit anion sorption, anion diffusion and exchange properties together with surface basicity making them materials of importance for many modern applications. In this article, we discuss many different ways of making anionic clays and compare and contrast the rich diversity of this class of materials with the better-known cationic clays.

  11. Anion binding in biological systems

    Energy Technology Data Exchange (ETDEWEB)

    Feiters, Martin C [Department of Organic Chemistry, Institute for Molecules and Materials, Faculty of Science, Radboud University Nijmegen, Heyendaalseweg 135, 6525 AJ Nijmegen (Netherlands); Meyer-Klaucke, Wolfram [EMBL Hamburg Outstation at DESY, Notkestrasse 85, D-22607 Hamburg (Germany); Kostenko, Alexander V; Soldatov, Alexander V [Faculty of Physics, Southern Federal University, Sorge 5, Rostov-na-Donu, 344090 (Russian Federation); Leblanc, Catherine; Michel, Gurvan; Potin, Philippe [Centre National de la Recherche Scientifique and Universite Pierre et Marie Curie Paris-VI, Station Biologique de Roscoff, Place Georges Teissier, BP 74, F-29682 Roscoff cedex, Bretagne (France); Kuepper, Frithjof C [Scottish Association for Marine Science, Dunstaffnage Marine Laboratory, Oban, Argyll PA37 1QA, Scotland (United Kingdom); Hollenstein, Kaspar; Locher, Kaspar P [Institute of Molecular Biology and Biophysics, ETH Zuerich, Schafmattstrasse 20, Zuerich, 8093 (Switzerland); Bevers, Loes E; Hagedoorn, Peter-Leon; Hagen, Wilfred R, E-mail: m.feiters@science.ru.n [Department of Biotechnology, Delft University of Technology, Julianalaan 67, 2628 BC Delft (Netherlands)

    2009-11-15

    We compare aspects of biological X-ray absorption spectroscopy (XAS) studies of cations and anions, and report on some examples of anion binding in biological systems. Brown algae such as Laminaria digitata (oarweed) are effective accumulators of I from seawater, with tissue concentrations exceeding 50 mM, and the vanadate-containing enzyme haloperoxidase is implicated in halide accumulation. We have studied the chemical state of iodine and its biological role in Laminaria at the I K edge, and bromoperoxidase from Ascophyllum nodosum (knotted wrack) at the Br K edge. Mo is essential for many forms of life; W only for certain archaea, such as Archaeoglobus fulgidus and the hyperthermophilic archaeon Pyrococcus furiosus, and some bacteria. The metals are bound and transported as their oxo-anions, molybdate and tungstate, which are similar in size. The transport protein WtpA from P. furiosus binds tungstate more strongly than molybdate, and is related in sequence to Archaeoglobus fulgidus ModA, of which a crystal structure is known. We have measured A. fulgidus ModA with tungstate at the W L{sub 3} (2p{sub 3/2}) edge, and compared the results with the refined crystal structure. XAS studies of anion binding are feasible even if only weak interactions are present, are biologically relevant, and give new insights in the spectroscopy.

  12. Anion binding in biological systems

    Science.gov (United States)

    Feiters, Martin C.; Meyer-Klaucke, Wolfram; Kostenko, Alexander V.; Soldatov, Alexander V.; Leblanc, Catherine; Michel, Gurvan; Potin, Philippe; Küpper, Frithjof C.; Hollenstein, Kaspar; Locher, Kaspar P.; Bevers, Loes E.; Hagedoorn, Peter-Leon; Hagen, Wilfred R.

    2009-11-01

    We compare aspects of biological X-ray absorption spectroscopy (XAS) studies of cations and anions, and report on some examples of anion binding in biological systems. Brown algae such as Laminaria digitata (oarweed) are effective accumulators of I from seawater, with tissue concentrations exceeding 50 mM, and the vanadate-containing enzyme haloperoxidase is implicated in halide accumulation. We have studied the chemical state of iodine and its biological role in Laminaria at the I K edge, and bromoperoxidase from Ascophyllum nodosum (knotted wrack) at the Br K edge. Mo is essential for many forms of life; W only for certain archaea, such as Archaeoglobus fulgidus and the hyperthermophilic archaeon Pyrococcus furiosus, and some bacteria. The metals are bound and transported as their oxo-anions, molybdate and tungstate, which are similar in size. The transport protein WtpA from P. furiosus binds tungstate more strongly than molybdate, and is related in sequence to Archaeoglobus fulgidus ModA, of which a crystal structure is known. We have measured A. fulgidus ModA with tungstate at the W L3 (2p3/2) edge, and compared the results with the refined crystal structure. XAS studies of anion binding are feasible even if only weak interactions are present, are biologically relevant, and give new insights in the spectroscopy.

  13. IMPROVING OF ANION EXCHANGERES REGENERATION

    Directory of Open Access Journals (Sweden)

    Muzher M. Ibrahim

    2013-05-01

    Full Text Available Inthis study, Different basis [NaOH and KOH] of variable concentration are usedto reactivate Anion exchangers employing different schemes .The Laboratoryresults showed large improvement in efficiency of these exchangers ( i.eoperating time was increased from 12 to 42 hours .The results of this work showed that the environmentalload (waste water can be reduced greatly when using the proposed regenerationscheme .

  14. Bacterial Degradation of Aromatic Compounds

    Directory of Open Access Journals (Sweden)

    Qing X. Li

    2009-01-01

    Full Text Available Aromatic compounds are among the most prevalent and persistent pollutants in the environment. Petroleum-contaminated soil and sediment commonly contain a mixture of polycyclic aromatic hydrocarbons (PAHs and heterocyclic aromatics. Aromatics derived from industrial activities often have functional groups such as alkyls, halogens and nitro groups. Biodegradation is a major mechanism of removal of organic pollutants from a contaminated site. This review focuses on bacterial degradation pathways of selected aromatic compounds. Catabolic pathways of naphthalene, fluorene, phenanthrene, fluoranthene, pyrene, and benzo[a]pyrene are described in detail. Bacterial catabolism of the heterocycles dibenzofuran, carbazole, dibenzothiophene, and dibenzodioxin is discussed. Bacterial catabolism of alkylated PAHs is summarized, followed by a brief discussion of proteomics and metabolomics as powerful tools for elucidation of biodegradation mechanisms.

  15. Synthesis, structure and electrical conductivity of fulvalenium salts of cobalt bis(dicarbollide) anion and its derivatives

    Indian Academy of Sciences (India)

    Vladimir Bregadze; Igor Sivaev; Irina Lobanova; Olga Kazheva; Grigorii Alexandrov; Andrey Kravchenko; Vladimir Starodub; Lev Buravov; Lev Titov; Oleg Dyachenko

    2010-01-01

    TTF, TTF-BMDT, TTF-BEDT and TMTSF cation radical salts of cobalt bis(dicarbollide) anion [3,3'-Co(1,2-C2B9H11)2]- and its derivatives are prepared and their crystal structures and electrical conductivities are determined. Some regularities in the crystal structures of the TTF-based radical cation salts prepared are also discussed.

  16. Investigation of hybrid molecular material prepared by ionic liquid and polyoxometalate anion

    Indian Academy of Sciences (India)

    T Rajkumar; G Ranga Rao

    2008-11-01

    A solid hybrid molecular material containing 1-butyl 3-methyl imidazolium cations and Keggin anions of phosphotungstic acid has been synthesized. It is fully characterized by CHN analysis, FTIR, XRD, UV-Vis-NIR DRS, 31P MAS NMR, TGA and SEM. The FTIR spectrum of the compound shows the fingerprint vibrational bands of both Keggin molecular anions and imidazolium cations. The aromatic C-H stretch region (2700-3250 cm-1) of imidazolium cation is split due to the interaction between the ring C-H and bulky Keggin anion. The red-shift in the UV-Vis spectra and the downfield 31P MAS NMR chemical shift also confirm the electrostatic interaction between the ions in the compound. Near IR spectral region (1000-2500 nm) shows the elimination of water in the compound which is hydrophobic.

  17. Study on the Free Radical Scavenging Activity of Sea Cucumber (Paracaudina chinens var.) Gelatin Hydrolysate

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Gelatin from the sea cucumber (Paracaudina chinens var.) was hydrolyzed by bromelain and the hydrolysate was found to have a high free radical scavenging activity. The hydrolysate was fractionated through an ultrafiltration membrane with 5 kDa molecular weight cutoff (MWCO). The portion (less than 5 kDa) was further separated by Sephadex G-25. The active peak was collected and assayed for free radical scavenging activity. The scavenging rates for superoxide anion radicals (O2·-) and hydroxyl radicals (·OH) of the fraction with the highest activity were 29.02% and 75.41%, respectively. A rabbit liver mitochondrial free radical damage model was adopted to study the free radical scavenging activity of the fraction. The results showed that the sea cucumber gelatin hydrolysate can prevent the damage of rabbit liver and mitochondria.

  18. Study on the free radical scavenging activity of sea cucumber (Paracaudina chinens var.) gelatin hydrolysate

    Science.gov (United States)

    Zeng, Mingyong; Xiao, Feng; Zhao, Yuanhui; Liu, Zunying; Li, Bafang; Dong, Shiyuan

    2007-07-01

    Gelatin from the sea cucumber (Paracaudina chinens var.) was hydrolyzed by bromelain and the hydrolysate was found to have a high free radical scavenging activity. The hydrolysate was fractionated through an ultrafiltration membrane with 5 kDa molecular weight cutoff (MWCO). The portion (less than 5 kDa) was further separated by Sephadex G-25. The active peak was collected and assayed for free radical scavenging activity. The scavenging rates for superoxide anion radicals (O2·-) and hydroxyl radicals (·OH) of the fraction with the highest activity were 29.02% and 75.41%, respectively. A rabbit liver mitochondrial free radical damage model was adopted to study the free radical scavenging activity of the fraction. The results showed that the sea cucumber gelatin hydrolysate can prevent the damage of rabbit liver and mitochondria.

  19. Hydroxyl radical reactivity at the air-ice interface

    Directory of Open Access Journals (Sweden)

    T. F. Kahan

    2010-01-01

    Full Text Available Hydroxyl radicals are important oxidants in the atmosphere and in natural waters. They are also expected to be important in snow and ice, but their reactivity has not been widely studied in frozen aqueous solution. We have developed a spectroscopic probe to monitor the formation and reactions of hydroxyl radicals in situ. Hydroxyl radicals are produced in aqueous solution via the photolysis of nitrite, nitrate, and hydrogen peroxide, and react rapidly with benzene to form phenol. Similar phenol formation rates were observed in aqueous solution and bulk ice. However, no reaction was observed at air-ice interfaces, or when bulk ice samples were crushed prior to photolysis to increase their surface area. We also monitored the heterogeneous reaction between benzene present at air-water and air-ice interfaces with gas-phase OH produced from HONO photolysis. Rapid phenol formation was observed on water surfaces, but no reaction was observed at the surface of ice. Under the same conditions, we observed rapid loss of the polycyclic aromatic hydrocarbon (PAH anthracene at air-water interfaces, but no loss was observed at air-ice interfaces. Our results suggest that the reactivity of hydroxyl radicals toward aromatic organics is similar in bulk ice samples and in aqueous solution, but is significantly suppressed in the quasi-liquid layer (QLL that exists at air-ice interfaces.

  20. Free Radical Reactions in Food.

    Science.gov (United States)

    Taub, Irwin A.

    1984-01-01

    Discusses reactions of free radicals that determine the chemistry of many fresh, processed, and stored foods. Focuses on reactions involving ascorbic acid, myoglobin, and palmitate radicals as representative radicals derived from a vitamin, metallo-protein, and saturated lipid. Basic concepts related to free radical structure, formation, and…

  1. IONIC CONDUCTIVITY IN THE COMPLEXES OF COMB-SHAPED POLYETHER WITH LITHIUM AROMATIC SULFONATE

    Institute of Scientific and Technical Information of China (English)

    ZHANG Shengshui; QIU Weihua; XUE Dacui; LIU Qingguo

    1993-01-01

    Complexes of comb-shaped polyether and lithium aromatic sulfonates bearing different negative charge number were prepared by in situ thermal polymerization. Their conductivity depends deeply on salt content, ambient temperature and negative charge number of the added salts. Results show that anions can be partly immobilized by increasing their negative charges at lower temperature.Against discharge time the short circuit current of the battery (Li/complex film/Lix V3O8) is stabilized by increasing the anionic charge number of the complex.

  2. Formation of OH radicals from radical cations of some substituted benzenes in aqueous solutions at 800 C and at room temperature: effect of oxygen

    International Nuclear Information System (INIS)

    The reactions of a number of simple substituted-benzene radical cations with water at 800 C and at room temperature have been investigated. The radical cations were produced by thermal decomposition of Na2S2O8. The authors searched for the formation of OH radicals, which they identified by their reaction with nitrobenzene to give nitrophenols. The thermal decomposition of peroxydisulfate in deoxygenated, nitrobenzene-saturated aqueous solutions of chlorobenzene, bromobenzene, and tert-butylbenzene gave o- and p-nitrophenols, whereas fluorobenzene, iodobenzene, phenol, and chlorophenols gave no nitrophenols. With nitrobenzene alone, no nitrophenols were obtained. The structural requirements for the reaction of aromatic radical cations with water to produce OH radicals are discussed. In the presence of oxygen, the yield of chlorophenols and bromophenols increased dramatically, producing mainly the para isomer, but in the bromobenzene case also significant amounts of m-bromophenol. The mechanism of this oxidation is discussed. 3 tables

  3. The formation of polycyclic aromatic hydrocarbons in evolved circumstellar environments

    CERN Document Server

    Cherchneff, Isabelle

    2010-01-01

    The formation of Polycyclic Aromatic Hydrocarbons in the circumstellar outflows of evolved stars is reviewed, with an emphasis on carbon stars on the Asymptotic Giant Branch. Evidence for PAHs present in their winds is provided by meteoritic studies and recent observations of the Unidentified Infrared bands. We detail the chemical processes leading to the closure of the first aromatic ring as well as the growth mechanisms leading to amorphous carbon grains. Existing studies on PAH formation in evolved stellar envelopes are reviewed and new results for the modelling of the inner wind of the archetype carbon star IRC+10216 are presented. Benzene, C6H6, forms close to the star, as well as water, H2O, as a result of non-equilibrium chemistry induced by the periodic passage of shocks. The growth process of aromatic rings may thus resemble that active in sooting flames due to the presence of radicals like hydroxyl, OH. Finally, we discuss possible formation processes for PAHs and aromatic compounds in the hydrogen-...

  4. Efficient Amide Based Halogenide Anion Receptors

    Institute of Scientific and Technical Information of China (English)

    Hong Xing WU; Feng Hua LI; Hai LIN; Shou Rong ZHU; Hua Kuan LIN

    2005-01-01

    In this paper, we present the synthesis and anion recognition properties of the amide based phenanthroline derivatives 1, 2 and 3. In all cases 1:1 receptor: anion complexes were observed. The receptors were found to be selective for fluoride and chloride respectively over other putative anionic guest species.

  5. Gangs, Terrorism, and Radicalization

    Directory of Open Access Journals (Sweden)

    Scott Decker

    2011-01-01

    Full Text Available What can street gangs tell us about radicalization and extremist groups? At first glance, these two groups seem to push the boundaries of comparison. In this article, we examine the important similarities and differences across criminal, deviant, and extremist groups. Drawing from research on street gangs, this article explores issues such as levels of explanation,organizational structure, group process, and the increasingly important role of technology and the Internet in the context of radicalization. There are points of convergence across these groups, but it is important to understand the differences between these groups. This review finds little evidence to support the contention that American street gangs are becoming increasingly radicalized. This conclusion is based largely on organizational differences between gangs and terror groups.

  6. Sexuality Following Radical Prostatectomy

    DEFF Research Database (Denmark)

    Fode, Mikkel; Serefoglu, Ege C; Albersen, Maarten;

    2016-01-01

    INTRODUCTION: Radical prostatectomies can result in urinary incontinence and sexual dysfunction. Traditionally, these issues have been studied separately, and the sexual problem that has received the most focus has been erectile dysfunction. AIM: To summarize the literature on sexually related side...... effects and their consequences after radical prostatectomy and focus on the occurrence and management of problems beyond erectile dysfunction. METHODS: The literature on sexuality after radical prostatectomy was reviewed through a Medline search. Original research using quantitative and qualitative...... methodologies was considered. Priority was given to studies exploring aspects of sexuality other than erectile function. MAIN OUTCOME MEASURES: The prevalence, predictive factors, and management of post-prostatectomy sexual problems beyond erectile dysfunction. RESULTS: Most patients will develop urinary...

  7. Toward the Oxidation of the Phenyl Radical and Prevention of PAH Formation in Combustion Systems.

    Science.gov (United States)

    Parker, Dorian S N; Kaiser, Ralf I; Troy, Tyler P; Kostko, Oleg; Ahmed, Musahid; Mebel, Alexander M

    2015-07-16

    The reaction of the phenyl radical (C6H5) with molecular oxygen (O2) plays a central role in the degradation of poly- and monocyclic aromatic radicals in combustion systems which would otherwise react with fuel components to form polycyclic aromatic hydrocarbons (PAHs) and eventually soot. Despite intense theoretical and experimental scrutiny over half a century, the overall reaction channels have not all been experimentally identified. Tunable vacuum ultraviolet photoionization in conjunction with a combustion simulating chemical reactor uniquely provides the complete isomer specific product spectrum and branching ratios of this prototype reaction. In the reaction of phenyl radicals and molecular oxygen at 873 K and 1003 K, ortho-benzoquinone (o-C6H4O2), the phenoxy radical (C6H5O), and cyclopentadienyl radical (C5H5) were identified as primary products formed through emission of atomic hydrogen, atomic oxygen and carbon dioxide. Furan (C4H4O), acrolein (C3H4O), and ketene (C2H2O) were also identified as primary products formed through ring opening and fragmentation of the 7-membered ring 2-oxepinoxy radical. Secondary reaction products para-benzoquinone (p-C6H4O2), phenol (C6H5OH), cyclopentadiene (C5H6), 2,4-cyclopentadienone (C5H4O), vinylacetylene (C4H4), and acetylene (C2H2) were also identified. The pyranyl radical (C5H5O) was not detected; however, electronic structure calculations show that it is formed and isomerizes to 2,4-cyclopentadienone through atomic hydrogen emission. In combustion systems, barrierless phenyl-type radical oxidation reactions could even degrade more complex aromatic radicals. An understanding of these elementary processes is expected to lead to a better understanding toward the elimination of carcinogenic, mutagenic, and environmentally hazardous byproducts of combustion systems such as PAHs. PMID:25354358

  8. Porphyrin Analogues of a Trityl Cation and Anion.

    Science.gov (United States)

    Kato, Kenichi; Kim, Woojae; Kim, Dongho; Yorimitsu, Hideki; Osuka, Atsuhiro

    2016-05-17

    Porphyrin-stabilized meso- or β-carbocations were generated upon treatment of the corresponding bis(4-tert-butylphenyl)porphyrinylcarbinols with trifluoroacetic acid (TFA). Bis(4-tert-butylphenyl)porphyrinylcarbinols were treated with TFA to generate the corresponding carbocations stabilized by a meso- or β-porphyrinyl group. The meso-porphyrinylmethyl carbocation displayed more effective charge delocalization with decreasing aromaticity compared with the β-porphyrinylmethyl carbocation. A propeller-like porphyrin trimer, tris(β-porphyrinyl)carbinol, was also synthesized and converted to the corresponding cation that displayed a more intensified absorption reaching over the NIR region. meso-Porphyrinylmethyl carbanion was generated as a stable species upon deprotonation of bis(4-tert-butylphenyl)(meso-porphyrinyl)methane with potassium bis(trimethylsilyl)amide (KHMDS) and [18]crown-6, whereas β-porphyrinylmethyl anions were highly unstable. PMID:26991021

  9. Laser Cooling of Molecular Anions

    CERN Document Server

    Yzombard, Pauline; Gerber, Sebastian; Doser, Michael; Comparat, Daniel

    2015-01-01

    We propose a scheme for laser cooling of negatively charged molecules. We briefly summarise the requirements for such laser cooling and we identify a number of potential candidates. A detailed computation study with C$\\_2^-$, the most studied molecular anion, is carried out. Simulations of 3D laser cooling in a gas phase show that this molecule could be cooled down to below 1 mK in only a few tens of milliseconds, using standard lasers. Sisyphus cooling, where no photo-detachment process is present, as well as Doppler laser cooling of trapped C$\\_2^-$, are also simulated. This cooling scheme has an impact on the study of cold molecules, molecular anions, charged particle sources and antimatter physics.

  10. Polymerization of anionic wormlike micelles.

    Science.gov (United States)

    Zhu, Zhiyuan; González, Yamaira I; Xu, Hangxun; Kaler, Eric W; Liu, Shiyong

    2006-01-31

    Polymerizable anionic wormlike micelles are obtained upon mixing the hydrotropic salt p-toluidine hydrochloride (PTHC) with the reactive anionic surfactant sodium 4-(8-methacryloyloxyoctyl)oxybenzene sulfonate (MOBS). Polymerization captures the cross-sectional radius of the micelles (approximately 2 nm), induces micellar growth, and leads to the formation of a stable single-phase dispersion of wormlike micellar polymers. The unpolymerized and polymerized micelles were characterized using static and dynamic laser light scattering, small-angle neutron scattering, 1H NMR, and stopped-flow light scattering. Stopped-flow light scattering was also used to measure the average lifetime of the unpolymerized wormlike micelles. A comparison of the average lifetime of unpolymerized wormlike micelles with the surfactant monomer propagation rate was used to elucidate the mechanism of polymerization. There is a significant correlation between the ratio of the average lifetime to the monomer propagation rate and the average aggregation number of the polymerized wormlike micelles. PMID:16430253

  11. Anion Solvation in Carbonate Electrolytes

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Zhengcheng

    2015-11-16

    With the correlation between Li+ solvation and interphasial chemistry on anodes firmly established in Li-ion batteries, the effect of cation–solvent interaction has gone beyond bulk thermodynamic and transport properties and become an essential element that determines the reversibility of electrochemistry and kinetics of Li-ion intercalation chemistries. As of now, most studies are dedicated to the solvation of Li+, and the solvation of anions in carbonate-based electrolytes and its possible effect on the electrochemical stability of such electrolytes remains little understood. As a mirror effort to prior Li+ solvation studies, this work focuses on the interactions between carbonate-based solvents and two anions (hexafluorophosphate, PF6–, and tetrafluoroborate, BF4–) that are most frequently used in Li-ion batteries. The possible correlation between such interaction and the interphasial chemistry on cathode surface is also explored.

  12. Homegrown religious radicalization

    DEFF Research Database (Denmark)

    Khawaja, Iram

    and their families. Existing literature and ways of thinking about the social psychological process of radicalization will be reviewed, such as social identity theory and transformative learning theory, and a theoretical framework based on a focus on belonging, recognition and the sense of community......It has been reported that a growing number of youngsters from Western Europe are engaging in conflicts motivated by religious and political conflicts in the Middle East. This paper aims at exploring the reasons behind this seemingly religious radicalization from the point of view of the youngsters...

  13. Substrate-dependent aromatic ring fission of catechol and 2-aminophenol with O2 catalyzed by a nonheme iron complex of a tripodal N4 ligand.

    Science.gov (United States)

    Lakshman, Triloke Ranjan; Chatterjee, Sayanti; Chakraborty, Biswarup; Paine, Tapan Kanti

    2016-06-01

    The catalytic reactivity of an iron(ii) complex [(TPA)Fe(II)(CH3CN)2](2+) (1) (TPA = tris(2-pyridylmethyl)amine) towards oxygenative aromatic C-C bond cleavage of catechol and 2-aminophenol is presented. Complex 1 exhibits catalytic and regioselective C-C bond cleavage of 3,5-di-tert-butylcatechol (H2DBC) to form intradiol products, whereas it catalyzes extradiol-type C-C bond cleavage of 2-amino-4,6-di-tert-butylphenol (H2AP). The catalytic reactions are found to be pH-dependent and the complex exhibits maximum turnovers at pH 5 in acetonitrile-phthalate buffer. An iron(iii)-catecholate complex [(TPA)Fe(III)(DBC)](+) (2) is formed in the ring cleavage of catechol. In the extradiol-type cleavage of H2AP, an iron(iii)-2-iminobenzosemiquinonate complex [(TPA)Fe(III)(ISQ)](2+) (3) (ISQ = 4,6-di-tert-butyl-2-iminobenzosemiquinonate radical anion) is observed in the reaction pathway. This work shows the importance of the nature of 'redox non-innocent' substrates in governing the mode of ring fission reactivity. PMID:27148606

  14. Polybenzimidazoles Via Aromatic Nucleophilic Displacement

    Science.gov (United States)

    Connell, John W. (Inventor); Hergerrother, Paul M. (Inventor); Smith, Joseph G., Jr. (Inventor)

    1997-01-01

    Novel molecular weight controlled and endcapped polybenzimidazoles (PBI) are prepared by the aromatic nucleophilic displacement reaction of di(hydroxyphenylbenzimidazole) monomers with activated aromatic dihalides or activated aromatic dinitro compounds. The PBI are endcapped with mono(hydroxyphenyl)benzimidazoles. The polymerizations are carried out in polar aprotic solvents such as N-methyl-2-pyrrolidinone or N,N-dimethylacetamide using alkali metal bases such as potassium carbonate at elevated temperatures under nitrogen. Mono(hydroxyphenyl)benzimidazoles are synthesized by reacting phenyl-4-hydroxybenzoate with aromatic (o-diamine)s in diphenylsulfone. Molecular weight controlled and endcapped PBI of new chemical structures are prepared that exhibit a favorable combination of physical and mechanical properties.

  15. Carbon–carbon bond cleavage for Cu-mediated aromatic trifluoromethylations and pentafluoroethylations

    Directory of Open Access Journals (Sweden)

    Tsuyuka Sugiishi

    2015-12-01

    Full Text Available This short review highlights the copper-mediated fluoroalkylation using perfluoroalkylated carboxylic acid derivatives. Carbon–carbon bond cleavage of perfluoroalkylated carboxylic acid derivatives takes place in fluoroalkylation reactions at high temperature (150–200 °C or under basic conditions to generate fluoroalkyl anion sources for the formation of fluoroalkylcopper species. The fluoroalkylation reactions, which proceed through decarboxylation or tetrahedral intermediates, are useful protocols for the synthesis of fluoroalkylated aromatics.

  16. Carbon–carbon bond cleavage for Cu-mediated aromatic trifluoromethylations and pentafluoroethylations

    Science.gov (United States)

    Sugiishi, Tsuyuka; Aikawa, Kohsuke

    2015-01-01

    Summary This short review highlights the copper-mediated fluoroalkylation using perfluoroalkylated carboxylic acid derivatives. Carbon–carbon bond cleavage of perfluoroalkylated carboxylic acid derivatives takes place in fluoroalkylation reactions at high temperature (150–200 °C) or under basic conditions to generate fluoroalkyl anion sources for the formation of fluoroalkylcopper species. The fluoroalkylation reactions, which proceed through decarboxylation or tetrahedral intermediates, are useful protocols for the synthesis of fluoroalkylated aromatics. PMID:26734112

  17. Synergism in the desorption of polycyclic aromatic hydrocarbons from soil models by mixed surfactant solutions.

    Science.gov (United States)

    Sales, Pablo S; Fernández, Mariana A

    2016-05-01

    This study investigates the effect of a mixed surfactant system on the desorption of polycyclic aromatic hydrocarbons (PAHs) from soil model systems. The interaction of a non-ionic surfactant, Tween 80, and an anionic one, sodium laurate, forming mixed micelles, produces several beneficial effects, including reduction of adsorption onto solid of the non-ionic surfactant, decrease in the precipitation of the fatty acid salt, and synergism to solubilize PAHs from solids compared with individual surfactants. PMID:26873826

  18. Energy Density Functionals From the Strong-Coupling Limit Applied to the Anions of the He Isoelectronic Series

    OpenAIRE

    Mirtschink, André; Umrigar, C. J.; Morgan III, John D.; Gori-Giorgi, Paola

    2014-01-01

    Anions and radicals are important for many applications including environmental chemistry, semiconductors, and charge transfer, but are poorly described by the available approximate energy density functionals. Here we test an approximate exchange-correlation functional based on the exact strong-coupling limit of the Hohenberg-Kohn functional on the prototypical case of the He isoelectronic series with varying nuclear charge $Z

  19. Synthetic ion transporters that work with anion-π interactions, halogen bonds, and anion-macrodipole interactions.

    Science.gov (United States)

    Vargas Jentzsch, Andreas; Hennig, Andreas; Mareda, Jiri; Matile, Stefan

    2013-12-17

    The transport of ions and molecules across lipid bilayer membranes connects cells and cellular compartments with their environment. This biological process is central to a host of functions including signal transduction in neurons and the olfactory and gustatory sensing systems, the translocation of biosynthetic intermediates and products, and the uptake of nutrients, drugs, and probes. Biological transport systems are highly regulated and selectively respond to a broad range of physical and chemical stimulation. A large percentage of today's drugs and many antimicrobial or antifungal agents take advantage of these systems. Other biological transport systems are highly toxic, such as the anthrax toxin or melittin from bee venom. For more than three decades, organic and supramolecular chemists have been interested in developing new transport systems. Over time, curiosity about the basic design has evolved toward developing of responsive systems with applications in materials sciences and medicine. Our early contributions to this field focused on the introduction of new structural motifs with emphasis on rigid-rod scaffolds, artificial β-barrels, or π-stacks. Using these scaffolds, we have constructed selective systems that respond to voltage, pH, ligands, inhibitors, or light (multifunctional photosystems). We have described sensing applications that cover the three primary principles of sensor development: immunosensors that use aptamers, biosensors (an "artificial" tongue), and differential sensors (an "artificial" nose). In this Account, we focus on our recent interest in applying synthetic transport systems as analytical tools to identify the functional relevance of less common noncovalent interactions, anion-π interactions, halogen bonds, and anion-macrodipole interactions. Anion-π interactions, the poorly explored counterpart of cation-π interactions, occur in aromatic systems with a positive quadrupole moment, such as TNT or hexafluorobenzene. To observe

  20. Hypochlorite and superoxide radicals can act synergistically to induce fragmentation of hyaluronan and chondroitin sulphates

    DEFF Research Database (Denmark)

    Rees, Martin D; Hawkins, Clare L; Davies, Michael Jonathan

    2004-01-01

    Activated phagocytes release the haem enzyme MPO (myeloperoxidase) and also generate superoxide radicals (O2*-), and hence H2O2, via an oxidative burst. Reaction of MPO with H2O2 in the presence of chloride ions generates HOCl (the physiological mixture of hypochlorous acid and its anion present ...

  1. NITRORADICAL ANION FORMATION FROM NITROFURANTOIN IN CARBON ELECTRODES

    Directory of Open Access Journals (Sweden)

    M. MERINO

    2000-03-01

    Full Text Available The electrochemical nitroreduction of nitrofurantoin has been studiedon carbon paste and glassy carbon electrodes. We can observe a monoelectronicreversible couple ArNO2/ArNO2.- and anirreversible peak due to the further reduction of nitro radical to thehidroxilamine via three electrons. According to the experimental results, the reduction process shows atypical behavior of an EC mechanism. The k2 obtained values showed that the nitroradical anion was better stabilized on carbon paste electrodeLa formación electroquímica del nitro anión radicalde nitrofurantoína ha sido estudiada sobre electrodos de carbonovítreo y pasta de carbono. Se encontró que sobre ambos tipos de electrodos, existe un proceso monoelectrónico reversible correspondientea la cupla redox ArNO2/ArNO2.-, seguido de un pico irreversible correspodiente a la reducción víatres electrones del anión radical a la correspondiente hidroxilamina.De acuerdo a los resultados obtenidos, el proceso de reducción ocurrea través de un mecanismo EC, donde los valores de k2 encontrados, indican que el anión radical nitro es mejor estabilizadosobre electrodos de pasta de carbono

  2. Bioassay of polycyclic aromatic hydrocarbons

    Energy Technology Data Exchange (ETDEWEB)

    Van Kirk, E.A.

    1980-08-01

    A positive relationship was found between the photodynamic activity of 24 polycyclic aromatic hydrocarbons versus published results on the mutagenicity, carcinogenicity, and initiation of unscheduled DNA synthesis. Metabolic activation of benzo(a)pyrene resulted in detection of increased mutagenesis in Paramecium tetraurelia as found also in the Ames Salmonella assay. The utility of P. tetraurelia as a biological detector of hazardous polycyclic aromatic hydrocarbons is discussed.

  3. Micropropagation of different aromatic plants

    OpenAIRE

    Koleva Gudeva, Liljana; Iljovska Tusev, Jasmina; Trajkova, Fidanka

    2014-01-01

    Aromatic plants have been used for centuries as species, natural flavor, raw material for essential-oil industry and other purposes. Micropropagation has advantage over conventional propagation because of high multiplication rate, but it depends on the performance of the starting material, media composition, phytohormones and environmental factors. In this study, aromatic plants as peppermint (Menta piperita L.) and Menta sp., rosemary (Rosmarinus sp.), rocket (Eruca sativa Mill.), coriand...

  4. Violent Radicalization in Europe

    DEFF Research Database (Denmark)

    Dalgaard-Nielsen, Anja

    2010-01-01

    When, why, and how do people living in a democracy become radicalized to the point of being willing to use or directly support the use of terrorist violence against fellow citizens? This question has been at the center of academic and public debate over the past years as terrorist attacks...

  5. Radical School Reform.

    Science.gov (United States)

    Gross, Beatrice, Ed.; Gross, Ronald, Ed.

    This book provides a comprehensive examination of the nature of the school crisis and the ways in which radical thinkers and educators are dealing with it. Excerpts from the writings of Jonathan Kozol, John Holt, Kenneth Clark, and others are concerned with the realities of education in ghettos and suburbs. Paul Goodman, Marshall McLuhan, Sylvia…

  6. Radically enhanced molecular recognition

    KAUST Repository

    Trabolsi, Ali

    2009-12-17

    The tendency for viologen radical cations to dimerize has been harnessed to establish a recognition motif based on their ability to form extremely strong inclusion complexes with cyclobis(paraquat-p-phenylene) in its diradical dicationic redox state. This previously unreported complex involving three bipyridinium cation radicals increases the versatility of host-guest chemistry, extending its practice beyond the traditional reliance on neutral and charged guests and hosts. In particular, transporting the concept of radical dimerization into the field of mechanically interlocked molecules introduces a higher level of control within molecular switches and machines. Herein, we report that bistable and tristable [2]rotaxanes can be switched by altering electrochemical potentials. In a tristable [2]rotaxane composed of a cyclobis(paraquat-p-phenylene) ring and a dumbbell with tetrathiafulvalene, dioxynaphthalene and bipyridinium recognition sites, the position of the ring can be switched. On oxidation, it moves from the tetrathiafulvalene to the dioxynaphthalene, and on reduction, to the bipyridinium radical cation, provided the ring is also reduced simultaneously to the diradical dication. © 2010 Macmillan Publishers Limited. All rights reserved.

  7. On Radical Feminism

    Institute of Scientific and Technical Information of China (English)

    翟良锴

    2015-01-01

    <正>All men are created equal.For centuries,human have been struggling for their rights.Women,as a special social force,are fighting vigorously for their equal rights with men.According to an introduction to feminism,there are three main types of feminism:socialist,reformist and radical(Feminism 101).In order

  8. Radical Financial Innovation

    OpenAIRE

    Robert J. Shiller

    2004-01-01

    Radical financial innovation is the development of new institutions and methods that permit risk management to be extended far beyond its former realm, covering important new classes of risks. This paper compares past such innovation with potential future innovation, looking at the process that produced past success and the possibilities for future financial innovation.

  9. OH radicals in the troposphere

    International Nuclear Information System (INIS)

    OH radicals are radicals which determine the photochemistry of the troposphere. The reactivity of OH radicals to organic substances is one of the fundamental criteria for the evaluation of abiotic decomposition. Details are given about the photochemical formation and reaction of OH radicals, the decomposition reactions of organic compounds in the gaseous phase, the determination of the specific rates of OH radical decomposition reactions, measuring methods for the determination of OH radical concentrations in the troposphere, selected results, OH concentration distributions obtained from model calculations, and the influence of trace gases on OH concentrations. A summary, conclusions, and research proposals are attached. (orig./BBR)

  10. Free radical transfer in polymers

    International Nuclear Information System (INIS)

    For the present study of free-radical transfer in polymers pulse radiolysis and product studies have been carried out in aqueous solutions using thus far only the water-soluble polymers polyacrylic acid, polymethacrylic acid and polyvinyl alcohol. When OH radicals, generated in the radiolysis of N2O-saturated aqueous solutions, react with polymers the lifetime of the polymer radical thus created very much depends on the number of radicals per polymer chain. When there are a large number of radicals per chain their bimolecular decay may be faster than the corresponding (diffusion controlled) decay of monomeric radicals, but when the macromolecule contains only few or even just one radical their lifetime is considerably prolonged. Highly charged polymers such as polyacrylic acid at high pH attain a rod-like conformation which again favors a long lifetime of the radicals. Under such conditions, radical transfer reactions can occur. For example, in polyacrylic acid OH radicals generate two kinds of radicals side by side. The radical in β-position to the carboxylate group converts into the thermodynamically more stable α-radicals by an H-transfer reaction as can be followed by spectrophotometry. Besides radical transfer reactions β-fragmentation reactions occur causing chain scission. Such reactions can be followed in a pulse radiolysis experiment by conductometry, because counter ions are released upon chain scission. Such a process is especially effective in the case of polymethacrylic acid, where it results in a chain depolymerization. An intramolecular H-abstraction is also observed in the γ-radiolysis of polyacrylic acid with the corresponding peroxyl radicals. This causes a chain reaction to occur. The resulting hydroperoxides are unstable and decarboxylate given rise to acetylacetone-like products. In polyvinyl alcohol the peroxyl radicals in α-position to the alcohol function undergo HO2-elimination. This prevents a scission of the polymer chain in the

  11. C-H and N-H bond dissociation energies of small aromatic hydrocarbons

    Energy Technology Data Exchange (ETDEWEB)

    Barckholtz, C.; Barckholtz, T.A.; Hadad, C.M.

    1999-01-27

    A survey of computational methods was undertaken to calculate the homolytic bond dissociation energies (BDEs) of the C-H and N-H bonds in monocyclic aromatic molecules that are representative of the functionalities present in coal. These include six-membered rings (benzene, pyridine, pyridazine, pyrimidine, pyrazine) and five-membered rings (furan, thiophene, pyrrole, oxazole). By comparison of the calculated C-H BDEs with the available experimental values for these aromatic molecules, the B3LYP/6-31G(d) level of theory was selected to calculate the BDEs of polycyclic aromatic hydrocarbons (PAHs), including carbonaceous PAHs (naphthalene, anthracene, pyrene, coronene) and heteroatomic PAHs (benzofuran, benzothiophene, indole, benzoxazole, quinoline, isoquinoline, dibenzofuran, carbazole). The cleavage of a C-H or a N-H bond generates a {sigma} radical that is, in general, localized at the site from which the hydrogen atom was removed. However, delocalization of the unpaired electron results in {approximately} 7 kcal {center{underscore}dot} mol{sup {minus}1} stabilization of the radical with respect to the formation of phenyl when the C-H bond is adjacent to a nitrogen atom in the azabenzenes. Radicals from five-membered rings are {approximately} 6 kcal {center{underscore}dot} mol{sup {minus}1} less stable than those formed from six-membered rings due to both localization of the spin density and geometric factors. The location of the heteroatoms in the aromatic ring affects the C-H bond strengths more significantly than does the size of the aromatic network. Therefore, in general, the monocyclic aromatic molecules can be used to predict the C-H BDE of the large PAHs within 1 kcal {center{underscore}dot} mol{sup {minus}1}.

  12. Interplay of ortho- with spiro-cyclisation during iminyl radical closures onto arenes and heteroarenes

    Directory of Open Access Journals (Sweden)

    Roy T. McBurney

    2013-06-01

    Full Text Available Sensitised photolyses of ethoxycarbonyl oximes of aromatic and heteroaromatic ketones yielded iminyl radicals, which were characterised by EPR spectroscopy. Iminyls with suitably placed arene or heteroarene acceptors underwent cyclisations yielding phenanthridine-type products from ortho-additions. For benzofuran and benzothiophene acceptors, spiro-cyclisation predominated at low temperatures, but thermodynamic control ensured ortho-products, benzofuro- or benzothieno-isoquinolines, formed at higher temperatures. Estimates by steady-state kinetic EPR established that iminyl radical cyclisations onto aromatics took place about an order of magnitude more slowly than prototypical C-centred radicals. The cyclisation energetics were investigated by DFT computations, which gave insights into factors influencing the two cyclisation modes.

  13. Free Radicals and Extrinsic Skin Aging

    Directory of Open Access Journals (Sweden)

    Borut Poljšak

    2012-01-01

    Full Text Available Human skin is constantly directly exposed to the air, solar radiation, environmental pollutants, or other mechanical and chemical insults, which are capable of inducing the generation of free radicals as well as reactive oxygen species (ROS of our own metabolism. Extrinsic skin damage develops due to several factors: ionizing radiation, severe physical and psychological stress, alcohol intake, poor nutrition, overeating, environmental pollution, and exposure to UV radiation (UVR. It is estimated that among all these environmental factors, UVR contributes up to 80%. UV-induced generation of ROS in the skin develops oxidative stress, when their formation exceeds the antioxidant defence ability of the target cell. The primary mechanism by which UVR initiates molecular responses in human skin is via photochemical generation of ROS mainly formation of superoxide anion (O2−•, hydrogen peroxide (H2O2, hydroxyl radical (OH•, and singlet oxygen (1O2. The only protection of our skin is in its endogenous protection (melanin and enzymatic antioxidants and antioxidants we consume from the food (vitamin A, C, E, etc.. The most important strategy to reduce the risk of sun UVR damage is to avoid the sun exposure and the use of sunscreens. The next step is the use of exogenous antioxidants orally or by topical application and interventions in preventing oxidative stress and in enhanced DNA repair.

  14. Environmental behavior of inorganic anions

    International Nuclear Information System (INIS)

    Recent efforts have addressed two aspects of anion behavior in the soil/plant system. The first involves evaluation of the gaseous component of the terrestrial iodine cycle in soils and plants. Field analyses of 129I in soils and vegetation adjacent to a fuels reprocessing facility, which was idle for 10 years prior to the study, indicated that there may be a significant gaseous component to the terrestrial iodine cycle. Soil substrates, including a silt-sand, organic forest soil, quartz sand, and a sterilized soil, were amended with radioiodide, and the rates and quality of the volatile components evaluated

  15. Toward Radicalizing Community Service Learning

    Science.gov (United States)

    Sheffield, Eric C.

    2015-01-01

    This article advocates a radicalized theoretical construction of community service learning. To accomplish this radicalization, I initially take up a discussion of traditional understandings of CSL rooted in pragmatic/progressive thought. I then suggest that this traditional structural foundation can be radicalized by incorporating Deborah…

  16. Bacterial degradation of monocyclic aromatic amines

    Directory of Open Access Journals (Sweden)

    Pankaj Kumar Arora

    2015-08-01

    Full Text Available Aromatic amines are an important group of industrial chemicals, which are widely used for manufacturing of dyes, pesticides, drugs, pigments, and other industrial products. These compounds have been considered highly toxic to human beings due to their carcinogenic nature. Three groups of aromatic amines have been recognized: monocyclic, polycyclic and heterocyclic aromatic amines. Bacterial degradation of several monocyclic aromatic compounds has been studied in a variety of bacteria, which utilizes monocyclic aromatic amines as their sole source of carbon and energy. Several degradation pathways have been proposed and the related enzymes and genes have also been characterized. Many reviews have been reviewed toxicity of monocyclic aromatic amines; however, there is lack of review on biodegradation of monocyclic aromatic amines. The aim of this review is to summarize bacterial degradation of monocyclic aromatic amines. This review will increase our current understanding of biochemical and molecular basis of bacterial degradation of monocyclic aromatic amines.

  17. Oligorotaxane Radicals under Orders

    OpenAIRE

    WANG, YUPING; Frasconi, Marco; Liu, Wei-Guang; Sun, Junling; Wu, Yilei; Nassar, Majed S.; Botros, Youssry Y.; Goddard, William A.; Wasielewski, Michael R.; Stoddart, J. Fraser

    2016-01-01

    A strategy for creating foldameric oligorotaxanes composed of only positively charged components is reported. Threadlike components—namely oligoviologens—in which different numbers of 4,4′-bipyridinium (BIPY2+) subunits are linked by p-xylylene bridges, are shown to be capable of being threaded by cyclobis(paraquat-p-phenylene) (CBPQT4+) rings following the introduction of radical-pairing interactions under reducing conditions. UV/vis/NIR spectroscopic and electrochemical investigations sugge...

  18. Oligorotaxane Radicals under Orders

    OpenAIRE

    WANG, YUPING; Frasconi, Marco; Liu, Wei-Guang; Sun, Junling; Wu, Yilei; Nassar, Majed S.; Botros, Youssry Y.; Goddard, William A.; Wasielewski, Michael R.; Stoddart, J. Fraser

    2016-01-01

    A strategy for creating foldameric oligorotaxanes composed of only positively charged components is reported. Threadlike components—namely oligoviologens—in which different numbers of 4,4′-bipyridinium (BIPY^(2+)) subunits are linked by p-xylylene bridges, are shown to be capable of being threaded by cyclobis(paraquat-p-phenylene) (CBPQT^(4+)) rings following the introduction of radical-pairing interactions under reducing conditions. UV/vis/NIR spectroscopic and electrochemical investigations...

  19. Aromatic-Aromatic Interactions in Biological System: Structure Activity Relationships

    Energy Technology Data Exchange (ETDEWEB)

    Rajagopal, Appavu; Deepa, Mohan [Molecular Biophysics Unit, Indian Institute of Sciences-Bangalore, Karnataka (India); Govindaraju, Munisamy [Bio-Spatial Technology Research Unit, Department of Environmental Biotechnology, School of Environmental Sciences, Bharathidasan University, Tiruchirappalli, Tamil Nadu (India)

    2016-02-26

    While, intramolecular hydrogen bonds have attracted the greatest attention in studies of peptide conformations, the recognition that several other weakly polar interactions may be important determinants of folded structure has been growing. Burley and Petsko provided a comprehensive overview of the importance of weakly polar interactions, in shaping protein structures. The interactions between aromatic rings, which are spatially approximate, have attracted special attention. A survey of the proximal aromatic residue pairs in proteins, allowed Burley and Petsko to suggest that, “phenyl ring centroids are separated by a preferential distance of between 4.5 and 7 Å, and dihedral angles approximately 90° are most common”.

  20. Aromatic-Aromatic Interactions in Biological System: Structure Activity Relationships

    International Nuclear Information System (INIS)

    While, intramolecular hydrogen bonds have attracted the greatest attention in studies of peptide conformations, the recognition that several other weakly polar interactions may be important determinants of folded structure has been growing. Burley and Petsko provided a comprehensive overview of the importance of weakly polar interactions, in shaping protein structures. The interactions between aromatic rings, which are spatially approximate, have attracted special attention. A survey of the proximal aromatic residue pairs in proteins, allowed Burley and Petsko to suggest that, “phenyl ring centroids are separated by a preferential distance of between 4.5 and 7 Å, and dihedral angles approximately 90° are most common”

  1. Aromatic-Aromatic Interactions in Biological System: Structure Activity Relationships

    Directory of Open Access Journals (Sweden)

    Rajagopal Appavu

    2016-03-01

    Full Text Available While, intramolecular hydrogen bonds have attracted the greatest attention in studies of peptide conformations, the recognition that several other weakly polar interactions may be important determinants of folded structure has been growing. Burley and Petsko provided a comprehensive overview of the importance of weakly polar interactions, in shaping protein structures. The interactions between aromatic rings, which are spatially approximate, have attracted special attention. A survey of the proximal aromatic residue pairs in proteins, allowed Burley and Petsko to suggest that, “phenyl ring centroids are separated by a preferential distance of between 4.5 and 7 Å, and dihedral angles approximately 90° are most common”.

  2. Effect of counter ions of arginine as an additive for the solubilization of protein and aromatic compounds.

    Science.gov (United States)

    Yoshizawa, Shunsuke; Arakawa, Tsutomu; Shiraki, Kentaro

    2016-10-01

    Arginine is widely used in biotechnological application, but mostly with chloride counter ion. Here, we examined the effects of various anions on solubilization of aromatic compounds and reduced lysozyme and on refolding of the lysozyme. All arginine salts tested increased the solubility of propyl gallate with acetate much more effectively than chloride. The effects of arginine salts were compared with those of sodium or guanidine salts, indicating that the ability of anions to modulate the propyl gallate solubility is independent of the cation. Comparison of transfer free energy of propyl gallate between sodium and arginine salts indicates that the interaction of propyl gallate is more favorable with arginine than sodium. On the contrary, the solubility of aromatic amino acids is only slightly modulated by anions, implying that there is specific interaction between acetic acid and propyl gallate. Unlike their effects on the solubility of small aromatic compounds, the solubility of reduced lysozyme was much higher in arginine chloride than in arginine acetate or sulfate. Consistent with high solubility, refolding of reduced lysozyme was most effective in arginine chloride. These results suggest potential broader applications of arginine modulated by different anions. PMID:27234496

  3. Radical chemistry of epigallocatechin gallate and its relevance to protein damage

    DEFF Research Database (Denmark)

    Hagerman, Ann E; Dean, Roger T; Davies, Michael Jonathan

    2003-01-01

    The radical chemistry of the plant polyphenolics epigallocatechin gallate (EGCG) and epigallocatechin (EGC) were investigated using electron paramagnetic resonance spectroscopy. Radical species formed spontaneously in aqueous solutions at low pH without external oxidant and were spin stabilized...... with Zn(II). The spectra were assigned to the gallyl radical and the anion gallyl radical, with only 10% of the signal assigned to a radical from the galloyl ester. Spectral simulations were used to establish a pK(a) of 4.8 for the EGCG radical and a pK(a) of 4.4 for the EGC radical. The...... electrochemical redox potentials of EGCG and EGC varied from 1000 mV at pH 3 to 400 mV at pH 8. The polyphenolics did not produce hydroxyl radicals unless reduced metal ions such as iron(II) were added to the system. Zinc(II)-stabilized EGCG radicals were more effective protein-precipitating agents than...

  4. Advances towards aromatic oligoamide foldamers

    DEFF Research Database (Denmark)

    Hjelmgaard, Thomas; Plesner, Malene; Dissing, Mette Marie; Andersen, Jeanette Marker; Frydenvang, Karla Andrea; Nielsen, John

    2014-01-01

    We have efficiently synthesized 36 arylopeptoid dimers with ortho-, meta-, and para-substituted aromatic backbones and tert-butyl or phenyl side chains. The dimers were synthesized by using a "submonomer method" on solid phase, by applying a simplified common set of reaction conditions. X......-ray crystallographic analysis of two of these dimers disclosed that the tert-butyl side chain invokes a cis amide conformation with a comparatively more closely packed structure of the surrounding aromatic backbone while the phenyl side chain results in a trans amide conformation with a more open, extended structure...... conformation with a more open, extended structure of the surrounding aromatic backbone. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim....

  5. Studies of phenolic chelating agents on free radical scavenging activities and inhibitory action in radiation-induced lipid peroxidation

    International Nuclear Information System (INIS)

    Effects of single molecular and double molecular substituted phenolic chelating agents on scavenging of superoxide anions and hydroxyl radicals and inhibition of rat liver mitochondria lipid peroxidation induced by irradiation were studied. The phenolic chelating agents were shown to different extent to scavenge oxygen free radical and the protect against radiation-induced lipid peroxidation, and their half inhibition concentrations (IC50) on hydroxyl radicals generation and lipid peroxidation were 1 x 10-6 mol/L, which of scavenging of superoxide anions were 1 x 10-3 mol/L. 7601(CBMIDA), 9501 and 9502 were the best among them. The free radical scavenging and antioxidant activities were close related to chemical structure and de-corporate bioactivity

  6. The formation of aromatics and PAH's in laminar flames

    Energy Technology Data Exchange (ETDEWEB)

    Marinov, N M; Pitz, W J; Westbrook, C K

    1999-04-01

    The formation of aromatics and PAH's is an important problem in combustion. These compounds are believed to contribute to the formation of soot whose emission from diesel engines is regulated widely throughout the industrial world. Additionally, the United States Environmental Protection Agency regulates the emission of many aromatics and PAH species from stationary industrial burners, under the 1990 Clean Air Act Amendments. The above emission regulations have created much interest in understanding how these species are formed in combustion systems. Much previous work has been done on aromatics and PAH's. The work is too extensive to review here, but is reviewed in Reference 1. A few recent developments are highlighted here. McEnally, Pfefferle and coworkers have studied aromatic, PAH and soot formation in a variety of non-premixed flames with hydrocarbon additives [2-4]. They found additives that contain a C5 ring increase the concentration of aromatics and soot [4]. Howard and coworkers have studied the formation of aromatic and PAH's in low pressure, premixed, laminar hydrocarbon flames. They found the cyclopentadienyl radical to be a key species in naphthalene formation in a fuel-rich, benzene/Ar/O2 flame [5].

  7. Reactions of substituted benzene anions with N and O atoms: Chemistry in Titan's upper atmosphere and the interstellar medium

    Science.gov (United States)

    Wang, Zhe-Chen; Bierbaum, Veronica M.

    2016-06-01

    The likely existence of aromatic anions in many important extraterrestrial environments, from the atmosphere of Titan to the interstellar medium (ISM), is attracting increasing attention. Nitrogen and oxygen atoms are also widely observed in the ISM and in the ionospheres of planets and moons. In the current work, we extend previous studies to explore the reactivity of prototypical aromatic anions (deprotonated toluene, aniline, and phenol) with N and O atoms both experimentally and computationally. The benzyl and anilinide anions both exhibit slow associative electron detachment (AED) processes with N atom, and moderate reactivity with O atom in which AED dominates but ionic products are also formed. The reactivity of phenoxide is dramatically different; there is no measurable reaction with N atom, and the moderate reactivity with O atom produces almost exclusively ionic products. The reaction mechanisms are studied theoretically by employing density functional theory calculations, and spin conversion is found to be critical for understanding some product distributions. This work provides insight into the rich gas-phase chemistry of aromatic ion-atom reactions and their relevance to ionospheric and interstellar chemistry.

  8. Oxidative phosphonylation of aromatic compounds

    OpenAIRE

    Effenberger, Franz; Kottmann, Hariolf

    1985-01-01

    Aryl phosphonates can be prepared in good yield from the respective arenes and tri- or dialkyphosphites by either chemical or anodic oxidation. The anodic oxidation proceeds either via phosphinium radical cations, which then attack the arenes electrophilically, or via arene radical cations, which add the trialkylphosphite as nucleophile. Aryl phosphonates are also obtained in good yield by chemical oxidation with peroxodisulfate/AgNO3 in acetonitrile/water or glacial acetic acid. The diethylp...

  9. Ursodeoxycholic acid and superoxide anion

    Institute of Scientific and Technical Information of China (English)

    Predrag Ljubuncic; Omar Abu-Salach; Arieh Bomzon

    2005-01-01

    AIM: To investigate the ability of ursodeoxycholic acid (UDCA) to scavenge superoxide anion (O2-).METHODS: We assessed the ability of UDCA to scavenge (O2-) generated by xanthine-xanthine oxidase (X-XO) in a cell-free system and its effect on the rate of O2--induced ascorbic acid (AA) oxidation in hepatic post-mitochondrial supernatants.RESULTS: UDCA at a concentration as high as 1 mmol/Ldid not impair the ability of the X-XO system to generate O2-, but could scavenge O2- at concentrations of 0.5 and 1 mmol/L, and decrease the rate of AA oxidation at a concentration of 100 μmol/L.CONCLUSION: UDCA can scavenge O2-, an action that may be beneficial to patients with primary biliary cirrhosis.

  10. Cyclohexane/benzene organic glasses and ethylene/styrene copolymers behaviour under ionizing radiations: energy and species transfers between aliphatic and aromatic moieties

    International Nuclear Information System (INIS)

    The aim of this study is to understand how aliphatic and aromatic groups interact under ionizing radiations. Three research orientations were explored: the determination of the relative contribution of energy and radical transfers, the determination of the intermolecular and intra-chain relative contribution, and the influence of the repartition of the aliphatic and aromatic units inside the polymer chain. Three systems composed of aromatic and aliphatic units were studied: the cyclohexane/benzene organic glasses (intermolecular reactions), the ethylene/styrene random copolymers (inter-chain and intra-chain reactions) and ethylene/styrene di-blocs copolymers (influence of the repartition of the aliphatic and aromatic units in the material). Considering the results obtained, we have concluded that energy transfers are important in the radiation protection effect of the aliphatic moiety by the aromatic one, although radical transfers are also contributing. Intermolecular transfers are efficient in the solid state and their efficiency seems equivalent to that of the intra-chain ones. Thanks to the use of infrared spectroscopy, we have shown an important effect of radiation sensitization of the aromatic moiety, whatever the irradiation temperature and the system studied: energy transfers to the aromatic moiety are carried out at the detriment of its stability. Finally, the repartition of the aliphatic and aromatic units in the polymer chain is not an important factor in the effects induced by the energy transfers. (author)

  11. A radical publishing collective: the Journal of Radical Librarianship

    OpenAIRE

    Simon Barron

    2015-01-01

    The Journal of Radical Librarianship is a new open-access journal publishing scholarly work in the field of radical librarianship. The focus on critical approaches to librarianship and anti-marketisation of information is reflected not only in our subject matter but in our publishing model, our licensing model, and our organisational practices. We hope to foster open and engaging discussions about radical approaches to librarianship and information studies.

  12. Tripodal Receptors for Cation and Anion Sensors

    Directory of Open Access Journals (Sweden)

    David N. Reinhoudt

    2006-08-01

    Full Text Available This review discusses different types of artificial tripodal receptors for the selectiverecognition and sensing of cations and anions. Examples on the relationship between structure andselectivity towards cations and anions are described. Furthermore, their applications as potentiometricion sensing are emphasised, along with their potential applications in optical sensors or optodes.

  13. Test procedure for anion exchange chromatography

    International Nuclear Information System (INIS)

    Plutonium from stored nitrate solutions will be sorbed onto anion exchange resins and converted to storable plutonium dioxide. Useful information will be simultaneously gained on the thermal stability and ion exchange capacity of four commercially available anion exchange resins over several years and under severe degradative conditions. This information will prove useful in predicting the safe and efficient lifetimes of these resins

  14. Simultaneous anion and cation mobility in polypyrrole

    DEFF Research Database (Denmark)

    Skaarup, Steen; Bay, Lasse; Vidanapathirana, K.;

    2003-01-01

    Polypyrrole (PPy) polymer films permanently doped with large, immobile anion dodecyl benzene sulfonate (DBS) have been characterized by cyclic voltammetry in order to clarify the roles of cations and anions in the aqueous electrolyte as mobile ions in the film. Aqueous solutions of 0.05-0.1 M alk...

  15. Survey of Recent Innovations in Aromatic Rice

    OpenAIRE

    Napasintuwong, Orachos

    2012-01-01

    This paper provides situations of aromatic rice demand, and international standards. The history and recent developments of traditional and evolved aromatic rice varieties, namely Basmati rice and Jasmine rice, are reviewed. The emerging aromatic rice innovations from developed countries such as the U.S. and other Asian countries generate a threat to these traditional aromatic rice producers such as India, Pakistan, and Thailand. Under WTO Trade Related Aspects of Intellectual Property Rights...

  16. Anion- interactions in layered structures of salts of 5-(hydroxyimino) quinolin-8-one and related salts

    Indian Academy of Sciences (India)

    Prithiviraj Khakhlary; Jubaraj B Baruah

    2015-01-01

    Relevance of anion- interactions in chloride, bromide, nitrate and perchlorate salts of 5-(hydroxyimino)quinolin-8-one are discussed. Structures of nitrate salt of 5-aminoquinoline as well as nitrate salt of 4-hydroxyquinazoline are compared with the structure of nitrate salt of 5-(hydroxyimino)quinolin-8-one. From such a comparison, two different arrangements of nitrate ions with respect to the respective cations are discerned. Nitrate ions are sandwiched between aromatic planes of cations in nitrate salts of 5-(hydroxyimino)quinolin-8-one or 4-hydroxyquinazoline; whereas, nitrate ions are in oblique positions with respect to aromatic planes of counter cations in nitrate salt of 5-aminoquinoline. Binding constants of different nitrate salts in solution are determined by UV-visible spectroscopic titrations. Solution study shows formation of ion-pairs of these salts in solution.

  17. Free radical formation in crystals of 2'-deoxyguanosine 5'-monophosphate irradiated at 15 K: an ESR study

    International Nuclear Information System (INIS)

    Radiation-induced radicals in single crystals of 2'-deoxyguanosine 5'-monophosphate (5'-dGMP) at 15 K have been studied by electron spin resonance (ESR) spectroscopy. At low temperatures three radicals were analyzed in detail. The negatively charged pi anion of the guanine base completely dominated the spectra. Weaker resonances were due to an alkoxy radical with the spin density in the C3'-O3' region of the sugar moiety as well as another sugar-centered radical. The anion rapidly decayed upon exposure to uv light at 15 K or by annealing above 25 K. In both cases no successor radical was observed. The second sugar-centered radical decays at 200 K with a concomitant appearance of the resonance from the C8 H-addition radical. By annealing at 295 K the latter resonance was the only one observed. After irradiation at 295 K, however, an additional resonance from a sugar-centered radical, which has been analyzed previously by B. Rakvin and J. N. Herak (Radiat. Res. 88, 240-250 (1981)) was observed. A reinvestigation of this resonance was performed

  18. Photoelectron spectroscopic and computational study of the PtMgH3,5(-) cluster anions.

    Science.gov (United States)

    Zhang, Xinxing; Ganteför, Gerd; Alexandrova, Anastassia N; Bowen, Kit

    2016-07-28

    The two cluster anions, PtMgH3(-) and PtMgH5(-), were studied by photoelectron spectroscopy and theoretical calculations. Experimentally-determined electron affinity (EA) and vertical detachment energy (VDE) values were compared with those predicted by our computations; excellent agreement was found. The calculated structures of PtMgH3(-) and PtMgH3 both exhibit η2-bonded H2 moieties. Activation of these H2 moieties is implied by the elongation of their bond lengths relative to the bond length of free H2. The calculated structures of PtMgH5(-) and PtMgH5 both exhibit all-hydrogen, five-member, σ-aromatic rings. These attributes are responsible for this anion's special stability. PMID:27373793

  19. Counterintuitive interaction of anions with benzene derivatives

    Science.gov (United States)

    Quiñonero, David; Garau, Carolina; Frontera, Antonio; Ballester, Pau; Costa, Antonio; Deyà, Pere M.

    2002-06-01

    Ab initio calculations were carried out on complexes between 1,3,5-trinitrobenzene (TNB) and anions, where the anion is positioned over the ring along the C3 axis. This study combines crystallographic and computational evidences to demonstrate an attractive interaction between the anion and the π-cloud of TNB. This interaction is rationalized based on the important role of the quadrupole moment of TNB and the anion-induced polarization. In addition, this study has been extended to 1,3,5-trifluorobenzene (TFB), which possesses a very small quadrupole moment. As a result, minimum energy complexes have been found between TFB and both anions and cations due to the stabilization obtained from the ion-induced polarization.

  20. Oligorotaxane Radicals under Orders.

    Science.gov (United States)

    Wang, Yuping; Frasconi, Marco; Liu, Wei-Guang; Sun, Junling; Wu, Yilei; Nassar, Majed S; Botros, Youssry Y; Goddard, William A; Wasielewski, Michael R; Stoddart, J Fraser

    2016-02-24

    A strategy for creating foldameric oligorotaxanes composed of only positively charged components is reported. Threadlike components-namely oligoviologens-in which different numbers of 4,4'-bipyridinium (BIPY(2+)) subunits are linked by p-xylylene bridges, are shown to be capable of being threaded by cyclobis(paraquat-p-phenylene) (CBPQT(4+)) rings following the introduction of radical-pairing interactions under reducing conditions. UV/vis/NIR spectroscopic and electrochemical investigations suggest that the reduced oligopseudorotaxanes fold into highly ordered secondary structures as a result of the formation of BIPY(•+) radical cation pairs. Furthermore, by installing bulky stoppers at each end of the oligopseudorotaxanes by means of Cu-free alkyne-azide cycloadditions, their analogous oligorotaxanes, which retain the same stoichiometries as their progenitors, can be prepared. Solution-state studies of the oligorotaxanes indicate that their mechanically interlocked structures lead to the enforced interactions between the dumbbell and ring components, allowing them to fold (contract) in their reduced states and unfold (expand) in their fully oxidized states as a result of Coulombic repulsions. This electrochemically controlled reversible folding and unfolding process, during which the oligorotaxanes experience length contractions and expansions, is reminiscent of the mechanisms of actuation associated with muscle fibers. PMID:27163033

  1. Bursectomy at radical gastrectomy

    Institute of Scientific and Technical Information of China (English)

    Cuneyt; Kayaalp

    2015-01-01

    Radical gastrectomy with extended lymph node dissec tion and prophylactic resection of the omentum, peri toneum over the posterior lesser sac, pancreas and/o spleen was advocated at the beginning of the 1960 s in Japan. In time, prophylactic routine resections of the pancreas and/or spleen were abandoned because of the high incidence of postoperative complications. However omentectomy and bursectomy continued to be standard parts of traditional radical gastrectomy. The bursaomentalis was thought to be a natural barrier against invasion of cancer cells into the posterior part of the stomach. The theoretical rationale for bursectomy was to reduce the risk of peritoneal recurrences by eliminating the peritoneum over the lesser sac, which might include free cancer cells or micrometastases. Over time, the indication for bursectomy was gradually reduced to only patients with posterior gastric wall tumors penetrating the serosa. Despite its theoretical advantages, its benefit for recurrence or survival has not been proven yet. The possible reasons for this inconsistency are discussed in this review. In conclusion, the value of bursectomy in the treatment of gastric cancer is still under debate and large-scale randomized studies are necessary. Until clear evidence of patient benefit is obtained, its routine use cannot be recommended.

  2. Nickel(ii) radical complexes of thiosemicarbazone ligands appended by salicylidene, aminophenol and aminothiophenol moieties.

    Science.gov (United States)

    Kochem, Amélie; Gellon, Gisèle; Jarjayes, Olivier; Philouze, Christian; du Moulinet d'Hardemare, Amaury; van Gastel, Maurice; Thomas, Fabrice

    2015-07-28

    The nickel(ii) complexes of three unsymmetrical thiosemicarbazone-based ligands featuring a sterically hindered salicylidene (1), aminophenol (2) or thiophenol (3) moiety were synthesized and structurally characterized. The metal ion lies in an almost square planar geometry in all the complexes. The cyclic voltammetry (CV) curve of 1 shows an irreversible oxidation wave at E = 0.49 V, which is assigned to the phenoxyl/phenolate redox couple. The CV curves of 2 and 3 display a reversible one-electron oxidation wave (E1/2 = 0.26 and 0.22 V vs. Fc(+)/Fc, respectively) and an one-electron reduction wave (E1/2 = -1.55 and -1.46 V, respectively). The cations 2(+) and 3(+) as well as the anions 2(-) and 3(-) were generated. The EPR spectra of the cations in THF show a rhombic signal at g1 = 2.034, g2 = 2.010 and g3 = 1.992 (2(+)) and g1 = 2.069, g2 = 2.018, g3 = 1.986 (3(+)) that is consistent with a main radical character of the complexes. The difference in anisotropy is assigned to the different nature of the radical, iminosemiquinonate vs. iminothiosemiquinonate. The anions display an isotropic EPR signal at giso = 2.003 (2(+)) and 2.006 (3(+)), which is indicative of a main α-diimine radical character of the compounds. Both the anions and cations exhibit charge transfer transitions of low to moderate intensity in their visible spectrum. Quantum chemical calculations (B3LYP) reproduce both the g-values and Vis-NIR spectra of the complexes. The radical anions readily react with dioxygen to give the radical cations. 2(+) catalyzes the aerobic oxidation of benzyl alcohol into benzaldehyde. PMID:26086684

  3. Electron attachment and positive ion chemistry of monohydrogenated fluorocarbon radicals

    International Nuclear Information System (INIS)

    Rate coefficients and product branching fractions for electron attachment and for reaction with Ar+ are measured over the temperature range 300–585 K for three monohydrogenated fluorocarbon (HFC) radicals (CF3CHF, CHF2CF2, and CF3CHFCF2), as well as their five closed-shell precursors (1-HC2F4I, 2-HC2F4I, 2-HC2F4Br, 1-HC3F6I, 2-HC3F6Br). Attachment to the HFC radicals is always fairly inefficient (between 0.1% and 10% of the Vogt–Wannier capture rate), but generally faster than attachment to analogous perfluorinated carbon radicals. The primary products in all cases are HF-loss to yield CnFm−1− anions, with only a minor branching to F− product. In all cases the temperature dependences are weak. Attachment to the precursor halocarbons is near the capture rate with a slight negative temperature dependence in all cases except for 2-HC2F4Br, which is ∼10% efficient at 300 K and becomes more efficient, approaching the capture rate at higher temperatures. All attachment kinetics are successfully reproduced using a kinetic modeling approach. Reaction of the HFC radicals with Ar+ proceeds at or near the calculated collisional rate coefficient in all cases, yielding a wide variety of product ions

  4. Competition between photodetachment and autodetachment of the 21ππ* state of the green fluorescent protein chromophore anion

    International Nuclear Information System (INIS)

    Using a combination of photoelectron spectroscopy measurements and quantum chemistry calculations, we have identified competing electron emission processes that contribute to the 350–315 nm photoelectron spectra of the deprotonated green fluorescent protein chromophore anion, p-hydroxybenzylidene-2,3-dimethylimidazolinone. As well as direct electron detachment from S0, we observe resonant excitation of the 21ππ* state of the anion followed by autodetachment. The experimental photoelectron spectra are found to be significantly broader than photoelectron spectrum calculated using the Franck-Condon method and we attribute this to rapid (∼10 fs) vibrational decoherence, or intramolecular vibrational energy redistribution, within the neutral radical

  5. Competition between photodetachment and autodetachment of the {2^1π π ^*} state of the green fluorescent protein chromophore anion

    Science.gov (United States)

    Mooney, Ciarán R. S.; Parkes, Michael A.; Zhang, Lijuan; Hailes, Helen C.; Simperler, Alexandra; Bearpark, Michael J.; Fielding, Helen H.

    2014-05-01

    Using a combination of photoelectron spectroscopy measurements and quantum chemistry calculations, we have identified competing electron emission processes that contribute to the 350-315 nm photoelectron spectra of the deprotonated green fluorescent protein chromophore anion, p-hydroxybenzylidene-2,3-dimethylimidazolinone. As well as direct electron detachment from S0, we observe resonant excitation of the 21ππ* state of the anion followed by autodetachment. The experimental photoelectron spectra are found to be significantly broader than photoelectron spectrum calculated using the Franck-Condon method and we attribute this to rapid (˜10 fs) vibrational decoherence, or intramolecular vibrational energy redistribution, within the neutral radical.

  6. Perturbing peptide cation-radical electronic states by thioxoamide groups: formation, dissociations, and energetics of thioxopeptide cation-radicals.

    Science.gov (United States)

    Zimnicka, Magdalena; Chung, Thomas W; Moss, Christopher L; Tureček, František

    2013-02-14

    Thioxodipeptides Gly-thio-Lys (GtK), Ala-thio-Lys (AtK), and Ala-thio-Arg (AtR) in which the amide group has been modified to a thioxoamide were made into dications by electrospray ionization and converted to cation-radicals, (GtK + 2H)(+•), (AtK + 2H)(+•), and (AtR + 2H)(+•), by electron transfer dissociation (ETD) tandem mass spectrometry using fluoranthene anion-radical as an electron donor. The common and dominant dissociation of these cation-radicals was the loss of a hydrogen atom. The dissociation products were characterized by collision-induced dissociation (CID) multistage tandem mass spectrometry up to CID-MS(5). The ground electronic states of several (GtK + 2H)(+•), (AtK + 2H)(+•), and (AtR + 2H)(+•) conformers were explored by extensive ab initio and density functional theory calculations of the potential energy surface. In silico electron transfer to the precursor dications, (GtK + 2H)(2+), (AtK + 2H)(2+), and (AtR + 2H)(2+), formed zwitterionic intermediates containing thioenol anion-radical and ammonium cation groups that were local energy minima on the potential energy surface of the ground electronic state. The zwitterions underwent facile isomerization by N-terminal ammonium proton migration to the thioenol anion-radical group forming aminothioketyl intermediates. Combined potential energy mapping and RRKM calculations of dissociation rate constants identified N-C(α) bond cleavages as the most favorable dissociation pathways, in a stark contrast to the experimental results. This discrepancy is interpreted as being due to the population upon electron transfer of low-lying excited electronic states that promote loss of hydrogen atoms. For (GtK + 2H)(+•), these excited states were characterized by time-dependent density functional theory as A-C states that had large components of Rydberg-like 3s molecular orbitals at the N-terminal and lysine ammonium groups that are conducive to hydrogen atom loss. PMID:22765351

  7. Prediction of liquid−liquid equilibria of (aromatic + aliphatic + ionic liquid) systems using the Cosmo-SAC model

    International Nuclear Information System (INIS)

    Highlights: ► Aromatic/aliphatic hydrocarbons separation by ionic liquids. ► Cosmo-SAC thermodynamic model for prediction of LLE by quantum chemical calculations. ► Predictions successful for some ionic liquids. ► Correlation by single parameter for other ionic liquids. ► Preliminary screening of additional ionic liquids for aromatic/aliphatic separation. - Abstract: The extraction of aromatic hydrocarbons from aliphatic hydrocarbons is an important problem. This process can be used to enhance the capacity of ethylene crackers by prior removal of aromatics that cannot be cracked. Ionic liquids have been investigated extensively for liquid–liquid extraction of aromatics from aliphatics. The choice of a suitable ionic liquid may be made by measuring liquid−liquid equilibria. However, the large number of ionic liquids, formed by the various cation and anion combinations, makes the experimental measurements expensive and time consuming. Hence, a predictive thermodynamic model called Cosmo-SAC that uses quantum chemical calculations for calculating liquid−liquid equilibria has been evaluated. A priori predictions are accurate for some ionic liquids and inaccurate for some ionic liquids. However, it has been shown that even when a priori predictions are inaccurate, the data can be correlated using a single parameter that is characteristic of the ionic liquid and accurate predictions can be made for additional aromatic/aliphatic combinations for the same ionic liquid. A comparison with the NRTL and UNIQUAC models has also been carried out. In addition, a preliminary screening of ionic liquids for aromatic/aliphatic separations has been carried out using the Cosmo-SAC model. Finally, the “Cosmo” files for eight cations and sixteen anions corresponding to 128 potential ionic liquids have been provided for the use of the general scientific community to predict any thermodynamic equilibria involving ionic liquids without the use of any molecular modeling

  8. Radical cystectomy in eldery

    Directory of Open Access Journals (Sweden)

    Bančević Vladimir

    2015-01-01

    Full Text Available Background/Aim. Radical cystectomy is the method of choice for the treatment of muscle invasive bladder cancer. This major surgery is associated with many complications, especially in older patients. The aim of this study was to analyze preoperative comorbidity, and intraoperative and postoperative complicatons in patients older than 75 years. Methods. This clinical, retrospective study included 46 patients over 75 years, who underwent radical cystectomy. Indications for surgery, and complications during and after the surgery were followed up. Results. Preoperatively, anemia caused by hematuria was registered in 76% of the patients. In 52% of the patients urine derivation was performed by ileal conduit, in 35% by ureterocutaneostomy and in 13% orthotopic ileal neobladder was created. The average duration of surgery was 190 (120-300 min. A total of 76% of the patients were treated by blood supstitution intraoperatively, average 630 (310-1230 mL. Concerning pathological stage of transitional cell carcinoma of urinary bladder, 26% of the patients had T2, 4% T3a, 52% T3b, and 14% T4a stage. In one case, planocellular carcinoma was diagnosed by patohistological examination, and in 2 cases prostate carcinoma was incidentally found. The average duration of hospitalization was 16 (8-35 days. Conclusion. The main reason for cystectomy in patients over 70 and 80 years was gross hematuria caused by bladder cancer, with consecutive anemia which could not be solved using endoscopic treatment or blood supstitution. As expected, a prolonged stay in hospital after cystectomy, and a higher rate of complications were recorded in this population.

  9. Copper(II)-salt-promoted oxidative ring-opening reactions of bicyclic cyclopropanol derivatives via radical pathways

    OpenAIRE

    Hasegawa, Eietsu; Tateyama, Minami; Nagumo, Ryosuke; Tayama, Eiji; Iwamoto, Hajime

    2013-01-01

    Copper(II)-salt-promoted oxidative ring-opening reactions of bicyclic cyclopropanol derivatives were investigated. The regioselectivities of these processes were found to be influenced by the structure of cyclopropanols as well as the counter anion of the copper(II) salts. A mechanism involving rearrangement reactions of radical intermediates and their competitive trapping by copper ions is proposed.

  10. Copper(II-salt-promoted oxidative ring-opening reactions of bicyclic cyclopropanol derivatives via radical pathways

    Directory of Open Access Journals (Sweden)

    Eietsu Hasegawa

    2013-07-01

    Full Text Available Copper(II-salt-promoted oxidative ring-opening reactions of bicyclic cyclopropanol derivatives were investigated. The regioselectivities of these processes were found to be influenced by the structure of cyclopropanols as well as the counter anion of the copper(II salts. A mechanism involving rearrangement reactions of radical intermediates and their competitive trapping by copper ions is proposed.

  11. Nucleophilic fluorination of aromatic compounds

    Energy Technology Data Exchange (ETDEWEB)

    Satyamurthy, Nagichettiar; Barrio, Jorge R

    2014-03-18

    Iodylbenzene derivatives substituted with electron donating as well as electron withdrawing groups on the aromatic ring are used as precursors in aromatic nucleophilic substitution reactions. The iodyl group (IO.sub.2) is regiospecifically substituted by nucleophilic fluoride to provide the corresponding fluoroaryl derivatives. No-carrier-added [F-18]fluoride ion derived from anhydrous [F-18](F/Kryptofix, [F-18]CsF or a quaternary ammonium fluoride (e.g., Me.sub.4NF, Et.sub.4NF, n-Bu.sub.4NF, (PhCH.sub.2).sub.4NF) exclusively substitutes the iodyl moiety in these derivatives and provides high specific activity F-18 labeled fluoroaryl analogs. Iodyl derivatives of a benzothiazole analog and 6-iodyl-L-dopa derivatives have been synthesized as precursors and have been used in the preparation of no-carrier-added [F-18]fluorobenzothiazole as well as 6-[F-18]fluoro-L-dopa.

  12. Radical Chemistry and Cytotoxicity of Bioreductive 3-Substituted Quinoxaline Di-N-Oxides.

    Science.gov (United States)

    Anderson, Robert F; Yadav, Pooja; Shinde, Sujata S; Hong, Cho R; Pullen, Susan M; Reynisson, Jóhannes; Wilson, William R; Hay, Michael P

    2016-08-15

    The radical chemistry and cytotoxicity of a series of quinoxaline di-N-oxide (QDO) compounds has been investigated to explore the mechanism of action of this class of bioreductive drugs. A series of water-soluble 3-trifluoromethyl (4-10), 3-phenyl (11-19), and 3-methyl (20-21) substituted QDO compounds were designed to span a range of electron affinities consistent with bioreduction. The stoichiometry of loss of QDOs by steady-state radiolysis of anaerobic aqueous formate buffer indicated that one-electron reduction of QDOs generates radicals able to initiate chain reactions by oxidation of formate. The 3-trifluoromethyl analogues exhibited long chain reactions consistent with the release of the HO(•), as identified in EPR spin trapping experiments. Several carbon-centered radical intermediates, produced by anaerobic incubation of the QDO compounds with N-terminal truncated cytochrome P450 reductase (POR), were characterized using N-tert-butyl-α-phenylnitrone (PBN) and 5-(diethoxyphosphoryl)-5-methyl-1-pyrroline-N-oxide (DEPMPO) spin traps and were observed by EPR. Experimental data were well simulated for the production of strongly oxidizing radicals, capable of H atom abstraction from methyl groups. The kinetics of formation and decay of the radicals produced following one-electron reduction of the parent compounds, both in oxic and anoxic solutions, were determined using pulse radiolysis. Back oxidation of the initially formed radical anions by molecular oxygen did not compete effectively with the breakdown of the radical anions to form oxidizing radicals. The QDO compounds displayed low hypoxic selectivity when tested against oxic and hypoxic cancer cell lines in vitro. The results from this study form a kinetic description and explanation of the low hypoxia-selective cytotoxicity of QDOs against cancer cells compared to the related benzotriazine 1,4-dioxide (BTO) class of compounds. PMID:27380897

  13. Biodegradation of Polycyclic Aromatic Hydrocarbons

    OpenAIRE

    DEMİR, İsmail; DEMİRBAĞ, Zihni

    1999-01-01

    Polycylic aromatic hydrocarbons (PAHs), such as petroleum and petroleum derivatives, are widespread organic pollutants entering the environment, chiefly, through oil spills and incomplete combustion of fossil fuels. Since most PAHs are persist in the environment for a long period of time and bioaccumulate, they cause environmental pollution and effect biological equilibrium dramatically. Biodegradation of some PAHs by microorganisms has been biochemically and genetically investigated. Ge...

  14. Analysis of heterocyclic aromatic amines.

    Science.gov (United States)

    Murkovic, M

    2007-09-01

    Heterocyclic aromatic amines are formed in protein and amino acid-rich foods at temperatures above 150 degrees C. Of more than twenty heterocyclic aromatic amines identified ten have been shown to have carcinogenic potential. As nutritional hazards, their reliable determination in prepared food, their uptake and elimination in living organisms, including humans, and assessment of associated risks are important food-safety issues. The concentration in foods is normally in the low ng g(-1) range, which poses a challenge to the analytical chemist. Because of the complex nature of food matrixes, clean-up and enrichment of the extracts are also complex, usually involving both cation-exchange (propylsulfonic acid silica gel, PRS) and reversed-phase purification. The application of novel solid-phase extraction cartridges with a wettable apolar phase combined with cation-exchange characteristics simplified this process--both the polar and apolar heterocyclic aromatic amines were recovered in one fraction. Copper phthalocyanine trisulfonate bonded to cotton ("blue cotton") or rayon, and molecular imprinted polymers have also been successfully used for one-step sample clean-up. For analysis of the heterocyclic aromatic amines, liquid chromatography with base-deactivated reversed-phase columns has been used, and, recently, semi-micro and capillary columns have been introduced. The photometric, fluorimetric, or electrochemical detectors used previously have been replaced by mass spectrometers. Increased specificity and sub-ppb sensitivities have been achieved by the use of the selected-reaction-monitoring mode of detection of advanced MS instrumentation, for example the triple quadrupole and Q-TOF instrument combination. Gas chromatography, also with mass-selective detection, has been used for specific applications; the extra derivatization step needed for volatilization has been balanced by the higher chromatographic resolution. PMID:17546447

  15. Novel Easy Preparations of Some Aromatic Iodine(I, III, and V) Reagents, Widely Applied in Modern Organic Synthesis

    OpenAIRE

    Lech Skulski

    2003-01-01

    We report our novel (or considerably improved) methods for the synthesis of aromatic iodides, (dichloroiodo)arenes, (diacetoxyiodo)arenes, [bis(trifluoroacetoxy)-iodo]arenes, iodylarenes and diaryliodonium salts, as well as some facile, oxidative anion metatheses in crude diaryliodonium or tetraalkylammonium halides and, for comparison, potassium halides. All our formerly published papers were discussed and explained in our review “Organic Iodine(I, III, and V) Chemistry: 10 Years of Dev...

  16. Organo/LDH nanocomposite as an adsorbent of polycyclic aromatic hydrocarbons in water and soil-water systems

    OpenAIRE

    Bruna González, Felipe; de Celis, R; Real Ojeda, Miguel; Cornejo, J.

    2012-01-01

    Polycyclic aromatic hydrocarbons (PAHs) are considered as priority pollutants because of their high risk to human health. In this paper, we addressed the issue of using hydrotalcite-based nanocomposites as adsorbents of six low molecular weight PAHs (acenaphthene, fluorene, phenanthrene, anthracene, fluoranthene and pyrene) to reduce their negative effects on the environment. A nanocomposite (HTDDS) was prepared by intercalating the organic anion dodecylsulfate (DDS) in a Mg¿Al hydrotalcite (...

  17. Deuterated polycyclic aromatic hydrocarbons: Revisited

    CERN Document Server

    Doney, Kirstin D; Mori, Tamami; Onaka, Takashi; Tielens, A G G M

    2016-01-01

    The amount of deuterium locked up in polycyclic aromatic hydrocarbons (PAHs) has to date been an uncertain value. We present a near-infrared (NIR) spectroscopic survey of HII regions in the Milky Way, Large Magellanic Cloud (LMC), and Small Magellanic Cloud (SMC) obtained with AKARI, which aims to search for features indicative of deuterated PAHs (PAD or Dn-PAH) to better constrain the D/H ratio of PAHs. Fifty-three HII regions were observed in the NIR (2.5-5 {\\mu}m), using the Infrared Camera (IRC) on board the AKARI satellite. Through comparison of the observed spectra with a theoretical model of deuterated PAH vibrational modes, the aromatic and (a)symmetric aliphatic C-D stretch modes were identified. We see emission features between 4.4-4.8 {\\mu}m, which could be unambiguously attributed to deuterated PAHs in only six of the observed sources, all of which are located in the Milky Way. In all cases, the aromatic C-D stretching feature is weaker than the aliphatic C-D stretching feature, and, in the case o...

  18. Study of compounds suppressing free radical generation from UV-exposed ketoprofen.

    Science.gov (United States)

    Nakajima, Ayako; Tahara, Maiko; Yoshimura, Yoshihiro; Nakazawa, Hiroyuki

    2007-10-01

    Ketoprofen [(RS)-2-(3-benzoylphenyl)propanoic acid] is widely used for the treatment of inflammatory diseases and musculoskeletal injury. However, there is concern regarding its potential for photosensitization as a side effect. Free radicals and active oxygen species generated from ketoprofen on exposure to ultraviolet (UV) light have been implicated in phototoxicity and photosensitization. In this study, we examined the suppressing ability of some compounds for the free radicals and active oxygen species generated by the photodynamic reaction of ketoprofen, to determine a new resist of photosensitization by ketoprofen. Eight compounds, including six known free radical scavengers were individually mixed with ketoprofen, and the mixtures were exposed to UV. Then, the free radicals and the active oxygen species were determined by the electron spin resonance spectrometry to estimate suppressing and scavenging ability of compounds. The compounds that show promise in suppressing superoxide anion generation from UV-exposed ketoprofen were further evaluated using the on-line photo-irradiated superoxide anion detection system. It was confirmed that quercetin, a flavonoid, strongly suppresses the generation of free radicals and active oxygen species from UV-exposed ketoprofen. The experiments using the experimental formulation of an adhesive skin patch of ketoprofen containing quercetine and the Chemiluminescence analyzer (CLA) indicated that quercetin has high potential for use as an excipient in ketoprofen ointments to suppress phototoxicity and photosensitization by ketoprofen. PMID:17917284

  19. Studies of radiation-produced radicals and radical ions

    International Nuclear Information System (INIS)

    The radiolytic oxidation of anti-5-methylbicyclo[2.1.0]pentane gives the 1-methylcyclopentene radical cation as the sole rearrangement product H migration whereas oxidation of its syn isomer results in the highly selective formation of the 3-methylcyclopentene radical cation by methyl group migration. Since exactly the same stereoselectivity of olefin formation was observed in corresponding PET (photosensitized electron transfer) studies in the liquid phase, it is concluded that the rearrangement in this case also occurs through the intermediacy of radical cations. Clearly, the radical cation rearrangement must occur very rapidly (10-8--10-9s) under liquid-phase conditions at room temperature to compete with back electron transfer, and therefore the hydrogen (or methyl) migration is a fast process under these conditions. An intramolecular cycloaddition reaction was demonstrated in the radical cation rearrangement of 4-vinylcyclohexene to bicyclo[3.2.1]oct-2-ene. ESR studies show that the radiolytic oxidation of quadricyclane in Freon matrices under conditions of high substrate dilution leads to the bicyclo[3.2.0]hepta-2,6-diene radical cation as well as the previously reported norbornadiene radical cation, the former species predominating at sufficiently low concentrations

  20. Comparison of antioxidant activity between aromatic indolinonic nitroxides and natural and synthetic antioxidants.

    Science.gov (United States)

    Damiani, Elisabetta; Belaid, Chokri; Carloni, Patricia; Greci, Lucedio

    2003-07-01

    In view of the possible employment of nitroxide compounds in various fields, it is important to know how they compare with other synthetic antioxidant compounds currently used in several industries and with naturally occurring antioxidants. To address this issue, the antioxidant activity of two aromatic indolinonic nitroxides synthesized by us was compared with both commercial phenolic antioxidants (BHT and BHA) and with natural phenolic antioxidants (alpha-hydroxytyrosol, tyrosol, caffeic acid, alpha-tocopherol). DPPH radical scavenging ability and the inhibition of both lipid and protein oxidation induced by the peroxyl-radical generator, AAPH, were evaluated. The results obtained show that overall: (i) the reduced forms of the nitroxide compounds are better scavengers of DPPH radical than butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BLT) but less efficient than the natural compounds; (ii) the nitroxides inhibit both linolenic acid micelles and bovine serum albumin (BSA) oxidation to similar extents as most of the other compounds in a concentration-dependent fashion. Since the aromatic nitroxides tested in this study are less toxic than BHT, these compounds may be regarded as potential, alternative sources for several applications. The mechanisms underlying the antioxidant activity of nitroxides were further confirmed by UV-Vis absorption spectroscopy experiments and macroscale reactions in the presence of radicals generated by thermolabile azo-compounds. Distribution coefficients in octanol/buffer of the nitroxides and the other compounds were also determined as a measure of lipophilicity. PMID:12911269

  1. Surprisingly Long-Lived Ascorbyl Radicals in Acetonitrile: Concerted Proton-Electron Transfer Reactions and Thermochemistry

    OpenAIRE

    Warren, Jeffrey J.; Mayer, James M.

    2008-01-01

    Proton-coupled electron transfer (PCET) reactions and thermochemistry of 5,6-isopropylidene ascorbate (iAscH−) have been examined in acetonitrile solvent.iAscH− is oxidized by 2,4,6-tBu3C6H2O• and by excess TEMPO• to give the corresponding 5,6-isopropylidene ascorbyl radical anion (iAsc•−), which persists for hours at 298 K in dry MeCN solution. The stability of iAsc•− is surprising in light of the transience of the ascorbyl radical in aqueous solutions, and is due to the lack of the protons ...

  2. Molecular physiology of EAAT anion channels.

    Science.gov (United States)

    Fahlke, Christoph; Kortzak, Daniel; Machtens, Jan-Philipp

    2016-03-01

    Glutamate is the major excitatory neurotransmitter in the mammalian central nervous system. After release from presynaptic nerve terminals, glutamate is quickly removed from the synaptic cleft by a family of five glutamate transporters, the so-called excitatory amino acid transporters (EAAT1-5). EAATs are prototypic members of the growing number of dual-function transport proteins: they are not only glutamate transporters, but also anion channels. Whereas the mechanisms underlying secondary active glutamate transport are well understood at the functional and at the structural level, mechanisms and cellular roles of EAAT anion conduction have remained elusive for many years. Recently, molecular dynamics simulations combined with simulation-guided mutagenesis and experimental analysis identified a novel anion-conducting conformation, which accounts for all experimental data on EAAT anion currents reported so far. We here review recent findings on how EAATs accommodate a transporter and a channel in one single protein. PMID:26687113

  3. Renal elimination of organic anions in cholestasis

    Institute of Scientific and Technical Information of China (English)

    Adriana Mónica Tortes

    2008-01-01

    The disposition of most drugs is highly dependent on specialized transporters.OAT1 and OAT3 are two organic anion transporters expressed in the basolateral membrane of renal proximal tubule cells,identified as contributors to xenobiotic and endogenous organic anion secretion.It is well known that cholestasis may cause renal damage.Impairment of kidney function produces modifications in the renal elimination of drugs.Recent studies have demonstrated that the renal abundance of OAT1 and OAT3 plays an important role in the renal elimination of organic anions in the presence of extrahepatic cholestasis.Time elapsed after obstructive cholestasis has an important impact on the regulation of both types of organic anion transporters.The renal expression of OAT1 and OAT3 should be taken into account in order to improve pharmacotherapeutic efficacy and to prevent drug toxicity during the onset of this hepatic disease.

  4. Noncomparative scaling of aromaticity through electron itinerancy

    International Nuclear Information System (INIS)

    Aromaticity is a multidimensional concept and not a directly observable. These facts have always stood in the way of developing an appropriate theoretical framework for scaling of aromaticity. In the present work, a quantitative account of aromaticity is developed on the basis of cyclic delocalization of π-electrons, which is the phenomenon leading to unique features of aromatic molecules. The stabilization in molecular energy, caused by delocalization of π-electrons is obtained as a second order perturbation energy for archetypal aromatic systems. The final expression parameterizes the aromatic stabilization energy in terms of atom to atom charge transfer integral, onsite repulsion energy and the population of spin orbitals at each site in the delocalized π-electrons. An appropriate computational platform is framed to compute each and individual parameter in the derived equation. The numerical values of aromatic stabilization energies obtained for various aromatic molecules are found to be in close agreement with available theoretical and experimental reports. Thus the reliable estimate of aromaticity through the proposed formalism renders it as a useful tool for the direct assessment of aromaticity, which has been a long standing problem in chemistry

  5. Towards predictable transmembrane transport: QSAR analysis of anion binding and anion transport

    OpenAIRE

    Gale, Philip A.; Busschaert, Nathalie; Bradberry, Samuel J.; Wenzel, Marco; Haynes, Cally; Hiscock, Jennifer R.; Kirby, Isabelle; Karagiannidis, Louise E.; Moore, Stephen J.; Wells, Neil; Herniman, Julie; Langley, John; Horton, Peter; Mark E. Light; Marques, Igor

    2013-01-01

    The transport of anions across biological membranes by small molecules is a growing research field due to the potential therapeutic benefits of these compounds. However, little is known about the exact mechanism by which these drug-like molecules work and which molecular features make a good transporter. An extended series of 1-hexyl-3-phenylthioureas were synthesized, fully characterized (NMR, mass spectrometry, IR and single crystal diffraction) and their anion binding and anion transport p...

  6. Influence of metal ions binding on free radical concentration in humic acids. A quantitative electron paramagnetic resonance study

    Energy Technology Data Exchange (ETDEWEB)

    Jerzykiewicz, M.; Jezierski, A. [Wroclaw Univ. (Poland). Faculty of Chemistry; Czechowski, F. [Wroclaw Univ. of Technology (Poland). Inst. of Organic Chemistry, Biochemistry and Biotechnology; Drozd, J. [Agricultural Univ. of Wroclaw (Poland). Inst. of Soil Science and Agricultural Environment Protection

    2002-07-01

    The influence of metal ions, e.g. Co(II), Cu(II), Mn(II), Ni(II), Fe(II), on free radical concentration in humic acids isolated from soil, peat and compost was investigated by electron paramagnetic resonance (EPR). The results show that metal ions with unfilled d-shell exhibit antiferromagnetic interactions with semiquinone radicals. Moreover, coordinated metals shift the quinone-semiquinone-hydroquinone equilibrium in the macromolecular matrix of humic acids. A strong decrease of semiquinone radical concentration in humic acid-metal complexes is observed. This effect is caused by interactions of metal ions with oxygen-containing stable radicals occurring in the aromatic systems of humic acids. Furthermore, the effect of metal coordination on free radical concentration in humic acids-metal complexes depends on the humic acid origin. FTIR spectroscopy was also used as an additional tool for studies of the metal ions interactions with carboxylic groups. [author].

  7. Benzo-thia-fused [n]Thienoacenequinodimethanes with Small to Moderate Diradical Characters: The Role of Pro-aromaticity versus Anti-aromaticity

    KAUST Repository

    Shi, Xueliang

    2016-01-19

    Open-shell singlet diradicaloids recently have received much attention due to their unique optical, electronic and magnetic properties and promising applications in materials science. Among various diradicaloids, quinoidal π-conjugated molecules have become the prevailing designs. However, there still lacks fundamental understanding on how the fusion mode and pro-aromaticity/anti-aromaticity affect their diradical character and physical properties. In this work, a series of pro-aromatic benzo-thia-fused [n]thienoacenequinodimethanes (Thn-TIPS (n=1-3) and BDTh-TIPS) were synthesized and compared with the previously reported anti-aromatic bisindeno-[n]thienoacenes (Sn-TIPS, n=1-4). The ground-state geometric and electronic structures of these new quinoidal molecules were systematically investigated by X-ray crystallographic analysis, variable temperature NMR, ESR, SQUID, Raman, and electronic absorption spectroscopy, assisted by DFT calculations. It was found that the diradical character index (y0) increased from nearly zero for Th1-TIPS to 2.4% for Th2-TIPS, 18.2% for Th3-TIPS, and 38.2% for BDTh-TIPS, due to the enhanced aromatic stabilization. Consequently, with the extension of molecular size, the one-photon absorption spectra are gradually red-shifted, the two-photon absorption (TPA) cross section values increase, and the singlet excited state lifetimes decrease. By comparison with the corresponding anti-aromatic analogues Sn-TIPS (n=1-3), the pro-aromatic Thn-TIPS (n=1-3) exhibit larger diradical character, longer singlet excited state lifetime and larger TPA cross section value. At the same time, they display distinctively different electronic absorption spectra and improved electrochemical amphotericity. Spectroelectrochemical studies revealed a good linear relationship between the optical energy gaps and the molecular length in the neutral, radical cationic and dicationic forms. Our research work disclosed the significant difference between the pro-aromatic

  8. A Supramolecular Sensing Platform for Phosphate Anions and an Anthrax Biomarker in a Microfluidic Device

    Directory of Open Access Journals (Sweden)

    Jurriaan Huskens

    2011-10-01

    Full Text Available A supramolecular platform based on self-assembled monolayers (SAMs has been implemented in a microfluidic device. The system has been applied for the sensing of two different analyte types: biologically relevant phosphate anions and aromatic carboxylic acids, which are important for anthrax detection. A Eu(III-EDTA complex was bound to β-cyclodextrin monolayers via orthogonal supramolecular host-guest interactions. The self-assembly of the Eu(III-EDTA conjugate and naphthalene β-diketone as an antenna resulted in the formation of a highly luminescent lanthanide complex on the microchannel surface. Detection of different phosphate anions and aromatic carboxylic acids was demonstrated by monitoring the decrease in red emission following displacement of the antenna by the analyte. Among these analytes, adenosine triphosphate (ATP and pyrophosphate, as well as dipicolinic acid (DPA which is a biomarker for anthrax, showed a strong response. Parallel fabrication of five sensing SAMs in a single multichannel chip was performed, as a first demonstration of phosphate and carboxylic acid screening in a multiplexed format that allows a general detection platform for both analyte systems in a single test run with µM and nM detection sensitivity for ATP and DPA, respectively.

  9. Role of superoxide anion radicals in ethanol metabolism by blood monocyte-derived human macrophages

    OpenAIRE

    1989-01-01

    The effects of a number of additives on the rate of conversion of ethanol (1 mg/ml; 21.7 mM) to acetate by monolayers of blood monocyte- derived human macrophages were investigated. The additives studied were superoxide dismutase (SOD; 1,500 U/ml), catalase (1,500 U/ml), tetrahydrofurane (20 mM), and PMA (20 nM), either singly or in various combinations. SOD, catalase, SOD plus catalase, tetrahydrofurane, and tetrahydrofurane plus SOD inhibited ethanol oxidation by 49.2, 12.1, 52.9, 60.4, and...

  10. Spectroscopic and Computational Investigations of Stable Radical Anions of Triosmium Benzoheterocycle Clusters

    Czech Academy of Sciences Publication Activity Database

    Nervi, C.; Gobetto, R.; Milone, L.; Viale, A.; Rosenberg, E.; Rokhsana, D.; Fiedler, Jan

    2003-01-01

    Roč. 9, - (2003), s. 5749-5756. ISSN 0947-6539 R&D Projects: GA MŠk OC D15.10; GA ČR GA203/03/0821 Institutional research plan: CEZ:AV0Z4040901 Keywords : cluster compounds * electron transfer * osmium Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 4.353, year: 2003

  11. Fenton-like Degradation of MTBE: Effects of Iron Counter Anion and Radical Scavengers

    Science.gov (United States)

    Fenton-driven oxidation of Methyl tert-butyl ether (MTBE) (0.11-0.16 mM) in batch reactors containing ferric iron (5 mM), hydrogen peroxide (H2O2) (6 mM) (pH=3) was performed to investigate MTBE transformation mechanisms. Independent variables included the form of iron (Fe) (Fe2(...

  12. An ESR study of the gamma radiolysis of aromatic polyesters containing isomeric naphthalene links

    International Nuclear Information System (INIS)

    Six polyesters were synthesised from 4,4'-oxy-bis(benzoyl chloride) and 1,4-, 1,5-, 1,6-, 2,3-, 2,6-, and 2,7-naphthalenediol isomers. The structures of the polyesters were characterised by means of IR, inherent viscosities in tetrachloroethane (TCE), solutions at 303 K and thermal analysis. The glass transition temperatures were in the range of 425-494 K by DSC thermal analysis. All of the polyesters were irradiated in an AECL Gammacell 220 unit at a dose rate of approximately 6.7 kGy/h to doses in the range of 0-15 kGy at 77 and 300 K. ESR spectroscopy was used to examine the radicals formed during radiolysis and to measure their yields. The G-values for radical formation in the polyesters were found to be in the range 0.18-1.41 at 77 K and 0.19-0.78 at 300 K. At 77 K, up to 15% of the radicals formed on radiolysis were found to be photo-bleachable anion radicals. Annealing experiments were carried out in order to identify the neutral radicals, which were assigned to naphthyl- or phenyl- and phenoxyl-type radicals

  13. Radiation effects on crystalline L-asparagine, revisited: Radical formation by EMR and periodic DFT after X-irradiation at 275 K

    International Nuclear Information System (INIS)

    Radical formation by X-irradiation of single crystals of L-asparagine monohydrate at 275 K has been investigated at 240 K and 295 K using Electron Paramagnetic Resonance (EPR), Electron Nuclear DOuble Resonance (ENDOR) and ENDOR-Induced EPR spectroscopic techniques. Free radical structures suggested by detailed analysis of the experimental data were assessed by Density Functional Theory calculations in a periodic approach. The combined experimental and computational evidence revealed three stable radical species at room temperature. Two of these could reliably be established as net H-abstracted species, one from the methylene group in the amino acid side chain and the second from the amino acid back-bone carbon atom. For the third room temperature radical species, a variety of deamination- and decarboxylation products were investigated and dismissed. Even if an unambiguous structure could not be established, this radical is tentatively suggested to descend from a side-chain O3-protonated amide anion by hydrogen atom transfer from the C3 to the C4 position. - Highlights: • Radicals in L-aspargine at 295 K investigated using EPR, ENDOR, EIE and DFT. • Radicals by net loss of H-atom from the backbone and sidechain are identified. • A possible successor from a primary side-chain amide anion has been observed. • Radical characterization has been supported by periodic boundary DFT calculations. • Deamination and decarboxylation radicals at room temperature were not observed

  14. Radical production in biological systems

    International Nuclear Information System (INIS)

    This paper describes our effort to develop a metric for radiation exposure that is more fundamental than adsorbed dose and upon which a metric for exposure to chemicals could be based. This metric is based on the production of radicals by the two agents. Radicals produced by radiation in biological systems commonly assumed to be the same as those produced in water despite the presence of a variety of complex molecules. This may explain why the extensive efforts to describe the relationship between energy deposition (track structure) and molecular damage to DNA, based on the spectrum of radicals produced, have not been successful in explaining simple biological effects such as cell killing. Current models assume that DNA and its basic elements are immersed in water-like media and only model the production and diffusion of water-based radicals and their interaction with DNA structures; these models lack the cross sections associated with each macro-component of DNA and only treat water-based radicals. It has been found that such models are not realistic because DNA is not immersed in pure water. A computer code capable of simulating electron tracks, low-energy electrons, energy deposition in small molecules, and radical production and diffusion in water like media has been developed. This code is still in at a primitive stage and development is continuing. It is being used to study radical production by radiation, and radical diffusion and interactions in simple molecular systems following their production. We are extending the code to radical production by chemicals to complement our PBPK modeling efforts. It therefore has been developed primarily for use with radionuclides that are in biological materials, and not for radiation fields

  15. Free radical scavenging activity of novel thiazolidine-2,4-dione derivatives.

    Science.gov (United States)

    Berczyński, Paweł; Kruk, Irena; Piechowska, Teresa; Ceylan-Unlusoy, Meltem; Bozdağ-Dündar, Oya; Aboul-Enein, Hassan Y

    2013-01-01

    Free radical activity towards superoxide anion radical (O2•¯), hydroxyl radical (HO(•)) and 2,2-diphenyl-1-picrylhydrazyl (DPPH(•)) of a series of novel thiazolidine-2,4-dione derivatives (TSs) was examined using chemiluminescence, electron paramagnetic resonance (EPR) and EPR spin trapping techniques. 5,5-Dimethyl-1-pyrroline-N-oxide (DMPO) was applied as the spin trap. Superoxide radical was produced in the potassium superoxide/18-crown-6 ether dissolved in dimethyl sulfoxide. Hydroxyl radical was generated in the Fenton reaction (Fe(II) + H2O2. It was found that TSs showed a slight scavenging effect (15-38% reduction at 2.5 mmol/L concentration) of the DPPH radical and a high scavenging effect of O2•¯ (41-88%). The tested compounds showed inhibition of HO(•)-dependent DMPO-OH spin adduct formation (the amplitude of EPR signal decrease ranged from 20 to 76% at 2.5 mmol/L concentration. Our findings present new group compounds of relatively high reactivity towards free radicals. PMID:23225772

  16. Photochemical synthesis of simple organic free radicals on simulated planetary surfaces - An ESR study

    Science.gov (United States)

    Tseng, S.-S.; Chang, S.

    1975-01-01

    Electron spin resonance (ESR) spectroscopy provided evidence for formation of hydroxyl radicals during ultraviolet photolysis (254 nm) at -170 C of H2O adsorbed on silica gel or of silica gel alone. The carboxyl radical was observed when CO or CO2 or a mixture of CO and CO2 adsorbed on silica gel at -170 C was irradiated. The ESR signals of these radicals slowly disappeared when the irradiated samples were warmed to room temperature. However, reirradiation of CO or CO2, or the mixture CO and CO2 on silica gel at room temperature then produced a new species, the carbon dioxide anion radical, which slowly decayed and was identical with that produced by direct photolysis of formic acid adsorbed on silica gel. The primary photochemical process may involve formation of hydrogen and hydroxyl radicals. Subsequent reactions of these radicals with adsorbed CO or CO2 or both yield carboxyl radicals, CO2H, the precursors of formic acid. These results confirm the formation of formic acid under simulated Martian conditions and provide a mechanistic basis for gauging the potential importance of gas-solid photochemistry for chemical evolution on other extraterrestrial bodies, on the primitive earth, and on dust grains in the interstellar medium.

  17. Mechanisms of strand breaks in DNA induced by OH radicals in aqueous solution

    International Nuclear Information System (INIS)

    The gamma irradiation of N2O-saturated aqueous solutions of DNA in the absence of O2 leads to the formation of three detached altered sugars. It is predominantly OH radical which leads to the permanent and biological significant damage of DNA, and it is especially the OH radical which produces chain breaks. The OH radicals in aqueous solutions react with DNA predominantly (about 80%) by addition to the C=C bonds of the bases, and about 20% abstracts H atoms from sugar moiety. All three isolated sugars show new C=O bonds only at the position C-4. Chain-breaking reaction is identified as the heterolytic splitting of the sugar phosphoric acid ester bond, producing a cation radical of the sugar moiety and an anion of the DNA phosphoric acid ester (SN1 reaction). The formation of the observed detached and attached altered sugars as end products is explained by the reaction of the cation radical with water in which branching in the reaction occurs, and by the subsequent reaction of the radicals formed. Two important features of the Scheme I mechanism are, first, the much faster bond breaking at the position 3' as compared with that at the position 5', and secondly, the formation of not only detached altered sugars but also altered sugar end groups. Quantitative results show that a large fraction of DNA chain breaks induced by OH radicals can be accounted for by the Scheme I. (Yamashita, S.)

  18. Guest Editorial: Processes of Radicalization and De-Radicalization

    Directory of Open Access Journals (Sweden)

    Donatella Della Porta

    2012-05-01

    Full Text Available The study of radicalization and de-radicalization, understood as processes leading towards the increased or decreased use of political violence, is central to the question of how political violence emerges, how it can be prevented, and how it can be contained. The focus section of this issue of the International Journal of Conflict and Violence addresses radicalization and de-radicalization, seeking to develop a more comprehensive understanding of the processes, dynamics, and mechanisms involved and taking an interdisciplinary approach to overcome the fragmentation into separate disciplines and focus areas. Contributions by Pénélope Larzillière, Felix Heiduk, Bill Kissane, Hank Johnston, Christian Davenport and Cyanne Loyle, Veronique Dudouet, and Lasse Lindekilde address repressive settings, legitimacy, institutional aspects, organizational outcomes, and dynamics in Europe, Asia, Africa, and North and South America.

  19. Free radical scavenging and antimicrobial properties of extracts of wild mushrooms

    OpenAIRE

    Oyetayo, V.O.

    2009-01-01

    Antioxidant and antimicrobial potentials of extracts obtained from four wild mushrooms, Termitomyces clypeatus (TCE), Termitomyces robustus (TRE), Lentinus subnudus (LSE) and Lenzites species (LZE) collected in Nigeria were investigated. LSE and LZE displayed good scavenging activity against 2, 2-Diphenyl-1-Picrylhydrazyl (DPPH) and ferrous ion radicals at concentration of 2 mg/mL. However, TRE and TCE exhibited better superoxide anion scavenging effect at 2 mg/mL. All extracts (TCE, TRE, LSE...

  20. Multimer Radical Ions and Electron/Hole Localization in Polyatomic Molecular Liquids: A critical review

    OpenAIRE

    Shkrob, Ilya A.; Sauer, Jr., Myran C.

    2004-01-01

    While ionization of some polyatomic molecular liquids (such as water and aliphatic alcohols) yields so-called "solvated electrons" in which the excess electron density is localized in the interstices between the solvent molecules, most organic and inorganic liquids yield radical anions and cations in which the electron and spin densities reside on the solvent molecule or, more commonly, a group of such molecules. The resulting multimer ions have many unusual properties, such as high rates of ...

  1. Antioxidative capacity and enzyme activity in Haematococcus pluvialis cells exposed to superoxide free radicals

    Institute of Scientific and Technical Information of China (English)

    刘建国; 张晓丽; 孙延红; 林伟

    2010-01-01

    The antioxidative capacity of astaxanthin and enzyme activity of reactive oxygen eliminating enzymes such as superoxide dismutase (SOD),peroxidase (POD),catalase (CAT) and ascorbate peroxidase (APX) were studied in three cell types of Haematococcus pluvialis exposed to high concentrations of a superoxide anion radical (O2ˉ).The results show that defensive enzymes and astaxanthin-related mechanisms were both active in H.pluvialis during exposure to reactive oxygen species (ROS) such as Oˉ2.Astaxanthin reacte...

  2. Efficiency of adsorption concentration of single-charged inorganic anions

    International Nuclear Information System (INIS)

    Results of adsorption concentration of inorganic anions Br-, I-, SCN- from diluted aqueous solutions using of N-alkylpyridinium chlorides (alkyl C13-C16) are presented. It is ascertained that interaction between extracted anion and surfactant cation, determining the efficiency of foam flotation of the anions investigated, increases with the decrease in anion hydration in the series Br-, I-, SCN-

  3. Mechanistic studies on the OH-initiated atmospheric oxidation of selected aromatic hydrocarbons

    Energy Technology Data Exchange (ETDEWEB)

    Nehr, Sascha

    2012-07-01

    Benzene, toluene, the xylenes, and the trimethylbenzenes are among the most abundant aromatic trace constituents of the atmosphere mainly originating from anthropogenic sources. The OH-initiated atmospheric photo-oxidation of aromatic hydrocarbons is the predominant removal process resulting in the formation of O{sub 3} and secondary organic aerosol. Therefore, aromatics are important trace constituents regarding air pollution in urban environments. Our understanding of aromatic photo-oxidation processes is far from being complete. This work presents novel approaches for the investigation of OH-initiated atmospheric degradation mechanisms of aromatic hydrocarbons. Firstly, pulsed kinetic studies were performed to investigate the prompt HO{sub 2} formation from OH+ aromatic hydrocarbon reactions under ambient conditions. For these studies, the existing OH reactivity instrument, based on the flash photolysis/laser-induced fluorescence (FP/LIF) technique, was extended to the detection of HO{sub 2} radicals. The experimental design allows for the determination of HO{sub 2} formation yields and kinetics. Results of the pulsed kinetic experiments complement previous product studies and help to reduce uncertainties regarding the primary oxidation steps. Secondly, experiments with aromatic hydrocarbons were performed under atmospheric conditions in the outdoor atmosphere simulation chamber SAPHIR (Simulation of Atmospheric PHotochemistry In a large Reaction chamber) located at Forschungszentrum Juelich. The experiments were aimed at the evaluation of up-to-date aromatic degradation schemes of the Master Chemical Mechanism (MCMv3.2). The unique combination of analytical instruments operated at SAPHIR allows for a detailed investigation of HO{sub x} and NO{sub x} budgets and for the determination of primary phenolic oxidation product yields. MCMv3.2 deficiencies were identified and most likely originate from shortcomings in the mechanistic representation of ring

  4. Classical density functional theory & simulations on a coarse-grained model of aromatic ionic liquids.

    Science.gov (United States)

    Turesson, Martin; Szparaga, Ryan; Ma, Ke; Woodward, Clifford E; Forsman, Jan

    2014-05-14

    A new classical density functional approach is developed to accurately treat a coarse-grained model of room temperature aromatic ionic liquids. Our major innovation is the introduction of charge-charge correlations, which are treated in a simple phenomenological way. We test this theory on a generic coarse-grained model for aromatic RTILs with oligomeric forms for both cations and anions, approximating 1-alkyl-3-methyl imidazoliums and BF₄⁻, respectively. We find that predictions by the new density functional theory for fluid structures at charged surfaces are very accurate, as compared with molecular dynamics simulations, across a range of surface charge densities and lengths of the alkyl chain. Predictions of interactions between charged surfaces are also presented. PMID:24718295

  5. Use of anions of C{sub 60} as electrogenerated bases

    Energy Technology Data Exchange (ETDEWEB)

    Niyazymbetov, M.E.; Evans, D.H. [Univ. of Delaware, Newark, DE (United States). Dept. of Chemistry and Biochemistry

    1995-08-01

    C{sub 60} was reduced in the mixed solvent acetonitrile-toluene (2:3) to form a series of three electrogenerated bases of successively increasing basicity. These were the radical anion, the dianion, and the radical trianion of the fullerene. Cyclic voltammograms indicated that the radical anion was capable of deprotonating the relatively strong C-H acid, ethyl nitroacetate. The weaker acid, diethyl malonate, required the stronger base C{sub 60}{sup 2{minus}} in order to observe deprotonation on the voltammetric time scale. Other weak acids that react with C{sub 60}{sup 2{minus}} include diethyl methylalonate, 2-nitropropane, and n-octanethiol. The anionic electrogenerated bases were used to carry out efficient base-catalyzed synthetic reactions. These included the C{sub 60}{sup {minus}{sm_bullet}}-catalyzed reaction of ethyl nitroacetate with ethyl acrylate and acrylonitrile to form double addition products. The dianion promoted reaction of nitromethane with ethyl acrylate to form a triple addition product in good yield, as well as the reaction of diethyl malonate with acrylonitrile to give a double addition product. In this case it was demonstrated that the fullerene probase may be recycled at least two times. The dianion was also used to catalyze the addition of n-octanethiol to styrene oxide. The reactions of still weaker acids could be promoted by the highly basic C{sub 60}{sup 3{minus}}. These included the addition of pyrrole to acrylonitrile and the Wittig-Horner reaction of diethyl benzylphosphonate with benzaldehyde.

  6. Electron spin resonance spectrum of [(MeO)3B.B(OMe)3]-. A novel sigma radical with a one-electron bond

    International Nuclear Information System (INIS)

    The esr spectrum of crystalline B(OMe)3, gamma irradiated at 770K, showed the existence of a paramagnetic color center containing two equivalent borom atoms, the dimer radical anion of trimethyl borate. In addition the spectrum shows the characteristic line shapes of parallel and perpendicular components. Orientation of the crystal in a magnetic field enhanced the parallel features. It was concluded that the unpaired electron in the dimer radical anion is largely concentrated in the sigma-bonding orbital between two non planar B(OMe)3 units

  7. Utilizing the σ-complex stability for quantifying reactivity in nucleophilic substitution of aromatic fluorides

    Directory of Open Access Journals (Sweden)

    Magnus Liljenberg

    2013-04-01

    Full Text Available A computational approach using density functional theory to compute the energies of the possible σ-complex reaction intermediates, the “σ-complex approach”, has been shown to be very useful in predicting regioselectivity, in electrophilic as well as nucleophilic aromatic substitution. In this article we give a short overview of the background for these investigations and the general requirements for predictive reactivity models for the pharmaceutical industry. We also present new results regarding the reaction rates and regioselectivities in nucleophilic substitution of fluorinated aromatics. They were rationalized by investigating linear correlations between experimental rate constants (k from the literature with a theoretical quantity, which we call the sigma stability (SS. The SS is the energy change associated with formation of the intermediate σ-complex by attachment of the nucleophile to the aromatic ring. The correlations, which include both neutral (NH3 and anionic (MeO− nucleophiles are quite satisfactory (r = 0.93 to r = 0.99, and SS is thus useful for quantifying both global (substrate and local (positional reactivity in SNAr reactions of fluorinated aromatic substrates. A mechanistic analysis shows that the geometric structure of the σ-complex resembles the rate-limiting transition state and that this provides a rationale for the observed correlations between the SS and the reaction rate.

  8. Rosemary Aromatization of Extra Virgin Olive Oil and Process Optimization Including Antioxidant Potential and Yield

    Directory of Open Access Journals (Sweden)

    Erkan Karacabey

    2016-08-01

    Full Text Available Aromatization of olive oil especially by spices and herbs has been widely used technique throughout the ages in Mediterranean diets. The present study was focused on aromatization of olive oil by rosemary (Rosmarinus officinalis L.. Aromatization process was optimized by response surface methodology as a function of malaxation’s conditions (temperature and time. According to authors’ best knowledge it was first time for examination of oil yield performance with antioxidant potential and pigments under effect of aromatization parameters. For all oil samples, values of the free acidity, peroxide, K232 and K270 as quality parameters fell within the ranges established for the highest quality category “extra virgin oil”. Oil yield (mL oil/kg olive paste changed from 158 to 208 with respect to design parameters. Total phenolic content and free radical scavenging activity as antioxidant potential of olive oil samples were varied in the range of 182.44 – 348.65 mg gallic acid equivalent/kg oil and 28.91 – 88.75 % inhibition of 2,2-Diphenyl-1-picrylhydrazyl-(DPPH•, respectively. Total contents of carotenoid, chlorophyll and pheophytin a as pigments in oil samples were found to be in between 0.09 – 0.48 mg carotenoid/kg oil, 0.11 – 0.96 mg chlorophyll/kg oil, 0.15 – 4.44 mg pheo α/kg oil, respectively. The proposed models for yield, pigments and antioxidant potential responses were found to be good enough for successful prediction of experimental results. Total phenolics, carotenoids and free radical scavenging activity of aromatized olive oil and oil yield were maximized to gather and optimal conditions were determined as 25°C, 84 min, and 2 % (Rosemary/olive paste; w/w.

  9. HOCCO versus OCCO: Comparative spectroscopy of the radical and diradical reactive intermediates

    Science.gov (United States)

    Dixon, Andrew R.; Xue, Tian; Sanov, Andrei

    2016-06-01

    We present a photoelectron imaging study of three glyoxal derivatives: the ethylenedione anion (OCCO-), ethynediolide (HOCCO-), and glyoxalide (OHCCO-). These anions provide access to the corresponding neutral reactive intermediates: the OCCO diradical and the HOCCO and OHCCO radicals. Contrasting the straightforward deprotonation pathway in the reaction of O- with glyoxal (OHCCHO), which is expected to yield glyoxalide (OHCCO-), OHCCO- is shown to be a minor product, with HOCCO- being the dominant observed isomer of the m/z = 57 anion. In the HOCCO/OHCCO anion photoelectron spectrum, we identify several electronic states of this radical system and determine the adiabatic electron affinity of HOCCO as 1.763(6) eV. This result is compared to the corresponding 1.936(8) eV value for ethylenedione (OCCO), reported in our recent study of this transient diradical [A. R. Dixon, T. Xue, and A. Sanov, Angew. Chem., Int. Ed. 54, 8764-8767 (2015)]. Based on the comparison of the HOCCO-/OHCCO- and OCCO- photoelectron spectra, we discuss the contrasting effects of the hydrogen connected to the carbon framework or the terminal oxygen in OCCO.

  10. Studies of anions sorption on natural zeolites.

    Science.gov (United States)

    Barczyk, K; Mozgawa, W; Król, M

    2014-12-10

    This work presents results of FT-IR spectroscopic studies of anions-chromate, phosphate and arsenate - sorbed from aqueous solutions (different concentrations of anions) on zeolites. The sorption has been conducted on natural zeolites from different structural groups, i.e. chabazite, mordenite, ferrierite and clinoptilolite. The Na-forms of sorbents were exchanged with hexadecyltrimethylammonium cations (HDTMA(+)) and organo-zeolites were obtained. External cation exchange capacities (ECEC) of organo-zeolites were measured. Their values are 17mmol/100g for chabazite, 4mmol/100g for mordenite and ferrierite and 10mmol/100g for clinoptilolite. The used initial inputs of HDTMA correspond to 100% and 200% ECEC of the minerals. Organo-modificated sorbents were subsequently used for immobilization of mentioned anions. It was proven that aforementioned anions' sorption causes changes in IR spectra of the HDTMA-zeolites. These alterations are dependent on the kind of anions that were sorbed. In all cases, variations are due to bands corresponding to the characteristic Si-O(Si,Al) vibrations (occurring in alumino- and silicooxygen tetrahedra building spatial framework of zeolites). Alkylammonium surfactant vibrations have also been observed. Systematic changes in the spectra connected with the anion concentration in the initial solution have been revealed. The amounts of sorbed CrO4(2-), AsO4(3-) and PO4(3-) ions were calculated from the difference between their concentrations in solutions before (initial concentration) and after (equilibrium concentration) sorption experiments. Concentrations of anions were determined by spectrophotometric method. PMID:25002191

  11. Quantum transport through aromatic molecules

    International Nuclear Information System (INIS)

    In this paper, we study the electronic transport properties through aromatic molecules connected to two semi-infinite leads. The molecules are in different geometrical configurations including arrays. Using a nearest neighbor tight-binding approach, the transport properties are analyzed into a Green's function technique within a real-space renormalization scheme. We calculate the transmission probability and the Current-Voltage characteristics as a function of a molecule-leads coupling parameter. Our results show different transport regimes for these systems, exhibiting metal-semiconductor-insulator transitions and the possibility to employ them in molecular devices

  12. Very Efficient Nucleophilic Aromatic Fluorination Reaction in Molten Salts: A Mechanistic Study

    International Nuclear Information System (INIS)

    We report a quantum chemical study of an extremely efficient nucleophilic aromatic fluorination in molten salts. We describe that the mechanism involves solvent anion interacting with the ion pair nucleophile M+F- (M = Na, K, Rb, Cs) to accelerate the reaction. We show that our proposed mechanism may well explain the excellent efficiency of molten salts for SNAr reactions, the relative efficacy of the metal cations, and also the observed large difference in rate constants in two molten salts (n-C4H9)4N+ CX3SO3-, (X=H, F) with slightly different sidechain (-CH3 vs. -CF3)

  13. Substrate specific hydrolysis of aromatic and aromatic-aliphatic esters in orchid tissue cultures

    OpenAIRE

    Agnieszka Mironowicz; Krystyna Kukułczanka; Antoni Siewiński

    2014-01-01

    We found that tissue cultures of higher plants were able, similarly as microorganisms, to transform low-molecular-weight chemical compounds. In tissue cultures of orchids (Cymbidium 'Saint Pierre' and Dendrobium phalaenopsis) acetates of phenols and aromatic-aliphatic alcohols were hydrolyzed, whereas methyl esters of aromatic and aromatic-aliphatic acids did not undergo this reaction. Acetates of racemic aromatic-aliphatic alcohols were hydrolyzed with distinct enantiospecificity.

  14. Redox Properties of Free Radicals.

    Science.gov (United States)

    Neta, P.

    1981-01-01

    Describes pulse radiolysis as a useful means in studing one-electron redox potentials. This method allows the production of radicals and the determination of their concentration and rates of reaction. (CS)

  15. Radical polymerization of monoethyl itaconate

    OpenAIRE

    Katsikas Lynne; Nišević Nataša; Ignjatović Milka; Adamović Vladimir; Đakov Tatjana A.; Popović Ivanka G.

    2003-01-01

    The radical polymerization of monoethyl itaconate (MEI) was investigated in bulk and in solution at 60°C using a,a'-azobisisobutyronitrile as initiator. It was established that the obtained polymer poly(monoethyl itaconate) was insoluble in its monomer, implying that the bulk polymerization of MEI was a precipitation polymerization. The polymerization kinetics of MEI were discussed and compared to the polymerization kinetics of structurally similar alkyl itaconates. The homogeneous radical po...

  16. Ecoporn, Irrationalities and Radical Environmentalism

    OpenAIRE

    Măntescu, Liviu

    2016-01-01

    This study explores the ‘irrationalities’ of deep ecology activism in the context of radical environmentalism by using the empirical example of ecoporn. Fuck For Forest is an environmental Non-Governmental Organisation which undertakes fund-raising for re-forestation and forest protection by means of pornography. Following twelve months of ethnographic fieldwork, this study presents first research results on a radical environmental project which does not promote democratic and established pro...

  17. Mechanism and kinetic study on the gas-phase reactions of OH radical with carbamate insecticide isoprocarb

    Science.gov (United States)

    Zhang, Chenxi; Yang, Wenbo; Bai, Jing; Zhao, Yuyang; Gong, Chen; Sun, Xiaomin; Zhang, Qingzhu; Wang, Wenxing

    2012-12-01

    As one of the most important carbamate insecticides, isoprocarb [2-(1-methylethyl) phenyl methylcarbamate, MIPC] is widely used in agricultural and cotton spraying. The atmospheric chemical reaction mechanism and kinetics of MIPC with OH radical have been researched using the density functional theory in this paper. The study shows that OH radical is more easily added to the C atoms of aromatic ring than to carbon-oxygen double bond, while the H atom is abstracted more difficulty from -CONH- group and aromatic ring than from the -CH3- group and the -CH- group. At room temperature, the total rate constant of MIPC with OH radical is about 5.1 × 10-12 cm3 molecule-l s-l. OH radical addition reaction and H atom abstraction reaction are both important for the OH-initiated reaction of MIPC. The energy-rich adducts (MIPC-OH) and the MIPC's radical isomers are open-shell activated radicals and can be further oxidized in the atmosphere.

  18. Synthesis, Characterization, and Pharmacological Evaluation of Selected Aromatic Amines

    Directory of Open Access Journals (Sweden)

    Hammad Ismail

    2015-01-01

    Full Text Available Aromatic amines 1-amino-4-phenoxybenzene (A-1A, 2-(4-aminophenoxy naphthalene (A-2A, and 1-(4-aminophenoxy naphthalene (A-3A were synthesized by the reduction of corresponding nitroaromatics with hydrazine monohydrate and Pd/C 5% (w/w. The newly synthesized compounds were characterized by FTIR, 1H NMR, 13C NMR, UV-visible spectrophotometer, and mass spectrometry and their biological activities were investigated along with structurally similar 4-(4-aminophenyloxy biphenyl (A-A. Results of brine shrimp cytotoxicity assay showed that almost all of the compounds had LD50 values <1 μg/mL. The compounds also showed significant antitumor activity with IC50 values ranging from 67.45 to 12.2 µgmL−1. The cytotoxicity and antitumor studies correlate the results which suggests the anticancerous nature of compounds. During the interaction study of these compounds with DNA, all of the compounds showed hyperchromic effect indicating strong interaction through binding with the grooves of DNA. Moreover, A-3A also showed decrease in λmax confirming higher propensity for DNA groove binding. In DPPH free radical scavenging assay, all the compounds showed potential antioxidant capability. The compounds were highly active in protecting DNA against hydroxyl free radicals. DNA interaction and antioxidant results back up each other indicating that these compounds have potential to be used as cancer chemopreventive agents. Additionally, one compound (A-1A showed significant antibacterial and antifungal activity as well.

  19. The games radicals play : special issue on free radicals and radical ions

    OpenAIRE

    Walton, John C; Ffrancon Williams

    2015-01-01

    Chemistry and Physics have aptly been described as “most excellent children of Intellect and Art” [1]. Both these “children” engage with many playthings, and molecules rank as one of their first favorites, especially radicals, which are amongst the most lively and exciting. Checking out radicals dancing to the music of entropy round their potential energy ballrooms is surely both entertaining and enlightening. Radicals’ old favorite convolutions are noteworthy, but the new styles, modes and a...

  20. Recognition of anions by protonated methylazacalixpyridines

    Institute of Scientific and Technical Information of China (English)

    Han-yuan GONG; De-xian WANG; Zhi-tang HUANG; Mei-xiang WANG

    2009-01-01

    Methylazacalixpyridines are a unique kind of macro-cyclic molecules that are able to self-regulate their conformations to best fit the guests. They had shown good recognition to both neutral molecules such as diols and fullerenes and cations. After protonation, the conformation of methylazacalixpyridines became more flexible and could serve as receptors for anions.In the solution, the protonated methylazacalix[2]pyri-dine[2]arene formed complexes with halides yield-ing biding constants of 79(mol/L)-1 for chloride,10 (mol/L)-1 for bromide, and 79 (mol/L)-1 for iodide,respectively. The crystal structures of the complexes between protonated methylazaealix[4]pyridine (MACP-4), methylazacalix[2]pyridine[2] arene (MACP-2-A-2), and iodide anion showed a multiple interaction mode including electrostatic attraction,hydrogen bonding, and anion-π interactions.

  1. Beyond organic chemistry: aromaticity in atomic clusters.

    Science.gov (United States)

    Boldyrev, Alexander I; Wang, Lai-Sheng

    2016-04-28

    We describe joint experimental and theoretical studies carried out collaboratively in the authors' labs for understanding the structures and chemical bonding of novel atomic clusters, which exhibit aromaticity. The concept of aromaticity was first discovered to be useful in understanding the square-planar unit of Al4 in a series of MAl4(-) bimetallic clusters that led to discoveries of aromaticity in many metal cluster systems, including transition metals and similar cluster motifs in solid compounds. The concept of aromaticity has been found to be particularly powerful in understanding the stability and bonding in planar boron clusters, many of which have been shown to be analogous to polycyclic aromatic hydrocarbons in their π bonding. Stimulated by the multiple aromaticity in planar boron clusters, a design principle has been proposed for stable metal-cerntered aromatic molecular wheels of the general formula, M@Bn(k-). A series of such borometallic aromatic wheel complexes have been produced in supersonic cluster beams and characterized experimentally and theoretically, including Ta@B10(-) and Nb@B10(-), which exhibit the highest coordination number in two dimensions. PMID:26864511

  2. Crystalline bipyridinium radical complexes and uses thereof

    Energy Technology Data Exchange (ETDEWEB)

    Fahrenbach, Albert C.; Barnes, Jonathan C.; Li, Hao; Stoddart, J. Fraser; Basuray, Ashish Neil; Sampath, Srinivasan

    2015-09-01

    Described herein are methods of generating 4,4'-bipyridinium radical cations (BIPY.sup..cndot.+), and methods for utilizing the radical-radical interactions between two or more BIPY.sup..cndot.+ radical cations that ensue for the creation of novel materials for applications in nanotechnology. Synthetic methodologies, crystallographic engineering techniques, methods of physical characterization, and end uses are described.

  3. Crystalline bipyridinium radical complexes and uses thereof

    Science.gov (United States)

    Fahrenbach, Albert C.; Barnes, Jonathan C.; Li, Hao; Stoddart, J. Fraser; Basuray, Ashish Neil; Sampath, Srinivasan

    2015-09-01

    Described herein are methods of generating 4,4'-bipyridinium radical cations (BIPY.sup..cndot.+), and methods for utilizing the radical-radical interactions between two or more BIPY.sup..cndot.+ radical cations that ensue for the creation of novel materials for applications in nanotechnology. Synthetic methodologies, crystallographic engineering techniques, methods of physical characterization, and end uses are described.

  4. Identification and characterization of anion binding sites in RNA

    Energy Technology Data Exchange (ETDEWEB)

    Kieft, Jeffrey S.; Chase, Elaine; Costantino, David A.; Golden, Barbara L. (Purdue); (Colorado)

    2010-05-24

    Although RNA molecules are highly negatively charged, anions have been observed bound to RNA in crystal structures. It has been proposed that anion binding sites found within isolated RNAs represent regions of the molecule that could be involved in intermolecular interactions, indicating potential contact points for negatively charged amino acids from proteins or phosphate groups from an RNA. Several types of anion binding sites have been cataloged based on available structures. However, currently there is no method for unambiguously assigning anions to crystallographic electron density, and this has precluded more detailed analysis of RNA-anion interaction motifs and their significance. We therefore soaked selenate into two different types of RNA crystals and used the anomalous signal from these anions to identify binding sites in these RNA molecules unambiguously. Examination of these sites and comparison with other suspected anion binding sites reveals features of anion binding motifs, and shows that selenate may be a useful tool for studying RNA-anion interactions.

  5. Vibronic Emission Spectroscopy of Benzyl-Type Radicals Generated by Corona Discharge

    Science.gov (United States)

    Yi, Eun Hye; Yoon, Young; Lee, Sang

    2014-06-01

    Benzyl radical is a prototypical aromatic free radical and has been the subject of numerous spectroscopic studies. On the other hand, ring-substituted benzyl radicals, benzyl-type radicals, have received less attention due to the difficulties associated with production in corona discharge and analysis of spectra. We report vibronic emission spectra of hetero halogen multi-substituted benzyl radicals generated by corona discharge of corresponding toluene derivatives using a pinhole-type glass nozzle, from which visible vibronic emission spectra were recorded using a long-path monochromator. The spectra show nice features of strongest origin band and a series of vibronic bands in the lower energies originating from the vibrationless D_1 state. From the analysis of the spectra observed, we determined the energies of the D_1 → D_0 electronic transition and vibrational mode frequencies in the ground electronic state. On the other hand, all substituted benzyl radicals show the origin bands shifted to red region with respect to the parental benzyl radical at 22002 cm-1. The shifts of multi-substituted benzyl radicals can be well estimated using the method developed from mono-substituted benzyl radicals as well as the positions of nodal point and mutual orientation of substituents, which could be useful for scientists to set a proper scanning range of their spectrometers for the spectroscopic observation of transient molecules. In this presentation, we will discuss the substituent effect on electronic transition energy and the experimental technique developed in this laboratory. Y. W. Yoon and S. K. Lee, J. Phys. Chem. A, 117, 2485 (2013). Y. W. Yoon, S. Y. Chae, and S. K. Lee, Chem. Phys. Lett., 584, 37 (2013). Y. W. Yoon and S. K. Lee, Chem. Phys. Lett., 570, 29 (2013).

  6. Peroxy radical partitioning during the AMMA radical intercomparison exercise

    Directory of Open Access Journals (Sweden)

    M. D. Andrés-Hernández

    2010-11-01

    Full Text Available Peroxy radicals were measured onboard two scientific aircrafts during the AMMA (African Monsoon Multidisciplinary Analysis campaign in summer 2006. This paper reports results from the flight on 16 August 2006 during which measurements of HO2 by laser induced fluorescence spectroscopy at low pressure (LIF-FAGE and total peroxy radicals (RO2* = HO2+ΣRO2, R = organic chain by two similar instruments based on the peroxy radical chemical amplification (PeRCA technique were subject of a blind intercomparison. The German DLR-Falcon and the British FAAM-BAe-146 flew wing tip to wing tip for about 30 min making concurrent measurements on 2 horizontal level runs at 697 and 485 hPa over the same geographical area in Burkina Faso. A full set of supporting measurements comprising photolysis frequencies, and relevant trace gases like CO, NO, NO2, NOy, O3 and a wider range of VOCs were collected simultaneously.

    Results are discussed on the basis of the characteristics and limitations of the different instruments used. Generally, no data bias are identified and the RO2* data available agree quite reasonably within the instrumental errors. The [RO2*]/[HO2] ratios, which vary between 1:1 and 3:1, as well as the peroxy radical variability, concur with variations in photolysis rates and in other potential radical precursors. Model results provide additional information about dominant radical formation and loss processes.

  7. Peroxy radical partitioning during the AMMA radical intercomparison exercise

    Directory of Open Access Journals (Sweden)

    M. D. Andrés-Hernández

    2010-04-01

    Full Text Available Peroxy radicals were measured onboard two scientific aircrafts during the AMMA (African Monsoon Multidisciplinary Analysis campaign in summer 2006. This paper reports results from the flight on 16 August 2006 during which measurements of HO2 by laser induced fluorescence spectroscopy at low pressure (LIF-FAGE and total peroxy radicals (RO2*=HO2+ΣRO2, R= organic chain by two similar instruments based on the peroxy radical chemical amplification (PerCA technique were subject of a blind intercomparison. The German DLR-Falcon and the British FAAM-BAe-146 flew wing tip to wing tip for about 30 min making concurrent measurements on 2 horizontal level runs at 697 and 485 hPa over the same geographical area in Burkina Faso. A full set of supporting measurements comprising photolysis frequencies, and relevant trace gases like CO, NO, NO2, NOy, O3 and a wider range of VOCs were collected simultaneously.

    Results are discussed on the basis of the characteristics and limitations of the different instruments used. Generally, no data bias are identified and the RO2* data available agree quite reasonably within the instrumental errors. The [RO2*]/[HO2] ratios, which vary between 1:1 and 3:1, as well as the peroxy radical variability, concur with variations in photolysis rates and in other potential radical precursors. Model results provide additional information about dominant radical formation and loss processes.

  8. Radical Compatibility with Nonaqueous Electrolytes and Its Impact on an All-Organic Redox Flow Battery

    Energy Technology Data Exchange (ETDEWEB)

    Wei, Xiaoliang; Xu, Wu; Huang, Jinhua; Zhang, Lu; Walter, Eric D.; Lawrence, Chad W.; Vijayakumar, M.; Henderson, Wesley A.; Liu, Tianbiao L.; Cosimbescu, Lelia; Li, Bin; Sprenkle, Vincent L.; Wang, Wei

    2015-07-20

    Nonaqueous redox flow batteries hold the promise to achieve higher energy density ascribed to the broader voltage window than their aqueous counterparts, but their current performance is limited by low redox material concentration, poor cell efficiency, and inferior cycling stability. We report a new nonaqueous total-organic flow battery based on high concentrations of 9-fluorenone as negative and 2,5-di-tert-butyl-1-methoxy-4-[2’-methoxyethoxy]benzene as positive redox materials. The supporting electrolytes are found to greatly affect the cycling stability of flow cells through varying chemical stabilities of the charged radical species, especially the 9-fluorenone radical anions, as confirmed by electron spin resonance. Such an electrolyte optimization sheds light on mechanistic understandings of capacity fading in flow batteries employing organic radical-based redox materials and demonstrates that rational design of supporting electrolyte is vital for stable cyclability.

  9. Radical Compatibility with Nonaqueous Electrolytes and Its Impact on an All-Organic Redox Flow Battery.

    Science.gov (United States)

    Wei, Xiaoliang; Xu, Wu; Huang, Jinhua; Zhang, Lu; Walter, Eric; Lawrence, Chad; Vijayakumar, M; Henderson, Wesley A; Liu, Tianbiao; Cosimbescu, Lelia; Li, Bin; Sprenkle, Vincent; Wang, Wei

    2015-07-20

    Nonaqueous redox flow batteries hold the promise of achieving higher energy density because of the broader voltage window than aqueous systems, but their current performance is limited by low redox material concentration, cell efficiency, cycling stability, and current density. We report a new nonaqueous all-organic flow battery based on high concentrations of redox materials, which shows significant, comprehensive improvement in flow battery performance. A mechanistic electron spin resonance study reveals that the choice of supporting electrolytes greatly affects the chemical stability of the charged radical species especially the negative side radical anion, which dominates the cycling stability of these flow cells. This finding not only increases our fundamental understanding of performance degradation in flow batteries using radical-based redox species, but also offers insights toward rational electrolyte optimization for improving the cycling stability of these flow batteries. PMID:25891480

  10. Standard Electrode Potentials Involving Radicals in Aqueous Solution: Inorganic Radicals

    Energy Technology Data Exchange (ETDEWEB)

    Armstrong, David A.; Huie, Robert E.; Koppenol, Willem H.; Lymar, Sergei V.; Merenyi, Gabor; Neta, Pedatsur; Ruscic, Branko; Stanbury, David M.; Steenken, Steen; Wardman, Peter

    2015-12-01

    Recommendations are made for standard potentials involving select inorganic radicals in aqueous solution at 25 °C. These recommendations are based on a critical and thorough literature review and also by performing derivations from various literature reports. The recommended data are summarized in tables of standard potentials, Gibbs energies of formation, radical pKa’s, and hemicolligation equilibrium constants. In all cases, current best estimates of the uncertainties are provided. An extensive set of Data Sheets is appended that provide original literature references, summarize the experimental results, and describe the decisions and procedures leading to each of the recommendations

  11. Radical-Enhanced Chinese Character Embedding

    OpenAIRE

    Sun, Yaming; Lin, Lei; Tang, Duyu; Yang, Nan; Ji, Zhenzhou; Wang, Xiaolong

    2014-01-01

    We present a method to leverage radical for learning Chinese character embedding. Radical is a semantic and phonetic component of Chinese character. It plays an important role as characters with the same radical usually have similar semantic meaning and grammatical usage. However, existing Chinese processing algorithms typically regard word or character as the basic unit but ignore the crucial radical information. In this paper, we fill this gap by leveraging radical for learning continuous r...

  12. Highly conductive side chain block copolymer anion exchange membranes.

    Science.gov (United States)

    Wang, Lizhu; Hickner, Michael A

    2016-06-28

    Block copolymers based on poly(styrene) having pendent trimethyl styrenylbutyl ammonium (with four carbon ring-ionic group alkyl linkers) or benzyltrimethyl ammonium groups with a methylene bridge between the ring and ionic group were synthesized by reversible addition-fragmentation radical (RAFT) polymerization as anion exchange membranes (AEMs). The C4 side chain polymer showed a 17% increase in Cl(-) conductivity of 33.7 mS cm(-1) compared to the benzyltrimethyl ammonium sample (28.9 mS cm(-1)) under the same conditions (IEC = 3.20 meq. g(-1), hydration number, λ = ∼7.0, cast from DMF/1-propanol (v/v = 3 : 1), relative humidity = 95%). As confirmed by small angle X-ray scattering (SAXS), the side chain block copolymers with tethered ammonium cations showed well-defined lamellar morphologies and a significant reduction in interdomain spacing compared to benzyltrimethyl ammonium containing block copolymers. The chemical stabilities of the block copolymers were evaluated under severe, accelerated conditions, and degradation was observed by (1)H NMR. The block copolymer with C4 side chain trimethyl styrenylbutyl ammonium motifs displayed slightly improved stability compared to that of a benzyltrimethyl ammonium-based AEM at 80 °C in 1 M NaOD aqueous solution for 30 days. PMID:27216558

  13. Polycyclic aromatic hydrocarbons with SPICA

    CERN Document Server

    Berne, O; Mulas, G; Tielens, A G G M; Goicoechea, J R

    2009-01-01

    Thanks to high sensitivity and angular resolution and broad spectral coverage, SPICA will offer a unique opportunity to better characterize the nature of polycyclic aromatic hydrocarbons (PAHs) and very small grains (VSGs), to better use them as probes of astrophysical environments. The angular resolution will enable to probe the chemical frontiers in the evolution process from VSGs to neutral PAHs, to ionized PAHs and to "Grand-PAHs" in photodissotiation regions and HII regions, as a function of G$_0$/n (UV radiation field / density). High sensitivity will favor the detection of the far-IR skeletal emission bands of PAHs, which provide specific fingerprints and could lead to the identification of individual PAHs. This overall characterization will allow to use PAH and VSG populations as tracers of physical conditions in spatially resolved protoplanetary disks and nearby galaxies (using mid-IR instruments), and in high redshift galaxies (using the far-IR instrument), thanks to the broad spectral coverage SPIC...

  14. Electron attachment and positive ion chemistry of monohydrogenated fluorocarbon radicals

    Energy Technology Data Exchange (ETDEWEB)

    Wiens, Justin P.; Shuman, Nicholas S.; Miller, Thomas M.; Viggiano, Albert A., E-mail: afrl.rvborgmailbox@kirtland.af.mil [Air Force Research Laboratory, Space Vehicles Directorate, Kirtland AFB, New Mexico 87117 (United States)

    2015-08-21

    Rate coefficients and product branching fractions for electron attachment and for reaction with Ar{sup +} are measured over the temperature range 300–585 K for three monohydrogenated fluorocarbon (HFC) radicals (CF{sub 3}CHF, CHF{sub 2}CF{sub 2}, and CF{sub 3}CHFCF{sub 2}), as well as their five closed-shell precursors (1-HC{sub 2}F{sub 4}I, 2-HC{sub 2}F{sub 4}I, 2-HC{sub 2}F{sub 4}Br, 1-HC{sub 3}F{sub 6}I, 2-HC{sub 3}F{sub 6}Br). Attachment to the HFC radicals is always fairly inefficient (between 0.1% and 10% of the Vogt–Wannier capture rate), but generally faster than attachment to analogous perfluorinated carbon radicals. The primary products in all cases are HF-loss to yield C{sub n}F{sub m−1}{sup −} anions, with only a minor branching to F{sup −} product. In all cases the temperature dependences are weak. Attachment to the precursor halocarbons is near the capture rate with a slight negative temperature dependence in all cases except for 2-HC{sub 2}F{sub 4}Br, which is ∼10% efficient at 300 K and becomes more efficient, approaching the capture rate at higher temperatures. All attachment kinetics are successfully reproduced using a kinetic modeling approach. Reaction of the HFC radicals with Ar{sup +} proceeds at or near the calculated collisional rate coefficient in all cases, yielding a wide variety of product ions.

  15. Electron Photodetachment from Aqueous Anions. III. Dynamics of Geminate Pairs Derived from Photoexcitation of Mono- vs. Poly- atomic Anions

    CERN Document Server

    Lian, R; Crowell, R A; Shkrob, I A; Chen, X; Bradforth, S E; Lian, Rui; Oulianov, Dmitri A.; Crowell, Robert A.; Shkrob, Ilya A.; Bradforth, Stephen E.

    2005-01-01

    Photostimulated electron detachment from aqueous inorganic anions is the simplest example of solvent-mediated electron transfer. Here we contrast the behavior of halide anions with that of small polyatomic anions, such as pseudohalide anions (e.g., HS-) and common polyvalent anions (e.g., SO32-). Geminate recombination dynamics of hydrated electrons generated by 200 nm photoexcitation of aqueous anions (I-, Br-, OH-, HS-, CNS-, CO32-, SO32-, and Fe(CN)64-) have been studied. Prompt quantum yields for the formation of solvated, thermalized electrons and quantum yields for free electrons were determined. Pump-probe kinetics for 200 nm photoexcitation were compared with kinetics obtained at lower photoexcitation energy (225 nm or 242 nm) for the same anions, where possible. Free diffusion and mean force potential models of geminate recombination dynamics were used to analyze these kinetics. These analyses suggest that for polyatomic anions (including all polyvalent anions studied) the initial electron distributi...

  16. The assessment of pellicular anion-exchange resins for the determination of anions by ion chromatography

    International Nuclear Information System (INIS)

    Because pellicular anion-exchange resins suitable for the determination, by ion chromatography, of anions with alkaline eluents were unavailable in South Africa at the inception of this work, an attempt was made to prepare such resins. In this study it is shown that the pellicular resins produced are more efficient than the surface-aminated resins used previously. The simultaneous separation and determination of five common anions is demonstrated. The method was applied to the analysis of uranium leach liquors, effluent samples, and a solid sample of ferric oxide (goethite)

  17. Photoelectron spectroscopy and theoretical studies of anion-π interactions: binding strength and anion specificity.

    Science.gov (United States)

    Zhang, Jian; Zhou, Bin; Sun, Zhen-Rong; Wang, Xue-Bin

    2015-02-01

    Proposed in theory and then their existence confirmed, anion-π interactions have been recognized as new and important non-covalent binding forces. Despite extensive theoretical studies, numerous crystal structural identifications, and a plethora of solution phase investigations, anion-π interaction strengths that are free from complications of condensed-phase environments have not been directly measured in the gas phase. Herein we present a joint photoelectron spectroscopic and theoretical study on this subject, in which tetraoxacalix[2]arene[2]triazine 1, an electron-deficient and cavity self-tunable macrocyclic, was used as a charge-neutral molecular host to probe its interactions with a series of anions with distinctly different shapes and charge states (spherical halides Cl(-), Br(-), I(-), linear thiocyanate SCN(-), trigonal planar nitrate NO3(-), pyramidic iodate IO3(-), and tetrahedral sulfate SO4(2-)). The binding energies of the resultant gaseous 1 : 1 complexes (1·Cl(-), 1·Br(-), 1·I(-), 1·SCN(-), 1·NO3(-), 1·IO3(-) and 1·SO4(2-)) were directly measured experimentally, exhibiting substantial non-covalent interactions with pronounced anion-specific effects. The binding strengths of Cl(-), NO3(-), IO3(-) with 1 are found to be strongest among all singly charged anions, amounting to ca. 30 kcal mol(-1), but only about 40% of that between 1 and SO4(2-). Quantum chemical calculations reveal that all the anions reside in the center of the cavity of 1 with an anion-π binding motif in the complexes' optimized structures, where 1 is seen to be able to self-regulate its cavity structure to accommodate anions of different geometries and three-dimensional shapes. Electron density surface and charge distribution analyses further support anion-π binding formation. The calculated binding energies of the anions and 1 nicely reproduce the experimentally estimated electron binding energy increase. This work illustrates that size-selective photoelectron

  18. Highly active and reusable catalyst from Fe-Mg-hydrotalcite anionic clay for Friedel-Crafts type benzylation reactions

    Indian Academy of Sciences (India)

    Vasant R Choudhary; Rani Jha; Pankaj A Choudhari

    2005-11-01

    Fe-Mg-hydrotalcite (Mg/Fe = 3) anionic clay with or without calcination (at 200-800°C) has been used for the benzylation of toluene and other aromatic compounds by benzyl chloride. Hydrotalcite before and after its calcination was characterized for surface area, crystalline phases and basicity. Both the hydrotalcite, particularly after its use in the benzylation reaction, and the catalyst derived from it by its calcination at 200-800°C show high catalytic activity for the benzylation of toluene and other aromatic compounds. The catalytically active species present in the catalyst in its most active form are the chlorides and oxides of iron on the catalyst surface.

  19. Structure-Activity Relationships for Rates of Aromatic Amine Oxidation by Manganese Dioxide.

    Science.gov (United States)

    Salter-Blanc, Alexandra J; Bylaska, Eric J; Lyon, Molly A; Ness, Stuart C; Tratnyek, Paul G

    2016-05-17

    New energetic compounds are designed to minimize their potential environmental impacts, which includes their transformation and the fate and effects of their transformation products. The nitro groups of energetic compounds are readily reduced to amines, and the resulting aromatic amines are subject to oxidation and coupling reactions. Manganese dioxide (MnO2) is a common environmental oxidant and model system for kinetic studies of aromatic amine oxidation. In this study, a training set of new and previously reported kinetic data for the oxidation of model and energetic-derived aromatic amines was assembled and subjected to correlation analysis against descriptor variables that ranged from general purpose [Hammett σ constants (σ(-)), pKas of the amines, and energies of the highest occupied molecular orbital (EHOMO)] to specific for the likely rate-limiting step [one-electron oxidation potentials (Eox)]. The selection of calculated descriptors (pKa, EHOMO, and Eox) was based on validation with experimental data. All of the correlations gave satisfactory quantitative structure-activity relationships (QSARs), but they improved with the specificity of the descriptor. The scope of correlation analysis was extended beyond MnO2 to include literature data on aromatic amine oxidation by other environmentally relevant oxidants (ozone, chlorine dioxide, and phosphate and carbonate radicals) by correlating relative rate constants (normalized to 4-chloroaniline) to EHOMO (calculated with a modest level of theory). PMID:27074054

  20. Exploring mild enzymatic sustainable routes for the synthesis of bio-degradable aromatic-aliphatic oligoesters.

    Science.gov (United States)

    Pellis, Alessandro; Guarneri, Alice; Brandauer, Martin; Acero, Enrique Herrero; Peerlings, Henricus; Gardossi, Lucia; Guebitz, Georg M

    2016-05-01

    The application of Candida antarctica lipase B in enzyme-catalyzed synthesis of aromatic-aliphatic oligoesters is here reported. The aim of the present study is to systematically investigate the most favorable conditions for the enzyme catalyzed synthesis of aromatic-aliphatic oligomers using commercially available monomers. Reaction conditions and enzyme selectivity for polymerization of various commercially available monomers were considered using different inactivated/activated aromatic monomers combined with linear polyols ranging from C2 to C12 . The effect of various reaction solvents in enzymatic polymerization was assessed and toluene allowed to achieve the highest conversions for the reaction of dimethyl isophthalate with 1,4-butanediol and with 1,10-decanediol (88 and 87% monomer conversion respectively). Mw as high as 1512 Da was obtained from the reaction of dimethyl isophthalate with 1,10-decanediol. The obtained oligomers have potential applications as raw materials in personal and home care formulations, for the production of aliphatic-aromatic block co-polymers or can be further functionalized with various moieties for a subsequent photo- or radical polymerization. PMID:26762794

  1. Formation of Polycyclic Aromatic Hydrocarbons and Nitrogen Containing Polycyclic Aromatic Compounds in Titan's Atmosphere, the Interstellar Medium and Combustion

    Science.gov (United States)

    Landera, Alexander

    2013-12-01

    Several different mechanisms leading to the formation of (substituted) naphthalene and azanaphthalenes were examined using theoretical quantum chemical calculations. As a result, a series of novel synthetic routes to Polycyclic Aromatic Hydrocarbons (PAHs) and Nitrogen Containing Polycyclic Aromatic Compounds (N-PACs) have been proposed. On Earth, these aromatic compounds originate from incomplete combustion and are released into our environment, where they are known to be major pollutants, often with carcinogenic properties. In the atmosphere of a Saturn's moon Titan, these PAH and N-PACs are believed to play a critical role in organic haze formation, as well as acting as chemical precursors to biologically relevant molecules. The theoretical calculations were performed by employing the ab initio G3(MP2,CC)/B3LYP/6-311G** method to effectively probe the Potential Energy Surfaces (PES) relevant to the PAH and N-PAC formation. Following the construction of the PES, Rice-Ramsperger-Kassel-Markus (RRKM) theory was used to evaluate all unimolecular rate constants as a function of collision energy under single-collision conditions. Branching ratios were then evaluated by solving phenomenological rate expressions for the various product concentrations. The most viable pathways to PAH and N-PAC formation were found to be those where the initial attack by the ethynyl (C2H) or cyano (CN) radical toward a unsaturated hydrocarbon molecule led to the formation of an intermediate which could not effectively lose a hydrogen atom. It is not until ring cyclization has occurred, that hydrogen elimination leads to a closed shell product. By quenching the possibility of the initial hydrogen atom elimination, one of the most competitive processes preventing the PAH or N-PAC formation was avoided, and the PAH or N-PAC formation was allowed to proceed. It is concluded that these considerations should be taken into account when attempting to explore any other potential routes towards

  2. Chemical characterization of SOA formed from aqueous-phase reactions of phenols with the triplet excited state of carbonyl and hydroxyl radical

    Energy Technology Data Exchange (ETDEWEB)

    Yu, Lu; Smith, Jeremy; Laskin, Alexander; Anastasio, Cort N.; Laskin, Julia; Zhang, Qi

    2014-01-01

    Phenolic compounds, which are emitted in significant amounts from biomass burning, can undergo fast reactions in atmospheric aqueous phases to form secondary organic aerosol (aqSOA). In this study, we investigate the reactions of phenol and two methoxy-phenols (syringol and guaiacol) with two major aqueous phase oxidants – the triplet excited states of an aromatic carbonyl (3C*) and hydroxyl radical (•OH). We thoroughly characterize the low-volatility species produced from these reactions and interpret their formation mechanisms using aerosol mass spectrometry (AMS), desorption electrospray ionization mass spectrometry (DESIMS), and ion chromatography (IC). A large number of oxygenated molecules are identified, including oligomers containing up to six monomer units, functionalized monomer and oligomers with carbonyl, carboxyl, and hydroxyl groups, and small organic acid anions (e.g., formate, acetate, oxalate, and malate). The average atomic oxygen-to-carbon (O/C) ratios of phenolic aqSOA are in the range of 0.85-1.23, similar to those of low-volatility oxygenated organic aerosol (LV-OOA) observed in ambient air. The aqSOA compositions are overall similar for the same precursor, but the reactions mediated by 3C* are faster than •OH-mediated reactions and produce more oligomers and hydroxylated species at the point when 50% of the phenol had reacted. Profiles determined using a thermodenuder indicate that the volatility of phenolic aqSOA is influenced by both oligomer content and O/C ratio. In addition, the aqSOA shows enhanced light absorption in the UV-vis region, suggesting that aqueous-phase reactions of phenols are likely an important source of brown carbon in the atmosphere, especially in regions influenced by biomass burning.

  3. Donnan Membrane Technique (DMT) for Anion Measurement

    NARCIS (Netherlands)

    Alonso Vega, M.F.; Weng, L.P.; Temminghoff, E.J.M.; Riemsdijk, van W.H.

    2010-01-01

    Donnan membrane technique (DMT) is developed and tested for determination of free anion concentrations. Time needed to reach the Donnan membrane equilibrium depends on type of ions and the background. The Donnan membrane equilibrium is reached in 1 day for Cl-, 1-2 days for NO3-, 1-4 days for SO42-

  4. Gas-Phase Reactivity of Microsolvated Anions

    DEFF Research Database (Denmark)

    Thomsen, Ditte Linde

    intrinsic factors and solvent effects is the enhanced reactivity of α-nucleophiles – nucleophiles with a lone-pair adjacent to the attacking site – referred to as the α-effect. This thesis concerns the reactivity of microsolvated anions and in particular how the presence of a single solvent molecule affects...

  5. Review: Formation of Peptide Radical Ions Through Dissociative Electron Transfer in Ternary Metal-Ligand-Peptide Complexes

    International Nuclear Information System (INIS)

    The formation and fragmentation of odd-electron ions of peptides and proteins is of interest to applications in biological mass spectrometry. Gas-phase redox chemistry occurring during collision-induced dissociation of ternary metal-ligand-peptide complexes enables the formation of a variety of peptide radicals including the canonical radical cations, M+#smbullet#, radical dications, (M+H)2+#smbullet#, radical anions, (M-2H)-#smbullet#. In addition, odd-electron peptide ions with well-defined initial location of the radical site are produced through side chain losses from the radical ions. Subsequent fragmentation of these species provides information on the role of charge and the location of the radical site on the competition between radical-induced and proton-driven fragmentation of odd-electron peptide ions. This account summarizes current understanding of the factors that control the efficiency of the intramolecular electron transfer (ET) in ternary metal-ligand-peptide complexes resulting in formation of odd-electron peptide ions. Specifically, we discuss the effect of the metal center, the ligand and the peptide structure on the competition between the ET, proton transfer (PT), and loss of neutral peptide and neutral peptide fragments from the complex. Fundamental studies of the structures, stabilities, and the energetics and dynamics of fragmentation of such complexes are also important for detailed molecular-level understanding of photosynthesis and respiration in biological systems.

  6. Laparoscopic radical and partial cystectomy

    Directory of Open Access Journals (Sweden)

    Challacombe Ben

    2005-01-01

    Full Text Available Radical cystectomy remains the standard treatment for muscle invasive organ confined bladder carcinoma. Laparoscopic radical cystoprostatectomy (LRC is an advanced laparoscopic procedure that places significant demands on the patient and the surgeon alike. It is a prolonged procedure which includes several technical steps and requires highly developed laparoscopic skills including intra-corporeal suturing. Here we review the development of the technique, the indications, complications and outcomes. We also examine the potential benefits of robotic-assisted LRC and explore the indications and technique of laparoscopic partial cystectomy.

  7. Radical democratic politics and feminism

    Directory of Open Access Journals (Sweden)

    Martínez Labrin, Soledad

    2006-05-01

    Full Text Available In the article I present a reflection around the radical democratic project proposed by Chantal Mouffe and Ernesto Laclau. Specifically, I examine the application of the project in the context of the “new social movements” and especially, of feminist movement. I state the need of drawing attention to universalism and essentialism as the main obstacles to generate a collective proposal without margins. Nevertheless, doubts remind about the possibility of building up a feminism tailored by the radical democratic project, in a stage in which the political action of such a movement is characterized by categories that are closed and crystallized

  8. Quantification of a radical beam source for methyl radicals

    International Nuclear Information System (INIS)

    A radical beam source for methyl radicals (CH3) was characterized applying ionization-threshold mass spectrometry. The beam source is based on thermal dissociation of methane (CH4) or azomethane (N2(CH3)2) in a heated tungsten capillary. A flux of (3±1)x1013 cm-2 s-1 CH3 radicals is produced using methane as precursor gas and a capillary temperature of 1650 K. Alternatively, a flux of (3±1)x1014 cm-2 s-1 CH3 is produced using azomethane as precursor gas and a capillary temperature of 1150 K. The dominant production of methyl from the precursor methane occurs due to reaction 2 CH4+M→2 CH3+H2+M at the hot tungsten surface. The dominant production of methyl from azomethane occurs due to the reaction N2(CH3)2→2 CH3+N2. Besides methyl radicals, only stable molecules contribute to the emitted flux; within the detection limit, no atomic hydrogen is observed. From the comparison of ionization-threshold mass spectrometry and standard mass spectrometry, it is concluded that the cracking pattern of methane varies with the methane gas temperature. This is explained by the vibrational assisted dissociation of methane

  9. Unifying Chemical and Physical Principles for Oxide Superconductivity Based on an Anionic Charge Order Model

    International Nuclear Information System (INIS)

    Subperoxidic O23- charge ordering presents a satisfying basis for a quantitative, conceptually realistic, and unifying understanding of cuprate superconductors. The activity of O- manifests itself in a variety of ways including a universal Tc scaling with O- per total O, or more generally, in the subperoxide radical concentration. Also, a characteristic crystal chemistry of O- placement is indicated. As an example, trends to preferential O- occupation of the apical sites are correlated with c axis and Tc decreases providing a new crystallographic interpretation of the overdoping question. Generally, subperoxides can be created on overoxidation or through various modes of self doping through lattice pressure-related factors. Accordingly, the role of peranion formation is seen as a most general chemical principle for ameliorating stacking mismatch through electronic liquefaction under internal stress . Cases are discussed (e.g., YBa2Cu3O6.5) where the tension on cooling can result in stratified self-doping steps. A variety of experiments indicating charge order properties, such as stripes and slow charge propagation, are interpreted on the anionic model. Subperoxidic pair formation and charge ordering energetics are discussed. Concepts are further generalized for other cases (e.g., carbides or nitrides) of anionic metallicity and superconductivity. Common aspects are mobile, paired charge orders of radicals coupled through bond polarizations

  10. Translation of an aromatic field image

    Science.gov (United States)

    Yastrebov, Anatoliy S.; Makarov, Leonid M.; Protasenya, Sergey V.; Vereshak, Evgeniy V.

    2005-04-01

    As is known, for a person there are possibilities of perception of audio, video, and aromatic information messages by means of touch systems available to him. Such packages of the messages are accepted remotely without direct contact to a message source. Now the direction bound with creation of devices capable to playback aromatic information images is actively developed. Such systems switched on in special transmission channels of information provide adequate perception of information highways describing actual event which happen in the enclosing world. One can present the aromatic-field image through a series of control codes for an aromatic field synthesizer, thereupon it is possible to transmit the image on telecommunication networks. For odor oscillators installation problems in compartments of automobiles, buses as well as of airplanes are widely discussed. In this work we deal with a device for synthesis of an image of an aromatic field which works under the control of a personal computer with an express program. In the given operation, the possibility of remote handle of an image of an aromatic field and, as a corollary, organization of a new tansmission channel for the information on the aromatic-field image through an existing synthesizer is considered.

  11. From small aromatic molecules to functional nanostructured carbon by pulsed laser-induced photochemical stitching

    Directory of Open Access Journals (Sweden)

    R. R. Gokhale

    2012-06-01

    Full Text Available A novel route employing UV laser pulses (KrF Excimer, 248 nm to cleave small aromatic molecules and stitch the generated free radicals into functional nanostructured forms of carbon is introduced. The process differs distinctly from any strategies wherein the aromatic rings are broken in the primary process. It is demonstrated that this pulsed laser-induced photochemical stitching (PLPS process when applied to routine laboratory solvents (or toxic chemical wastes when discarded Chlorobenzene and o-Dichlorobenzene yields Carbon Nanospheres (CNSs comprising of graphene-like sheets assembled in onion-like configurations. This room temperature process implemented under normal laboratory conditions is versatile and clearly applicable to the whole family of haloaromatic compounds without and with additions of precursors or other nanomaterials. We further bring out its applicability for synthesis of metal-oxide based carbon nanocomposites.

  12. Comparison And Assessment for Major Anions

    Directory of Open Access Journals (Sweden)

    Mayada Mohammed

    2013-05-01

    Full Text Available Four major anions (nitrate, phosphate, sulfate and chloride  are measured in Tigris river at Mosul in six locations since Sept.2005 to June 2006.  The same 4 anions are measured previously by researches or thesis, so their results are added to the former one for comparison. The variation of flow is also reported for the whole period in order to study the concentration-flow relationship. The nitrate and phosphate concentrations are increasing with the river flow increase and decreasing with its decrease for most periods, (reaching up to1.05mg/l at June for nitrate and 0.482mg/l at April for phosphate .The lowest concentrations are observed (as low as 0.285 mg/l at Dec. for nitrate and 0.07mg/l at Jan for phosphate. Sulfate and chloride concentration are varying oppositely to the river flow for most periods, both showing their peaks at Jan. and their lowest at June (reaching up to 170 mg/l for sulfate, and 33.4 mg/l for chloride while the minimum values are 68mg/l for sulfate, and 15.6 mg/l for chloride. The data of the previous years are not complete and data for only 8 years are available. It indicates that the anions concentrations variation corresponding to the river flow is similar to that of  the studied years. However the data with equal flow rate only are used for comparison purposes to achieve correct results. All of the studied anions are increasing since 1982-2006 in different percentages except the phosphate. The 4 major anions are lower than the standards and MCL for the recent and previous studies.

  13. Low Temperature Formation of Nitrogen-substituted Polycyclic Aromatic Hydrocarbons (PANHs)- Barrierless Routes to Dihydro(iso)quinolines

    Science.gov (United States)

    Parker, Dorian S. N.; Yang, Tao; Dangi, Beni B.; Kaiser, Ralf. I.; Bera, Partha P.; Lee, Timothy J.

    2015-12-01

    Meteorites contain bio-relevant molecules such as vitamins and nucleobases, which consist of aromatic structures with embedded nitrogen atoms. Questions remain over the chemical mechanisms responsible for the formation of nitrogen-substituted polycyclic aromatic hydrocarbons (PANHs) in extraterrestrial environments. By exploiting single collision conditions, we show that a radical mediated bimolecular collision between pyridyl radicals and 1,3-butadiene in the gas phase forms nitrogen-substituted polycyclic aromatic hydrocarbons (PANHs) 1,4-dihydroquinoline and to a minor amount 1,4-dihydroisoquinoline. The reaction proceeds through the formation of a van der Waals complex, which circumnavigates the entrance barrier implying it can operate at very low kinetic energy and therefore at low temperatures of 10 K as present in cold molecular clouds such as TMC-1. The discovery of facile de facto barrierless exoergic reaction mechanisms leading to PANH formation could play an important role in providing a population of aromatic structures upon which further photo-processing of ice condensates could occur to form nucleobases.

  14. Conservation of medicinal and aromatic plants

    Directory of Open Access Journals (Sweden)

    Šveistytė, Laima

    2016-07-01

    Full Text Available The conservation of medicinal and aromatic plants includes ex situ and in situ methods. The genetic recourses of medicinal and aromatic plants are stored, studied and constantly maintained in the field collections of the Institute of Botany of Nature Research Centre, Kaunas Botanical Garden of Vytautas Magnus University and Aleksandras Stulginskis University of Agriculture. Presently seeds of 214 accessions representing 38 species of medicinal and aromatic plants are stored in a long-term storage in the Plant Gene Bank. The data about national genetic resources are collected and stored in the Central Database of the Plant Gene Bank.

  15. Aromaticity influencing the thermostability of micellar dispersions

    Energy Technology Data Exchange (ETDEWEB)

    Davis, J.A.; Kunzman, W.J.

    1970-02-17

    The thermostability of a micellar dispersion is shifted to higher temperature ranges by increasing the aromaticity of the hydrocarbon within the dispersion. The micellar solution is composed of kerosene and light catalytic cycle oil (hydrocarbons), water, sodium or ammonium alkyl aryl naphthenic sulfonates (petroleum sulfonate surfactant), isopropanol (cosurfactant), and sodium sulfate (electrolyte). The aromatic content of the light catalytic cycle oil is higher than the aromatic content of the kerosene. By increasing the concentration of cycle oil to kerosene, stable micellar solutions at temperatures from ambient to 200/sup 0/F can be obtained. The aqueous medium can be soft, brackish, or a brine.

  16. Hexacoordinate bonding and aromaticity in silicon phthalocyanine.

    Science.gov (United States)

    Yang, Yang

    2010-12-23

    Si-E bondings in hexacoordinate silicon phthalocyanine were analyzed using bond order (BO), energy partition, atoms in molecules (AIM), electron localization function (ELF), and localized orbital locator (LOL). Bond models were proposed to explain differences between hexacoordinate and tetracoordinate Si-E bondings. Aromaticity of silicon phthalocyanine was investigated using nucleus-independent chemical shift (NICS), harmonic oscillator model of aromaticity (HOMA), conceptual density functional theory (DFT), ring critical point (RCP) descriptors, and delocalization index (DI). Structure, energy, bonding, and aromaticity of tetracoordinate silicon phthalocyanine were studied and compared with hexacoordinate one. PMID:21105726

  17. Competition between photodetachment and autodetachment of the 2{sup 1}ππ{sup *} state of the green fluorescent protein chromophore anion

    Energy Technology Data Exchange (ETDEWEB)

    Mooney, Ciarán R. S.; Parkes, Michael A.; Zhang, Lijuan; Hailes, Helen C.; Fielding, Helen H., E-mail: h.h.fielding@ucl.ac.uk [Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ (United Kingdom); Simperler, Alexandra; Bearpark, Michael J. [Department of Chemistry, Imperial College London, South Kensington, London SW7 2AZ (United Kingdom)

    2014-05-28

    Using a combination of photoelectron spectroscopy measurements and quantum chemistry calculations, we have identified competing electron emission processes that contribute to the 350–315 nm photoelectron spectra of the deprotonated green fluorescent protein chromophore anion, p-hydroxybenzylidene-2,3-dimethylimidazolinone. As well as direct electron detachment from S{sub 0}, we observe resonant excitation of the 2{sup 1}ππ* state of the anion followed by autodetachment. The experimental photoelectron spectra are found to be significantly broader than photoelectron spectrum calculated using the Franck-Condon method and we attribute this to rapid (∼10 fs) vibrational decoherence, or intramolecular vibrational energy redistribution, within the neutral radical.

  18. Supramolecular Chemistry of Selective Anion Recognition for Anions of Environmental Relevance

    International Nuclear Information System (INIS)

    The major thrust of this project, led by the University of Kansas (Prof. Kristin Bowman-James), entails an exploration of the basic determinants of anion recognition and their application to the design, synthesis, and testing of novel sulfate extractants. A key scientific inspiration for the work comes from the need, codified in simple-to-appreciate terms by the Oak Ridge National Laboratory component of the team (viz. Dr. Bruce Moyer), for chemical entities that can help in the extractive removal of species that have low solubilities in borosilicate glass. Among such species, sulfate anion, has been identified as particularly insidious. Its presence interferes with the vitrification process, thus rendering the remediation of tank waste from, e.g., the Hanford site far more difficult and expensive. The availability of effective extractants, that would allow for the separation of separating sulfate from the major competing anions in the waste, especially nitrate, could allow for pre-vitrification removal of sulfate via liquid-liquid extraction. The efforts at The University of Texas, the subject of this report, have thus concentrated on the development of new sulfate receptors. These systems are designed to increase our basic understanding of anion recognition events and set the stage for the development of viable sulfate anion extractants. In conjunction with the Oak Ridge National Laboratory (ORNL) members of the research team, several of these new receptors were studied as putative extractants, with two of the systems being shown to act as promising synergists for anion exchange.

  19. Detecting Social Polarization and Radicalization

    DEFF Research Database (Denmark)

    Qureshi, Pir Abdul Rasool; Memon, Nasrullah; Wiil, Uffe Kock;

    2011-01-01

    This paper proposes a novel system to detect social polarization and to estimate the chances of violent radicalization associated with it. The required processes for such a system are indicated; it is also analyzed how existing technologies can be integrated into the proposed system to fulfill the...

  20. Exploring the Theories of Radicalization

    Directory of Open Access Journals (Sweden)

    Maskaliūnaitė Asta

    2015-12-01

    Full Text Available After the London bombings in July 2005, the concern of terrorism scholars and policy makers has turned to “home-grown” terrorism and potential for political violence from within the states. “Radicalization” became a new buzz word. This article follows a number of reviews of the literature on radicalization and offers another angle for looking at this research. First, it discusses the term “radicalization” and suggests the use of the following definition of radicalization as a process by which a person adopts belief systems which justify the use of violence to effect social change and comes to actively support as well as employ violent means for political purposes. Next, it proposes to see the theories of radicalization focusing on the individual and the two dimensions of his/her motivation: whether that motivation is internal or external and whether it is due to personal choice or either internal (due to some psychological traits or external compulsion. Though not all theories fall neatly within these categories, they make it possible to make comparisons of contributions from a variety of different areas thus reflecting on the interdisciplinary nature of the study of terrorism in general and radicalization as a part of it.

  1. Kinetics of nitroxyl radical reactions

    International Nuclear Information System (INIS)

    Absolute rate-constants for the reaction of the nitroxyl free radicals TAN and TMPN with radiation-chemically-formed radicals and ions have been determined. k(TAN + X) (in M-1 sec-1) = 4.0 x 109 (for X =OH), 2.9 x 1010(esub(aq)-), 8.0 x 109 (H), 7.2 x 108 (CH2OH), 4.0 x 108 (CH3CHOH), 4.3 x 108 ((CH3)2COH), 2.8 x 108 (CH2(CH3)2COH), 5.9 x 107 (glucose radical), 4.0 x 108 (c-C5H9), and k(TMPN + X) = 3.4 x 109 (OH), 7.8 x 109 (esub(aq)-), 4.9 x 109 (H), 4.4 x 108 (CH2OH), 4.9 x 108 (CH3CHOH), 3.6 x 108 ((CH3)2COH), 1.5 x 108 (CH2(CH3)2COH), 4.9 x 107 (glucose radical), 4.3 x 108 (c-C5H9). Direct measurements by means of a pulse-radiolysis conductivity technique were based on the formation and destruction of charged species in these reactions within certain pH ranges. It is indicated that the radiosensitizing nitroxyles undergo both redox and addition reactions. (author)

  2. Reaction between protein radicals and other biomolecules

    DEFF Research Database (Denmark)

    Østdal, Henrik; Davies, Michael Jonathan; Andersen, Henrik J

    2002-01-01

    The present study investigates the reactivity of bovine serum albumin (BSA) radicals towards different biomolecules (urate, linoleic acid, and a polypeptide, poly(Glu-Ala-Tyr)). The BSA radical was formed at room temperature through a direct protein-to-protein radical transfer from H(2)O(2....... Subsequent analysis showed a decrease in the concentration of urate upon reaction with the BSA radical, while the BSA radical in the presence of poly(Glu-Ala-Tyr) resulted in increased formation of the characteristic protein oxidation product, dityrosine. Reaction between the BSA radical and a linoleic acid...

  3. Formation and Stabilization of Environmentally Persistent Free Radicals Induced by the Interaction of Anthracene with Fe(III)-Modified Clays.

    Science.gov (United States)

    Jia, Hanzhong; Nulaji, Gulimire; Gao, Hongwei; Wang, Fu; Zhu, Yunqing; Wang, Chuanyi

    2016-06-21

    Environmentally persistent free radicals (EPFRs) are occasionally detected in Superfund sites but the formation of EPFRs induced by polycyclic aromatic hydrocarbons (PAHs) is not well understood. In the present work, the formation of EPFRs on anthracene-contaminated clay minerals was quantitatively monitored via electron paramagnetic resonance (EPR) spectroscopy, and surface/interface-related environmental influential factors were systematically explored. The obtained results suggest that EPFRs are more readily formed on anthracene-contaminated Fe(III)-montmorillonite than in other tested systems. Depending on the reaction condition, more than one type of organic radicals including anthracene-based radical cations with g-factors of 2.0028-2.0030 and oxygenic carbon-centered radicals featured by g-factors of 2.0032-2.0038 were identified. The formed EPFRs are stabilized by their interaction with interlayer surfaces, and such surface-bound EPFRs exhibit slow decay with 1/e-lifetime of 38.46 days. Transformation pathway and possible mechanism are proposed on the basis of experimental results and quantum mechanical simulations. Overall, the formation of EPFRs involves single-electron-transfer from anthracene to Fe(III) initially, followed by H2O addition on formed aromatic radical cation. Because of their potential exposure in soil and atmosphere, such clay surface-associated EPFRs might induce more serious toxicity than PAHs and exerts significant impacts on human health. PMID:27224055

  4. Reversible photochromism of an N-salicylidene aniline anion.

    Science.gov (United States)

    Jacquemin, Pierre-Loïc; Robeyns, Koen; Devillers, Michel; Garcia, Yann

    2014-01-21

    The first N-salicylidene aniline anion showing reversible solid state thermochromic and photochromic properties is described. The photo-isomerization involves a trans-keto form which is stabilized thanks to the local anion surrounding. This photochromic anion can be used as a guest for the preparation of hybrid materials by insertion into a cationic host matrix. PMID:24022381

  5. Flash Vacuum Pyrolysis of Lignin Model Compounds: Reaction Pathways of Aromatic Methoxy Groups

    Energy Technology Data Exchange (ETDEWEB)

    Britt, P.F.; Buchanan, A.C., III; Martineau, D.R.

    1999-03-21

    Currently, there is interest in utilizing lignin, a major constituent of biomass, as a renewable source of chemicals and fuels. High yields of liquid products can be obtained from the flash or fast pyrolysis of biomass, but the reaction pathways that lead to product formation are not understood. To provide insight into the primary reaction pathways under process relevant conditions, we are investigating the flash vacuum pyrolysis (FVP) of lignin model compounds at 500 C. This presentation will focus on the FVP of {beta}-ether linkages containing aromatic methoxy groups and the reaction pathways of methoxy-substituted phenoxy radicals.

  6. Oxidative capacity of the Mexico City atmosphere – Part 1: A radical source perspective

    Directory of Open Access Journals (Sweden)

    M. J. Molina

    2007-04-01

    Full Text Available A detailed analysis of OH, HO2 and RO2 radical sources is presented for the near field photochemical regime inside the Mexico City Metropolitan Area (MCMA. During spring of 2003 (MCMA-2003 field campaign an extensive set of measurements was collected to quantify time resolved ROx (sum of OH, HO2, RO2 radical production rates from day- and nighttime radical sources. The Master Chemical Mechanism (MCMv3.1 was constrained by measurements of (1 concentration time-profiles of photosensitive radical precursors, i.e., nitrous acid (HONO, formaldehyde (HCHO, ozone (O3, glyoxal (CHOCHO, and other oxygenated volatile organic compounds (OVOCs; (2 respective photolysis-frequencies (J-values; (3 concentration time-profiles of alkanes, alkenes, and aromatic VOCs (103 compound are treated and oxidants, i.e., OH- and NO3 radicals, O3; and (4 NO, NO2, meteorological and other parameters. The ROx production rate was calculated directly from these observations; MCM was used to estimate further ROx production from unconstrained sources, and express overall ROx production as OH-equivalents (i.e., taking into account the propagation efficiencies of RO2 and HO2 radicals into OH radicals. Daytime radical production is found to be about 10-25 times higher than at night; it does not track the abundance of sunlight. 12-h average daytime contributions of individual sources are: HCHO and O3 photolysis, each about 20%; O3/alkene reactions and HONO photolysis, each about 15%; unmeasured sources about 30%. While the direct contribution of O3/alkene reactions appears to be moderately small, source-apportionment of ambient HCHO and HONO identifies O3/alkene reactions as being largely responsible for jump-starting photochemistry about one hour after sunrise. The peak radical production is found to be higher than in any other urban influenced environment studied to date; further, differences exist in the timing of radical production. Our measurements and analysis comprise a

  7. Pulse shape discrimination in non-aromatic plastics

    International Nuclear Information System (INIS)

    Recently it has been demonstrated that plastic scintillators have the ability to distinguish neutrons from gamma rays by way of pulse shape discrimination (PSD). This discovery has lead to new materials and new capabilities. Here we report our work with the effects of aromatic, non-aromatic, and mixed aromatic/non-aromatic matrices have on the performance of PSD plastic scintillators

  8. Volatilisation of aromatic hydrocarbons from soil

    DEFF Research Database (Denmark)

    Lindhardt, B.; Christensen, T.H.

    1996-01-01

    The non-steady-state fluxes of aromatic hydrocarbons were measured in the laboratory from the surface of soils contaminated with coal tar Four soil samples from a former gasworks site were used for the experiments. The fluxes were quantified for 11 selected compounds, 4 mono- and 7 polycyclic...... aromatic hydrocarbons, for a period of up to 8 or 16 days. The concentrations of the selected compounds in the soils were between 0.2 and 3,100 mu g/g. The study included the experimental determination of the distribution coefficient of the aromatic hydrocarbons between the sorbed phase and the water under...... saturated conditions. The determined distribution coefficients showed that the aromatic hydrocarbons were more strongly sorbed to the total organic carbon including the coal tar pitch - by a factor of 8 to 25 - than expected for natural organic matter. The fluxes were also estimated using an analytical...

  9. Graphite Oxide and Aromatic Amines : Size Matters

    NARCIS (Netherlands)

    Spyrou, Konstantinos; Calvaresi, Matteo; Diamanti, Evmorfi A. K.; Tsoufis, Theodoros; Gournis, Dimitrios; Rudolf, Petra; Zerbetto, Francesco

    2015-01-01

    Experimental and theoretical studies are performed in order to illuminate, for first time, the intercalation mechanism of polycyclic aromatic molecules into graphite oxide. Two representative molecules of this family, aniline and naphthalene amine are investigated. After intercalation, aniline molec

  10. International congress on aromatic and medicinal plants

    International Nuclear Information System (INIS)

    Full Text : In Morocco, medicinal and aromatic plants occupy an important place in the traditional care system of a large number of local people. They are also economically strong potential, but unfortunately they are not valued enough. Indeed, Morocco by its privileged geographical position in the Mediterranean basin and its floristic diversity (with a total of over 4,200 species and subspecies of which over 500 are recognized as medicinal and aromatic plants), is a leading provider of traditional global market. In this context and given the back label of the natural global, group research and studies on Aromatic and Medicinal Plants (GREPAM), the Faculty of Semlalia and University Cadi Ayyad, organize: the International Congress on Medicinal and Aromatic Plants CIPAM 2009. The organization of this conference is part of scientific research developed by the GREPAM.

  11. Activity relationships for aromatic crown ethers

    CERN Document Server

    Wilson, M J

    1998-01-01

    This thesis involves an investigation of aromatic crown ethers and a study of their binding constants for alkali metals. The study was motivated by the current needs of the semiconductor industry to improve the scavenging of mobile ions from fabricated circuits. A number of aromatic crown ethers have been sulphonated in an attempt to improve their water solubility and cation binding activity. These materials have been extensively studied and their binding activity determined. In collaboration with a molecular modelling study, the effect of ionisable sulphonate groups on the macrocycles' behaviour has been investigated. The broader issue of the effect of substituents in aromatic crown ethers has also been studied with the preparation of a wide range of substituted crown ethers. The cation binding activity of these materials has been found to bear a simple relationship to the electron withdrawing nature of the aromatic substituents. This relationship can be accurately monitored using electronic charge densities...

  12. Comments on Coulomb pairing in aromatic hydrocarbons

    CERN Document Server

    Huber, D L

    2013-01-01

    Recently reported anomalies in the double-photonionization spectra of aromatic molecules such as benzene, naphthalene, anthracene and coronene are attributed to Coulomb-pair resonances of pi electrons.

  13. PROTONATED POLYCYCLIC AROMATIC HYDROCARBONS REVISITED

    International Nuclear Information System (INIS)

    We reconsider the contribution that singly protonated polycyclic aromatic hydrocarbons (PAHs; HPAH+s) might make to the Class A component of the 6.2 μm interstellar emission feature in light of the recent experimental measurements of protonated naphthalene and coronene. Our calculations on the small HPAH+s have a band near 6.2 μm, as found in experiment. While the larger HPAH+s still have emission near 6.2 μm, the much larger intensity of the band near 6.3 μm overwhelms the weaker band at 6.2 μm, so that the 6.2 μm band is barely visible. Since the large PAHs are more representative of those in the interstellar medium, our work suggests that large HPAH+s cannot be major contributors to the observed emission at 6.2 μm (i.e., Class A species). Saturating large PAH cations with hydrogen atoms retains the 6.2 μm Class A band position, but the rest of the spectrum is inconsistent with observed spectra.

  14. Polycylcic Aromatic Hydrocarbons (PAH's) in dense cloud chemistry

    CERN Document Server

    Wakelam, Valentine

    2008-01-01

    Virtually all detailed gas-phase models of the chemistry of dense interstellar clouds exclude polycyclic aromatic hydrocarbons (PAH's). This omission is unfortunate because from the few studies that have been done on the subject, it is known that the inclusion of PAH's can affect the gas-phase chemistry strongly. We have added PAH's to our network to determine the role they play in the chemistry of cold dense cores. In the models presented here, we include radiative attachment to form PAH-, mutual neutralization between PAH anions and small positively-charged ions, and photodetachment. We also test the sensitivity of our results to changes in the size and abundance of the PAH's. Our results confirm that the inclusion of PAH's changes many of the calculated abundances of smaller species considerably. In TMC-1, the general agreement with observations is significantly improved contrary to L134N. This may indicate a difference in PAH properties between the two regions. With the inclusion of PAH's in dense cloud c...

  15. Dehydrogenative Aromatization of Saturated Aromatic Compounds by Graphite Oxide and Molecular Sieves

    Institute of Scientific and Technical Information of China (English)

    张轩; 徐亮; 王希涛; 马宁; 孙菲菲

    2012-01-01

    Graphite oxide (GO) has attracted much attention of material and catalysis chemists recently. Here we describe a combination of GO and molecular sieves for the dehydrogenative aromatization. GO prepared through improved Hummers method showed high oxidative activity in this reaction. Partially or fully saturated aromatic compounds were converted to their corresponding dehydrogenated aromatic products with fair to excellent conversions and selectivities. As both GO and molecular sieves are easily available, cheap, lowly toxic and have good tolerance to various functional groups, this reaction provides a facile approach toward aromatic compounds from their saturated precursors

  16. Dramatic enhancement of fullerene anion formation in polymer solar cells by thermal annealing: Direct observation by electron spin resonance

    International Nuclear Information System (INIS)

    Using electron spin resonance (ESR), we clarified the origin of the efficiency degradation of polymer solar cells containing a lithium-fluoride (LiF) buffer layer created by a thermal annealing process after the deposition of an Al electrode (post-annealing). The device structure was indium-tin-oxide/ poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate)/poly (3-hexylthiophene):phenyl-C61-butyric acid methyl ester (P3HT:PCBM)/LiF/Al. Three samples consisting of quartz/P3HT:PCBM/LiF/Al, quartz/P3HT:PCBM/Al, and quartz/PCBM/LiF/Al were investigated and compared. A clear ESR signal from radical anions on the PCBM was observed after LiF/Al was deposited onto a P3HT:PCBM layer because of charge transfer at the interface between the PCBM and the LiF/Al, which indicated the formation of PCBM−Li+ complexes. The number of radical anions on the PCBM was enhanced remarkably by the post-annealing process; this enhancement was caused by the surface segregation of PCBM and by the dissociation of LiF at the Al interface by the post-annealing process. The formation of a greater number of anions enhanced the electron scattering, decreased the electron-transport properties of the PCBM molecules, and caused an energy-level shift at the interface. These effects led to degradation in the device performance.

  17. Aromatic amines sources, environmental impact and remediation

    OpenAIRE

    Pereira, Luciana; Mondal, P. K.; Alves, M. M.

    2015-01-01

    Aromatic amines are widely used industrial chemicals as their major sources in the environment include several chemical industry sectors such as oil refining, synthetic polymers, dyes, adhesives, rubbers, perfume, pharmaceuticals, pesticides and explosives. They result also from diesel exhaust, combustion of wood chips and rubber and tobacco smoke. Some types of aromatic amines are generated during cooking, special grilled meat and fish, as well. The intensive use and production of these comp...

  18. Aromaticity influencing the thermostability of micellar dispersions

    Energy Technology Data Exchange (ETDEWEB)

    Davis, J.A.; Kunzman, W.J.

    1971-05-11

    A hydrocarbon, having sufficient aromaticity to obtain a stable micellar dispersion at the temperature of the formation, is mixed with a surfactant and aqueous medium for injection into the formation to recover crude oil. Higher reservoir temperatures require a greater degree of aromaticity in the hydrocarbon component of the micellar dispersion. This patent is a continuation of U.S. Patent Number 3,495,660 (item No. 118).

  19. Nonchemical weeding of medicinal and aromatic plants

    OpenAIRE

    Carrubba, Alessandra; Militello, Marcello

    2013-01-01

    Medicinal and aromatic plants are major crops of domestic and industrial interest. Medicinal and aromatic plants are increasingly organically grown to enhance profitability. However, the presence of weeds may lead to a decrease in both yield and quality. Therefore, nonchemical methods of weed control are needed. In this study, mechanical weeding, flaming, stale seedbed, and biodegradable mulch were tested from 2003/2004 to 2006/2007 on coriander, fennel, and psyllium. Biomass and seed yield w...

  20. Chemotaxis of Azospirillum Species to Aromatic Compounds

    OpenAIRE

    Lopez-de-Victoria, Geralyne; Lovell, Charles R.

    1993-01-01

    Chemotaxis of Azospirillum lipoferum Sp 59b and Azospirillum brasilense Sp 7 and Sp CD to malate and to the aromatic substrates benzoate, protocatechuate, 4-hydroxybenzoate, and catechol was assayed by the capillary method and direct cell counts. A. lipoferum required induction by growth on 4-hydroxybenzoate for positive chemotaxis to this compound. Chemotaxis of Azospirillum spp. to all other substrates did not require induction. Maximum chemotactic responses for most aromatic compounds occu...

  1. Oxidative capacity of the Mexico City atmosphere – Part 1: A radical source perspective

    Directory of Open Access Journals (Sweden)

    R. Volkamer

    2010-07-01

    Full Text Available A detailed analysis of OH, HO2 and RO2 radical sources is presented for the near field photochemical regime inside the Mexico City Metropolitan Area (MCMA. During spring of 2003 (MCMA-2003 field campaign an extensive set of measurements was collected to quantify time-resolved ROx (sum of OH, HO2, RO2 radical production rates from day- and nighttime radical sources. The Master Chemical Mechanism (MCMv3.1 was constrained by measurements of (1 concentration time-profiles of photosensitive radical precursors, i.e., nitrous acid (HONO, formaldehyde (HCHO, ozone (O3, glyoxal (CHOCHO, and other oxygenated volatile organic compounds (OVOCs; (2 respective photolysis-frequencies (J-values; (3 concentration time-profiles of alkanes, alkenes, and aromatic VOCs (103 compound are treated and oxidants, i.e., OH- and NO3 radicals, O3; and (4 NO, NO2, meteorological and other parameters. The ROx production rate was calculated directly from these observations; the MCM was used to estimate further ROx production from unconstrained sources, and express overall ROx production as OH-equivalents (i.e., taking into account the propagation efficiencies of RO2 and HO2 radicals into OH radicals.

    Daytime radical production is found to be about 10–25 times higher than at night; it does not track the abundance of sunlight. 12-h average daytime contributions of individual sources are: Oxygenated VOC other than HCHO about 33%; HCHO and O3 photolysis each about 20%; O3/alkene reactions and HONO photolysis each about 12%, other sources <3%. Nitryl chloride photolysis could potentially contribute ~15% additional radicals, while NO2* + water makes – if any – a very small contribution (~2%. The peak radical production of ~7.5 107 molec cm−3 s−1 is

  2. Occurrence and sources of particulate nitro-polycyclic aromatic hydrocarbons in ambient air in Denmark

    DEFF Research Database (Denmark)

    Feilberg, A.; Poulsen, M.W.B.; Nielsen, T.;

    2001-01-01

    The occurrence of selected nitro-polycyclic aromatic hydrocarbons (nitro-PAHs) associated with atmospheric particulate matter has been investigated at an urban site and at a semi-rural site. For this purpose an analysis method based on gas chromatography and tandem ion trap mass spectrometry has...... been developed and applied. The nitro-PAK levels have been compared with levels of other air pollutants including unsubstituted PAHs, inorganic gases and particulate matter, as well as with meteorological parameters. Correlations and concentration ratios suggest that the dominant source of 9...... contribution of the OH initiated formation is estimated to be in the range of 90-100%. However, under wintertime conditions with cloudy weather implying low OH radical production, NO3 radicals may also be important as initiators of nitro-PAH formation. Samples influenced by transport of polluted air masses...

  3. σ-Aromaticity in polyhydride complexes of Ru, Ir, Os, and Pt.

    Science.gov (United States)

    Jimenez-Izal, Elisa; Alexandrova, Anastassia N

    2016-04-28

    Transition-metal hydrides represent a unique class of compounds, which are essential for catalysis, organic synthesis, and hydrogen storage. In this work we study IrH5(PPh3)2, (RuH5(P(i)Pr3)2)(-), (OsH5(P(i)Pr3)2)(-), and OsH4(PPhMe2)3 polyhydride complexes, inspired by the recent discovery of the σ-aromatic PtZnH5(-) cluster anion. The distinctive feature of these molecules is that, like in the PtZnH5(-) cluster, the metal is five-fold coordinated in-plane, and holds additional ligands at the axial positions. This work shows that the unusual coordination in these compounds indeed can be explained by σ-aromaticity in the pentagonal arrangement, stabilized by the atomic orbitals on the metal. Based on this newly elucidated bonding principle, we additionally propose a new family of polyhydrides that display a uniquely high coordination. We also report the first indications of how aromaticity may impact the reactivity of these molecules. PMID:26414992

  4. Adsorption behaviour of aromatic in different activated carbon: (Frendlich and Langmuir models)

    International Nuclear Information System (INIS)

    Adsorption behavior of p-Cresol, Benzoic acid and nitrobenzene on the two different activated carbons was carried out at 301 K and at controlled ph conditions. In acidic conditions, well below the pKa of all solutes, it was observed that the adsorbate solubility and the electron density of its aromatic ring were the influencing factors on the extent of the adsorption by affecting the extent of London dispersion forces. In higher solution ph conditions, on the other hand, it was found that the electrostatic forces played a significant role on the extent on adsorption. The Effect of ph must be considered from its combined effects on the carbon surface and on the solute molecules. It was found that the uptake of the molecular form of the aromatic solute was dependent on the substituents of the aromatic ring. Adsorption of the solutes in higher ph values was found to be dependent on the concentration of anionic form of the solutes. All isotherms on the F 100 and S E I were fitted into Langmuir and Freundlich isotherm Equations, respectively to find the relative factors

  5. From Radical Translation to Radical Interpretation and Back

    Directory of Open Access Journals (Sweden)

    António Zilhão

    2003-12-01

    Full Text Available Both Quine and Davidson put forth programs of empirical semantics satisfying the conditions that characterize the so-called “standpoint of interpretation.” Quine’s less ambitious program of radical translation rests upon two buttresses: causality and empathy. Davidson’s more ambitious program of radical interpretation replaces causality with truth and empathy with rationality. Although the replacement of causality with intersubjective truth seems to me to be a fully justified move, I nevertheless contend that it is more realistic to develop the work of interpretation drawing upon Quine’s less ambitious requirement of empathy than upon Davidson’s view of human agency as rational agency. In order to substantiate this contention, I present an argument to the effect that Davidson’s characterization of human agency as rational is not compatible with his other requirement that truth should pro-vide the essential link connecting speech with environment and action.

  6. The chemistry of gold as an anion.

    Science.gov (United States)

    Jansen, Martin

    2008-09-01

    Due to relativistic and classical shell structure effects, the 6s orbital of gold is significantly contracted and energetically stabilized. This is reflected by a strikingly high electron affinity, and a distinct tendency to adopt negatively polarized valence states. This tutorial review focuses on the chemistry of gold as an anion, displaying the integral ionic charge number of 1-. Two synthetic approaches to compounds containing monoatomic gold anions have become available: (1) reacting elemental gold with molten caesium and an oxide, e.g. Cs2O; (2) metathesis reactions involving Au- dissolved in liquid ammonia. Both procedures have proven to be rather versatile. Aurides synthesized along these routes are surveyed, in particular with respect to their structures and bonding properties. PMID:18762832

  7. Specific anion effects in Artemia salina.

    Science.gov (United States)

    Lo Nostro, Pierandrea; Ninham, Barry W; Carretti, Emiliano; Dei, Luigi; Baglioni, Piero

    2015-09-01

    The specific anion effect on the vitality of Artemia salina was investigated by measuring the Lethal Time LT50 of the crustaceans in the presence of different sodium salts solutions at room temperature and at the same ionic strength as natural seawater. Fluoride, thiocyanate and perchlorate are the most toxic agents, while chloride, bromide and sulfate are well tolerated. The rates of oxygen consumption of brine shrimps were recorded in mixed NaCl+NaF or NaCl+NaSCN solutions as a function of time. The results are discussed in terms of the Hofmeister series, and suggest that, besides the biochemical processes that involve F(-), SCN(-) and ClO4(-), the different physico-chemical properties of the strong kosmotropic and chaotropic anions may contribute in determining their strong toxicity for A. salina. PMID:25978674

  8. Infrared spectroscopy of organic free radicals related to combustion processes

    Energy Technology Data Exchange (ETDEWEB)

    Weisshaar, J.C. [Univ. of Wisconsin, Madison (United States)

    1993-12-01

    The primary long-term goal of this work is to develop new techniques for measuring vibrational spectra of polyatomic neutral free radicals. The authors explore a variation of resonant two-photon ionization (R2PI) in which tunable {omega}{sub IR} excites the radical vibrationally and {omega}{sub UV} selectively ionizes only the vibrationally excited molecules. Development of the IR + UV R2PI experiment is underway. In the meantime, the authors have used optical R2PI and pulsed field ionization (PFI) detection to obtain new vibrational spectra of species such as the benzyl and phenylsilane cations. In benzyl, a great deal was learned about the vibronic coupling mechanism in the mixed q{sup 2}A{sub 2}-2{sup 2}B{sub 2} system near 450 nm by projecting the mixed states onto the manifold of cation vibrational states. In phenylsilane{sup +}, we find that the sixfold barrier to internal rotation of the silyl group is small (V{sub 6} = +19 cm{sup {minus}1}). We are beginning to understand the mechanisms of coupling of torsional states with vibration, overall rotation, and other electronic states. In addition, we are developing a new model of internal rotation in aromatic compounds based on Prof. Frank Weinhold`s natural resonance theory.

  9. Politseiuuringud kooskõlastamisele / Liivia Anion

    Index Scriptorium Estoniae

    Anion, Liivia

    2003-01-01

    1. aprillil 2003. a. moodustatud uurimistööde kooskõlastamise komisjoni tegevuse eesmärk on saada ülevaade kõrgkoolides õppivate töötajate poolt politseis korraldatavatest uurimustest, kasutada saadud infot politsei kasuks ja vältida teenistujate tööd segavate uurimuste tegemist. Komisjoni liige Liivia Anion teeb ülevaate komisjoni otsustuspädevuse valdkondadest ja töökorraldusest

  10. Polynuclear aromatic hydrocarbons for fullerene synthesis in flames

    Science.gov (United States)

    Alford, J. Michael; Diener, Michael D.

    2006-12-19

    This invention provides improved methods for combustion synthesis of carbon nanomaterials, including fullerenes, employing multiple-ring aromatic hydrocarbon fuels selected for high carbon conversion to extractable fullerenes. The multiple-ring aromatic hydrocarbon fuels include those that contain polynuclear aromatic hydrocarbons. More specifically, multiple-ring aromatic hydrocarbon fuels contain a substantial amount of indene, methylnapthalenes or mixtures thereof. Coal tar and petroleum distillate fractions provide low cost hydrocarbon fuels containing polynuclear aromatic hydrocarbons, including without limitation, indene, methylnapthalenes or mixtures thereof.

  11. Several hemicyanine dyes as fluorescence chemosensors for cyanide anions

    Science.gov (United States)

    Liang, Muhan; Wang, Kangnan; Guan, Ruifang; Liu, Zhiqiang; Cao, Duxia; Wu, Qianqian; Shan, Yanyan; Xu, Yongxiao

    2016-05-01

    Four hemicyanine dyes as chemosensors for cyanide anions were synthesized easily. Their photophysical properties and recognition properties for cyanide anions were investigated. The results indicate that all the dyes can recognize cyanide anions with obvious color, absorption and fluorescence change. The recognition mechanism analysis basing on in situ 1H NMR and Job plot data indicates that to the compounds with hydroxyl group, the recognition mechanism is intramolecular hydrogen bonding interaction. However, to the compounds without hydroxyl group, cyanide anion is bonded to carbon-carbon double bond in conjugated bridge and induces N+ CH3 to neutral NCH3. Fluorescence of the compounds is almost quenched upon the addition of cyanide anions.

  12. The Scavenging of Free Radical and Oxygen Species Activities and Hydration Capacity of Collagen Hydrolysates from Walleye Pollock (Theragra chalcogramma) Skin

    Institute of Scientific and Technical Information of China (English)

    ZHUANG Yongliang; LI Bafang; ZHAO Xue

    2009-01-01

    Fish skin collagen hydrolysates (FSCH) were prepared from walleye pollock (Theragra chalcogramma) using a mixture of enzymes, namely trypsin and flavourzyme. The degree of hydrolysis of the skin collagen was 27.3%. FSCH was mainly composed of low-molecular-weight peptides and the relative proportion of <1000Da fraction was 70.6%. Free radical and oxygen species scavenging activities of FSCH were investigated in four model systems, including diphenylpicrylhy-drazyl radical (DPPH), superox-ide anion radical, hydroxyl radical and hydrogen peroxide model, and compared with that of a native antioxidant, reduced glutathione (GSH). FSCH was also evaluated by water-absorbing and water-holding capacity. The results showed that FSCH was able to scav-enge free radical and oxygen species significantly and to enhance water-absorbing and water-holding capacity remarkably. Therefore, FSCH may have potential applications in the medicine and food industries.

  13. [In vitro anti-inflammatory and free radical scavenging activities of flavans from Ilex centrochinensis].

    Science.gov (United States)

    Li, Lu-jun; Yu, Li-juan; Li, Yan-ci; Liu, Meng-yuan; Wu, Zheng-zhi

    2015-04-01

    This study was carried out to evaluate the anti-inflammatory and free radical scavenging activities of flavans from flex centrochinensis S. Y. Hu in vitro and their structure-activity relationship. LPS-stimulated RAW 264.7 macrophage was used as inflammatory model. MTT assay for cell availability, Griess reaction for nitric oxide (NO) production, the content of TNF-alpha, IL-1beta, IL-6 and PGE, were detected with ELISA kits; DPPH, superoxide anion and hydroxyl free radicals scavenging activities were also investigated. According to the result, all flavans tested exhibited anti-inflammatory effect in different levels. Among them, compounds 1, 3, 4 and 6 showed potent anti-inflammatory effect through the inhibition of NO, TNF-alpha, IL-lp and IL-6, of which 1 was the most effective inhibitor, however, 2 and 5 were relatively weak or inactive. The order of free radical scavenging activities was similar to that of anti-inflammatory activities. Therefore, these results suggest that 3, 4 and 6, especially of 1, were,in part responsible for the anti-inflammatory and free radical scavenging activity of Ilex centrochinensis. Hydroxyl group at 4'-position of B-ring plays an important role in the anti-inflammatory and free radical scavenging capacities. PMID:26281592

  14. Radical Intermediates in Photoinduced Reactions on TiO2 (An EPR Spin Trapping Study

    Directory of Open Access Journals (Sweden)

    Dana Dvoranová

    2014-10-01

    Full Text Available The radical intermediates formed upon UVA irradiation of titanium dioxide suspensions in aqueous and non-aqueous environments were investigated applying the EPR spin trapping technique. The results showed that the generation of reactive species and their consecutive reactions are influenced by the solvent properties (e.g., polarity, solubility of molecular oxygen, rate constant for the reaction of hydroxyl radicals with the solvent. The formation of hydroxyl radicals, evidenced as the corresponding spin-adducts, dominated in the irradiated TiO2 aqueous suspensions. The addition of 17O-enriched water caused changes in the EPR spectra reflecting the interaction of an unpaired electron with the 17O nucleus. The photoexcitation of TiO2 in non-aqueous solvents (dimethylsulfoxide, acetonitrile, methanol and ethanol in the presence of 5,5-dimethyl-1-pyrroline N-oxide spin trap displayed a stabilization of the superoxide radical anions generated via electron transfer reaction to molecular oxygen, and various oxygen- and carbon-centered radicals from the solvents were generated. The character and origin of the carbon-centered spin-adducts was confirmed using nitroso spin trapping agents.

  15. Radical carbonylations using a continuous microflow system

    Directory of Open Access Journals (Sweden)

    Takahide Fukuyama

    2009-07-01

    Full Text Available Radical-based carbonylation reactions of alkyl halides were conducted in a microflow reactor under pressurized carbon monoxide gas. Good to excellent yields of carbonylated products were obtained via radical formylation, carbonylative cyclization and three-component coupling reactions, using tributyltin hydride or TTMSS as a radical mediator.

  16. EPR spin trapping of protein radicals

    DEFF Research Database (Denmark)

    Davies, Michael Jonathan; Hawkins, Clare L

    2004-01-01

    Electron paramagnetic resonance (EPR) spin trapping was originally developed to aid the detection of low-molecular-mass radicals formed in chemical systems. It has subsequently found widespread use in biology and medicine for the direct detection of radical species formed during oxidative stress...... selected examples of radical formation on proteins....

  17. Electron Paramagnetic Resonance Study of the Free Radical Scavenging Capacity of Curcumin and Its Demethoxy and Hydrogenated Derivatives.

    Science.gov (United States)

    Morales, Noppawan Phumala; Sirijaroonwong, Srisuporn; Yamanont, Paveena; Phisalaphong, Chada

    2015-01-01

    The quantitative free radical scavenging capacity of curcumin and its demethoxy derivatives (demethoxycurcumin (Dmc) and bisdemethoxycurcumin (Bdmc)) and hydrogenated derivatives (tetrahydrocurcumin (THC), hexahydrocurcumin (HHC) and octahydrocurcumin (OHC)) towards 1,1-diphenyl-2-picryl hydrazyl (DPPH), nitric oxide radical (NO), hydroxyl radical (HO(·)) and superoxide anion radical (O2(·)) were investigated by electron paramagnetic resonance (EPR) spectroscopy. One mole of the hydrogenated derivatives scavenged about 4 mol of the DPPH radical, while curcumin and Dmc scavenged about 3 mol of the DPPH radical. Curcumin and THC showed moderate scavenging activity towards NO, yielding 200 mmol of NO scavenged per 1 mol of the scavenger. In contrast, curcumin and its derivatives showed very low scavenging activity towards HO(·) and O2(·), yielding approximately only 3-12 mmol scavenged per 1 mol of the tested compounds. Our results suggest that curcumin and its derivatives principally act as chain breaking antioxidants rather than as direct free radical scavengers. Furthermore, we showed that the ortho-methoxyphenolic group and the heptadione linkage of these molecules greatly contributed to their DPPH and NO scavenging activity. PMID:26424013

  18. Enzyme-controlled scavenging of ascorbyl and 2,6-dimethoxy-semiquinone free radicals in Ehrlich ascites tumor cells.

    OpenAIRE

    Pethig, R; Gascoyne, P R; McLaughlin, J. A.; Szent-Györgyi, A

    1985-01-01

    The rate of scavenging by Ehrlich ascites cells of anionic ascorbyl and 2,6-dimethoxy-p-semiquinone free radicals has been investigated by electron spin resonance spectroscopy both for viable cells and for subcellular fractions obtained by differential centrifugation. The scavenging activity is concluded to be associated with an NAD(P)H enzyme containing an active sulfhydryl group. Attempts to identify the enzyme with the reported properties of either semi-dehydro-ascorbate reductase or DT-di...

  19. Free radicals and Dupuytren's contracture.

    OpenAIRE

    Murrell, G. A.; Francis, M. J.; Bromley, L.

    1987-01-01

    The concentration of substrate expressed as hypoxanthine capable of reacting with xanthine oxidase to release superoxide free radicals (O2-) was measured in control and Dupuytren's contracture palmar fascia. In Dupuytren's contracture palmar fascia the concentration of hypoxanthine was six times that of control and was greatest in "nodular" areas. Xanthine oxidase activity was also detected in Dupuytren's contracture palmar fascia. These results suggest a greater potential for hypoxanthine-xa...

  20. Studies of transition states and radicals by negative ion photodetachment

    Energy Technology Data Exchange (ETDEWEB)

    Metz, R.B.

    1991-12-01

    Negative ion photodetachment is a versatile tool for the production and study of transient neutral species such as reaction intermediates and free radicals. Photodetachment of the stable XHY{sup {minus}} anion provides a direct spectroscopic probe of the transition state region of the potential energy surface for the neutral hydrogen transfer reaction X + HY {yields} XH + Y, where X and Y are halogen atoms. The technique is especially sensitive to resonances, which occur at a specific energy, but the spectra also show features due to direct scattering. We have used collinear adiabatic simulations of the photoelectron spectra to evaluate trail potential energy surfaces for the biomolecular reactions and have extended the adiabatic approach to three dimensions and used it to evaluate empirical potential energy surfaces for the I + Hl and Br + HI reactions. In addition, we have derived an empirical, collinear potential energy surface for the Br + HBr reaction that reproduces our experimental results and have extended this surface to three dimensions. Photodetachment of a negative ion can be also used to study neutral free radicals. We have studied the vibrational and electronic spectroscopy of CH{sub 2}NO{sub 2} by photoelectron spectroscopy of CH{sub 2}NO{sub 2}{sup {minus}}, determining the electron affinity of CH{sub 2}NO{sub 2}, gaining insight on the bonding of the {sup 2}B{sub 1} ground state and observing the {sup 2}A{sub 2} excited state for the first time. Negative ion photodetachment also provides a novel and versatile source of mass-selected, jet-cooled free radicals. We have studied the photodissociation of CH{sub 2}NO{sub 2} at 270, 235, and 208 nm, obtaining information on the dissociation products by measuring the kinetic energy release in the photodissociation.

  1. Ozonation of pyridine and other N-heterocyclic aromatic compounds: Kinetics, stoichiometry, identification of products and elucidation of pathways.

    Science.gov (United States)

    Tekle-Röttering, Agnes; Reisz, Erika; Jewell, Kevin S; Lutze, Holger V; Ternes, Thomas A; Schmidt, Winfried; Schmidt, Torsten C

    2016-10-01

    Pyridine, pyridazine, pyrimidine and pyrazine were investigated in their reaction with ozone. These compounds are archetypes for heterocyclic aromatic amines, a structural unit that is often present in pharmaceuticals, pesticides and dyestuffs (e.g., enoxacin, pyrazineamide or pyrimethamine). The investigated target compounds react with ozone with rate constants ranging from 0.37 to 57 M(-1) s(-1), hampering their degradation during ozonation. In OH radical scavenged systems the reaction of ozone with pyridine and pyridazine is characterized by high transformation (per ozone consumed) of 55 and 54%, respectively. In non scavenged system the transformation drops to 52 and 12%, respectively. However, in the reaction of pyrimidine and pyrazine with ozone this is reversed. Here, in an OH radical scavenged system the compound transformation is much lower (2.1 and 14%, respectively) than in non scavenged one (22 and 25%, respectively). This is confirmed by corresponding high N-oxide formation in the ozonation of pyridine and pyridazine, but probably low formation in the reaction of pyrimidine and pyrazine with ozone. With respect to reaction mechanisms, it is suggested that ozone adduct formation at nitrogen is the primary step in the ozonation of pyridine and pyridazine. On the contrary, ozone adduct formation to the aromatic ring seems to occur especially in the ozonation of pyrimidine as inferred from hydrogen peroxide yield. However, also OH radical reactions are supposed processes in the case of pyrimidine and in particular for pyrazine, albeit negligible OH radical yields are obtained. The low compound transformation in OH radical scavenged system can prove this. As a result of negligible OH radical yields in all cases (less than 6%) electron transfer as primary reaction pathway plays a subordinate role. PMID:27448509

  2. An overview of the AROMAT campaigns

    Science.gov (United States)

    Merlaud, Alexis; Dekemper, Emmanuel; Van Roozendael, Michel; Constantin, Daniel; Georgescu, Lucian; Meier, Andreas; Richter, Andreas; Den Hoed, Mirjam; Allaart, Marc; Boscornea, Andreea; Vajaiac, Sorin; Bellegante, Livio; Nemuc, Anca; Nicolae, Doina; Shaifangar, Reza; Dörner, Steffen; Wagner, Thomas; Stebel, Kerstin; Schuettemeyer, Dirk

    2016-04-01

    The Airborne ROmanian Measurements of Aerosols and Trace gases (AROMAT) campaign and its follow-up AROMAT-2 were held in September 2014 and August 2015, respectively. Both campaigns focused on two geophysical targets: the city of Bucharest and the large power plants of the Jiu Valley, which are located in a rural area 170 km West of Bucharest. These two areas are complementary in terms of emitted chemical species and their spatial distributions. The objectives of the AROMAT campaigns were (i) to test recently developed airborne observation systems dedicated to air quality satellite validation studies such as the AirMAP imaging DOAS system (University of Bremen), the NO2 sonde (KNMI), and the compact SWING whiskbroom imager (BIRA), and (ii) to prepare the validation programme of the future Atmospheric Sentinels, starting with Sentinel-5 Precursor (S5P) to be launched in early summer 2016. We present results from the different airborne instrumentations and from coincident ground-based measurements (lidar, in-situ, and mobile DOAS systems) performed during both campaigns. The AROMAT dataset addresses several of the mandatory products of TROPOMI/S5P, in particular NO2 and SO2 (horizontal distribution and profile from aircraft, plume image with ground-based SO2 and NO2 cameras, transects with mobile DOAS, in-situ), H2CO (mobile MAX-DOAS), and aerosols (lidar, airborne FUBISS-ASA2 sun-photometer, and aircraft in-situ). We investigate the information content of the AROMAT dataset for satellite validation studies based on co-located OMI and GOME-2 data, and simulations of TROPOMI measurements. The experience gained during AROMAT and AROMAT-2 will be used in support of a large-scale TROPOMI/S5P validation campaign in Romania scheduled for summer 2017.

  3. Gas phase structures and charge localization in small aluminum oxide anions: Infrared photodissociation spectroscopy and electronic structure calculations

    Science.gov (United States)

    Song, Xiaowei; Fagiani, Matias R.; Gewinner, Sandy; Schöllkopf, Wieland; Asmis, Knut R.; Bischoff, Florian A.; Berger, Fabian; Sauer, Joachim

    2016-06-01

    We use cryogenic ion trap vibrational spectroscopy in combination with quantum chemical calculations to study the structure of mono- and dialuminum oxide anions. The infrared photodissociation spectra of D2-tagged AlO1-4- and Al2O3-6- are measured in the region from 400 to 1200 cm-1. Structures are assigned based on a comparison to simulated harmonic and anharmonic IR spectra derived from electronic structure calculations. The monoaluminum anions contain an even number of electrons and exhibit an electronic closed-shell ground state. The Al2O3-6- anions are oxygen-centered radicals. As a result of a delicate balance between localization and delocalization of the unpaired electron, only the BHLYP functional is able to qualitatively describe the observed IR spectra of all species with the exception of AlO3-. Terminal Al-O stretching modes are found between 1140 and 960 cm-1. Superoxo and peroxo stretching modes are found at higher (1120-1010 cm-1) and lower energies (850-570 cm-1), respectively. Four modes in-between 910 and 530 cm-1 represent the IR fingerprint of the common structural motif of dialuminum oxide anions, an asymmetric four-member Al-(O)2-Al ring.

  4. Supramolecular chemistry of selective anion recognition for anions of environmental relevance. 1998 annual progress report

    Energy Technology Data Exchange (ETDEWEB)

    Bowman-James, K.; Wilson, G.S.; Kuczera, K. [Univ. of Kansas, Lawrence, KS (US); Moyer, B. [Oak Ridge National Lab., TN (US)

    1998-06-01

    'This project has as its focus the design and synthesis of polyammonium macrocyclic receptors for oxoanions of environmental importance. The basic research aspects of this project involve: (1) synthesis (and the search for improved synthetic methods); (2) solid state structure determination and thermodynamics studies (to ascertain structural criteria for and strength of anion binding); and (3) molecular dynamics simulations (to assess solution characteristics of the interactions between anions and their receptors). Applications-oriented goals include the fabrication of more selective anion-selective electrodes and the use of these compounds in liquid-liquid separations. The latter goal comprises the subcontract with Dr. Bruce Moyer at Oak Ridge National Laboratory. This report summarizes work after 1 year and 7 months of a 3-year project. To date, the authors have focussed on the design and synthesis of selective receptors for nitrate and phosphate.'

  5. Expanded Porphyrin-Anion Supramolecular Assemblies: Environmentally Responsive Sensors for Organic Solvents and Anions.

    Science.gov (United States)

    Zhang, Zhan; Kim, Dong Sub; Lin, Chung-Yon; Zhang, Huacheng; Lammer, Aaron D; Lynch, Vincent M; Popov, Ilya; Miljanić, Ognjen Š; Anslyn, Eric V; Sessler, Jonathan L

    2015-06-24

    Porphyrins have been used frequently to construct supramolecular assemblies. In contrast, noncovalent ensembles derived from expanded porphyrins, larger congeners of naturally occurring tetrapyrrole macrocycles, are all but unknown. Here we report a series of expanded porphyrin-anion supramolecular assemblies. These systems display unique environmentally responsive behavior. Addition of polar organic solvents or common anions to the ensembles leads to either a visible color change, a change in the fluorescence emission features, or differences in solubility. The actual response, which could be followed easily by the naked eye, was found to depend on the specifics of the assembly, as well as the choice of analyte. Using the ensembles of this study, it proved possible to differentiate between common solvents, such as diethyl ether, THF, ethyl acetate, acetone, alcohol, acetonitrile, DMF, and DMSO, identify complex solvent systems, as well as distinguish between the fluoride, chloride, bromide, nitrate, and sulfate anions. PMID:25965790

  6. 3D Printing of Micropatterned Anion Exchange Membranes.

    Science.gov (United States)

    Seo, Jiho; Kushner, Douglas I; Hickner, Michael A

    2016-07-01

    Micropatterned anion exchange membranes (AEMs) have been 3D printed via a photoinitiated free radical polymerization and quaternization process. The photocurable formulation, consisting of diurethane dimethacrylate (DUDA), poly(ethylene glycol) diacrylate (PEGDA), dipentaerythritol penta-/hexa- acrylate, and 4-vinylbenzyl chloride (VBC), was directly cured into patterned films using a custom 3D photolithographic printing process similar to stereolithography. Measurements of water uptake, permselectivity, and ionic resistance were conducted on the quaternized poly(DUDA-co-PEGDA-co-VBC) sample series to determine their suitability as ion exchange membranes. The water uptake of the polymers increased as the ion exchange capacity (IEC) increased due to greater quaternized VBC content. Samples with IEC values between 0.98 to 1.63 mequiv/g were synthesized by varying the VBC content from 15 to 25 wt %. The water uptake was sensitive to the PEGDA content in the network resulting in water uptake values ranging from 85 to 410 wt % by varying the PEGDA fractions from 0 to 60 wt %. The permselectivity of the AEM samples decreased from 0.91 (168 wt %, 1.63 mequiv/g) to 0.85 (410 wt %, 1.63 mequiv/g) with increasing water uptake and to 0.88 (162 wt %, 0.98 mequiv/g) with decreasing IEC. Permselectivity results were relatively consistent with the general understanding of the correlation between permselectivity, water uptake, and ion content of the membrane. Lastly, it was revealed that the ionic resistance of patterned membranes was lower than that of flat membranes with the same material volume or equivalent thickness. A parallel resistance model was used to explain the influence of patterning on the overall measured ionic resistance. This model may provide a way to maximize ion exchange membrane performance by optimizing surface patterns without chemical modification to the membrane. PMID:27218137

  7. Cyclopropenyl Anions: Carbon Tunneling or Diradical Formation? A Contest between Jahn-Teller and Hund.

    Science.gov (United States)

    Kozuch, Sebastian

    2015-07-14

    The π bond shifting (automerization) by carbon tunneling of cyclopropenyl anions was computationally analyzed by the small curvature tunneling methodology. Similar to other antiaromatic cases, the process is hindered by substituents departing from planarity, since these groups must be realigned along with the π bond shifting. With hydrogens as substituents the tunneling is extremely fast, in a case of both heavy and light atom tunneling. But, with more massive substituents (such as Me and F), and especially with longer groups (such as CN), the tunneling probability is reduced or even virtually canceled. The automerization of triphenylcyclopropyl anion by tunneling was supposed to be impossible due to the high mass of the phenyl groups. However, it was found that the ground state of this species is actually a D3h aromatic triplet, a single-well system that cannot undergo automerization. For this and other systems with π acceptor groups, the superposition of states that generates the second-order Jahn-Teller distortion is diminished, and by Hund's rule, the triplet results in the ground state. PMID:26575745

  8. Energy Density Functionals From the Strong-Coupling Limit Applied to the Anions of the He Isoelectronic Series

    CERN Document Server

    Mirtschink, André; Morgan, John D; Gori-Giorgi, Paola

    2014-01-01

    Anions and radicals are important for many applications including environmental chemistry, semiconductors, and charge transfer, but are poorly described by the available approximate energy density functionals. Here we test an approximate exchange-correlation functional based on the exact strong-coupling limit of the Hohenberg-Kohn functional on the prototypical case of the He isoelectronic series with varying nuclear charge $Z$, which includes weakly bound negative ions and a quantum phase transition at a critical value of $Z$, representing a big challenge for density functional theory. We use accurate calculations to validate our results, comparing energies and Kohn-Sham potentials. We show that our functional is able to bind H$^-$ and to capture in general the physics of loosely bound anions, with a tendency to overbind that can be proven mathematically. We also include corrections based on the uniform electron gas which largely improve the results.

  9. Degradation of methyl and ethyl mercury into inorganic mercury by oxygen free radical-producing systems: involvement of hydroxyl radical.

    Science.gov (United States)

    Suda, I; Totoki, S; Takahashi, H

    1991-01-01

    Degradation of methyl mercury (MeHg) and ethyl Hg (EtHg) with oxygen free radicals was studied in vitro by using three well-known hydroxyl radical (.OH)-producing systems, namely Cu2(+)-ascorbate, xanthine oxidase (XOD)-hypoxanthine (HPX)-Fe(III)EDTA and hydrogen peroxide (H2O2)-ultraviolet light B. For this purpose, the direct determination method for inorganic Hg was employed. MeHg and EtHg were readily degraded by these three systems, though the amounts of inorganic Hg generated from MeHg were one half to one third those from EtHg. Degradation activity of XOD-HPX-Fe(III)EDTA system was inhibited by superoxide dismutase, catalase and the .OH scavengers and stimulated by H2O2. Deletion of the .OH formation promoter Fe(III)EDTA from XOD-HPX-Fe(III)EDTA system resulted in the decreased degradation of MeHg and EtHg, which was enhanced by further addition of the iron chelator diethylenetriamine pentaacetic acid. In all these cases, a good correlation was observed between alkyl Hg degradation and deoxyribose oxidation determining .OH. By contrast, their degradation appeared to be unrelated to either superoxide anion (O2-) production or H2O2 production alone. We further confirmed that H2O2 (below 2 mM) itself did not cause significant degradation of MeHg and EtHg. These results suggested that .OH, but not O2- and H2O2, might be the oxygen free radical mainly responsible for the degradation of MeHg and EtHg. PMID:1647758

  10. Characterization of Anion Exchange Membrane Containing Epoxy Ring and C–Cl Bond Quaternized by Various Amine Groups for Application in Fuel Cells

    OpenAIRE

    Sung Kuk Jeong; Ju Sung Lee; Sahng Hyuck Woo; Jin Ah Seo; Byoung Ryul Min

    2015-01-01

    Anion exchange membranes were synthesized from different compositions of glycidyl methacrylate (GMA) and vinylbenzyl chloride (VBC), with constant content of divinyl benzene (DVB) by radical polymerization using benzoyl peroxide (BPO) on non-woven polyethylene terephthalate (PET) substrate. Polymerized membranes were then quaternized by soaking in trimethylamine (TMA), triethylamine (TEA), tripropylamine (TPA), and 1,4-diazabicyclo [2.2.2] octane (DABCO). Characteristics of membranes were con...

  11. Characterization of Anion Exchange Membrane Containing Epoxy Ring and C–Cl Bond Quaternized by Various Amine Groups for Application in Fuel Cells

    OpenAIRE

    Sung Kuk Jeong; Ju Sung Lee; Sahng Hyuck Woo; Jin Ah Seo; Byoung Ryul Min

    2015-01-01

    Anion exchange membranes were synthesized from different compositions of glycidyl methacrylate (GMA) and vinylbenzyl chloride (VBC), with constant content of divinyl benzene (DVB) by radical polymerization using benzoyl peroxide (BPO) on non-woven polyethylene terephthalate (PET) substrate. Polymerized membranes were then quaternized by soaking in trimethylamine (TMA), triethylamine (TEA), tripropylamine (TPA), and 1,4-diazabicyclo [2.2.2] octane (DABCO). Characteristics of membranes were co...

  12. Imidazole π cation and barbital π anion trapped in a cocrystalline complex x-irradiated at 12 K: An ESR--ENDOR study

    International Nuclear Information System (INIS)

    The predominant free radicals trapped in single crystals of the 1:1 intermolecular complex of imidazole and 5,5-diethylbarbituric acid (barbital) x-irradiated at 12 K have been identified by ESR and ENDOR. The electron abstraction and electron addition products are found to be the imidazole π cation and the barbital π anion, respectively. The π cation provides experimental evidence of evenly distributed unpaired electron density at positions C2, C4, and C5 of the five membered imidazole ring. In the π anion the unpaired electron density is localized primarily on C4 of barbital. It is suggested that π anions are trapped in barbital in preference to imidazole because barbital has a higher cross section for electron capture than imidazole. On the other hand, π cations are trapped in imidazole in preference to barbital because the barbital π cation has a higher cross section for destruction than the imidazole π cation

  13. Anionic complexes of Cu(I) with the closo-decaborate anion

    International Nuclear Information System (INIS)

    General procedures for synthesis of anionic Cu(I) complexes with the closo-decaborate anion were worked out; they make it possible to prepare coordination compounds with a wide set of organic cations. The interaction of onium closo-decaborates with [Cu2B10H10] in acetonitrile acidified with anhydrous trifluoroacetic acid was found to be the most effective synthetic method that secures high yield and quality of the obtained products. The structure of {(C2H5)3NH[CuB10H10]} was determined by X-ray diffraction analysis

  14. Novel Easy Preparations of Some Aromatic Iodine(I, III, and V Reagents, Widely Applied in Modern Organic Synthesis

    Directory of Open Access Journals (Sweden)

    Lech Skulski

    2003-01-01

    Full Text Available We report our novel (or considerably improved methods for the synthesis of aromatic iodides, (dichloroiodoarenes, (diacetoxyiodoarenes, [bis(trifluoroacetoxy-iodo]arenes, iodylarenes and diaryliodonium salts, as well as some facile, oxidative anion metatheses in crude diaryliodonium or tetraalkylammonium halides and, for comparison, potassium halides. All our formerly published papers were discussed and explained in our review “Organic Iodine(I, III, and V Chemistry: 10 Years of Development at the Medical University of Warsaw, Poland” (1990-2000 [1]. Our newest results are discussed below.

  15. Novel application of cyclolipopeptide amphisin: feasibility study as additive to remediate polycyclic aromatic hydrocarbon (PAH) contaminated sediments.

    Science.gov (United States)

    Groboillot, Anne; Portet-Koltalo, Florence; Le Derf, Franck; Feuilloley, Marc J G; Orange, Nicole; Poc, Cécile Duclairoir

    2011-01-01

    To decontaminate dredged harbor sediments by bioremediation or electromigration processes, adding biosurfactants could enhance the bioavailability or mobility of contaminants in an aqueous phase. Pure amphisin from Pseudomonas fluorescens DSS73 displays increased effectiveness in releasing polycyclic aromatic hydrocarbons (PAHs) strongly adsorbed to sediments when compared to a synthetic anionic surfactant. Amphisin production by the bacteria in the natural environment was also considered. DSS73's growth is weakened by three model PAHs above saturation, but amphisin is still produced. Estuarine water feeding the dredged material disposal site of a Norman harbor (France) allows both P. fluorescens DSS73 growth and amphisin production. PMID:21673923

  16. Novel Application of Cyclolipopeptide Amphisin: Feasibility Study as Additive to Remediate Polycyclic Aromatic Hydrocarbon (PAH Contaminated Sediments

    Directory of Open Access Journals (Sweden)

    Anne Groboillot

    2011-03-01

    Full Text Available To decontaminate dredged harbor sediments by bioremediation or electromigration processes, adding biosurfactants could enhance the bioavailability or mobility of contaminants in an aqueous phase. Pure amphisin from Pseudomonas fluorescens DSS73 displays increased effectiveness in releasing polycyclic aromatic hydrocarbons (PAHs strongly adsorbed to sediments when compared to a synthetic anionic surfactant. Amphisin production by the bacteria in the natural environment was also considered. DSS73’s growth is weakened by three model PAHs above saturation, but amphisin is still produced. Estuarine water feeding the dredged material disposal site of a Norman harbor (France allows both P. fluorescens DSS73 growth and amphisin production.

  17. Chemical repair of trypsin-histidinyl radical

    International Nuclear Information System (INIS)

    Oxyl radicals, such as hydroxyl, alkoxyl and peroxyl, react with biomolecules to produce bioradicals. Unless chemically repaired by suitable antioxidants, these bioradicals form stable products. This leads to loss of biological function of parent biomolecules with deleterious biological results, such as mutagenesis and cancer. Consequently, the understanding of the mechanisms of oxyl radical damage to biomolecules and chemical repair of such damage is crucial for the development of strategies for anticarcinogenesis and radioprotection. In this study the chemical repair of the histidinyl radical generated upon the trichloromethylperoxyl radical reaction with trypsin vas investigated by gamma radiolysis. The trypsin histidinyl radical is a resonance-stabilized heterocyclic free radical which was found to be unreactive with oxygen. The efficacy of the chemical repair of the trypsin-histidinyl radical by endogenous antioxidants which are electron donors (e.g. 5-hydroxytryptophan, uric acid) is compared to that of antioxidants which are H-atom donors (e. g. glutathione). 9 refs., 2 figs., 1 tab

  18. Catechol oxidation by ozone and hydroxyl radicals at the air-water interface.

    Science.gov (United States)

    Pillar, Elizabeth A; Camm, Robert C; Guzman, Marcelo I

    2014-12-16

    Anthropogenic emissions of aromatic hydrocarbons promptly react with hydroxyl radicals undergoing oxidation to form phenols and polyphenols (e.g., catechol) typically identified in the complex mixture of humic-like substances (HULIS). Because further processing of polyphenols in secondary organic aerosols (SOA) can continue mediated by a mechanism of ozonolysis at interfaces, a better understanding about how these reactions proceed at the air-water interface is needed. This work shows how catechol, a molecular probe of the oxygenated aromatic hydrocarbons present in SOA, can contribute interfacial reactive species that enhance the production of HULIS under atmospheric conditions. Reactive semiquinone radicals are quickly produced upon the encounter of 40 ppbv-6.0 ppmv O3(g) with microdroplets containing [catechol] = 1-150 μM. While the previous pathway results in the instantaneous formation of mono- and polyhydroxylated aromatic rings (PHA) and chromophoric mono- and polyhydroxylated quinones (PHQ), a different channel produces oxo- and dicarboxylic acids of low molecular weight (LMW). The cleavage of catechol occurs at the 1,2 carbon-carbon bond at the air-water interface through the formation of (1) an ozonide intermediate, (2) a hydroperoxide, and (3) cis,cis-muconic acid. However, variable [catechol] and [O3(g)] can affect the ratio of the primary products (cis,cis-muconic acid and trihydroxybenzenes) and higher order products observed (PHA, PHQ, and LMW oxo- and dicarboxylic acids). Secondary processing is confirmed by mass spectrometry, showing the production of crotonic, maleinaldehydic, maleic, glyoxylic, and oxalic acids. The proposed pathway can contribute precursors to aqueous SOA (AqSOA) formation, converting aromatic hydrocarbons into polyfunctional species widely found in tropospheric aerosols with light-absorbing brown carbon. PMID:25423038

  19. A Comparative Study of the Formation of Aromatics in Rich Methane Flames Doped by Unsaturated Compounds

    CERN Document Server

    Gueniche, Hadj-Ali; Glaude, Pierre-Alexandre; Fournet, René; Battin-Leclerc, Frédérique; 10.1016/j.fuel.2009.03.006

    2009-01-01

    For a better modeling of the importance of the different channels leading to the first aromatic ring, we have compared the structures of laminar rich premixed methane flames doped with several unsaturated hydrocarbons: allene and propyne, because they are precursors of propargyl radicals which are well known as having an important role in forming benzene, 1,3-butadiene to put in evidence a possible production of benzene due to reactions of C4 compounds, and, finally, cyclopentene which is a source of cyclopentadienylmethylene radicals which in turn are expected to easily isomerizes to give benzene. These flames have been stabilized on a burner at a pressure of 6.7 kPa (50 Torr) using argon as dilutant, for equivalence ratios (?) from 1.55 to 1.79. A unique mechanism, including the formation and decomposition of benzene and toluene, has been used to model the oxidation of allene, propyne, 1,3 butadiene and cyclopentene. The main reaction pathways of aromatics formation have been derived from reaction rate and ...

  20. Formation of aromatics in rich methane flames doped by unsaturated compounds

    CERN Document Server

    Gueniche, Hadj-Ali; Fournet, René; Battin-Leclerc, Frédérique

    2009-01-01

    In order to better understand the importance of the different channels leading to the first aromatic ring, we have investigated, the structure of a laminar rich premixed methane flame doped with several unsaturated hydrocarbons: allene and propyne, as they are precursors of propargyl radicals, which are well known as having an important role in forming benzene, 1,3-butadiene, to put in evidence a possible production of benzene due to reactions of C4 compounds, and, finally, cyclopentene, which is a source of cyclopentadienyl methylene radicals which are supposed to easily isomerizes to give benzene. A ratio additive / CH4 of 16 % and an equivalence ratio of 1.79 have been used. These flames have been stabilized on a burner at a pressure of 6.7 kPa using argon as dilutant. A new mechanism for the oxidation of allene, propyne, 1,3 butadiene and cyclopentene has been proposed including the formation and decomposition of benzene and toluene. The main reaction pathways of formation of aromatics have been derived f...

  1. Free radicals and antioxidant systems in reflux esophagitis and Barrett's esophagus

    Institute of Scientific and Technical Information of China (English)

    Pilar Jiménez; Elena Piazuelo; M. Teresa Sánchez; Javier Ortego; Fernando Soteras; Angel Lanas

    2005-01-01

    AIM: Experimental studies suggest that free radicals are involved in acid and pepsin-induced damage of esophageal mucosa. The profile and balance between free radicals and antioxidant systems in human esophagitis are unknown. METHODS: Superoxide anion and its powerful oxidant reaction with nitric oxide (peroxynitrite) generation were determined in esophageal mucosal biopsies from 101 patients with different gastro-esophageal reflux diseases and 28 controls. Activity of both superoxide dismutase (SOD) and catalase, and reduced glutathione (GSH) levels,were also assessed. Expression of Cu,ZnSOD, MnSOD and tyrosine-nitrated MnSOD were analyzed by Western blot and/or immunohistochemistry.RESULTS: The highest levels of superoxide anion generation were found in patients with severe lesions of esophagitis. Peroxynitrite generation was intense in Barrett's biopsies, weaker in esophagitis and absent/weak in normal mucosa. Expression of Cu,ZnSOD and MnSOD isoforms were present in normal mucosa and increased according to the severityof the lesion, reaching the highest level in Barrett's esophagus. However, SOD mucosal activity significantly decreased in patients with esophagitis and Barrett's esophagus, which was, at least in part, due to nitration of its tyrosine residues. Catalase activity and GSH levels were significanUy increased in mucosal specimens from patients with esophagitis and/or Barrett's esophagus.CONCLUSION: A decrease in SOD antioxidant activity leading to increased mucosal levels of superoxide anion and peroxynitrite radicals may contribute to the development of esophageal damage and Barrett's esophagus in patients with gastroesophageal reflux. Administration of SOD may be a therapeutic target in the treatment of patients with esophagitis and Barrett's esophagus.

  2. Organic superconductors with an incommensurate anion structure

    Directory of Open Access Journals (Sweden)

    Tadashi Kawamoto and Kazuo Takimiya

    2009-01-01

    Full Text Available Superconducting incommensurate organic composite crystals based on the methylenedithio-tetraselenafulvalene (MDT-TSF series donors, where the energy band filling deviates from the usual 3/4-filled, are reviewed. The incommensurate anion potential reconstructs the Fermi surface for both (MDT-TSF(AuI20.436 and (MDT-ST(I30.417 neither by the fundamental anion periodicity q nor by 2q, but by 3q, where MDT-ST is 5H-2-(1,3-dithiol-2-ylidene-1,3-diselena-4,6-dithiapentalene, and q is the reciprocal lattice vector of the anion lattice. The selection rule of the reconstructing vectors is associated with the magnitude of the incommensurate potential. The considerably large interlayer transfer integral and three-dimensional superconducting properties are due to the direct donor–donor interactions coming from the characteristic corrugated conducting sheet structure. The materials with high superconducting transition temperature, Tc, have large ratios of the observed cyclotron masses to the bare ones, which indicates that the strength of the many-body effect is the major determinant of Tc. (MDT-TS(AuI20.441 shows a metal–insulator transition at TMI=50 K, where MDT-TS is 5H-2-(1,3-diselenol-2-ylidene-1,3,4,6-tetrathiapentalene, and the insulating phase is an antiferromagnet with a high Néel temperature (TN=50 K and a high spin–flop field (Bsf=6.9 T. There is a possibility that this material is an incommensurate Mott insulator. Hydrostatic pressure suppresses the insulating state and induces superconductivity at Tc=3.2 K above 1.05 GPa, where Tc rises to the maximum, Tcmax=4.9 K at 1.27 GPa. This compound shows a usual temperature–pressure phase diagram, in which the superconducting phase borders on the antiferromagnetic insulating phase, despite the unusual band filling.

  3. Infrared Spectroscopy of Discrete Uranyl Anion Complexes

    Energy Technology Data Exchange (ETDEWEB)

    Gary S. Groenewold; Anita K. Gianotto; Michael E. McIlwain; Michael J. Van Stipdonk; Michael Kullman; Travis J. Cooper; David T. Moore; Nick Polfer; Jos Oomens; Ivan Infante; Lucas Visscher; Bertrand Siboulet; Wibe A. de Jong

    2007-12-01

    The Free-Electron Laser for Infrared Experiments, FELIX, was used to study the wavelength-resolved multiphoton dissociation of discrete, gas phase uranyl (UO22+) complexes containing a single anionic ligand (A), with or without ligated solvent molecules (S). The apparent uranyl antisymmetric and symmetric stretching frequencies were measured for complexes with general formula [UO2A(S)n]+, where A was either hydroxide, methoxide or acetate, S was water, ammonia, acetone or acetonitrile, and n = 0-2. The values for the antisymmetric stretching frequency for uranyl ligated with only an anion ([UO2A]+) were as low or lower than measurements for [UO2]2+ ligated with as many as five strong neutral donor ligands, and are comparable to solution phase values. This result was surprising because initial DFT calculations using B3LYP predicted values that were 30 – 40 cm-1 higher, consistent with intuition but not with the data. Modification of the basis set and use of alternative functionals improved computational accuracy for the methoxide and acetate complexes, but calculated values for the hydroxide were greater than the measurement regardless of the computational method used. Attachment of a neutral donor ligand S to [UO2A]+ produced [UO2AS]+, which resulted only very modest changes to the uranyl frequency, and did not universally shift values lower. DFT calculations for [UO2AS]+ were in accord with trends in the data, and showed that attachment of the solvent was accommodated by weakening of the U-anion bond as well as the uranyl. When uranyl frequencies were compared for [UO2AS]+ species having different solvent neutrals, values decreased with increasing neutral nucleophilicity.

  4. Infared Spectroscopy of Discrete Uranyl Anion Complexes

    Energy Technology Data Exchange (ETDEWEB)

    Groenewold, G. S.; Gianotto, Anita K.; McIIwain, Michael E.; Van Stipdonk, Michael J.; Kullman, Michael; Moore, David T.; Polfer, Nick; Oomens, Jos; Infante, Ivan A.; Visscher, Lucas; Siboulet, Bertrand; De Jong, Wibe A.

    2008-01-24

    The Free-Electron Laser for Infrared Experiments (FELIX) w 1 as used to study the wavelength-resolved multiple photon photodissociation of discrete, gas phase uranyl (UO2 2 2+) complexes containing a single anionic ligand (A), with or without ligated solvent molecules (S). The uranyl antisymmetric and symmetric stretching frequencies were measured for complexes with general formula [UO2A(S)n]+, where A was either hydroxide, methoxide, or acetate; S was water, ammonia, acetone, or acetonitrile; and n = 0-3. The values for the antisymmetric stretching frequency for uranyl ligated with only an anion ([UO2A]+) were as low or lower than measurements for [UO2]2+ ligated with as many as five strong neutral donor ligands, and are comparable to solution phase values. This result was surprising because initial DFT calculations predicted values that were 30–40 cm-1 higher, consistent with intuition but not with the data. Modification of the basis sets and use of alternative functionals improved computational accuracy for the methoxide and acetate complexes, but calculated values for the hydroxide were greater than the measurement regardless of the computational method used. Attachment of a neutral donor ligand S to [UO2A]+ produced [UO2AS]+, which produced only very modest changes to the uranyl antisymmetric stretch frequency, and did not universally shift the frequency to lower values. DFT calculations for [UO2AS]+ were in accord with trends in the data, and showed that attachment of the solvent was accommodated by weakening of the U-anion bond as well as the uranyl. When uranyl frequencies were compared for [UO2AS]+ species having different solvent neutrals, values decreased with increasing neutral nucleophilicity.

  5. Infrared Spectroscopy of Discrete Uranyl Anion Complexes

    International Nuclear Information System (INIS)

    The Free-Electron Laser for Infrared Experiments (FELIX) w 1 as used to study the wavelength-resolved multiple photon photodissociation of discrete, gas phase uranyl (UO2 2 2+) complexes containing a single anionic ligand (A), with or without ligated solvent molecules (S). The uranyl antisymmetric and symmetric stretching frequencies were measured for complexes with general formula [UO2A(S)n]+, where A was either hydroxide, methoxide, or acetate; S was water, ammonia, acetone, or acetonitrile; and n = 0-3. The values for the antisymmetric stretching frequency for uranyl ligated with only an anion ([UO2A]+) were as low or lower than measurements for [UO2]2+ ligated with as many as five strong neutral donor ligands, and are comparable to solution phase values. This result was surprising because initial DFT calculations predicted values that were 30-40 cm-1 higher, consistent with intuition but not with the data. Modification of the basis sets and use of alternative functionals improved computational accuracy for the methoxide and acetate complexes, but calculated values for the hydroxide were greater than the measurement regardless of the computational method used. Attachment of a neutral donor ligand S to [UO2A]+ produced [UO2AS]+, which produced only very modest changes to the uranyl antisymmetric stretch frequency, and did not universally shift the frequency to lower values. DFT calculations for [UO2AS]+ were in accord with trends in the data, and showed that attachment of the solvent was accommodated by weakening of the U-anion bond as well as the uranyl. When uranyl frequencies were compared for [UO2AS]+ species having different solvent neutrals, values decreased with increasing neutral nucleophilicity

  6. Silicone elastomers with aromatic voltage stabilizers

    DEFF Research Database (Denmark)

    A Razak, Aliff Hisyam; Skov, Anne Ladegaard

    insulation cables.3–5 As an alternative to utilise additives as voltage stabilizers, grafting aromatic compounds to silicone backbones may overcome the common problem of insolubility of the aromatic voltage stabilizer in the silicone elastomers due to phase separation. Preventing phase separation during...... via hydrosilylation by a vinyl-functional crosslinker. The mechanism of electron-trapping by aromatic compounds grafted to silicone backbones in a crosslinked PDMS is illustrated in Fig. 1. The electrical breakdown strength, the storage modulus and the loss modulus of the elastomer were investigated...... attached to the silicone backbone. The dielectric relative permittivity of PDMS-PPMS copolymers remained between 2 to 3 with low conductivity and low dielectric loss as well as high storage moduli with low viscous loss, thereby maintaining the electro-mechanical integrity of the elastomer....

  7. Chemotaxis of Azospirillum species to aromatic compounds

    Energy Technology Data Exchange (ETDEWEB)

    Lopez-de-Victoria, G.; Lovell, C.R. (Univ. of South Carolina, Columbia, SC (United States))

    1993-09-01

    Azospirillum sspeciesare free-living nitrogen fixing bacteria commonly found in soils and in association with plant roots, including important agricultural crops. Rhizosphere colonization my Azospirillum species has been shown to stimulate growth of a variety of plant species. Chemotaxis is one of the properties which may contribute to survival, rhizosphere colonization and the initiation of mutualistic interactions by Azospirillum species. This study evaluates the chemotactic responses of three Azospirillum stains to a variety of aromatic compounds:benzoate, catechol, 4-HB, and PCA. Results indicate that the same aromatic substance can elicit different chemotactic responses from different Azospirillum species, and that Azospirillum can detect aromatic substrates at concentrations similar to those they encounter naturally. 36 refs., 1 fig., 6 tabs.

  8. Comparison of the radical scavenging potential of polar and lipidic fractions of olive oil and other vegetable oils under normal conditions and after thermal treatment.

    Science.gov (United States)

    Valavanidis, Athanasios; Nisiotou, Christala; Papageorgiou, Yiannis; Kremli, Ioulia; Satravelas, Nikolaos; Zinieris, Nikolaos; Zygalaki, Helen

    2004-04-21

    The antioxidant activity (IC(50)) of extra virgin olive oil (EVOO), commercial olive oil, and other vegetable oils (soybean, sunflower, and corn oil) was determined by UV-vis and by electron paramagnetic resonance (EPR) spectroscopy of the stable radical 2,2-diphenyl-1-picrylhydrazyl (DPPH). Also, we studied the antioxidant activity of the methanol soluble phase (methanolic, MF) and the nonsoluble phase (lipidic, LF) of oils by the same methods. Similarly, we studied the effect of heating on the antioxidant activity at 160 and 190 degrees C. Also, the MF, containing the polyphenolic substances, was used for measurements of the radical scavenging capacity toward the most important oxygen free radicals, superoxide anion (O(2)(*)(-)) and hydroxyl (HO(*)) radicals. Results showed that soybean oil and EVOO had the highest antioxidant potential and thermal stability. In the case of soybean oil, the antioxidant capacity is the result of its high content of gamma- and delta-tocopherols (with the highest antioxidant capacity and thermostabilities), whereas in EVOO, the antioxidant potential is the result of the combination of specific antioxidant polyphenols, which are acting additionally as effective stabilizers of alpha-tocopherol. The high content of EVOO in tyrosol, hydrotyrosol, and oleuropein and other polyphenolics with radical scavenging abilities toward superoxide anion and hydroxyl radical suggests that olive oil possesses biological properties that could partially account for the observed beneficial health effects of the Mediterranean diet. PMID:15080646

  9. Very High Pressure Single Pulse Shock Tube Studies of Aromatic Species

    Energy Technology Data Exchange (ETDEWEB)

    Brezinsky, K.

    2006-11-28

    The principal focus of this research program is aimed at understanding the oxidation and pyrolysis chemistry of primary aromatic molecules and radicals with the goal of developing a comprehensive kinetic model at conditions that are relevant to practical combustion devices. A very high pressure single pulse shock tube is used to obtain experimental data over a wide pressure range in the high pressure regime, 5-1000 bars, at pre-flame temperatures for fuel pyrolysis and oxidation over a broad spectrum of equivalence ratios. Stable species sampled from the shock tube are analyzed using standard chromatographic techniques using GC/MS-PDD and GC/TCD-FID. Experimental data from the HPST (stable species profiles) and data from other laboratories (if available) are simulated using kinetic models (if available) to develop a comprehensive model that can describe aromatics oxidation and pyrolysis over a wide range of experimental conditions. The shock tube has been heated (1000C) recently to minimize effects due to condensation of aromatic, polycyclic and other heavy species. Work during this grant period has focused on 7 main areas summarized in the final technical report.

  10. Electron-flux infrared response to varying π-bond topology in charged aromatic monomers.

    Science.gov (United States)

    Álvaro Galué, Héctor; Oomens, Jos; Buma, Wybren Jan; Redlich, Britta

    2016-01-01

    The interaction of delocalized π-electrons with molecular vibrations is key to charge transport processes in π-conjugated organic materials based on aromatic monomers. Yet the role that specific aromatic motifs play on charge transfer is poorly understood. Here we show that the molecular edge topology in charged catacondensed aromatic hydrocarbons influences the Herzberg-Teller coupling of π-electrons with molecular vibrations. To this end, we probe the radical cations of picene and pentacene with benchmark armchair- and zigzag-edges using infrared multiple-photon dissociation action spectroscopy and interpret the recorded spectra via quantum-chemical calculations. We demonstrate that infrared bands preserve information on the dipolar π-electron-flux mode enhancement, which is governed by the dynamical evolution of vibronically mixed and correlated one-electron configuration states. Our results reveal that in picene a stronger charge π-flux is generated than in pentacene, which could justify the differences of electronic properties of armchair- versus zigzag-type families of technologically relevant organic molecules. PMID:27577323

  11. Prediction of (liquid + liquid) equilibrium for binary and ternary systems containing ionic liquids with the bis[(trifluoromethyl)sulfonyl]imide anion using the ASOG method

    International Nuclear Information System (INIS)

    Highlights: • ASOG model was used to predict LLE data for ionic liquid systems. • Twenty five binary and seven ternary systems that include the NTf2 anion were used. • New group interaction parameters were determined. • The results are satisfactory, with rms deviations of about 3%. - Abstract: Ionic liquids are neoteric, environmentally friendly solvents (as they do not produce emissions) composed of large organic cations and relatively small inorganic anions. They have favorable physical properties, such as negligible volatility and a wide range of liquid existence. (Liquid + liquid) equilibrium (LLE) data for systems including ionic liquids, although essential for the design, optimization and operation of separation processes, remain scarce. However, some recent studies have presented ternary LLE data involving several ionic liquids and organic compounds such as alkanes, alkenes, alkanols, ethers and aromatics, as well as water. In this work, the ASOG model for the activity coefficient is used to predict LLE data for 25 binary and 07 ternary systems at 101.3 kPa and several temperatures; all the systems are formed by ionic liquids including the bis[(trifluoromethyl)sulfonyl]imide (NTf2) anion plus alkanes, alkenes, cycloalkanes, alkanols, water, thiophene and aromatics. New group interaction parameters were determined using a modified Simplex method, minimizing a composition-based objective function of experimental data obtained from the literature. The results are satisfactory, with rms deviations of approximately 3%

  12. Iron and iron derived radicals

    International Nuclear Information System (INIS)

    We have discussed some reactions of iron and iron-derived oxygen radicals that may be important in the production or treatment of tissue injury. Our conclusions challenge, to some extent, the usual lines of thought in this field of research. Insofar as they are born out by subsequent developments, the lessons they teach are two: Think fast! Think small! In other words, think of the many fast reactions that can rapidly alter the production and fate of highly reactive intermediates, and when considering the impact of competitive reactions on such species, think how they affect the microenvironment (on the molecular scale) ''seen'' by each reactive molecule. 21 refs., 3 figs., 1 tab

  13. Laser spectroscopy of hydrocarbon radicals

    Energy Technology Data Exchange (ETDEWEB)

    Chen, P. [Harvard Univ., Cambridge, MA (United States)

    1993-12-01

    The author reports the application of supersonic jet flash pyrolysis to the specific preparation of a range of organic radicals, biradicals, and carbenes in a skimmed molecular beam. Each species was produced cleanly and specifically, with little or no secondary reactions by the thermal dissociation of appropriately designed and synthesized organic precursors. Photoelectron spectra of the three isomeric C{sub 3}H{sub 2} carbenes, ortho-benzyne, and the {alpha},3-dehydrotoluene biradical, were used to establish adiabatic ionization potentials for use in thermochemical determinations.

  14. Structure and Function of Benzylsuccinate Synthase and Related Fumarate-Adding Glycyl Radical Enzymes.

    Science.gov (United States)

    Heider, Johann; Szaleniec, Maciej; Martins, Berta M; Seyhan, Deniz; Buckel, Wolfgang; Golding, Bernard T

    2016-01-01

    The pathway of anaerobic toluene degradation is initiated by a remarkable radical-type enantiospecific addition of the chemically inert methyl group to the double bond of a fumarate cosubstrate to yield (R)-benzylsuccinate as the first intermediate, as catalyzed by the glycyl radical enzyme benzylsuccinate synthase. In recent years, it has become clear that benzylsuccinate synthase is the prototype enzyme of a much larger family of fumarate-adding enzymes, which play important roles in the anaerobic metabolism of further aromatic and even aliphatic hydrocarbons. We present an overview on the biochemical properties of benzylsuccinate synthase, as well as its recently solved structure, and present the results of an initial structure-based modeling study on the reaction mechanism. Moreover, we compare the structure of benzylsuccinate synthase with those predicted for different clades of fumarate-adding enzymes, in particular the paralogous enzymes converting p-cresol, 2-methylnaphthalene or n-alkanes. PMID:26959246

  15. Production of aromatics from di- and polyoxygenates

    Energy Technology Data Exchange (ETDEWEB)

    Beck, Taylor; Blank, Brian; Jones, Casey; Woods, Elizabeth; Cortright, Randy

    2016-08-02

    Methods, catalysts, and reactor systems for producing in high yield aromatic chemicals and liquid fuels from a mixture of oxygenates comprising di- and polyoxygenates are disclosed. Also disclosed are methods, catalysts, and reactor systems for producing aromatic chemicals and liquid fuels from oxygenated hydrocarbons such as carbohydrates, sugars, sugar alcohols, sugar degradation products, and the like; and methods, catalysts, and reactor systems for producing the mixture of oxygenates from oxygenated hydrocarbons such as carbohydrates, sugars, sugar alcohols, sugar degradation products, and the like. The disclosed catalysts for preparing the mixture of oxygenates comprise a Ni.sub.nSn.sub.m alloy and a crystalline alumina support.

  16. Global aromatics supply. Today and tomorrow

    Energy Technology Data Exchange (ETDEWEB)

    Bender, M. [BASF SE, Ludwigshafen (Germany)

    2013-11-01

    Aromatics are the essential building blocks for some of the largest petrochemical products in today's use. To the vast majority they are consumed to produce intermediates for polymer products and, hence, contribute to our modern lifestyle. Their growth rates are expected to be in line with GDP growth in future. This contrasts the significantly lower growth rates of the primary sources for aromatics - fuel processing and steam cracking of naphtha fractions. A supply gap can be expected to open up in future for which creative solutions will be required. (orig.)

  17. Electron beam irradiation effects on aromatic polymers

    International Nuclear Information System (INIS)

    Electron irradiation effects on aromatic polymers having various molecular structures were studied to elucidate the following subjects; (1) relation between radiation stability and molecular structure of repeating units, (2) mechanism of deterioration and (3) adaptability to matrix resin for radiation resistant FRP. Results are summarized as follows: (1) An order of radiation stability of units is; imide ring > diphenyl ether, diphenyl ketone > aromatic amide >> bis-phenol A > diphenyl sulphone. (2) Poly (ether-ether-ketone) and most polyimide are crosslinkable but polysulphones and polyarylate are chain degradation type polymers. (3) Newly developed thermoplastic polyimides have possibilities for use as matrix materials in radiation resistant FRP. (author)

  18. Detection of a secondary muoniated radical

    Energy Technology Data Exchange (ETDEWEB)

    McCollum, Brett M.; Brodovitch, Jean-Claude [TRIUMF and Department of Chemistry, Simon Fraser University, Burnaby, BC, V5A 1S6 (Canada); Clyburne, Jason A.C. [Department of Chemistry, Saint Mary' s University, Halifax, NS, B3H 3C3 (Canada); Percival, Paul W., E-mail: percival@sfu.c [TRIUMF and Department of Chemistry, Simon Fraser University, Burnaby, BC, V5A 1S6 (Canada); West, Robert [Organosilicon Research Center, University of Wisconsin, Madison, WI 53706 (United States)

    2009-04-15

    Muoniated free radicals are formed by addition of muonium to unsaturated molecules. Successful detection by transverse-field muon spin rotation (muSR) usually requires pure or highly concentrated samples and a muonium reaction rate in excess of 10{sup 9} M{sup -1}s{sup -1} to ensure that the muon spin polarization is coherently transferred to the radical. For this reason muoniated radicals reported to date are all the primary radical products of Mu reaction. Thus, it was expected that Mu addition to a silylene would result in detection of a silyl radical. However, the muon hyperfine constant determined by experiment is much smaller than the value predicted by density functional calculations. Instead, it is consistent with a disilanyl radical, the secondary radical formed by reaction of the initially formed silyl radical with a second silylene molecule. From an analysis of the signal amplitude it was deduced that the second-order rate constant for reaction of the muoniated silyl radical with the parent silylene is 5.7x10{sup 8} M{sup -1}s{sup -1}. This work represents the first example of direct detection of a secondary radical product by transverse-field muSR.

  19. Preorganized anion traps for exploiting anion-π interactions: an experimental and computational study.

    Science.gov (United States)

    Bretschneider, Anne; Andrada, Diego M; Dechert, Sebastian; Meyer, Steffen; Mata, Ricardo A; Meyer, Franc

    2013-12-01

    1,3-Bis(pentafluorophenyl-imino)isoindoline (A(F)) and 3,6-di-tert-butyl-1,8-bis(pentafluorophenyl)-9H-carbazole (B(F)) have been designed as preorganized anion receptors that exploit anion-π interactions, and their ability to bind chloride and bromide in various solvents has been evaluated. Both receptors A(F) and B(F) are neutral but provide a central NH hydrogen bond that directs the halide anion into a preorganized clamp of the two electron-deficient appended arenes. Crystal structures of host-guest complexes of A(F) with DMSO, Cl(-), or Br(-) (A(F):DMSO, A(F):Cl(-), and A(2)(F):Br(-)) reveal that in all cases the guest is located in the cleft between the perfluorinated flaps, but NMR spectroscopy shows a more complex situation in solution because of E,Z/Z,Z isomerism of the host. In the case of the more rigid receptor B(F), Job plots evidence 1:1 complex formation with Cl(-) and Br(-), and association constants up to 960 M(-1) have been determined depending on the solvent. Crystal structures of B(F) and B(F):DMSO visualize the distinct preorganization of the host for anion-π interactions. The reference compounds 1,3-bis(2-pyrimidylimino)isoindoline (A(N)) and 3,6-di-tert-butyl-1,8-diphenyl-9H-carbazole (B(H)), which lack the perfluorinated flaps, do not show any indication of anion binding under the same conditions. A detailed computational analysis of the receptors A(F) and B(F) and their host-guest complexes with Cl(-) or Br(-) was carried out to quantify the interactions in play. Local correlation methods were applied, allowing for a decomposition of the ring-anion interactions. The latter were found to contribute significantly to the stabilization of these complexes (about half of the total energy). Compounds A(F) and B(F) represent rare examples of neutral receptors that are well preorganized for exploiting anion-π interactions, and rare examples of receptors for which the individual contributions to the binding energy have been quantified. PMID

  20. Photoelectron Spectroscopy and Theoretical Studies of Anion-pi Interactions: Binding Strength and Anion Specificity

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Jian; Zhou, Bin; Sun, Zhenrong; Wang, Xue B.

    2015-01-01

    Proposed in theory and confirmed to exist, anion–π interactions have been recognized as new and important non-covalent binding forces. Despite extensive theoretical studies, numerous crystal structural identifications, and a plethora of solution phase investigations, intrinsic anion–π interaction strengths that are free from complications of condensed phases’ environments, have not been directly measured in the gas phase. Herein we present a joint photoelectron spectroscopic and theoretical study on this subject, in which tetraoxacalix[2]arene[2]triazine 1, an electron-deficient and cavity self-tunable macrocyclic was used as a charge-neutral molecular host to probe its interactions with a series of anions with distinctly different shapes and charge states (spherical halides Cl⁻, Br⁻, I⁻, linear thiocyanate SCN⁻, trigonal planar nitrate NO₃⁻, pyramidic iodate IO₃⁻, and tetrahedral sulfate SO₄²⁻). The binding energies of the resultant gaseous 1:1 complexes (1•Cl⁻,1•Br⁻, 1•I⁻, 1•SCN⁻, 1•NO₃⁻, 1•IO₃⁻ and 1•SO₄²⁻) were directly measured experimentally, exhibiting substantial non-covalent interactions with pronounced anion specific effects. The binding strengths of Cl⁻, NO₃⁻, IO₃⁻ with 1 are found to be strongest among all singly charged anions, amounting to ca. 30 kcal/mol, but only about 40% of that between 1 and SO₄²⁻. Quantum chemical calculations reveal that all anions reside in the center of the cavity of 1 with anion–π binding motif in the complexes’ optimized structures, where 1 is seen to be able to self-regulate its cavity structure to accommodate anions of different geometries and three-dimensional shapes. Electron density surface and natural bond orbital charge distribution analysis further support anion–π binding formation. The calculated binding energies of the anions and 1 nicely reproduce the experimentally estimated electron binding energy increase. This work