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Sample records for vibrational c-h overtone

  1. Vibrational overtone spectrum of matrix isolated cis, cis-HOONO

    Science.gov (United States)

    Zhang, Xu; Nimlos, Mark R.; Ellison, G. Barney; Varner, Mychel E.; Stanton, John F.

    2007-05-01

    Cis, cis-peroxynitrous acid is known to be an intermediate in atmospheric reactions between OH and NO2 as well as HOO and NO. The infrared absorption spectra of matrix-isolated cc-HOONO and cc-DOONO in argon have been observed in the range of 500-8000cm-1. Besides the seven fundamental vibrational modes that have been assigned earlier for this molecule [Zhang et al., J. Chem. Phys. 124, 084305 (2006)], more than 50 of the overtone and combination bands have been observed for cc-HOONO and cc-DOONO. Ab initio CCSD(T)/atomic natural orbital anharmonic force field calculations were used to help guide the assignments. Based on this study of the vibrational overtone transitions of cis, cis-HOONO that go as high as 8000cm-1 and the earlier paper on the vibrational fundamentals, we conclude that the CCSD(T)/ANO anharmonic frequencies seem to correct to ±35cm-1. The success of the theoretically predicted anharmonic frequencies {υ } in assigning overtone spectra of HOONO up to 8000cm-1 suggests that the CCSD(T)/ANO method is producing a reliable potential energy surface for this reactive molecule.

  2. Stretching vibrational overtone and combination states in silicon tetrafluoride

    Science.gov (United States)

    Halonen, Lauri

    1986-11-01

    A simple three-parameter model is shown to account for the observed SiF stretching vibrational states of silicon tetrafluoride. A symmetrized anharmonic bond oscillator basis set is used to calculate stretching overtone and combination eigen values, all of which are given up to v1 + v3 = 5. The results show that the highest levels of the nν3 manifold move gradually out of resonances with n quanta of ν3 as n increases, which indicates that anharmonic resonances between the ν3 ladder and some other vibrational ladders and (or) multiphoton resonances are needed to explain the observed multiphoton processes.

  3. Dissociative ionization of liquid water induced by vibrational overtone excitation

    Energy Technology Data Exchange (ETDEWEB)

    Natzle, W.C.

    1983-03-01

    Photochemistry of vibrationally activated ground electronic state liquid water to produce H/sup +/ and OH/sup -/ ions has been initiated by pulsed, single-photon excitation of overtone and combination transitions. Transient conductivity measurements were used to determine quantum yields as a function of photon energy, isotopic composition, and temperature. The equilibrium relaxation rate following perturbation by the vibrationally activated reaction was also measured as a function of temperature reaction and isotopic composition. In H/sub 2/O, the quantum yield at 283 +- 1 K varies from 2 x 10/sup -9/ to 4 x 10/sup -5/ for wave numbers between 7605 and 18140 cm/sup -1/. In D/sub 2/O, the dependence of quantum yield on wavelength has the same qualitative shape as for H/sub 2/O, but is shifted to lower quantum yields. The position of a minimum in the quantum yield versus hydrogen mole fraction curve is consistent with a lower quantum yield for excitation of HOD in D/sub 2/O than for excitation of D/sub 2/O. The ionic recombination distance of 5.8 +- 0.5 A is constant within experimental error with temperature in H/sub 2/O and with isotopic composition at 25 +- 1/sup 0/C.

  4. C-H local modes in cyclobutene. II. Laser photoacoustic studies 10 000-17 000 cm-1. Vibrational structure and C-H local mode dynamics

    Science.gov (United States)

    Baggott, J. E.; Law, D. W.; Lightfoot, P. D.; Mills, I. M.

    1986-11-01

    In part I of this study [Baggott, Clase, and Mills, Spectrochim. Acta Part A 42, 319 (1986)] we presented FTIR spectra of gas phase cyclobutene and modeled the v=1-3 stretching states of both olefinic and methylenic C-H bonds in terms of a local mode model. In this paper we present some improvements to our original model and make use of recently derived ``x,K relations'' to find the equivalent normal mode descriptions. The use of both the local mode and normal mode approaches to modeling the vibrational structure is described in some detail. We present evidence for Fermi resonance interactions between the methylenic C-H stretch overtones and ring C-C stretch vibrations, revealed in laser photoacoustic spectra in the v=4-6 region. An approximate model vibrational Hamiltonian is proposed to explain the observed structure and is used to calculate the dynamics of the C-H stretch local mode decay resulting from interaction with lower frequency ring modes. The implications of our experimental and theoretical studies for mode-selective photochemistry are discussed briefly.

  5. Vibrational spectroscopy of triacetone triperoxide (TATP): Anharmonic fundamentals, overtones and combination bands

    Science.gov (United States)

    Brauer, Brina; Dubnikova, Faina; Zeiri, Yehuda; Kosloff, Ronnie; Gerber, R. Benny

    2008-12-01

    The vibrational spectrum of triacetone triperoxide (TATP) is studied by the correlation-corrected vibrational self-consistent field (CC-VSCF) method which incorporates anharmonic effects. Fundamental, overtone, and combination band frequencies are obtained by using a potential based on the PM3 method and yielding the same harmonic frequencies as DFT/cc-pVDZ calculations. Fundamentals and overtones are also studied with anharmonic single-mode (without coupling) DFT/cc-pVDZ calculations. Average deviations from experiment are similar for all methods: 2.1-2.5%. Groups of degenerate vibrations form regions of numerous combination bands with low intensity: the 5600-5800 cm -1 region contains ca. 70 overtones and combinations of CH stretches. Anharmonic interactions are analyzed.

  6. Determination of the Oscillator Strengths for the Third and Fourth Vibrational Overtone Transitions in Simple Alcohols

    Science.gov (United States)

    Wallberg, Jens; Kjaergaard, Henrik G.

    2017-06-01

    Absolute measurements of the weak transitions require sensitive spectroscopic techniques. With our recently constructed pulsed cavity ring down (CRD) spectrometer, we have recorded the third and fourth vibrational overtone of the OH stretching vibration in a series of simple alcohols: methanol (MeOH), ethanol (EtOH), 1-propanol (1-PrOH), 2-propanol (2-PrOH) and tert-butanol (tBuOH). The CRD setup (in a flow cell configuration) is combined with a conventional FTIR spectrometer to determine the partial pressure of the alcohols from the fundamental transitions of the OH-stretching vibration. The oscillator strengths of the overtone transitions are determined from the integrated absorbances of the overtone spectra and the partial pressures. Furthermore, the oscillator strengths were calculated using vibrational local mode theory with energies and dipole moments calculated at CCSD(T)/aug-cc-pVTZ level of theory. We find a good agreement between the observed and calculated oscillator strengths across the series of alcohols.

  7. Relative vibrational overtone intensity of cis-cis and trans-perp peroxynitrous acid

    Science.gov (United States)

    Matthews, Jamie; Sinha, Amitabha; Francisco, Joseph S.

    2004-06-01

    The vibrational overtone spectrum of HOONO is examined in the region of the 2νOH and 3νOH bands using action spectroscopy in conjunction with ab initio intensity calculations. The present measurements indicate that the oscillator strength associated with the higher energy trans-perp conformer of HOONO is stronger relative to the lower energy cis-cis conformer for both these vibrational overtone levels. Ab initio intensity calculations carried out at the QCISD level of theory suggest that this disparity in oscillator strength apparently arises from differences in the second derivative of the transition dipole moment function of the two isomers. The calculations indicate that the oscillator strength for the trans-perp isomer is ˜5.4 times larger than that of the cis-cis isomer for the 2νOH band and ˜2 times larger for 3νOH band. The band positions and intensities predicted by the calculations are used to aid in the assignment of features in the experimental action spectra associated with the OH stretching overtones of HOONO. The observed relative intensities in the experimental action spectra when normalized to the calculated oscillator strengths appears to suggest that the concentration of the higher energy trans-perp isomer is comparable to the concentration of the cis-cis isomer in these room temperature experiments.

  8. Phase shift cavity ring down and Fourier transform infrared measurements of C-H vibrational transitions, energy levels, and intensities of (CH3)3Si-C≡C-H

    Science.gov (United States)

    Barroso, Jenny Z.; Perez-Delgado, Yasnahir; Manzanares, Carlos E.

    2013-07-01

    Phase shift cavity ring down and Fourier transform IR techniques have been used to observe the C-H stretch fundamental and overtone absorptions of the acetylenic (Δυ = 1-5) and methyl (Δυ = 1-6) C-H bonds of trimethyl-silyl-acetylene [(CH3)3CSi≡CH] at 295 K. Harmonic frequencies ω(ν1), ωa, and ωs and anharmonicities x(ν1), ωaxa, ωsxs were calculated for the acetylenic, methyl out-of-plane, and methyl in-plane C-H bonds, respectively. The harmonically coupled anharmonic oscillator (HCAO) model was used to determine the overtone energy levels and assign the absorption bands to vibrational transitions of methyl C-H bonds. A hot band, assigned as υν1 + ν24 - ν24 is observed for transitions with Δυ = 1-5 in a region near the acetylenic stretch. The intensity of the hot band is reduced considerably at 240 K. The strength of a Fermi resonance between C-Ha transition (υνa) and the combination band ((υ-1)νa + 2νbend) with (υ = 3-6) was calculated using the experimental perturbed energies and relative intensities. The main bands are separated by computer deconvolution and are integrated at each level to get the experimental band strengths. For methyl absorptions, the dipole moment function is expanded as a function of two C-H stretching coordinates and the intensities are calculated in terms of the HCAO model where only the C-H modes are considered. Acetylenic intensities are derived with a one dimensional dipole moment function. The expansion coefficients are obtained from molecular orbital calculations. The intensities are calculated without using adjustable parameters and they are of the same order of magnitude of the experimental intensities for all C-H transitions.

  9. Quantum Interference in the Vibrational Relaxation of the O-H Stretch Overtone of Liquid H2O.

    Science.gov (United States)

    van der Post, Sietse T; Woutersen, Sander; Bakker, Huib J

    2016-05-26

    Using femtosecond two-color infrared pump-probe spectroscopy, we study the vibrational relaxation of the O-H stretch vibrations of liquid H2O after excitation of the overtone transition. The overtone transition has its maximum at 6900 cm(-1) (1.45 μm), which is a relatively high frequency in view of the central frequency of 3400 cm(-1) of the fundamental transition. The excitation of the overtone leads to a transient induced absorption of two-exciton states of the O-H stretch vibrations. When the overtone excitation frequency is tuned from 6600 to 7200 cm(-1), the vibrational relaxation time constant of the two-exciton states increases from 400 ± 50 fs to 540 ± 40 fs. These values define a limited range of relatively long relaxation time constants compared to the range of relaxation time constants of 250-550 fs that we recently observed for the one-exciton O-H stretch vibrational state of liquid H2O ( S. T. van der Post et al., Nature Comm. 2015 , 6 , 8384 ). We explain the high central frequency and the limited range of relatively long relaxation time constants of the overtone transition from the destructive quantum interference of the mechanical and electrical anharmonic contributions to the overtone transition probability. As a result of this destructive interference, the overtone transition of liquid H2O is dominated by molecules of which the O-H groups donate relatively weak hydrogen bonds to other H2O molecules.

  10. Infrared spectroscopy and Density Functional Theory of crystalline β-2,4,6,8,10,12-hexanitrohexaaziosowurtzitane (β CL-20) in the region of its C-H stretching vibrations

    Science.gov (United States)

    Behler, K. D.; Pesce-Rodriguez, R.; Cabalo, J.; Sausa, R.

    2013-10-01

    Molecular vibrational spectroscopy provides a useful tool for material characterization and model verification. We examine the CH stretching fundamental and overtones of energetic material β-2,4,6,8,10,12-hexanitrohexaaziosowurtzitane (β-CL-20) by Raman spectroscopy, Fourier Transform Infrared Spectroscopy, and Laser Photoacoustic Overtone Spectroscopy, and utilize Density Functional Theory to calculate the C-H bond energy of β-CL-20 in a crystal. The spectra reveal four intense and distinct features, whose analysis yields C-H stretching fundamental frequencies and anharmonicity values that range from 3137 to 3170 cm-1 and 53.8 to 58.8 cm-1, respectively. From these data, we estimate an average value of 42,700 cm-1 (5.29 eV) for the C-H bond energy, a value that agrees with our quantum mechanical calculations.

  11. Fundamental and overtone vibrational spectroscopy, enthalpy of hydrogen bond formation and equilibrium constant determination of the methanol-dimethylamine complex.

    Science.gov (United States)

    Du, Lin; Mackeprang, Kasper; Kjaergaard, Henrik G

    2013-07-07

    We have measured gas phase vibrational spectra of the bimolecular complex formed between methanol (MeOH) and dimethylamine (DMA) up to about 9800 cm(-1). In addition to the strong fundamental OH-stretching transition we have also detected the weak second overtone NH-stretching transition. The spectra of the complex are obtained by spectral subtraction of the monomer spectra from spectra recorded for the mixture. For comparison, we also measured the fundamental OH-stretching transition in the bimolecular complex between MeOH and trimethylamine (TMA). The enthalpies of hydrogen bond formation (ΔH) for the MeOH-DMA and MeOH-TMA complexes have been determined by measurements of the fundamental OH-stretching transition in the temperature range from 298 to 358 K. The enthalpy of formation is found to be -35.8 ± 3.9 and -38.2 ± 3.3 kJ mol(-1) for MeOH-DMA and MeOH-TMA, respectively, in the 298 to 358 K region. The equilibrium constant (Kp) for the formation of the MeOH-DMA complex has been determined from the measured and calculated transition intensities of the OH-stretching fundamental transition and the NH-stretching second overtone transition. The transition intensities were calculated using an anharmonic oscillator local mode model with dipole moment and potential energy curves calculated using explicitly correlated coupled cluster methods. The equilibrium constant for formation of the MeOH-DMA complex was determined to be 0.2 ± 0.1 atm(-1), corresponding to a ΔG value of about 4.0 kJ mol(-1).

  12. Theoretical Investigation of C-H Vibrational Spectroscopy. 1. Modeling of Methyl and Methylene Groups of Ethanol with Different Conformers.

    Science.gov (United States)

    Wang, Lin; Ishiyama, Tatsuya; Morita, Akihiro

    2017-09-14

    A flexible and polarizable molecular model of ethanol is developed to extend our investigation of thermodynamic, structural, and vibrational properties of the liquid and interface. A molecular dynamics (MD) simulation with the present model confirmed that this model well reproduces a number of properties of liquid ethanol, including density, heat of vaporization, surface tension, molecular dipole moment, and trans/gauche ratio. In particular, the present model can describe vibrational IR, Raman, and sum frequency generation (SFG) spectra of ethanol and partially deuterated analogues with reliable accuracy. The improved accuracy is largely attributed to proper modeling of the conformational dependence and the intramolecular couplings including Fermi resonance in C-H vibrations. Precise dependence of torsional motions is found to be critical in representing vibrational spectra of the C-H bending. This model allows for further vibrational analysis of complicated alkyl groups widely observed in various organic molecules with MD simulation.

  13. Simultaneous dual-gas QEPAS detection based on a fundamental and overtone combined vibration of quartz tuning fork

    Science.gov (United States)

    Wu, Hongpeng; Yin, Xukun; Dong, Lei; Pei, Kailong; Sampaolo, Angelo; Patimisco, Pietro; Zheng, Huadan; Ma, Weiguang; Zhang, Lei; Yin, Wangbao; Xiao, Liantuan; Spagnolo, Vincenzo; Jia, Suotang; Tittel, Frank K.

    2017-03-01

    A dual-gas quartz-enhanced photoacoustic spectroscopy (QEPAS) sensor system based on a frequency division multiplexing technique of a quartz tuning fork (QTF) was developed and experimentally demonstrated. Two beams from two independently modulated lasers are focused at two different positions between the QTF prongs to excite both the QTF fundamental and 1st overtone flexural modes simultaneously. The 2f-wavelength modulation technique is employed by applying two sinusoidal dithers, whose frequencies are equal to a half of the QTF fundamental and 1st overtone frequencies, respectively, to the currents of two excitation lasers. The resonance frequency difference between two flexural modes ensures that the correlated photoacoustic signals generated by different target gases do not interfere with each other. The proposed QEPAS methodology realizes a continuous real-time dual-gas monitoring with a simple setup and small sensor size compared with previous multi-gas QEPAS sensors.

  14. Torsional excitation in the 2CH vibrational overtone of the C2H2-CO2 and C2H2-N2O van der Waals complexes

    Science.gov (United States)

    Lauzin, C.; Didriche, K.; Földes, T.; Herman, M.

    2011-09-01

    Infrared spectra of the weakly-bound C2H2-CO2 and C2H2-N2O complexes in the region of the 2CH acetylene overtone band (∼1.52 µm) were recorded using CW-cavity ring down spectroscopy in a continuous supersonic expansion. A new, c-type combination band is observed in each case. The rotational analysis of low J, K lines is performed and rotational constants are obtained. The band origins are 40.491(2) and 40.778(2) cm-1 higher in energy than the 2CH excitation bands for C2H2-CO2 and C2H2-N2O, respectively. The combination band is assigned in each case as involving intermolecular torsional excitation combined to 2CH. The values of the torsional vibrational frequency and of the xCH/torsion anharmonicity constant are briefly discussed.

  15. Free radical and overtone spectroscopy

    Science.gov (United States)

    Reilly, James P.

    1991-01-01

    In the fall of 1987 during a photoacoustic study of hydrogen peroxide's fourth vibrational overtone band, the remarkably clear and well resolved spectrum was observed. Its periodicity and K subband structure suggested that the spectrum was not of hydrogen peroxide but of a smaller near-prolate symmetric top molecule. Furthermore, the time dependent behavior of the signal indicated that chemical changes were taking place within the photoacoustic apparatus.

  16. Comparison of the cis-bending and C-H stretching vibration on the reaction of C2H2+ with H2 using laser induced reactions.

    Science.gov (United States)

    Schlemmer, Stephan; Asvany, Oskar; Giesen, Thomas

    2005-04-07

    Laser induced reaction (LIR) of C2H2(+) + H2 in a 22-pole ion trap at 90 K has been employed to detect the v3 C-H stretching vibration and the v5 cis bending vibration of the acetylene parent ion using the wide tunability of the free electron laser FELIX. The vibrational frequency of the bending vibration, omega5, and the corresponding Renner-Teller parameter, epsilon5, are determined to be 710 cm(-1) and 0.03, respectively. These results differ quite substantially from previous experimental work but are in line with the most recent and advanced theoretical work. The dependence of the LIR-signal of the two vibrational modes is studied systematically with respect to the laser power, storage time, and number density of the hydrogen collision partner. A reaction scheme describing all steps involved in the LIR process is set up. The corresponding rate equation system is solved numerically. From this solution the lifetimes for the vibrational excited states, tau3 = (3 +/- 1) ms and t5 = (200 +/- 50) ms and the vibrational dipole moments micro3 = 0.19(2) D and micro2 = 0.21(2) D are determined under the assumption that the excited parent ion relaxes or reacts with a net rate coefficient equal to the Langevin limit. The lifetime for the C-H stretching vibration is in agreement with a previous LIR experiment and with ab initio calculations. C-H stretching turns out to be about an order of magnitude more efficient than bending in promoting hydrogen abstraction. This strong mode dependence is discussed on the basis of the energetics for hydrogen abstraction and a possible inhibition of complex formation in the entrance channel of the C2H2+..H2 collision system.

  17. The Overtone Fiddle: an Actuated Acoustic Instrument

    DEFF Research Database (Denmark)

    Overholt, Daniel

    2011-01-01

    The Overtone Fiddle is a new violin-family instrument that incorporates electronic sensors, integrated DSP, and physical actuation of the acoustic body. An embedded tactile sound transducer creates extra vibrations in the body of the Overtone Fiddle, allowing performer control and sensation via...... both traditional violin techniques, as well as extended playing techniques that incorporate shared man/machine control of the resulting sound. A magnetic pickup system is mounted to the end of the fiddle’s fingerboard in order to detect the signals from the vibrating strings, deliberately not capturing...

  18. Importance of C*-H based modes and large amplitude motion effects in vibrational circular dichroism spectra: the case of the chiral adduct of dimethyl fumarate and anthracene.

    Science.gov (United States)

    Passarello, Marco; Abbate, Sergio; Longhi, Giovanna; Lepri, Susan; Ruzziconi, Renzo; Nicu, Valentin Paul

    2014-06-19

    The role played by the C*-H based modes (C* being the chiral carbon atom) and the large amplitude motions in the vibrational absorption (VA) and vibrational circular dichroism (VCD) spectra is investigated. The example of an adduct of dimethyl fumarate and anthracene, i.e., dimethyl-(+)-(11R,12R)-9,10-dihydro-9,10-ethanoanthracene-11,12-dicarboxylate, and two deuterated isotopomers thereof specially synthesized for this goal, are considered. By comparing the experimental and DFT calculated spectra of the undeuterated and deuterated species, we demonstrate that the C*-H bending, rocking, and stretching modes in the VA and VCD spectra are clearly identified in well defined spectroscopic features. Further, significant information about the conformer distribution is gathered by analyzing the VA and VCD data of both the fingerprint and the C-H stretching regions, with particular attention paid to the band shape data. Effects related to the large amplitude motions of the two methoxy moieties have been simulated by performing linear transit (LT) calculations, which consists of varying systematically the relative positions of the two methoxy moieties and calculating VCD spectra for the partially optimized structures obtained in this way. The LT method allows one to improve the quality of calculated spectra, as compared to experimental results, especially in regard to relative intensities and bandwidths.

  19. Quartz-enhanced photoacoustic spectroscopy exploiting tuning fork overtone modes

    Science.gov (United States)

    Sampaolo, A.; Patimisco, P.; Dong, L.; Geras, A.; Scamarcio, G.; Starecki, T.; Tittel, F. K.; Spagnolo, V.

    2015-12-01

    We report on a quartz-enhanced photoacoustic sensor (QEPAS) based on a custom-made quartz tuning fork (QTF) to operate in both the fundamental and the first overtone vibrational mode resonances. The QTF fundamental mode resonance falls at ˜3 kHz and the first overtone at ˜18 kHz. Electrical tests showed that the first overtone provides a higher quality factor and increased piezoelectric current peak values, with respect to the fundamental flexural mode. To evaluate the QTF acousto-electric energy conversion efficiency, we operated the QEPAS in the near-IR and selected water vapor as the target gas. The first overtone resonance provides a QEPAS signal-to-noise ratio ˜5 times greater with respect to that measured for the fundamental mode. These results open the way to employing QTF overtone vibrational modes for QEPAS based trace gas sensing.

  20. Quantum-state-resolved reactivity of overtone excited CH4 on Ni(111): Comparing experiment and theory.

    Science.gov (United States)

    Hundt, P Morten; van Reijzen, Maarten E; Beck, Rainer D; Guo, Han; Jackson, Bret

    2017-02-07

    Quantum state resolved reactivity measurements probe the role of vibrational symmetry on the vibrational activation of the dissociative chemisorption of CH4 on Ni(111). IR-IR double resonance excitation in a molecular beam was used to prepare CH4 in three different vibrational symmetry components, A1, E, and F2, of the 2ν3 antisymmetric stretch overtone vibration as well as in the ν1+ν3 symmetric plus antisymmetric C-H stretch combination band of F2 symmetry. The quantum state specific dissociation probability S0 (sticking coefficient) was measured for each of the four vibrational states by detecting chemisorbed carbon on Ni(111) as the product of CH4 dissociation by Auger electron spectroscopy. We observe strong mode specificity, where S0 for the most reactive state ν1+ν3 is an order of magnitude higher than for the least reactive, more energetic 2ν3-E state. Our first principles quantum scattering calculations show that as molecules in the ν1 state approach the surface, the vibrational amplitude becomes localized on the reacting C-H bond, making them very reactive. This behavior results from the weakening of the reacting C-H bond as the molecule approaches the surface, decoupling its motion from the three non-reacting C-H stretches. Similarly, we find that overtone normal mode states with more ν1 character are more reactive: S0(2ν1) > S0(ν1 + ν3) > S0(2ν3). The 2ν3 eigenstates excited in the experiment can be written as linear combinations of these normal mode states. The highly reactive 2ν1 and ν1 + ν3 normal modes, being of A1 and F2 symmetry, can contribute to the 2ν3-A1 and 2ν3-F2 eigenstates, respectively, boosting their reactivity over the E component, which contains no ν1 character due to symmetry.

  1. 2005: The Overtone Violin

    DEFF Research Database (Denmark)

    Overholt, Daniel

    2017-01-01

    The pursuit of novel interfaces for new music performance is a very interesting angle from which to approach the design of a musical instrument, but without the proper perspective the result can be hard to differentiate between a musically useful device and a simple gadget. There is of course the...... with additional gestural capabilities. The Overtone Violin fits into this category....

  2. Crystallization of polylactide and its stereocomplex investigated by two-dimensional fourier transform infrared correlation spectroscopy employing carbonyl overtones.

    Science.gov (United States)

    Opaprakasit, Pakorn; Opaprakasit, Mantana; Tangboriboonrat, Pramaun

    2007-12-01

    The band origins and transitions of weak vibrational modes developed in the 3500 cm(-1) region of polylactide (PLA) spectra during crystallization are investigated. The band assignment to the OH stretching mode of terminal hydroxyls is unlikely because the trace amount of chain-ends is negligible considering the long chain of high molecular weight polymer. The band intensity can be enhanced for quantitative study by increasing the sample film thickness. The results show that the transition patterns of these bands mimic those of C=O stretching modes. Therefore, these are assigned to C=O overtones. Two bands associated with crystalline and amorphous characteristics are revealed during cold crystallization. The crystalline C=O bands of PDLA and its stereocomplex counterpart are located at 3510 cm(-1) and 3482 cm(-1), respectively, indicating a weaker C=O bond in the latter crystal structure. Two-dimensional Fourier transform infrared (2D-FT-IR) correlation spectroscopy is then applied to study the correlation between C=O overtones and the crystalline characteristic band located near 900 cm(-1). The transitions of the two vibrational modes observed in crystallization of the stereocomplex are in-phase with each other. This reflects an involvement of short-range hydrogen bonding in the stereocomplex crystal structure. In contrast, crystallization of PDLA shows that the C=O overtone varies prior to that of the C-H character, indicating that dipole-dipole force is a crystal-induced interaction.

  3. The high overtone and combination levels of SF6 revisited at Doppler-limited resolution: A global effective rovibrational model for highly excited vibrational states

    Science.gov (United States)

    Faye, M.; Boudon, V.; Loëte, M.; Roy, P.; Manceron, L.

    2017-03-01

    Sulfur hexafluoride is an important prototypal molecule for modeling highly excited vibrational energy flow and multi quanta absorption processes in hexafluoride molecules of technological importance. It is also a strong greenhouse gas of anthropogenic origin. This heavy species, however, features many hot bands at room temperature (at which only 30% of the molecules lie in the ground vibrational state), especially those originating from the lowest, v6=1 vibrational state. Using a cryogenic long path cell with variable optical path length and temperatures regulated between 120 and 163 K, coupled to Synchrotron Radiation and a high resolution interferometer, Doppler-limited spectra of the 2ν1 +ν3 , ν1 +ν2 +ν3 , ν1 +ν3 , ν2 +ν3 , 3ν3, ν2 + 3ν3 and ν1 + 3ν3 from 2000 to 4000 cm-1 near-infrared region has been recorded. Low temperature was used to limit the presence of hot bands. The spectrum has been analyzed thanks to the XTDS software package. Combining with previously observed weak difference bands in the far infrared region involving the v1, v2, v3=1 states, we are thus able to use the tensorial model to build a global fit of spectroscopic parameters for v1=1,2, v2=1, v3=1,2,3. The model constitutes a consistent set of molecular parameters and enable spectral rovibrational simulation for all multi-quanta transitions involving v1, v2 and v3 up to v1-3 = 3 . Tests simulation on rovibrational transitions not yet rovibrationally assigned are presented and compared to new experimental data.

  4. High-resolution overtone spectra of molecular complexes

    Science.gov (United States)

    Didriche, K.; Földes, T.

    2013-02-01

    A high-resolution spectrum of the acetylene-water complex has been recorded in the overtone range. Two bands of C2H2-D2O were analysed, corresponding to the overtone excitations of either the acetylene or the water units. The vibrational shifts and the upper states rotational constants were retrieved, demonstrating that the geometry of the complex is only slightly modified by the excitation. A larger linewidth was observed for the 2CH band than for the 2OD + DOD band, probably due to the direct coupling of the 2CH excitation with the dissociation coordinate.

  5. Molecular dynamics simulations and instantaneous normal-mode analysis of the vibrational relaxation of the C-H stretching modes of N-methylacetamide-d in liquid deuterated water.

    Science.gov (United States)

    Bastida, Adolfo; Soler, Miguel A; Zúñiga, José; Requena, Alberto; Kalstein, Adrián; Fernández-Alberti, Sebastian

    2010-11-04

    Nonequilibrium molecular dynamics (MD) simulations and instantaneous normal mode (INMs) analyses are used to study the vibrational relaxation of the C-H stretching modes (ν(s)(CH₃)) of deuterated N-methylacetamide (NMAD) in aqueous (D2O) solution. The INMs are identified unequivocally in terms of the equilibrium normal modes (ENMs), or groups of them, using a restricted version of the recently proposed Min-Cost assignment method. After excitation of the parent ν(s)(CH₃) modes with one vibrational quantum, the vibrational energy is shown to dissipate through both intramolecular vibrational redistribution (IVR) and intermolecular vibrational energy transfer (VET). The decay of the vibrational energy of the ν(s)(CH₃) modes is well fitted to a triple exponential function, with each characterizing a well-defined stage of the entire relaxation process. The first, and major, relaxation stage corresponds to a coherent ultrashort (τ(rel) = 0.07 ps) energy transfer from the parent ν(s)(CH₃) modes to the methyl bending modes δ(CH₃), so that the initially excited state rapidly evolves into a mixed stretch-bend state. In the second stage, characterized by a time of 0.92 ps, the vibrational energy flows through IVR to a number of mid-range-energy vibrations of the solute. In the third stage, the vibrational energy accumulated in the excited modes dissipates into the bath through an indirect VET process mediated by lower-energy modes, on a time scale of 10.6 ps. All the specific relaxation channels participating in the whole relaxation process are properly identified. The results from the simulations are finally compared with the recent experimental measurements of the ν(s)(CH₃) vibrational energy relaxation in NMAD/D₂O(l) reported by Dlott et al. (J. Phys. Chem. A 2009, 113, 75.) using ultrafast infrared-Raman spectroscopy.

  6. Controlling cross pumping between C-N and C-H vibration in nitromethane by selective fluorescence-enhanced stimulated Raman scattering

    National Research Council Canada - National Science Library

    Wang, Shenghan; Fang, Wenhui; Li, Tianyu; Li, Fangfang; Sun, Chenglin; Li, Zuowei; Men, Zhiwei

    2016-01-01

    To investigate the vibrational features of nitromethane (NM), which is a kind of energy material and a well known low-sensitivity and high explosive, experiments are performed to obtain the stimulated Raman scattering (SRS...

  7. Vibrational Overtone Spectroscopy of Pyrrole and Pyrrolidine

    Science.gov (United States)

    1991-05-23

    general pattern is a strong peak accompanied by two or three weaker peaks to lower energy. For instance, the 13,305 cm-I band in pyrrole has three weaker...Orza, J.M. Anales de Quimica 1984, 80, 59. 29. Navarro, R.; Orza, J.M. Anales de Quimica 1982, 79, 557. 30. Xie, Y; Fan, K.; Boggs,J., Molec. Phys

  8. Second OH overtone excitation and statistical dissociation dynamics of peroxynitrous acid

    Science.gov (United States)

    Konen, Ian M.; Li, Eunice X. J.; Stephenson, Thomas A.; Lester, Marsha I.

    2005-11-01

    The second OH overtone transition of the trans-perp conformer of peroxynitrous acid (tp-HOONO) is identified using infrared action spectroscopy. HOONO is produced by the recombination of photolytically generated OH and NO2 radicals, and then cooled in a pulsed supersonic expansion. The second overtone transition is assigned to tp-HOONO based on its vibrational frequency (10195.3cm-1) and rotational band contour, which are in accord with theoretical predictions and previous observations of the first overtone transition. The transition dipole moment associated with the overtone transition is rotated considerably from the OH bond axis, as evident from its hybrid band composition, indicating substantial charge redistribution upon OH stretch excitation. The overtone band exhibits homogeneous line broadening that is attributed to intramolecular vibrational redistribution, arising from the coupling of the initially excited OH stretch to other modes that ultimately lead to dissociation. The quantum state distributions of the OH XΠ2 (ν =0) products following first and second OH overtone excitation of tp-HOONO are found to be statistical by comparison with three commonly used statistical models. The product state distributions are principally determined by the tp-HOONO binding energy of 16.2(1)kcalmol-1. Only a small fraction of the OH products are produced in ν =1 following the second overtone excitation, consistent with statistical predictions.

  9. Infrared overtone spectroscopy and unimolecular decay dynamics of peroxynitrous acid

    Science.gov (United States)

    Konen, Ian M.; Pollack, Ilana B.; Li, Eunice X. J.; Lester, Marsha I.; Varner, Mychel E.; Stanton, John F.

    2005-03-01

    Peroxynitrous acid (HOONO) is generated in a pulsed supersonic expansion through recombination of photolytically generated OH and NO2 radicals. A rotationally resolved infrared action spectrum of HOONO is obtained in the OH overtone region at 6971.351(4)cm-1 (origin), providing definitive spectroscopic identification of the trans-perp (tp) conformer of HOONO. Analysis of the rotational band structure yields rotational constants for the near prolate asymmetric top, the ratio of the a-type to c-type components of the transition dipole moment for the hybrid band, and a homogeneous linewidth arising from intramolecular vibrational energy redistribution and/or dissociation. The quantum state distribution of the OH (ν =0,JOH) products from dissociation is well characterized by a microcanonical statistical distribution constrained only by the energy available to products, 1304±38cm-1. This yields a 5667±38cm-1 [16.2(1)kcalmol-1] binding energy for tp-HOONO. An equivalent available energy and corresponding binding energy are obtained from the highest observed OH product state. Complementary high level ab initio calculations are carried out in conjunction with second-order vibrational perturbation theory to predict the spectroscopic observables associated with the OH overtone transition of tp-HOONO including its vibrational frequency, rotational constants, and transition dipole moment. The same approach is used to compute frequencies and intensities of multiple quantum transitions that aid in the assignment of weaker features observed in the OH overtone region, in particular, a combination band of tp-HOONO involving the HOON torsional mode.

  10. Calculation of Anharmonicities in Overtone Modes and Small-Cluster Shifts of Spherical-Top Molecules

    Science.gov (United States)

    Fuhr, Javier D.; Fiol, Juan; Cortizo, Eduardo; Fainstein, Pablo D.; Fregenal, Daniel E.; Guozden, Tomás; Kaúl, Enrique; Knoblauch, Pablo; Lamagna, Alberto; Maceira, Pablo; Rozas, Guillermo; Zarco, Martín

    2014-06-01

    Harmonic and anharmonic vibrational self-consistent field (VSCF) calculations were employed to investigate the fundamental and overtone modes of SF6 molecules. Determination of the Potential Energy Surface (PES) on a multidimensional grid of more than 65000 nodes was performed, and a system of 1D coupled-equations was solved. Corrections to the harmonic approximation for the frequencies of the fundamental modes and their overtones were obtained. Ab-initio calculations to the interaction potential between two molecules as a function of their position and orientation, and the corresponding energies for dimer formation, have been computed. Finally, the effect of dimerization on the molecular frequencies is investigated.

  11. 2017 ISCB Overton Prize: Christoph Bock.

    Science.gov (United States)

    Fogg, Christiana N; Kovats, Diane E; Berger, Bonnie

    2017-01-01

    The International Society for Computational Biology (ISCB) each year recognizes the achievements of an early to mid-career scientist with the Overton Prize. This prize honors the untimely death of Dr. G. Christian Overton, an admired computational biologist and founding ISCB Board member. Winners of the Overton Prize are independent investigators who are in the early to middle phases of their careers and are selected because of their significant contributions to computational biology through research, teaching, and service. ISCB is pleased to recognize Dr. Christoph Bock, Principal Investigator at the CeMM Research Center for Molecular Medicine of the Austrian Academy of Sciences in Vienna, Austria, as the 2017 winner of the Overton Prize. Bock will be presenting a keynote presentation at the 2017 International Conference on Intelligent Systems for Molecular Biology/European Conference on Computational Biology (ISMB/ECCB) in Prague, Czech Republic being held during July 21-25, 2017.

  12. Analysis of overtone flexural modes operation in quartz-enhanced photoacoustic spectroscopy.

    Science.gov (United States)

    Tittel, Frank K; Sampaolo, Angelo; Patimisco, Pietro; Dong, Lei; Geras, Antonina; Starecki, Tomasz; Spagnolo, Vincenzo

    2016-03-21

    A detailed investigation of a set of custom quartz tuning forks (QTFs), operating in the fundamental and first overtone flexural modes is reported. Support losses are the dominant energy dissipation processes when the QTFs vibrate at the first overtone mode. These losses can be decreased by increasing the ratio between the prong length and its thickness. The QTFs were implemented in a quartz enhanced photoacoustic spectroscopy (QEPAS) based sensor operating in the near-IR spectral range and water vapor was selected as the gas target. QTF flexural modes having the highest quality factor exhibit the largest QEPAS signal, demonstrating that, by optimizing the QTF prongs sizes, overtone modes can provide a higher QEPAS sensor performance with respect to using the fundamental mode.

  13. Second overtone pulsators among {delta} scuti stars

    Energy Technology Data Exchange (ETDEWEB)

    Bono, G. [Osservatorio Astronomico di Trieste, via G.B. Tiepolo 11, 34131 Trieste (Italy); Caputo, F. [Osservatorio Astronomico di Capodimonte, via Moiariello 16, 80131 Napoli (Italy); Cassisi, S. [Osservatorio Astronomico di Teramo, via M. Maggini, 64100 Teramo (Italy)]|[Dipartimento di Fisica, Universita de LAquila, via Vetoio, 67100 LAquila (Italy); Castellani, V. [Dipartimento di Fisica, Universita di Pisa, Piazza Torricelli 2, 56100 Pisa (Italy)]|[Osservatorio Astronomico di Teramo, via M. Maggini, 64100 Teramo (Italy); Marconi, M. [Dipartimento di Fisica, Universita di Pisa, Piazza Torricelli 2, 56100 Pisa (Italy); Stellingwerf, R.F. [Los Alamos National Laboratory, X-1 Division, MS F645, Los Alamos, New Mexico 87545 (United States)

    1997-03-01

    We investigate the modal stability of stellar models at masses and luminosity levels corresponding to post-main-sequence luminous {delta} Scuti pulsators. The envelope models have been computed at fixed mass value (M/M{sub sun}=2.0), luminosity level [log(L/L{sub sun})=1.7], and chemical composition (Y=0.28, Z=0.02). According to a nonlinear approach to radial oscillations, the present investigation for the first time predicts the occurrence of stable second overtone pulsators. More generally, we found that when moving inside the instability strip from lower to higher effective temperatures, the models show a stable limit cycle in three different pulsation modes: fundamental and first and second overtones. The shapes of both light and velocity curves are presented and discussed, providing a useful tool for the identification of second overtone pulsators among the known groups of radially pulsating stars. Comparison with observations shows that our nonlinear, nonlocal, and time-dependent convective models provide light curves in agreement with observed values, suggesting that second overtone pulsators have already been observed, though misclassified as fundamental pulsators. In a limited region of the instability strip we also found some models presenting mixed-mode features, i.e., radial pulsators that show a stable limit cycle in more than one pulsational mode. The period ratios of mixed-mode pulsators obtained by perturbing the first and the second overtone radial eigenfunctions are in agreement with observed values. This result is a crucial point for understanding the pulsation properties of {delta} Scuti stars, since it provides sound evidence that these variables during their evolution off the main sequence are pure or mixed-mode radial pulsators. Finally, the physical structure and the dynamical properties of second overtone pulsators are discussed in detail. {copyright} {ital 1997} {ital The American Astronomical Society}

  14. Overtone Spectroscopy of Peroxyacetic Acid and Peroxyformic Acid : Influence of Intramolecular Hydrogen Bonding

    Science.gov (United States)

    Hazra, Montu K.; Kuang, Michelle; Sinha, Amitabha

    2010-06-01

    The absorption of solar radiation by hydrogen-bonded (H-bonded) complex, particularly those containing water, is important in atmospheric chemistry. However, because of their low concentration, intermolecular hydrogen bonded complexes of atmospheric interest are difficult to study in the gas phase. Consequently, our initial efforts have been directed towards investigating the spectroscopy of molecules with internal hydrogen bonds. In this talk, we present the vapor phase vibrational overtone spectra of peroxyacetic acid (PAA) and peroxyformic acid (PFA), two molecules of atmospheric importance, and discuss the effect of intramolecular hydrogen-bonding on their OH stretching overtone transition strength and band positions. A comparison of the results of PAA and PFA with those of other intramolecular H-bonded and non-H-bonded molecules provides a useful gauge of the extent of hydrogen bonding in these peroxyacids.

  15. Overtone spectroscopy of some benzaldehyde derivatives

    Indian Academy of Sciences (India)

    chlorobenzaldehyde has been studied in 2000–12000 cm-½ region. Vibrational frequencies and anharmonicity constants for aryl as well as alkyl CH stretch vibrations have been determined. We have also determined the internuclear distances for the ...

  16. Correlated High-Frequency Molecular Motions in Neat Liquid Probed with Ultrafast Overtone Two-Dimensional Infrared Spectroscopy.

    Science.gov (United States)

    Li, Donghai; Yang, Fan; Han, Chen; Zhao, Juan; Wang, Jianping

    2012-12-06

    In this work, an overtone two-dimensional infrared (2D IR) method is shown to allow correlated molecular motions at the frequencies of overtone transitions to be studied. Waiting-time-dependent overtone 2D IR results of the C-O stretching in neat liquid methanol reveal that the autocorrelation of the v = 0 → 2 transition and the cross correlation of the v = 0 → 2/v = 2 → 4 transitions differ considerably (relaxation time being 700 fs and 2 ps, respectively), suggesting different spectral diffusion dynamics. Quantum-chemical computations in combination with ab initio molecular dynamics simulations show that the overtone transition frequency of the C-O stretching mode in liquid methanol is of more structural sensitivity than the fundamental frequency. This work demonstrates a new 2D IR approach to examining the structural sensitivities of the anharmonic potential parameters of higher vibrational states, which can be used to gain new insight into the ultrafast structural dynamics particularly for neat liquids.

  17. The electron–phonon coupling of fundamental, overtone, and combination modes and its effects on the resonance Raman spectra

    Energy Technology Data Exchange (ETDEWEB)

    Li, Shuo [State Key Laboratory of Superhard Materials, Jilin University, Changchun 130012 (China); College of Physics, Jilin University, Changchun 130012 (China); Li, Zhanlong; Wang, Shenghan; Gao, Shuqin [College of Physics, Jilin University, Changchun 130012 (China); Sun, Chenglin, E-mail: chenglin@jlu.edu.cn [State Key Laboratory of Superhard Materials, Jilin University, Changchun 130012 (China); College of Physics, Jilin University, Changchun 130012 (China); Li, Zuowei [College of Physics, Jilin University, Changchun 130012 (China)

    2015-12-15

    Highlights: • The Huang–Rhys factors and electron–phonon coupling constants are calculated. • The changes of overtone mode are larger than those of fundamental mode. • The variation pattern of electron–phonon coupling well interprets the changes of spectra. - Abstract: External field plays a very important role in the interaction between the π-electron transition and atomic vibration of polyenes. It has significant effects on both the Huang–Rhys factor and the electron–phonon coupling. In this paper, the visible absorption and resonance Raman spectra of all-trans-β-carotene are measured in the 345–295 K temperature range and it is found that the changes of the 0–1 and 0–2 vibration bands of the absorption spectra with the temperature lead to the different electron–phonon coupling of fundamental, overtone, and combination modes. The electron-phonon coupling constants of all the modes are calculated and analyzed under different temperatures. The variation law of the electron–phonon coupling with the temperature well interprets the changes of the resonance Raman spectra, such as the shift, intensity and line width of the overtone and combination modes, which are all greater than those of the fundamental modes.

  18. Vibrationally Driven Hydrogen Abstraction Reaction by Bromine Radical in Solution

    Science.gov (United States)

    Shin, Jae Yoon; Shalowski, Michael A.; Crim, F. Fleming

    2013-06-01

    Previously, we have shown that preparing reactants in specific vibrational states can affect the product state distribution and branching ratios in gas phase reactions. In the solution phase, however, no vibrational mediation study has been reported to date. In this work, we present our first attempt of vibrationally mediated bimolecular reaction in solution. Hydrogen abstraction from a solvent by a bromine radical can be a good candidate to test the effect of vibrational excitation on reaction dynamics because this reaction is highly endothermic and thus we can suppress any thermally initiated reaction in our experiment. Br radical quickly forms CT (charge transfer) complex with solvent molecule once it is generated from photolysis of a bromine source. The CT complex strongly absorbs visible light, which allows us to use electronic transient absorption for tracking Br radical population. For this experiment, we photolyze bromoform solution in dimethyl sulfoxide (DMSO) solvent with 267 nm to generate Br radical and excite the C-H stretch overtone of DMSO with 1700 nm a few hundred femtoseconds after the photolysis. Then, we monitor the population of Br-DMSO complex with 400 nm as a function of delay time between two pump beams and probe beam. As a preliminary result, we observed the enhancement of loss of Br-DMSO complex population due to the vibrational excitation. We think that increased loss of Br-DMSO complex is attributed to more loss of Br radical that abstracts hydrogen from DMSO and it is the vibrational excitation that promotes the reaction. To make a clear conclusion, we will next utilize infrared probing to directly detect HBr product formation.

  19. Palladium Catalyzed Allylic C-H Alkylation

    DEFF Research Database (Denmark)

    Engelin, Casper Junker; Fristrup, Peter

    2011-01-01

    -H alkylation reaction which is the topic of the current review. Particular emphasis is put on current mechanistic proposals for the three reaction types comprising the overall transformation: C-H activation, nucleophillic addition, and re-oxidation of the active catalyst. Recent advances in C-H bond activation...

  20. Feasibility of non-invasive optical blood-glucose detection using overtone circular dichroism

    CERN Document Server

    Hokr, Brett H; Meng, Zhaokai; Petrov, Georgi I; Yakovlev, Vladislav V

    2016-01-01

    Diabetes is one of the most debilitating and costly diseases currently plaguing humanity. It is a leading cause of death and dismemberment in the world, and we know how to treat it. Accurate, continuous monitoring and control of blood glucose levels via insulin treatments are widely known to mitigate the majority of detrimental effects caused by the disease. The primary limitation of continuous glucose monitoring is patient non-compliance due to the unpleasant nature of "finger-stick" testing methods. This limitation can be largely, or even completely, removed by non-invasive testing methods. In this report, we demonstrate the vibrational overtone circular dichroism properties of glucose and analyze its use as a method of non-invasive glucose monitoring, capable of assuaging this trillion dollar scourge.

  1. Optimal control of vibrational transitions of HCl

    Indian Academy of Sciences (India)

    Control of fundamental and overtone transitions of a vibration are studied for the diatomic molecule, HCl. Specifically, the results of the effect of variation of the penalty factor on the physical attributes of the system (i.e., probabilities) and pulse (i.e., amplitudes) considering three different pulse durations for each value of the ...

  2. The 4ν(CH) overtone of 12C2H2: sub-MHz precision spectrum reveals perturbations.

    Science.gov (United States)

    Liu, A-W; Li, X-F; Wang, J; Lu, Y; Cheng, C-F; Sun, Y R; Hu, S-M

    2013-01-07

    The third CH stretching vibration overtone (4ν(CH)) of the acetylene molecule has been a prototype for intra-molecular dynamics studies. Using a sensitive cavity ring-down spectrometer calibrated with precise atomic transitions, the absolute line frequencies of 50 lines of this band have been determined with sub-MHz accuracy, or relatively 2 × 10(-9). The accuracy is also confirmed by the combination differences between the transitions sharing the same upper level. The improved accuracy, two orders of magnitude better than previous studies, allows us to reveal finer ro-vibrational couplings. Fitting of the rotational energies indicates that the J-dependent interactions take place after J > 7. The precise line positions present useful confinements to the models of the intra-molecular interactions of the acetylene molecule.

  3. Sunlight-Initiated Photochemistry: Excited Vibrational States of Atmospheric Chromophores

    Directory of Open Access Journals (Sweden)

    Veronica Vaida

    2008-01-01

    Full Text Available Atmospheric chemical reactions are often initiated by ultraviolet (UV solar radiation since absorption in that wavelength range coincides to typical chemical bond energies. In this review, we present an alternative process by which chemical reactions occur with the excitation of vibrational levels in the ground electronic state by red solar photons. We focus on the O–H vibrational manifold which can be an atmospheric chromophore for driving vibrationally mediated overtone-induced chemical reactions. Experimental and theoretical O–H intensities of several carboxylic acids, alcohols, and peroxides are presented. The importance of combination bands in spectra at chemically relevant energies is examined in the context of atmospheric photochemistry. Candidate systems for overtone-initiated chemistry are provided, and their lowest energy barrier for reaction and the minimum quanta of O–H stretch required for reaction are calculated. We conclude with a discussion of the major pathways available for overtone-induced reactions in the atmosphere.

  4. Infrared Optothermal Spectroscopy of N(2)- and OC-DCCH: The C-H Stretching Region.

    Science.gov (United States)

    Hünig; Oudejans; Miller

    2000-11-01

    High-resolution optothermal laser spectroscopy is reported for the C-H stretching vibrations of the binary complexes formed between monodeuterated acetylene and carbon monoxide and nitrogen. In contrast with a previous study of the corresponding C(2)H(2) complexes, where the C-H fundamental spectra were highly perturbed [R. D. Beck, A. G. Maki, S.-H. Tseng, and R. O. Watts, J. Mol. Spectrosc. 158, 306-317 (1993)], the present spectra are well described by a simple linear-rotor Hamiltonian. This is presumed to result from the fact that the C-H vibration in the monodeuterated complexes is decoupled from the intermolecular degrees of freedom. Copyright 2000 Academic Press.

  5. Sunlight-Initiated Photochemistry: Excited Vibrational States of Atmospheric Chromophores

    OpenAIRE

    Veronica Vaida; Karl J. Feierabend; Nabilah Rontu; Kaito Takahashi

    2008-01-01

    Atmospheric chemical reactions are often initiated by ultraviolet (UV) solar radiation since absorption in that wavelength range coincides to typical chemical bond energies. In this review, we present an alternative process by which chemical reactions occur with the excitation of vibrational levels in the ground electronic state by red solar photons. We focus on the O–H vibrational manifold which can be an atmospheric chromophore for driving vibrationally mediated overtone-induced chemical re...

  6. C2H2 Overtones Near 12300 cm-1 Revisited with a Very Sensitive Cavity Ring-down Spectrometer

    Science.gov (United States)

    Gao, Bo; Liu, An-wen; Wu, Rui-xue; Ning, Wei; Hu, Shui-ming

    2009-12-01

    A cavity ring-down spectrometer (CRDS) is constructed with a single-mode continuous-wave Ti: Sapphire laser. It allows attaining a minimum detectable absorption of 1.8 × 10-10 cm-1. The spectrometer is applied to record the overtone spectrum of 12C2H2 in the 12240-12350 cm-1. Compared with the previous CRDS and intra-cavity laser absorption spectroscopy studies in the same region, the present measurement achieved better sensitivity and better precision as well. As a result, the ro-vibrational parameters of the high overtone bands of acetylene at 12290.12, 12311.82, and 12350.61 cm-1 have been refined. The advantages of the present CRD spectrometer is also demonstrated by the newly observed and well characterized perturbation on the f component of the very weak band near 12289 cm-1. The quantitative measurement capability of the spectrometer is verified with the measurement of the water lines and employed to give the absolute band intensities of those three acetylene bands.

  7. Are asymmetric stretch Raman spectra by centrosymmetric molecules depolarized?: The 2ν3 overtone of CO2

    Science.gov (United States)

    Chrysos, M.; Verzhbitskiy, I. A.; Rachet, F.; Kouzov, A. P.

    2011-01-01

    Molecular vibrations that are not totally symmetrical give rise to depolarized lines [P. Atkins and J. de Paula, Atkins' Physical Chemistry (Oxford University Press, UK, 2006), p. 464]. But in the case of stretching vibrations in centrosymmetric molecules, the statement has so far not been conclusively verified. It is the purpose of this article to report a rigorous experimental and theoretical analysis of the 2ν _3 band of CO2—the first overtone of the asymmetrical stretch vibration. The anisotropic spectrum was extracted and its spectral moment calculated from light-scattering measurements, taken at room temperature and for a wide range of CO2-gas densities. Evidence for a near-entirely depolarized Raman band is provided, with integrated depolarization ratio η _{int}= 6/7.16, closely approaching the upper bound η _{max}=6/7. Agreement with theoretical predictions is found, on the basis of quality ab initio data for polarizability properties, provided that electro-optical and mechanical anharmonicity and intermode coupling effects between symmetric ν _1 and antisymmetric ν _3 stretching vibrations are incorporated.

  8. The photodissociation and reaction dynamics of vibrationally excited molecules

    Energy Technology Data Exchange (ETDEWEB)

    Crim, F.F. [Univ. of Wisconsin, Madison (United States)

    1993-12-01

    This research determines the nature of highly vibrationally excited molecules, their unimolecular reactions, and their photodissociation dynamics. The goal is to characterize vibrationally excited molecules and to exploit that understanding to discover and control their chemical pathways. Most recently the author has used a combination of vibrational overtone excitation and laser induced fluorescence both to characterize vibrationally excited molecules and to study their photodissociation dynamics. The author has also begun laser induced grating spectroscopy experiments designed to obtain the electronic absorption spectra of highly vibrationally excited molecules.

  9. The depolarized Raman 2ν3 overtone of CO2: a line-mixing shape analysis.

    Science.gov (United States)

    Verzhbitskiy, I A; Kouzov, A P; Rachet, F; Chrysos, M

    2011-05-21

    In a recent article we showed that the 2ν(3) transition of CO(2) gives rise to a Raman spectrum that is almost entirely depolarized [M. Chrysos, I. A. Verzhbitskiy, F. Rachet, and A. P. Kouzov, J. Chem. Phys. 134, 044318 (2011)]. In the present article, we go further forward in the study of this overtone by reporting a first-principles shape analysis of its depolarized spectrum at room temperature. As a first step in our analysis, a model assuming isolated Lorentzian line shapes was applied, which at low gas densities turns out to be sufficient for qualitative conclusions. As the next step, a sophisticated approach was developed on the basis of the extended strong-collision model in order to properly account for the heavy line mixing between rotational lines. Whereas a marked deviation between model and measured spectra was observed upon application of the simpler model, striking agreement even at the highest CO(2) density was found on applying the sophisticated one. Accurate calculated data were used for the rotational line broadening coefficients without resort to arbitrary parameters. Values for the vibrational shift scaling linearly with the density of the gas are given. © 2011 American Institute of Physics.

  10. Approximate thermochemical tables for some C-H and C-H-O species

    Science.gov (United States)

    Bahn, G. S.

    1973-01-01

    Approximate thermochemical tables are presented for some C-H and C-H-O species and for some ionized species, supplementing the JANAF Thermochemical Tables for application to finite-chemical-kinetics calculations. The approximate tables were prepared by interpolation and extrapolation of limited available data, especially by interpolations over chemical families of species. Original estimations have been smoothed by use of a modification for the CDC-6600 computer of the Lewis Research Center PACl Program which was originally prepared for the IBM-7094 computer Summary graphs for various families show reasonably consistent curvefit values, anchored by properties of existing species in the JANAF tables.

  11. Vibrational spectrum of CF4 isotopes in an algebraic model

    Indian Academy of Sciences (India)

    n this paper the stretching vibrational modes of CF4 isotopes are calculated up to first overtone using the one-dimensional vibron model for the first time. The model Hamiltonian so constructed seems to describe the C–F stretching modes accurately using a relatively small set of well-defined parameters.

  12. Nuclear spin/parity dependent spectroscopy and predissociation dynamics in vOH = 2 ← 0 overtone excited Ne-H2O clusters: Theory and experiment

    Science.gov (United States)

    Ziemkiewicz, Michael P.; Pluetzer, Christian; Loreau, Jérôme; van der Avoird, Ad; Nesbitt, David J.

    2017-12-01

    Vibrationally state selective overtone spectroscopy and state- and nuclear spin-dependent predissociation dynamics of weakly bound ortho- and para-Ne-H2O complexes (D0(ortho) = 34.66 cm-1 and D0(para) = 31.67 cm-1) are reported, based on near-infrared excitation of van der Waals cluster bands correlating with vOH = 2 ← 0 overtone transitions (|02-〉 and |02+〉) out of the ortho (101) and para (000) internal rotor states of the H2O moiety. Quantum theoretical calculations for nuclear motion on a high level potential energy surface [CCSD(T)/VnZf12 (n = 3, 4)], corrected for basis set superposition error and extrapolated to the complete basis set (CBS) limit, are employed to successfully predict and assign Π-Σ, Σ-Σ, and Σ-Π infrared bands in the spectra, where Σ or Π represent approximate projections of the body-fixed H2O angular momentum along the Ne-H2O internuclear axis. IR-UV pump-probe experimental capabilities permit real-time measurements of the vibrational predissociation dynamics, which indicate facile intramolecular vibrational energy transfer from the H2O vOH = 2 overtone vibrations into the VdWs (van der Waals) dissociation coordinate on the τprediss = 15-25 ns time scale. Whereas all predicted strong transitions in the ortho-Ne-H2O complexes are readily detected and assigned, vibrationally mediated photolysis spectra for the corresponding para-Ne-H2O bands are surprisingly absent despite ab initio predictions of Q-branch intensities with S/N > 20-40. Such behavior signals the presence of highly selective nuclear spin ortho-para predissociation dynamics in the upper state, for which we offer a simple mechanism based on Ne-atom mediated intramolecular vibrational relaxation in the H2O subunit (i.e., |02±〉 → {|01±〉; v2 = 2}), which is confirmed by the ab initio energy level predictions and the nascent OH rotational (N), spin orbit (Π1/2,3/2), and lambda doublet product distributions.

  13. Undirected, Homogeneous C?H Bond Functionalization: Challenges and Opportunities

    OpenAIRE

    Hartwig, John F.; Larsen, Matthew A.

    2016-01-01

    The functionalization of C?H bonds has created new approaches to preparing organic molecules by enabling new strategic ?disconnections? during the planning of a synthetic route. Such functionalizations also have created the ability to derivatize complex molecules by modifying one or more of the many C?H bonds. For these reasons, researchers are developing new types of functionalization reactions of C?H bonds and new applications of these processes. These C?H bond functionalization reactions c...

  14. Darling-Dennison resonance and Coriolis coupling in the bending overtones of the A 1A(u) state of acetylene, C2H2.

    Science.gov (United States)

    Merer, Anthony J; Yamakita, Nami; Tsuchiya, Soji; Steeves, Adam H; Bechtel, Hans A; Field, Robert W

    2008-08-07

    Rotational analyses have been carried out for the overtones of the nu(4) (torsion) and nu(6) (in-plane cis-bend) vibrations of the A (1)A(u) state of C(2)H(2). The v(4)+v(6)=2 vibrational polyad was observed in high-sensitivity one-photon laser-induced fluorescence spectra and the v(4)+v(6)=3 polyad was observed in IR-UV double resonance spectra via the ground state nu(3) (Sigma(+) (u)) and nu(3)+nu(4) (Pi(u)) vibrational levels. The structures of these polyads are dominated by the effects of vibrational angular momentum: Vibrational levels of different symmetry interact via strong a-and b-axis Coriolis coupling, while levels of the same symmetry interact via Darling-Dennison resonance, where the interaction parameter has the exceptionally large value K(4466)=-51.68 cm(-1). The K-structures of the polyads bear almost no resemblance to the normal asymmetric top patterns, and many local avoided crossings occur between close-lying levels with nominal K-values differing by one or more units. Least squares analysis shows that the coupling parameters change only slightly with vibrational excitation, which has allowed successful predictions of the structures of the higher polyads: A number of weak bands from the v(4)+v(6)=4 and 5 polyads have been identified unambiguously. The state discovered by Scherer et al. [J. Chem. Phys. 85, 6315 (1986)], which appears to interact with the K=1 levels of the 3(3) vibrational state at low J, is identified as the second highest of the five K=1 members of the v(4)+v(6)=4 polyad. After allowing for the Darling-Dennison resonance, the zero-order bending structure can be represented by omega(4)=764.71, omega(6)=772.50, x(44)=0.19, x(66)=-4.23, and x(46)=11.39 cm(-1). The parameters x(46) and K(4466) are both sums of contributions from the vibrational angular momentum and from the anharmonic force field. For x(46) these contributions are 14.12 and -2.73 cm(-1), respectively, while the corresponding values for K(4466) are -28.24 and -23

  15. Undirected, Homogeneous C-H Bond Functionalization: Challenges and Opportunities.

    Science.gov (United States)

    Hartwig, John F; Larsen, Matthew A

    2016-05-25

    The functionalization of C-H bonds has created new approaches to preparing organic molecules by enabling new strategic "disconnections" during the planning of a synthetic route. Such functionalizations also have created the ability to derivatize complex molecules by modifying one or more of the many C-H bonds. For these reasons, researchers are developing new types of functionalization reactions of C-H bonds and new applications of these processes. These C-H bond functionalization reactions can be divided into two general classes: those directed by coordination to an existing functional group prior to the cleavage of the C-H bond (directed) and those occurring without coordination prior to cleavage of the C-H bond (undirected). The undirected functionalizations of C-H bonds are much less common and more challenging to develop than the directed reactions. This outlook will focus on undirected C-H bond functionalization, as well as related reactions that occur by a noncovalent association of the catalyst prior to C-H bond cleavage. The inherent challenges of conducting undirected functionalizations of C-H bonds and the methods for undirected functionalization that are being developed will be presented, along with the factors that govern selectivity in these reactions. Finally, this outlook discusses future directions for research on undirected C-H functionalization, with an emphasis on the limitations that must be overcome if this type of methodology is to become widely used in academia and in industry.

  16. Structural trends in transition metal cation-acetylene complexes revealed through the C-H stretching fundamentals.

    Science.gov (United States)

    Walters, Richard S; Schleyer, Paul V R; Corminboeuf, Clemence; Duncan, Michael A

    2005-02-02

    Metal cation-acetylene complexes (M = V, Fe, Co, Ni) are produced in molecular beams and studied with infrared photodissociation spectroscopy in the C-H stretching region. Each complex has two vibrational bands corresponding to the symmetric and asymmetric stretches of acetylene that are shifted to the red of these vibrations in the isolated acetylene molecule. Density functional theory reveals the sources of the red-shifted vibrations and their relative magnitudes. Fe+, Co+, and Ni+ form pi-complexes with acetylene, while V+(C2H2) is a metallacycle.

  17. para-Selective C-H bond functionalization of iodobenzenes.

    Science.gov (United States)

    Zhao, Ying; Yan, Haiming; Lu, Hanwei; Huang, Zhiliang; Lei, Aiwen

    2016-09-15

    Selective C-H bond activation and functionalization is an invaluable and eco-friendly tool for new chemical bond construction. Recently, great progress has been made in the highly selective ortho- and meta-C-H bond functionalization of arene derivatives. In contrast, the remote para-C-H bond functionalization still remains a challenge. Herein, an oxidation-induced strategy for para-selective C-H bond functionalization of iodobenzenes towards the synthesis of various useful asymmetric diaryl ethers was demonstrated. This strategy not only provides a novel method for para-C-H bond functionalization, but also proposes a general idea for the development of new, highly selective para-C-H functionalization reactions.

  18. 14N overtone NMR spectra under magic angle spinning: Experiments and numerically exact simulations

    Science.gov (United States)

    O'Dell, Luke A.; Brinkmann, Andreas

    2013-02-01

    It was recently shown that high resolution 14N overtone NMR spectra can be obtained directly under magic angle spinning (MAS) conditions [L. A. O'Dell and C. I. Ratcliffe, Chem. Phys. Lett. 514, 168 (2011)], 10.1016/j.cplett.2011.08.030. Preliminary experimental results showed narrowed powder pattern widths, a frequency shift that is dependent on the MAS rate, and an apparent absence of spinning sidebands, observations which appeared to be inconsistent with previous theoretical treatments. Herein, we reproduce these effects using numerically exact simulations that take into account the full nuclear spin Hamiltonian. Under sample spinning, the 14N overtone signal is split into five (0, ±1, ±2) overtone sidebands separated by the spinning frequency. For a powder sample spinning at the magic angle, the +2ωr sideband is dominant while the others show significantly lower signal intensities. The resultant MAS powder patterns show characteristic quadrupolar lineshapes from which the 14N quadrupolar parameters and isotropic chemical shift can be determined. Spinning the sample at other angles is shown to alter both the shapes and relative intensities of the five overtone sidebands, with MAS providing the benefit of averaging dipolar couplings and shielding anisotropy. To demonstrate the advantages of this experimental approach, we present the 14N overtone MAS spectrum obtained from L-histidine, in which powder patterns from all three nitrogen sites are clearly resolved.

  19. Nanocomposite W-C : H diamond-like carbon coatings

    NARCIS (Netherlands)

    Strondl, Carl Gunnar Christian

    2007-01-01

    It has been demonstrated that the rotation speed of the substrate table and the gas flow rate of acetylene gas are important process parameters for determining the nano/micro-structure of W-C:H coatings. Either a homogeneous or a pronounced multilayer or a nanocomposite structure of the W-C:H

  20. Strong overtones modes in inelastic electron tunneling spectroscopy with cross-conjugated molecules

    DEFF Research Database (Denmark)

    Jørgensen, Jacob Lykkebo; Gagliardi, Alessio; Pecchia, Alessandro

    2013-01-01

    Cross-conjugated molecules are known to exhibit destructive quantum interference, a property that has recently received considerable attention in single-molecule electronics. Destructive quantum interference can be understood as an antiresonance in the elastic transmission near the Fermi energy...... is larger than for molecules without interference, the overall behavior of the molecule is still dominated by the quantum interference feature. Second, an ongoing challenge for single molecule electronics is understanding and controlling the local geometry at the molecule-surface interface...... that overtones are not observable in IETS. Here, overtones are predicted to be strong and, in some cases, the dominant spectroscopic features. We study the origin of the overtones and find that the interference features in these molecules are the key ingredient. The interference feature is a property...

  1. Crossover between liquidlike and gaslike behavior in C H4 at 400 K

    Science.gov (United States)

    Smith, D.; Hakeem, M. A.; Parisiades, P.; Maynard-Casely, H. E.; Foster, D.; Eden, D.; Bull, D. J.; Marshall, A. R. L.; Adawi, A. M.; Howie, R.; Sapelkin, A.; Brazhkin, V. V.; Proctor, J. E.

    2017-11-01

    We report experimental evidence for a crossover between a liquidlike state and a gaslike state in fluid methane (C H4 ). This crossover is observed in all of our experiments, up to a temperature of 397 K, 2.1 times the critical temperature of methane. The crossover has been characterized with both Raman spectroscopy and x-ray diffraction in a number of separate experiments, and confirmed to be reversible. We associate this crossover with the Frenkel line—a recently hypothesized crossover in dynamic properties of fluids extending to arbitrarily high pressure and temperature, dividing the phase diagram into separate regions where the fluid possesses liquidlike and gaslike properties. On the liquidlike side the Raman-active vibration increases in frequency linearly as pressure is increased, as expected due to the repulsive interaction between adjacent molecules. On the gaslike side this competes with the attractive van der Waals potential leading the vibration frequency to decrease as pressure is increased.

  2. Mixed Directing-Group Strategy: Oxidative C-H/C-H Bond Arylation of Unactivated Arenes by Cobalt Catalysis.

    Science.gov (United States)

    Du, Cong; Li, Peng-Xiang; Zhu, Xinju; Suo, Jian-Feng; Niu, Jun-Long; Song, Mao-Ping

    2016-10-17

    A mixed directing-group strategy for inexpensive [Co(acac)3 ]-catalyzed oxidative C-H/C-H bond arylation of unactivated arenes has been disclosed. This strategy enables the arylation of a wide range of benzamide and arylpyridines effectively to afford novel bifunctionalized biaryls, which are difficult to achieve by common synthetic routes. Two different pathways, namely, a single-electron-transmetalation process (8-aminoquinoline-directed) and a concerted metalation-deprotonation process (pyridine-directed), were involved to activate two different inert aromatic C-H bonds. Moreover, the aryl radicals have been trapped by 2,6-di-tert-butyl-4-methylphenol to form benzylated products. This unique strategy should be useful in the design of other arene C-H/C-H cross-couplings as well. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. Computational study on C-H...π interactions of acetylene with benzene, 1,3,5-trifluorobenzene and coronene.

    Science.gov (United States)

    Dinadayalane, Tandabany C; Paytakov, Guvanchmyrat; Leszczynski, Jerzy

    2013-07-01

    Meta-hybrid density functional theory calculations using M06-2X/6-31+G(d,p) and M06-2X/6-311+G(d,p) levels of theory have been performed to understand the strength of C-H(…)π interactions of two possible types for benzene-acetylene, 1,3,5-trifluorobenzene-acetylene and coronene-acetylene complexes. Our study reveals that the C-H(...)π interaction complex where acetylene located above to the center of benzene ring (classical T-shaped) is the lowest energy structure. This structure is twice more stable than the configuration characterized by H atom of benzene interacting with the π-cloud of acetylene. The binding energy of 2.91 kcal/mol calculated at the M06-2X/6-311+G(d,p) level for the lowest energy configuration (1A) is in very good agreement with the experimental binding energy of 2.7 ± 0.2 kcal/mol for benzene-acetylene complex. Interestingly, the C-H(...)π interaction of acetylene above to the center of the aromatic ring is not the lowest energy configuration for 1,3,5-trifluorobenzene-acetylene and coronene-acetylene complexes. The lowest energy configuration (2A) for the former complex possesses both C-H(...)π interaction and C-H(...)F hydrogen bond, while the lowest energy structure for the coronene-acetylene complex involves both π-π and C-H(...)π interactions. C-H stretching vibrational frequencies and the frequency shifts are reported and analyzed for all of the configurations. We observed red-shift of the vibrational frequency for the stretching mode of the C-H bond that interacts with the π-cloud. Acetylene in the lowest-energy structures of the complexes exhibits significant red-shift of the C-H stretching frequency and change in intensity of the corresponding vibrational frequency, compared to bare acetylene. We have examined the molecular electrostatic potential on the surfaces of benzene, 1,3,5-trifluorobenzene, coronene and acetylene to explain the binding strengths of various complexes studied here.

  4. The isotropic spectrum of the CO2 Raman 2ν3 overtone: a line-mixing band shape analysis at pressures up to several tens of atmospheres.

    Science.gov (United States)

    Verzhbitskiy, I A; Kouzov, A P; Rachet, F; Chrysos, M

    2011-06-14

    A line-mixing shape analysis of the isotropic remnant Raman spectrum of the 2ν(3) overtone of CO(2) is reported at room temperature and for densities, ρ, rising up to tens of amagats. The analysis, experimental and theoretical, employs tools of non-resonant light scattering spectroscopy and uses the extended strong collision model (ESCM) to simulate the strong line mixing effects and to evidence motional narrowing. Excellent agreement at any pressure is observed between the calculated spectra and our experiment, which, along with the easy numerical implementation of the ESCM, makes this model stand out clearly above other semiempirical models for band shape calculations. The hitherto undefined, explicit ρ-dependence of the vibrational relaxation rate is given. Our study intends to improve the understanding of pressure-induced phenomena in a gas that is still in the forefront of the news.

  5. Dirhodium-catalyzed C-H arene amination using hydroxylamines

    National Research Council Canada - National Science Library

    Paudyal, Mahesh P; Adebesin, Adeniyi Michael; Burt, Scott R; Ess, Daniel H; Ma, Zhiwei; Kürti, László; Falck, John R

    2016-01-01

    .... Here, we present a mild dirhodium-catalyzed C-H amination for conversion of structurally diverse monocyclic and fused aromatics to the corresponding primary and N-alkyl arylamines using NH2/NH(alkyl)-O-(sulfonyl...

  6. Rhodium-Catalyzed C-H Bond Functionalization with Amides by Double C-H/C-N Bond Activation.

    Science.gov (United States)

    Meng, Guangrong; Szostak, Michal

    2016-02-19

    The first C-H bond functionalization with amides as the coupling partners via selective activation of the amide N-C bond using rhodium(I) catalysts under highly chemoselective conditions is reported. Notably, this report constitutes the first catalytic activation of the amide N-C(O) bond by rhodium. We expect that this concept will have broad implications for using amides as coupling partners for C-H activation beyond the work described herein.

  7. New phenolic acids from Salvia yunnanensis C.H.Wright.

    Science.gov (United States)

    Yu, Yun; Wang, Yin-Ru; Dong, Zhen-Huan; Li, Wei; Li, Shu-Ming; Huang, Xue-Feng

    2017-11-01

    Two new phenolic acids, ethyl pro-lithospermate (1), n-butyl pro-lithospermate (2) were isolated from Salvia yunnanensis C.H.Wright, along with nineteen known compounds (3-21). The structures of the isolated compounds were elucidated on the basis of extensive spectrometry and by comparing their physical and spectroscopic data to the literature. Among them, compounds 11, 12 and 14-16 were firstly isolated from S. yunnanensis C.H.Wright. Some of the isolated compounds were evaluated for their neuroprotection. Compounds 10-12 showed significant neuroprotective effects in PC12 cells and compounds 1, 4-7 displayed moderate neuroprotective effects.

  8. Pathways for C-H bond cleavage of propane σ-complexes on PdO(101).

    Science.gov (United States)

    Antony, Abbin; Asthagiri, Aravind; Weaver, Jason F

    2012-09-21

    We used dispersion-corrected density functional theory (DFT-D3) calculations to investigate the initial C-H bond cleavage of propane σ-complexes adsorbed on the PdO(101) surface. The calculations predict that propane molecules adsorbed in η(1) configurations can undergo facile C-H bond cleavage on PdO(101), where the energy barrier for C-H bond activation is lower than that for desorption for each molecular complex. The preferred pathway for propane dissociation on PdO(101) corresponds to cleavage of a primary C-H bond of a so-called staggered p-2η(1) complex which initially coordinates with the surface by forming two H-Pd dative bonds, one at each CH(3) group. Among all of the adsorbed propane complexes, the staggered p-2η(1) complex has the highest binding energy and must overcome the lowest energy barrier for C-H bond scission. Analysis of the atomic charges reveals that propane C-H bond cleavage occurs heterolytically on PdO(101), and suggests that primary C-H bond activation is favored because a more stabilizing charge distribution develops within the 1-propyl transition state structures. Lastly, we conducted kinetic simulations using microkinetic models derived from the DFT-D3 structures, and find that the models reproduce the apparent activation energy for propane dissociation on PdO(101) to within 14% of that determined experimentally. We show that the entropic contributions of the adsorbed transition structures greatly exceed those predicted by the harmonic oscillator model, and that quantitative agreement with the apparent dissociation pre-factor may be obtained by approximating two of the frustrated adsorbate motions as free motions while treating the remaining modes as harmonic vibrations.

  9. The Dependence of 1 J(C, H)

    African Journals Online (AJOL)

    The INDO-FTP calculated 3J(C-5, H) values depend on the corresponding dihedral angle and the spatial relationships of the C=N double bond and the aryl group. Key Words: (C, H) coupling constants, Nitrogen lone-pair, Carbonyl group, INDO-FPT calculations, Diazepam South African Journal of Chemistry Vol.57 2004: ...

  10. Rhodium(0) metalloradicals in binuclear C-H activation

    NARCIS (Netherlands)

    Puschmann, F.F.; Grützmacher, H.; de Bruin, B.

    2010-01-01

    A reactive rhodium(0) metalloradical capable of binuclear activation of an aromatic C-H bond of PPh3 is disclosed. Kinetic measurements and density functional theory calculations reveal a binuclear mechanism: two metalloradicals add to a 'double bond' of the aromatic substrate while approaching the

  11. Toward Efficient Palladium-Catalyzed Allylic C-H Alkylation

    DEFF Research Database (Denmark)

    Jensen, Thomas; Fristrup, Peter

    2009-01-01

    Recent breakthroughs have proved that direct palladium (II)-catalyzed allylic C-H alkylation can be achieved. This new procedure shows that the inherent requirement for a leaving group in the Tsuji-Trost palladium-catalyzed allylic alkylation can be lifted. These initial reports hold great promise...

  12. Supplementary Information Table: S1 Calculated vibrational wave ...

    Indian Academy of Sciences (India)

    Administrator

    514. 511 w. 519 vvw. 6a ring o.p bend. 508. 496 s. 500 vvw. 16 b ring o.p bend. 390. 387 vvw. 16a ring o.p bend. 334. 328 vvw. 9b C-H i.p bend. 274. 267 vvw. Hydrogen bonded vibrations. 184. 171 vs. Hydrogen bonded vibrations. 112. 120 vvs. Hydrogen bonded vibrations. 64. 57 sh. Hydrogen bonded vibrations.

  13. Mechanistic Comparison Between Pd-Catalyzed Ligand Directed C-H Chlorination and C-H Acetoxylation

    Science.gov (United States)

    Stowers, Kara J.; Sanford, Melanie S.

    2009-01-01

    This communication describes detailed investigations of the mechanism of the Pd-catalyzed C-H chlorination and acetoxylation of 2-ortho-tolylpyridine. Under the conditions examined, both reactions proceed via rate limiting cyclopalladation. However, substrate and catalyst order as well as Hammett data indicate that the intimate mechanism of cyclopalladation differs significantly between PdCl2-catalyzed chlorination and Pd(OAc)2-catalyzed acetoxylation. PMID:19754074

  14. Cepheids in Magellanic Cloud star clusters - Fundamental and overtone pulsators in NGC 2157

    Science.gov (United States)

    Mateo, Mario; Olszewski, Edward W.; Madore, Barry F.

    1990-01-01

    CCD survey data are employed to examine Cepheids in young Magellanic Cloud star clusters. The properties of three Cepheids observed in NGC 2157 are described. It is detected that the two short-period (3 days) Cepheids have photometric properties that correspond to overtone pulsators and the long-period (7.7 days) Cepheid pulses in the fundamental mode. The pulsational masses for the three Cepheids are calculated to be about 5 solar masses. This mass value does not correlate with the average pulsational mass for Cepheids of 3.0 + or - 0.4 solar masses. The potential cause of this deviation in evolutionary/pulsational mass is investigated.

  15. Vibrational Spectroscopy of Intramolecular Hydrogen Bonds in the Infrared and Near-Infrared Regions

    DEFF Research Database (Denmark)

    Schrøder, Sidsel Dahl

    and 1,4-diaminobutane). Experimentally, the hydrogen bonds have been studied with vibrational spectroscopy in the infrared and near-infrared regions. The focus is primarily on spectra recorded in the near-infrared regions, which in these studies are dominated by O-H and N-H stretching overtones....... Overtone spectra have been recorded with intracavity laser photoacoustic laser spectroscopy and conventional long path absorption spectroscopy. Theoretically, a combination of electronic structure calculations and local mode models have been employed to guide the assignment of bands in the vibrational......, weak intramolecular hydrogen bonds in methyl lactate, allyl carbinol and methallyl carbinol have been identified and characterized. The effect of substitution of two hydrogen atoms on one of the methylene groups with either methyl groups or tri uoromethyl groups on the intramolecular...

  16. Human development XIII: the connection between the structure of the overtone system and the tone language of music. Some implications for our understanding of the human brain.

    Science.gov (United States)

    Ventegodt, Søren; Hermansen, Tyge Dahl; Kandel, Isack; Merrick, Joav

    2008-07-13

    The functioning brain behaves like one highly-structured, coherent, informational field. It can be popularly described as a "coherent ball of energy", making the idea of a local highly-structured quantum field that carries the consciousness very appealing. If that is so, the structure of the experience of music might be a quite unique window into a hidden quantum reality of the brain, and even of life itself. The structure of music is then a mirror of a much more complex, but similar, structure of the energetic field of the working brain. This paper discusses how the perception of music is organized in the human brain with respect to the known tone scales of major and minor. The patterns used by the brain seem to be similar to the overtones of vibrating matter, giving a positive experience of harmonies in major. However, we also like the minor scale, which can explain brain patterns as fractal-like, giving a symmetric "downward reflection" of the major scale into the minor scale. We analyze the implication of beautiful and ugly tones and harmonies for the model. We conclude that when it comes to simple perception of harmonies, the most simple is the most beautiful and the most complex is the most ugly, but in music, even the most disharmonic harmony can be beautiful, if experienced as a part of a dynamic release of musical tension. This can be taken as a general metaphor of painful, yet meaningful, and developing experiences in human life.

  17. Investigation of the C2H2-CO2 van der Waals complex in the overtone range using cw cavity ring-down spectroscopy

    Science.gov (United States)

    Lauzin, C.; Didriche, K.; Liévin, J.; Herman, M.; Perrin, A.

    2009-05-01

    A slit nozzle supersonic expansion containing acetylene [492 SCCM (SCCM denotes cubic centimeter per minute at STP)] and carbon dioxide (740 SCCM) seeded into Ar (837 SCCM) is investigated using cw-cavity ring-down spectroscopy, in the 1.5 μm range. The C2H2-CO2 van der Waals complex is observed around the ν1+ν3 acetylenic band. The rotational temperature is estimated to be close to 60 K from the comparison between observed and simulated spectra. The analysis of the main, perturbed B-type band centered near 6 549.280 cm-1, is performed. It is attributed to a dimer with the known planar, C2v geometry. The present overtone data, involving ground state levels with higher J /K states (J ≤35 and Ka≤20) than previously reported, are combined to 3 μm data [D. G. Prichard, R. N. Nandi, J. S. Muenter, and B. J. Howard, J. Chem. Phys. 89, 1245 (1988); Z. S. Huang and R. E. Miller, Chem. Phys. 132, 185 (1989)] to determine improved ground state parameters. The major perturbations affecting the upper state are accounted for through C-type Coriolis resonances involving one dark state, whose symmetry must therefore be A1. Upper state constants are obtained for the bright and dark states. The dependence upon vibrational excitation is demonstrated to arise from excitation in the acetylene unit, only, for the former, but cannot be unravelled for the latter.

  18. The overtone transitions of {sup 12}CO{sub 2} and {sup 13}CO{sub 2} beyond the Venus bands

    Energy Technology Data Exchange (ETDEWEB)

    Yang, X.; Noda, C. [Univ. of New Hampshire, Durham, NH (United States)

    1995-12-31

    Vibrational transitions of {sup 12}CO{sub 2} and {sup 13}CO{sub 2} beyond the Venus bands were observed by means of photoacoustic spectroscopy in the near infrared. These transitions include 5v3+(2v1, v1+ 2v2,4v2) triad and the stronger components of the 3v3+(4v1, 3v1+2v2,2v1+4v2, v1+6v2, 8v2) pentad for both species. The head positions of these bands were determined by using the water lines in the same spectral range. Assignments were performed by comparing the measured positions with calculated values. In addition, some of the hot bands associated with those overtone transitions were identified. Intensity shifts were observed within a given polyad especially for higher order polyad. It was found that the experimental measurements on transition energy, relative position and intensity are in good agreement with the theoretical calculations.

  19. Spectroscopic Study of Plasma Polymerized a-C:H Films Deposited by a Dielectric Barrier Discharge

    Directory of Open Access Journals (Sweden)

    Thejaswini Halethimmanahally Chandrashekaraiah

    2016-07-01

    Full Text Available Plasma polymerized a-C:H thin films have been deposited on Si (100 and aluminum coated glass substrates by a dielectric barrier discharge (DBD operated at medium pressure using C2Hm/Ar (m = 2, 4, 6 gas mixtures. The deposited films were characterized by Fourier transform infrared reflection absorption spectroscopy (FT-IRRAS, Raman spectroscopy, and ellipsometry. FT-IRRAS revealed the presence of sp3 and sp2 C–H stretching and C–H bending vibrations of bonds in the films. The presence of D and G bands was confirmed by Raman spectroscopy. Thin films obtained from C2H4/Ar and C2H6/Ar gas mixtures have ID/IG ratios of 0.45 and 0.3, respectively. The refractive indices were 2.8 and 3.1 for C2H4/Ar and C2H6/Ar films, respectively, at a photon energy of 2 eV.

  20. Catalytic Asymmetric Reactions for Organic Synthesis: The Combined C-H Activation/Cope Rearrangement

    National Research Council Canada - National Science Library

    Huw M. L. Davies; Qihui Jin; Jack Halpern

    2004-01-01

    .... This article describes the synthetic utility of the combined C-H activation/Cope rearrangement, achieved by dirhodium tetraprolinate-catalyzed reaction of vinyldiazoacetates with compounds containing allylic C-H bonds...

  1. Near-near-infrared thermal lens spectroscopy to assess overtones and combination bands of sulfentrazone pesticide

    Science.gov (United States)

    Ventura, M.; Silva, J. R.; Andrade, L. H. C.; Scorza Júnior, R. P.; Lima, S. M.

    2018-01-01

    Thermal lens spectroscopy (TLS) in the near-near-infrared region was used to explore the absorptions of overtones and combination bands of sulfentrazone (SFZ) herbicide diluted in methanol. This spectroscopic region was chosen in order to guarantee that only thermal lens effect is noted during the experimental procedure. The results showed that it was possible to detect very low concentrations ( 2 ng/μL) of SFZ in methanol by determining its thermal diffusivity or the absorption coefficient due to the 3ν(NH) + 1δ(CH) combination band. This minimum SFZ concentration is the limit observed by chromatography method. The findings demonstrated that the TLS can be used for precise and accurate assessment of pesticides in ecosystems. Besides, the 3ν(NH) + 1δ(CH) combination band at 960 nm can be used as a marker for SFZ in methanol.

  2. Rayleigh wave phase velocity and error maps up to the fifth overtone

    Science.gov (United States)

    Durand, Stéphanie; Debayle, Eric; Ricard, Yanick

    2015-05-01

    We present a global data set of phase velocity maps for Rayleigh waves, with their errors. These maps are obtained from the tomographic inversion of phase velocity curves measured in the period range 40-250 s by Debayle and Ricard (2012), completed with new measurements at longer periods, between 150 and 360 s. The full data set includes ˜22,000,000 phase velocity measurements combined to build 60 phase velocity maps covering the period range 40-360 s for the fundamental mode and up to the fifth overtone. Each phase velocity map is provided with its a posteriori error, resulting in a unique data set which can be combined with other seismic measurements (surface waves, normal modes, and body waves) in regional and global tomographic studies. A preliminary inversion of this data set shows that it provides constraints on the shear velocity structure down to 1000 km depth.

  3. Role of OH-stretch/torsion coupling and quantum yield effects in the first OH overtone spectrum of cis-cis HOONO

    Science.gov (United States)

    McCoy, Anne B.; Fry, Juliane L.; Francisco, Joseph S.; Mollner, Andrew K.; Okumura, Mitchio

    2005-03-01

    A joint theoretical and experimental investigation is undertaken to study the effects of OH-stretch/HOON torsion coupling and of quantum yield on the previously reported first overtone action spectrum of cis-cis HOONO (peroxynitrous acid). The minimum energy path along the HOON dihedral angle is computed at the coupled cluster singles and doubles with perturbative triples level with correlation consistent polarized quadruple ζ basis set, at the structure optimized using the triple ζ basis set (CCSD(T)/cc-pVQZ//CCSD(T)/cc-pVTZ). The two-dimensional ab initio potential energy and dipole moment surfaces for cis-cis HOONO are calculated as functions of the HOON torsion and OH bond length about the minimum energy path at the CCSD(T)/cc-pVTZ and QCISD/AUG-cc-pVTZ (QCISD—quadratic configuration interaction with single and double excitation and AUG-augmented with diffuse functions) level of theory/basis, respectively. The OH-stretch vibration depends strongly on the torsional angle, and the torsional potential possesses a broad shelf at ˜90°, the cis-perp conformation. The calculated electronic energies and dipoles are fit to simple functional forms and absorption spectra in the region of the OH fundamental and first overtone are calculated from these surfaces. While the experimental and calculated spectra of the OH fundamental band are in good agreement, significant differences in the intensity patterns are observed between the calculated absorption spectrum and the measured action spectrum in the 2νOH region. These differences are attributed to the fact that several of the experimentally accessible states do not have sufficient energy to dissociate to OH+NO2 and therefore are not detectable in an action spectrum. Scaling of the intensities of transitions to these states, assuming D0=82.0kJ/mol, is shown to produce a spectrum that is in good agreement with the measured action spectrum. Based on this agreement, we assign two of the features in the spectrum to Δn=0

  4. Rhodium (II) carbene C-H insertion in water and catalyst reuse; Insercao C-H de carbenoides de rodio em agua e reutilizacao do catalisador

    Energy Technology Data Exchange (ETDEWEB)

    Candeias, Nuno R.; Gois, Pedro M.P.; Afonso, Carlos A.M. [Instituto Superior Tecnico, Lisboa (Portugal)]. E-mail: carlosafonso@ist.utl.pt

    2007-07-01

    A five-session laboratory experiment is described for the synthesis of a beta-lactam via Rh(II) catalysed intramolecular C-H insertion of a alpha-diazo-alpha-ethoxycarbonyl acetamide. The metallo-carbene, responsible for the C-H bond activation, was generated from the diazo substrate and the catalyst Rh{sub 2}(OAc){sub 4}. The high stability and solubility of the catalyst and the exclusive C-H insertion of the Rh-carbene allows the synthesis of this important heterocycle in water and the catalyst reutilization. (author)

  5. Monitoring vibrations

    Energy Technology Data Exchange (ETDEWEB)

    Tiryaki, B. [Hacettepe University (Turkey). Dept. of Mining Engineering

    2003-12-01

    The paper examines the prediction and optimisation of machine vibrations in longwall shearers. Underground studies were carried out at the Middle Anatolian Lignite Mine, between 1993 and 1997. Several shearer drums with different pick lacing arrangements were designed and tested on double-ended ranging longwall shearers employed at the mine. A computer program called the Vibration Analysis Program (VAP) was developed for analysing machine vibrations in longwall shearers. Shearer drums that were tested underground, as well as some provided by leading manufacturers, were analyzed using these programs. The results of the experiments and computer analyses are given in the article. 4 refs., 9 figs.

  6. Spectroscopic investigation of the vibrational quasi-continuum arising from internal rotation of a methyl group

    Energy Technology Data Exchange (ETDEWEB)

    Hougen, J.T. [NIST, Gaithersburg, MD (United States)

    1993-12-01

    The goal of this project is to use spectroscopic techniques to investigate in detail phenomena involving the vibrational quasi-continuum in a simple physical system. Acetaldehyde was chosen for the study because: (i) methyl groups have been suggested to be important promotors of intramolecular vibrational relaxation, (ii) the internal rotation of a methyl group is an easily describle large-amplitude motion, which should retain its simple character even at high levels of excitation, and (iii) the aldehyde carbonyl group offers the possibility of both vibrational and electronic probing. The present investigation of the ground electronic state has three parts: (1) understanding the {open_quotes}isolated{close_quotes} internal-rotation motion below, at, and above the top of the torsional barrier, (2) understanding in detail traditional (bond stretching and bending) vibrational fundamental and overtone states, and (3) understanding interactions involving states with multiquantum excitations of at least one of these two kinds of motion.

  7. Vibrational Diver

    Science.gov (United States)

    Kozlov, Victor; Ivanova, Alevtina; Schipitsyn, Vitalii; Stambouli, Moncef

    2014-10-01

    The paper is concerned with dynamics of light solid in cavity with liquid subjected to rotational vibration in the external force field. New vibrational phenomenon - diving of a light cylinder to the cavity bottom is found. The experimental investigation of a horizontal annulus with a partition has shown that under vibration a light body situated in the upper part of the layer is displaced in a threshold manner some distance away from the boundary. In this case the body executes symmetric tangential oscillations. An increase of the vibration intensity leads to a tangential displacement of the body near the external boundary. This displacement is caused by the tangential component of the vibrational lift force, which appears as soon as the oscillations lose symmetry. In this case the trajectory of the body oscillatory motion has the form of a loop. The tangential lift force makes stable the position of the body on the inclined section of the layer and even in its lower part. A theoretical interpretation has been proposed, which explains stabilization of a quasi-equilibrium state of a light body near the cavity bottom in the framework of vibrational hydromechanics.

  8. Inner Warm Disk of ESO Hα 279a Revealed by NA I and CO Overtone Emission Lines

    Science.gov (United States)

    Lyo, A.-Ran; Kim, Jongsoo; Lee, Jae-Joon; Kim, Kyoung-Hee; Kang, Jihyun; Byun, Do-Young; Mace, Gregory; Sokal, Kimberly R.; Park, Chan; Chun, Moo-Young; Oh, Heeyoung; Yu, Young Sam; Sok Oh, Jae; Jeong, Ueejeong; Kim, Hwihyun; Pak, Soojong; Hwang, Narae; Park, Byeong-Gon; Lee, Sungho; Kaplan, Kyle; Lee, Hye-In; Nguyen Le, Huynh Anh; Jaffe, Daniel; Friends of AASTeX Collaboration

    2017-07-01

    We present an analysis of near-infrared, high-resolution spectroscopy toward the flat-spectrum young stellar object (YSO) ESO Hα 279a (˜1.5M ⊙) in the Serpens star-forming region at a distance of 429 pc. Using the Immersion GRating INfrared Spectrometer (IGRINS; R ≈ 45,000), we detect emission lines originating from the accretion channel flow, jet, and inner disk. Specifically, we identify hydrogen Brackett series recombination, [Fe II], [Fe III], [Fe IV], Ca I, Na I, H2, H2O, and CO overtone emission lines. By modeling five bands of CO overtone emission lines and the symmetric double-peaked line profile for Na I emission lines, we find that ESO Hα 279a has an actively accreting Keplerian disk. From our Keplerian disk model, we find that Na I emission lines originate between 0.04 and 1.00 au, while the CO overtone emission lines are from the outer part of the disk, in the range between 0.22 and 3.00 au. The model reveals that the neutral atomic Na gas is a good tracer of the innermost region of the actively accreting disk. We derive a mass accretion rate of 2-10× 10-7 M ⊙ yr-1 from the measured Brγ emission luminosity of 1.78(±0.31) × 1031 erg s-1.

  9. Accurate ab initio dipole moment surfaces of ozone: First principle intensity predictions for rotationally resolved spectra in a large range of overtone and combination bands

    Science.gov (United States)

    Tyuterev, Vladimir G.; Kochanov, Roman V.; Tashkun, Sergey A.

    2017-02-01

    Ab initio dipole moment surfaces (DMSs) of the ozone molecule are computed using the MRCI-SD method with AVQZ, AV5Z, and VQZ-F12 basis sets on a dense grid of about 1950 geometrical configurations. The analytical DMS representation used for the fit of ab initio points provides better behavior for large nuclear displacements than that of previous studies. Various DMS models were derived and tested. Vibration-rotation line intensities of 16O3 were calculated from these ab initio surfaces by the variational method using two different potential functions determined in our previous works. For the first time, a very good agreement of first principle calculations with the experiment was obtained for the line-by-line intensities in rotationally resolved ozone spectra in a large far- and mid-infrared range. This includes high overtone and combination bands up to Δ V = 6. A particular challenge was a correct description of the B-type bands (even Δ V3 values) that represented major difficulties for the previous ab initio investigations and for the empirical spectroscopic models. The major patterns of various B-type bands were correctly described without empirically adjusted dipole moment parameters. For the 10 μ m range, which is of key importance for the atmospheric ozone retrievals, our ab initio intensity results are within the experimental error margins. The theoretical values for the strongest lines of the ν3 band lie in general between two successive versions of HITRAN (HIgh-resolution molecular TRANsmission) empirical database that corresponded to most extended available sets of observations. The overall qualitative agreement in a large wavenumber range for rotationally resolved cold and hot ozone bands up to about 6000 cm-1 is achieved here for the first time. These calculations reveal that several weak bands are yet missing from available spectroscopic databases.

  10. Human Development XIII: The Connection Between the Structure of the Overtone System and the Tone Language of Music. Some Implications for Our Understanding of the Human Brain

    Directory of Open Access Journals (Sweden)

    Søren Ventegodt

    2008-01-01

    Full Text Available The functioning brain behaves like one highly-structured, coherent, informational field. It can be popularly described as a “coherent ball of energy”, making the idea of a local highly-structured quantum field that carries the consciousness very appealing. If that is so, the structure of the experience of music might be a quite unique window into a hidden quantum reality of the brain, and even of life itself. The structure of music is then a mirror of a much more complex, but similar, structure of the energetic field of the working brain. This paper discusses how the perception of music is organized in the human brain with respect to the known tone scales of major and minor. The patterns used by the brain seem to be similar to the overtones of vibrating matter, giving a positive experience of harmonies in major. However, we also like the minor scale, which can explain brain patterns as fractal-like, giving a symmetric “downward reflection” of the major scale into the minor scale. We analyze the implication of beautiful and ugly tones and harmonies for the model. We conclude that when it comes to simple perception of harmonies, the most simple is the most beautiful and the most complex is the most ugly, but in music, even the most disharmonic harmony can be beautiful, if experienced as a part of a dynamic release of musical tension. This can be taken as a general metaphor of painful, yet meaningful, and developing experiences in human life.

  11. Asymmetric Iron-Catalyzed C-H Alkylation Enabled by Remote Ligand meta-Substitution.

    Science.gov (United States)

    Loup, Joachim; Zell, Daniel; Oliveira, João C A; Keil, Helena; Stalke, Dietmar; Ackermann, Lutz

    2017-11-06

    Highly enantioselective iron-catalyzed C-H alkylations by inner-sphere C-H activation were accomplished with ample scope. High levels of enantiocontrol proved viable through a novel ligand design that exploits a remote meta-substitution on N-heterocyclic carbenes within a facile ligand-to-ligand H-transfer C-H cleavage. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. Remote meta C-H bond functionalization of 2-phenethylsulphonic acid and 3-phenylpropanoic acid derivatives.

    Science.gov (United States)

    Modak, Atanu; Mondal, Anirban; Watile, Rahul; Mukherjee, Semanti; Maiti, Debabrata

    2016-11-24

    This discovery illustrates selective meta C-H bond activation from multiple non-equivalent C-H bonds present in medicinally relevant arylethanesulfonic acid and the 2-arylpropanoic acid moiety using weakly coordinating nitrile as a directing group. Transformation of the meta olefinated compounds to important organic molecules has been demonstrated. Efforts were made to obtain mechanistic detail of the meta C-H bond functionalization reaction.

  13. Selective Palladium(II)-Catalyzed Carbonylation of Methylene β-C-H Bonds in Aliphatic Amines.

    Science.gov (United States)

    Cabrera-Pardo, Jaime R; Trowbridge, Aaron; Nappi, Manuel; Ozaki, Kyohei; Gaunt, Matthew J

    2017-09-18

    Palladium(II)-catalyzed C-H carbonylation reactions of methylene C-H bonds in secondary aliphatic amines lead to the formation of trans-disubstituted β-lactams in excellent yields and selectivities. The generality of the C-H carbonylation process is aided by the action of xantphos-based ligands and is important in securing good yields for the β-lactam products. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Quantitative infrared and near-infrared gas-phase spectra for pyridine: Absolute intensities and vibrational assignments

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, T. J.; Aker, P. M.; Scharko, N. K.; Williams, S. D.

    2018-02-01

    Using vetted methods for generating quantitative absorption reference data, broadband infrared and near-infrared spectra (total range 11,000 – 600 cm-1) of pyridine vapor were recorded at 0.1 cm-1 spectral resolution, with the analyte thermostatted at 298 K and pressure-broadened to 1 atmosphere using N2 ballast gas. The quantitative spectrum is reported for the first time, and we have re-assigned some of the 27 fundamental modes. Fundamental assignments were confirmed by IR vapor phase band shapes, FT-Raman measurements and comparison with previous analyses. For the 760-Torr vapor-phase IR data several bands show resolved peaks (Q-branches). We have also assigned for the first time hundreds of combination and overtone bands in the mid- and near-IR. All assignments were made via comparison to theoretically calculated frequencies and intensities: The frequencies were computed with Gaussian03 with the anharmonic option, using MP2 and the ccpvtz basis set. The intensities were taken from a VSCF calculation in GAMESS using Hartree-Fock (for overtones and combination bands) or from the harmonic MP2 for fundamentals. Overtone and combination band harmonic and anharmonic frequencies, as well as intensities were also calculated using the CFOUR program. It is seen in the NIR spectrum near 6000 cm-1 that the very strong bands arise from the C-H first overtones, whereas only much weaker bands are observed for combination bands of C-H stretching modes. Certain features are discussed for their potential utility for atmospheric monitoring.

  15. Selective sp3 C-H alkylation via polarity-match-based cross-coupling

    Science.gov (United States)

    Le, Chip; Liang, Yufan; Evans, Ryan W.; Li, Ximing; MacMillan, David W. C.

    2017-07-01

    The functionalization of carbon-hydrogen (C-H) bonds is one of the most attractive strategies for molecular construction in organic chemistry. The hydrogen atom is considered to be an ideal coupling handle, owing to its relative abundance in organic molecules and its availability for functionalization at almost any stage in a synthetic sequence. Although many C-H functionalization reactions involve C(sp3)-C(sp2) coupling, there is a growing demand for C-H alkylation reactions, wherein sp3 C-H bonds are replaced with sp3 C-alkyl groups. Here we describe a polarity-match-based selective sp3 C-H alkylation via the combination of photoredox, nickel and hydrogen-atom transfer catalysis. This methodology simultaneously uses three catalytic cycles to achieve hydridic C-H bond abstraction (enabled by polarity matching), alkyl halide oxidative addition, and reductive elimination to enable alkyl-alkyl fragment coupling. The sp3 C-H alkylation is highly selective for the α-C-H of amines, ethers and sulphides, which are commonly found in pharmaceutically relevant architectures. This cross-coupling protocol should enable broad synthetic applications in de novo synthesis and late-stage functionalization chemistry.

  16. Enantioselective, intermolecular benzylic C-H amination catalysed by an engineered iron-haem enzyme

    Science.gov (United States)

    Prier, Christopher K.; Zhang, Ruijie K.; Buller, Andrew R.; Brinkmann-Chen, Sabine; Arnold, Frances H.

    2017-07-01

    C-H bonds are ubiquitous structural units of organic molecules. Although these bonds are generally considered to be chemically inert, the recent emergence of methods for C-H functionalization promises to transform the way synthetic chemistry is performed. The intermolecular amination of C-H bonds represents a particularly desirable and challenging transformation for which no efficient, highly selective, and renewable catalysts exist. Here we report the directed evolution of an iron-containing enzymatic catalyst—based on a cytochrome P450 monooxygenase—for the highly enantioselective intermolecular amination of benzylic C-H bonds. The biocatalyst is capable of up to 1,300 turnovers, exhibits excellent enantioselectivities, and provides access to valuable benzylic amines. Iron complexes are generally poor catalysts for C-H amination: in this catalyst, the enzyme's protein framework confers activity on an otherwise unreactive iron-haem cofactor.

  17. Surface-Controlled Mono/Diselective ortho C-H Bond Activation.

    Science.gov (United States)

    Li, Qing; Yang, Biao; Lin, Haiping; Aghdassi, Nabi; Miao, Kangjian; Zhang, Junjie; Zhang, Haiming; Li, Youyong; Duhm, Steffen; Fan, Jian; Chi, Lifeng

    2016-03-02

    One of the most charming and challenging topics in organic chemistry is the selective C-H bond activation. The difficulty arises not only from the relatively large bond-dissociation enthalpy, but also from the poor reaction selectivity. In this work, Au(111) and Ag(111) surfaces were used to address ortho C-H functionalization and ortho-ortho couplings of phenol derivatives. More importantly, the competition between dehydrogenation and deoxygenation drove the diversity of reaction pathways of phenols on surfaces, that is, diselective ortho C-H bond activation on Au(111) surfaces and monoselective ortho C-H bond activation on Ag(111) surfaces. The mechanism of this unprecedented phenomenon was extensively explored by scanning tunneling microscopy, density function theory, and X-ray photoelectron spectroscopy. Our findings provide new pathways for surface-assisted organic synthesis via the mono/diselective C-H bond activation.

  18. An investigation on structural, vibrational and nonlinear optical ...

    Indian Academy of Sciences (India)

    The electron rich regions residing on all the oxygen atoms O1, O1W, O2, O3, and O3W represent the electronegative regions and so, these are the binding sites for electrophilic attack. The values of HOMO, LUMO and Frontier orbital energy gap are given in table 2. 3.4 Vibrational Assignments. 3.4a C-H Vibration: Generally, ...

  19. Vibrating minds

    CERN Document Server

    2009-01-01

    Ed Witten is one of the leading scientists in the field of string theory, the theory that describes elementary particles as vibrating strings. This week he leaves CERN after having spent a few months here on sabbatical. His wish is that the LHC will unveil supersymmetry.

  20. Study of the hydrogen behavior in amorphous hydrogenated materials of type a - C:H and a - SiC:H facing fusion reactor plasma; Etude du comportament de l`hydrogene dans des materiaux amorphes hydrogenes de type a - C:H et a - SiC:H devant faire face au plasma des reacteurs a fusion

    Energy Technology Data Exchange (ETDEWEB)

    Barbier, G. [Lyon-1 Univ., 69 - Villeurbanne (France). Inst. de Physique Nucleaire

    1997-04-10

    Plasma facing components of controlled fusion test devices (tokamaks) are submitted to several constraints (irradiation, high temperatures). The erosion (physical sputtering and chemical erosion) and the hydrogen recycling (retention and desorption) of these materials influence many plasma parameters and thus affect drastically the tokamak running. First, we will describe the different plasma-material interactions. It will be pointed out, how erosion and hydrogen recycling are strongly related to both chemical and physical properties of the material. In order to reduce these interactions, we have selected two amorphous hydrogenated materials (a-C:H and a-SiC:H), which are known for their good thermal and chemical qualities. Some samples have been then implanted with lithium ions at different fluences. Our materials have been then irradiated with deuterium ions at low energy. From our results, it is shown that both the lithium implantation and the use of an a - SiC:H substrate can be beneficial in enhancing the hydrogen retention. These results were completed with thermal desorption studies of these materials. It was evidenced that the hydrogen fixation was more efficient in a-SiC:H than in a-C:H substrate. Results in good agreement with those described above have been obtained by exposing a - C:H and a - SiC:H samples to the scrape off layer of the tokamak of Varennes (TdeV, Canada). A modelling of hydrogen diffusion under irradiation has been also proposed. (author) 176 refs.

  1. Transition-Metal-Catalyzed Redox-Neutral and Redox-Green C-H Bond Functionalization.

    Science.gov (United States)

    Wang, Hongli; Huang, Hanmin

    2016-08-01

    Transition-metal-catalyzed C-H bond functionalization has become one of the most promising strategies to prepare complex molecules from simple precursors. However, the utilization of environmentally unfriendly oxidants in the oxidative C-H bond functionalization reactions reduces their potential applications in organic synthesis. This account describes our recent efforts in the development of a redox-neutral C-H bond functionalization strategy for direct addition of inert C-H bonds to unsaturated double bonds and a redox-green C-H bond functionalization strategy for realization of oxidative C-H functionalization with O2 as the sole oxidant, aiming to circumvent the problems posed by utilizing environmentally unfriendly oxidants. In principle, these redox-neutral and redox-green strategies pave the way for establishing new environmentally benign transition-metal-catalyzed C-H bond functionalization strategies. © 2016 The Chemical Society of Japan & Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Strong overtones modes in inelastic electron tunneling spectroscopy with cross-conjugated molecules: a prediction from theory.

    Science.gov (United States)

    Lykkebo, Jacob; Gagliardi, Alessio; Pecchia, Alessandro; Solomon, Gemma C

    2013-10-22

    Cross-conjugated molecules are known to exhibit destructive quantum interference, a property that has recently received considerable attention in single-molecule electronics. Destructive quantum interference can be understood as an antiresonance in the elastic transmission near the Fermi energy and leading to suppressed levels of elastic current. In most theoretical studies, only the elastic contributions to the current are taken into account. In this paper, we study the inelastic contributions to the current in cross-conjugated molecules and find that while the inelastic contribution to the current is larger than for molecules without interference, the overall behavior of the molecule is still dominated by the quantum interference feature. Second, an ongoing challenge for single molecule electronics is understanding and controlling the local geometry at the molecule-surface interface. With this in mind, we investigate a spectroscopic method capable of providing insight into these junctions for cross-conjugated molecules: inelastic electron tunneling spectroscopy (IETS). IETS has the advantage that the molecule interface is probed directly by the tunneling current. Previously, it has been thought that overtones are not observable in IETS. Here, overtones are predicted to be strong and, in some cases, the dominant spectroscopic features. We study the origin of the overtones and find that the interference features in these molecules are the key ingredient. The interference feature is a property of the transmission channels of the π system only, and consequently, in the vicinity of the interference feature, the transmission channels of the σ system and the π system become equally transmissive. This allows for scattering between the different transmission channels, which serves as a pathway to bypass the interference feature. A simple model calculation is able to reproduce the results obtained from atomistic calculations, and we use this to interpret these findings.

  3. Elemental (C, H, N) composition of zooplankton from north Arabian Sea

    Digital Repository Service at National Institute of Oceanography (India)

    Matondkar, S.G.P.; Bhat, K.L.; Ansari, Z.A.; Parulekar, A.H.

    Zooplankton samples collected from north Arabian Sea during March 1992 were analysed for elemental (C,H,N) composition. Estimated carbon, hydrogen and nitrogen concentrations displayed variations among different groups but their ratios were nearly...

  4. Synthesis of Dihydropyridines and Pyridines from Imines and Alkynes via C-H Activation

    Energy Technology Data Exchange (ETDEWEB)

    Ellman, Jonathan A.; Colby, Denise; Bergman, Robert

    2007-11-20

    A convenient one-pot C-H alkenylation/electrocyclization/aromatization sequence has been developed for the synthesis of highly substituted pyridine derivatives from alkynes and {alpha},{beta}-unsaturated N-benzyl aldimines and ketimines that proceeds through dihydropyridine intermediates. A new class of ligands for C-H activation was developed, providing broader scope for the alkenylation step than could be achieved with previously reported ligands. Substantial information was obtained about the mechanism of the reaction. This included the isolation of a C-H activated complex and its structure determination by X-ray analysis; in addition, kinetic simulations using the Copasi software were employed to determine rate constants for this transformation, implicating facile C-H oxidative addition and slow reductive elimination steps.

  5. Pd-Catalyzed C-H Bond Functionalization on the Indole and Pyrrole Nucleus

    Science.gov (United States)

    Beck, Elizabeth M.; Gaunt, Matthew J.

    This review details recent developments in the Pd-catalyzed C-H bond arylation and alkenylation of indoles and pyrroles, aromatic heterocycles that are frequently displayed in natural products and medicinal agents.

  6. Toward Ab Initio Anharmonic Vibrational Circular Dichroism Spectra in the Condensed Phase.

    Science.gov (United States)

    Cappelli, Chiara; Bloino, Julien; Lipparini, Filippo; Barone, Vincenzo

    2012-07-05

    The first implementation and calculation of anharmonic VCD rotational strengths for solvated systems is reported. Our approach, rooted in the polarizable continuum model (PCM) and in the second-order vibrational perturbation theory (VPT2), permits not only correction for anharmonicity in the signals associated with fundamental transitions but also calculation of rotational strengths of overtones and combination bands. This allows for a more physically consistent comparison between experiment and calculations together with the analysis of spectral regions dominated by anharmonic effects. The developed model is applied to a few test cases, and the computational outcomes are directly compared with experimental data.

  7. H/sub 3/ /sup +/: Ab initio calculation of the vibration spectrum

    Energy Technology Data Exchange (ETDEWEB)

    Carney, G.D.; Porter, R.N.

    1976-11-01

    The vibration spectrum of H/sub 3/ /sup +/ is calculated from the representation of a previously reported (J. Chem Phys. 60, 4251 (1974)) ab initio potential-energy surface in a fifth degree Simons--Parr--Finlan (SPF) expansion. Morse- and harmonic-oscillator basis functions are used to describe the motions of the three oscillators and the Harris--Engerholm--Gwinn quadrature technique is used to obtain matrix elements of the Hamiltonian in the basis of vibrational configurations. Our variational method is thus analogous to configuration--interaction calculations for electronic states. The ground state is found to have a zero-point energy of 4345 cm/sup -1/ and a vibrationally averaged geometry of R/sub 1/=R/sub 2/=0.91396 A, theta=60.0012degree, where theta is the angle between the two equivalent bonds. The transition frequencies for the E and A/sub 1/ fundamentals are nu-bar/sub E/=2516 cm/sup -1/ and nu-bar/sub A/=3185 cm/sup -1/ and those for the corresponding first overtones of the bending mode are 2nu-bar/sub E/=5004 +- 4 cm/sup -1/ and 2nu-bar/sub A/=4799 cm/sup -1/. The first overtone of the breathing mode is 6264 cm/sup -1/. The first-excited A/sub 1/ vibration state is metastable with a dipole--radiation lifetime of 3 sec. Transition frequencies, Einstein coefficients, and lifetimes are reported for a total of 21 transitions. Analysis of results for Dunham number and normal-coordinate expansions in comparison with those for SPF expansion show the latter to be superior for ab initio vibrational calculations. A scheme for possible direct measurement of the fundamental A/sub 1/ and E vibrational bands is suggested. (AIP)

  8. A catalytic, Brønsted base strategy for intermolecular allylic C-H amination.

    Science.gov (United States)

    Reed, Sean A; Mazzotti, Anthony R; White, M Christina

    2009-08-26

    A Brønsted base activation mode for oxidative, Pd(II)/sulfoxide-catalyzed, intermolecular C-H allylic amination is reported. N,N-diisopropylethylamine was found to promote amination of unactivated terminal olefins, forming the corresponding linear allylic amine products with high levels of stereo-, regio-, and chemoselectivity. The predictable and high selectivity of this C-H oxidation method enables late-stage incorporation of nitrogen into advanced synthetic intermediates and natural products.

  9. Palladium-catalysed C-H activation of aliphatic amines to give strained nitrogen heterocycles

    Science.gov (United States)

    McNally, Andrew; Haffemayer, Benjamin; Collins, Beatrice S. L.; Gaunt, Matthew J.

    2014-06-01

    The development of new chemical transformations based on catalytic functionalization of unactivated C-H bonds has the potential to simplify the synthesis of complex molecules dramatically. Transition metal catalysis has emerged as a powerful tool with which to convert these unreactive bonds into carbon-carbon and carbon-heteroatom bonds, but the selective transformation of aliphatic C-H bonds is still a challenge. The most successful approaches involve a `directing group', which positions the metal catalyst near a particular C-H bond, so that the C-H functionalization step occurs via cyclometallation. Most directed aliphatic C-H activation processes proceed through a five-membered-ring cyclometallated intermediate. Considering the number of new reactions that have arisen from such intermediates, it seems likely that identification of distinct cyclometallation pathways would lead to the development of other useful chemical transformations. Here we report a palladium-catalysed C-H bond activation mode that proceeds through a four-membered-ring cyclopalladation pathway. The chemistry described here leads to the selective transformation of a methyl group that is adjacent to an unprotected secondary amine into a synthetically versatile nitrogen heterocycle. The scope of this previously unknown bond disconnection is highlighted through the development of C-H amination and carbonylation processes, leading to the synthesis of aziridines and β-lactams (respectively), and is suggestive of a generic C-H functionalization platform that could simplify the synthesis of aliphatic secondary amines, a class of small molecules that are particularly important features of many pharmaceutical agents.

  10. Structure and Friction Behavior of CrNx/a-C:H Nanocomposite Films

    Directory of Open Access Journals (Sweden)

    Lunlin Shang

    2014-01-01

    Full Text Available CrN and CrNx/a-C:H nanocomposite films were deposited on Si substrates by the magnetron sputtering technique. The structure, chemical state, and friction behavior of the CrNx/a-C:H films prepared at various CH4 content were studied systematically. The CrN film shows strong (111 and (220 orientation, while the CrNx/a-C:H films consist of the nanocrystalline CrNx or Cr particles embedded in an amorphous hydrocarbon (a-C:H matrix and show weak diffraction peaks, which is in accordance with the XPS analysis results. The typical Raman D and G peaks are observed, indicating that the separated amorphous carbon or CNx phase appears in the CrNx/a-C:H films. However, no chromium carbide was observed in all the as-deposited samples. From the SEM graphs, all the deposited films depicted a dense and compact microstructure with well-attached interface with the substrate. The average friction coefficient of the CrNx/a-C:H films largely decreased with increasing CH4 content.

  11. Evolution of C-H Bond Functionalization from Methane to Methodology.

    Science.gov (United States)

    Hartwig, John F

    2016-01-13

    This Perspective presents the fundamental principles, the elementary reactions, the initial catalytic systems, and the contemporary catalysts that have converted C-H bond functionalization from a curiosity to a reality for synthetic chemists. Many classes of elementary reactions involving transition-metal complexes cleave C-H bonds at typically unreactive positions. These reactions, coupled with a separate or simultaneous functionalization process lead to products containing new C-C, C-N, and C-O bonds. Such reactions were initially studied for the conversion of light alkanes to liquid products, but they have been used (and commercialized in some cases) most often for the synthesis of the more complex structures of natural products, medicinally active compounds, and aromatic materials. Such a change in direction of research in C-H bond functionalization is remarkable because the reactions must occur at an unactivated C-H bond over functional groups that are more reactive than the C-H bond toward classical reagents. The scope of reactions that form C-C bonds or install functionality at an unactivated C-H bond will be presented, and the potential future utility of these reactions will be discussed.

  12. Overtone-based pitch selection in hermit thrush song: unexpected convergence with scale construction in human music.

    Science.gov (United States)

    Doolittle, Emily L; Gingras, Bruno; Endres, Dominik M; Fitch, W Tecumseh

    2014-11-18

    Many human musical scales, including the diatonic major scale prevalent in Western music, are built partially or entirely from intervals (ratios between adjacent frequencies) corresponding to small-integer proportions drawn from the harmonic series. Scientists have long debated the extent to which principles of scale generation in human music are biologically or culturally determined. Data from animal "song" may provide new insights into this discussion. Here, by examining pitch relationships using both a simple linear regression model and a Bayesian generative model, we show that most songs of the hermit thrush (Catharus guttatus) favor simple frequency ratios derived from the harmonic (or overtone) series. Furthermore, we show that this frequency selection results not from physical constraints governing peripheral production mechanisms but from active selection at a central level. These data provide the most rigorous empirical evidence to date of a bird song that makes use of the same mathematical principles that underlie Western and many non-Western musical scales, demonstrating surprising convergence between human and animal "song cultures." Although there is no evidence that the songs of most bird species follow the overtone series, our findings add to a small but growing body of research showing that a preference for small-integer frequency ratios is not unique to humans. These findings thus have important implications for current debates about the origins of human musical systems and may call for a reevaluation of existing theories of musical consonance based on specific human vocal characteristics.

  13. Urban vibrations

    DEFF Research Database (Denmark)

    Morrison, Ann; Knudsen, L.; Andersen, Hans Jørgen

    2012-01-01

      lab   studies   in   that   we   found   a   decreased   detection   rate   in   busy   environments.   Here   we   test   with   a   much   larger   sample   and   age   range,   and   contribute   with   the   first   vibration  sensitivity  testing  outside  the  lab  in  an  urban   public...

  14. Axial Ligand Coordination to the C-H Amination Catalyst Rh2(esp)2: A Structural and Spectroscopic Study.

    Science.gov (United States)

    Warzecha, Evan; Berto, Timothy C; Berry, John F

    2015-09-08

    The compound Rh2(esp)2 (esp = α,α,α',α'-tetramethyl-1,3-benzenediproponoate) is the most generally effective catalyst for nitrenoid amination of C-H bonds. However, much of its fundamental coordination chemistry is unknown. In this work, we study the effects of axial ligand coordination to the catalyst Rh2(esp)2. We report here crystal structures, cyclic voltammetry, UV-vis, IR, Raman, and (1)H NMR spectra for the complexes Rh2(esp)2L2 where L = pyridine, 3-picoline, 2,6-lutidine, acetonitrile, and methanol. The compounds all show well-defined π* → σ* electronic transitions in the 16500 to 20500 cm(-1) range, and Rh-Rh stretching vibrations in the range from 304 to 322 cm(-1). Taking these data into account we find that the strength of axial ligand binding to Rh2(esp)2 increases in the series CH3OH ∼ 2,6-lutidine < CH3CN < 3-methylpyridine ∼ pyridine. Quasi-reversible Rh2(4+/5+) redox waves are only obtained when either acetonitrile or no axial ligand is present. In the presence of pyridines, irreversible oxidation waves are observed, suggesting that these ligands destabilize the Rh2 complex under oxidative conditions.

  15. Polyvinylpyrrolidone surface modification with SiOx containing amorphous hydrogenated carbon (a-C:H/SiOx) and nitrogen-doped a-C:H/SiOx films using Hall-type closed drift ion beam source

    NARCIS (Netherlands)

    Lazauskas, A.; Grigaliunas, V.; Guobiene, A.; Puiso, J.; Prosycevas, I.; Baltrusaitis, Jonas

    2013-01-01

    In this study SiOx containing amorphous hydrogenated carbon (a-C:H/SiOx) and nitrogen-doped a-C:H/SiOx (a-C:H:N/SiOx) films were deposited on polyvinylpyrrolidone (PVP) templates of variable thickness using a Hall-type closed drift ion beam source with constant irradiation parameters. A detailed

  16. Isotopic Effects on Stereodynamics of the C+ + H2 → CH+ + H Reaction

    Science.gov (United States)

    Guo, Lu; Yang, Yun-Fan; Fan, Xiao-Xing; Ma, Feng-Cai; Li, Yong-Qing

    2017-05-01

    The effects of isotope substitution on stereodynamic properties for the reactions {C}++{H}2/{H D}/{H T}\\to {{C H}}++H/D/T have been studied applying a quasi classical trajectory method occurring on the new ground state {{C H}}2+ potential energy surface [J. Chem. Phys. 142 (2015) 124302]. In the center of mass coordinates applying the quasi classical trajectory method to investigate the orientation and the alignment of the product molecule. Differential cross section and three angle distribution functions P(θr), P(ϕr), P( {θ }r,{φ }r ) on the potential energy surface that fixed the collision energy with a value is 40 kcal/mol have been studied. The isotope effect becomes more and more important with the reagent molecules H 2 changing into HD and HT. P({θ }r,{φ }r) as the joint probability density function of both polar angles θ r and ϕ r , which can illustrate more detailed dynamics information. The isotope effect is obvious influence on the properties of stereodynamics in the reactions of {C}++{H}2/{H D}/{H T}\\to {{C H}}++H/D/T. Supported by the National Natural Science Foundation of China under Grant Nos. 11474141, 11274149, 11544015, the Program for Liaoning Excellent Talents in University under Grant No. LJQ2015040, and the Scientific Research Foundation for the Returned Overseas Chinese Scholars, State Education Ministry (2014-1685)

  17. Aromatic C-H addition of ketones to imines enabled by manganese catalysis.

    Science.gov (United States)

    Zhou, Bingwei; Hu, Yuanyuan; Liu, Ting; Wang, Congyang

    2017-10-27

    Selectivity control of varied C-H bonds in a complex molecule is a long-standing goal and still a great challenge in C-H activation field. Most often, such selectivity is achieved by the innate reactivity of different C-H bonds. In this context, the classic Mannich reaction of acetophenone derivatives and imines is ascribed to the more reactive C(sp(3))-H bonds α to the carbonyl, with the much less reactive aromatic C(sp(2))-H bonds remaining intact. Herein we report an aromatic C(sp(2))-H addition of ketones to imines enabled by manganese catalysis, which totally reverses the innate reactivity of C-H bonds α to the carbonyl and those on the aromatic ring. Diverse products of ortho-C-H aminoalkylated ketones, cyclized exo-olefinic isoindolines, and three-component methylated isoindolines can be successfully accessed under mild reaction conditions, which significantly expands the synthetic utilities of ketones as simple bulk chemicals.

  18. meta-C-H Bromination on Purine Bases by Heterogeneous Ruthenium Catalysis.

    Science.gov (United States)

    Warratz, Svenja; Burns, David J; Zhu, Cuiju; Korvorapun, Korkit; Rogge, Torben; Scholz, Julius; Jooss, Christian; Gelman, Dmitri; Ackermann, Lutz

    2017-02-01

    Methods for positionally selective remote C-H functionalizations are in high demand. Herein, we disclose the first heterogeneous ruthenium catalyst for meta-selective C-H functionalizations, which enabled remote halogenations with excellent site selectivity and ample scope. The versatile heterogeneous Ru@SiO 2 catalyst was broadly applicable and could be easily recovered and reused, which set the stage for the direct fluorescent labeling of purines. In contrast to palladium, rhodium, iridium, or cobalt complexes, solely the ruthenium catalysis manifold provided access to meta-halogenated purine derivatives, illustrating the unique power of ruthenium C-H activation catalysis. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Diverse sp3 C-H functionalization through alcohol β-sulfonyloxylation

    Science.gov (United States)

    Xu, Yan; Yan, Guobing; Ren, Zhi; Dong, Guangbin

    2015-10-01

    Site-selective C-H functionalization has emerged as an attractive tool for derivatizing complex synthetic intermediates, but its use for late-stage diversification is limited by the functional groups that can be introduced, especially at unactivated sp3-hybridized positions. To overcome this, we introduce a strategy that directly installs a sulfonyloxy group at a β-C-H bond of a masked alcohol and subsequently employs nucleophilic substitution reactions to prepare various derivatives. Hydroxyl groups are widely found in bioactive molecules and are thus readily available as synthetic handles. A directing group is easily added (and subsequently removed) from the alcohols such that a formal site-selective β-C-H sulfonyloxylation of these alcohols is achieved. Substitution reactions with carbon, nitrogen, oxygen and other nucleophiles then lead to diverse functionalizations that may help to streamline the synthesis of complex analogues for drug discovery.

  20. Diverse sp(3) C-H functionalization through alcohol β-sulfonyloxylation.

    Science.gov (United States)

    Xu, Yan; Yan, Guobing; Ren, Zhi; Dong, Guangbin

    2015-10-01

    Site-selective C-H functionalization has emerged as an attractive tool for derivatizing complex synthetic intermediates, but its use for late-stage diversification is limited by the functional groups that can be introduced, especially at unactivated sp(3)-hybridized positions. To overcome this, we introduce a strategy that directly installs a sulfonyloxy group at a β-C-H bond of a masked alcohol and subsequently employs nucleophilic substitution reactions to prepare various derivatives. Hydroxyl groups are widely found in bioactive molecules and are thus readily available as synthetic handles. A directing group is easily added (and subsequently removed) from the alcohols such that a formal site-selective β-C-H sulfonyloxylation of these alcohols is achieved. Substitution reactions with carbon, nitrogen, oxygen and other nucleophiles then lead to diverse functionalizations that may help to streamline the synthesis of complex analogues for drug discovery.

  1. Analyzing site selectivity in Rh2(esp)2-catalyzed intermolecular C-H amination reactions.

    Science.gov (United States)

    Bess, Elizabeth N; DeLuca, Ryan J; Tindall, Daniel J; Oderinde, Martins S; Roizen, Jennifer L; Du Bois, J; Sigman, Matthew S

    2014-04-16

    Predicting site selectivity in C-H bond oxidation reactions involving heteroatom transfer is challenged by the small energetic differences between disparate bond types and the subtle interplay of steric and electronic effects that influence reactivity. Herein, the factors governing selective Rh2(esp)2-catalyzed C-H amination of isoamylbenzene derivatives are investigated, where modification to both the nitrogen source, a sulfamate ester, and substrate are shown to impact isomeric product ratios. Linear regression mathematical modeling is used to define a relationship that equates both IR stretching parameters and Hammett σ(+) values to the differential free energy of benzylic versus tertiary C-H amination. This model has informed the development of a novel sulfamate ester, which affords the highest benzylic-to-tertiary site selectivity (9.5:1) observed for this system.

  2. Dielectric relaxation in hard, plasma-polymerized C:H films

    Science.gov (United States)

    Stundzia, V.; Biederman, H.; Slavínská, D.; Nedbal, J.; Hlídek, P.; Poskus, A.; Mackus, P. K.; Howson, R. P.

    2000-03-01

    The dielectric relaxation in hard, plasma-polymerized C:H films has been studied using the depolarization current method. These films were prepared by means of a dc unbalanced magnetron operated in a working gas mixture of Ar with n-hexane. The C:H films were sandwiched between two thin, aluminium-film electrodes. The measurements took place without breaking vacuum at temperatures ranging from 22 °C to 140 °C. The analysis of the respective depolarization currents was performed by means of the Kohlrausch-Williams-Watts depolarization function. Two dielectric relaxation processes were observed. The first is associated with high-dipole polar groups such as hydroxyl and carbonyl groups. The second relaxation process is observed only at the highest temperatures and cannot be explained in terms of permanent dipole reorientation. This finding shows that the C:H films are hard, highly crosslinked hydrocarbon plasma polymers.

  3. Facile P-C/C-H Bond-Cleavage Reactivity of Nickel Bis(diphosphine) Complexes.

    Science.gov (United States)

    Zhang, Shaoguang; Li, Haixia; Appel, Aaron M; Hall, Michael B; Bullock, R Morris

    2016-07-04

    Unusual cleavage of P-C and C-H bonds of the P2 N2 ligand, in heteroleptic [Ni(P2 N2 )(diphosphine)](2+) complexes under mild conditions, results in the formation of an iminium formyl nickelate featuring a C,P,P-tridentate coordination mode. The structures of both the heteroleptic [Ni(P2 N2 )(diphosphine)](2+) complexes and the resulting iminium formyl nickelate have been characterized by NMR spectroscopy and single-crystal X-ray diffraction analysis. Density functional theory (DFT) calculations were employed to investigate the mechanism of the P-C/C-H bond cleavage, which involves C-H bond cleavage, hydride rotation, Ni-C/P-H bond formation, and P-C bond cleavage. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. A steric tethering approach enables palladium-catalysed C-H activation of primary amino alcohols

    Science.gov (United States)

    Calleja, Jonas; Pla, Daniel; Gorman, Timothy W.; Domingo, Victoriano; Haffemayer, Benjamin; Gaunt, Matthew J.

    2015-12-01

    Aliphatic primary amines are a class of chemical feedstock essential to the synthesis of higher-order nitrogen-containing molecules, commonly found in biologically active compounds and pharmaceutical agents. New methods for the construction of complex amines remain a continuous challenge to synthetic chemists. Here, we outline a general palladium-catalysed strategy for the functionalization of aliphatic C-H bonds within amino alcohols, an important class of small molecule. Central to this strategy is the temporary conversion of catalytically incompatible primary amino alcohols into hindered secondary amines that are capable of undergoing a sterically promoted palladium-catalysed C-H activation. Furthermore, a hydrogen bond between amine and catalyst intensifies interactions around the palladium and orients the aliphatic amine substituents in an ideal geometry for C-H activation. This catalytic method directly transforms simple, easily accessible amines into highly substituted, functionally concentrated and structurally diverse products, and can streamline the synthesis of biologically important amine-containing molecules.

  5. 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}.

  6. Theory of vibration protection

    CERN Document Server

    Karnovsky, Igor A

    2016-01-01

    This text is an advancement of the theory of vibration protection of mechanical systems with lumped and distributed parameters. The book offers various concepts and methods of solving vibration protection problems, discusses the advantages and disadvantages of different methods, and the fields of their effective applications. Fundamental approaches of vibration protection, which are considered in this book, are the passive, parametric and optimal active vibration protection. The passive vibration protection is based on vibration isolation, vibration damping and dynamic absorbers. Parametric vibration protection theory is based on the Shchipanov-Luzin invariance principle. Optimal active vibration protection theory is based on the Pontryagin principle and the Krein moment method. The book also contains special topics such as suppression of vibrations at the source of their occurrence and the harmful influence of vibrations on humans. Numerous examples, which illustrate the theoretical ideas of each chapter, ar...

  7. Recent Advances in the C-H-Functionalization of the Distal Positions in Pyridines and Quinolines.

    Science.gov (United States)

    Stephens, David E; Larionov, Oleg V

    2015-11-18

    This review summarizes recent developments in the C-H-functionalization of the distal positions of pyridines, quinolines and related azaheterocycles. While the functionalization of the C2 position has been known for a long time and is facilitated by the proximity to N1, regioselective reactions in the distal positions are more difficult to achieve and have only emerged in the last decade. Recent advances in the transition metal-catalyzed distal C-H-functionalization of these synthetically-important azaheterocycles are discussed in detail, with the focus on the scope, site-selectivity and mechanistic aspects of the reactions.

  8. Room-temperature photoinduced direct C-H-arylation via base-promoted homolytic aromatic substitution.

    Science.gov (United States)

    Budén, María E; Guastavino, Javier F; Rossi, Roberto A

    2013-03-15

    Conceptually different approach toward biaryl syntheses by photoinduced direct C-H arylation of benzene and thiophene in the presence of t-BuOK is reported. The reaction proceeds through photo- and base-promoted homolytic aromatic substitution. The o-, m- and p- substituted ArI, as well as the electron-donating and electron-withdrawing nature of the substituents were found be good to excellent substrates. Heteroaryl, ArBr, ArCl and double C-H arylation were successfully achieved.

  9. Synthesis of a Benzodiazepine-derived Rhodium NHC Complex by C-H Bond Activation

    Energy Technology Data Exchange (ETDEWEB)

    Bergman, Roberg G.; Gribble, Jr., Michael W.; Ellman, Jonathan A.

    2008-01-30

    The synthesis and characterization of a Rh(I)-NHC complex generated by C-H activation of 1,4-benzodiazepine heterocycle are reported. This complex constitutes a rare example of a carbene tautomer of a 1,4-benzodiazepine aldimine stabilized by transition metal coordination and demonstrates the ability of the catalytically relevant RhCl(PCy{sub 3}){sub 2} fragment to induce NHC-forming tautomerization of heterocycles possessing a single carbene-stabilizing heteroatom. Implications for the synthesis of benzodiazepines and related pharmacophores via C-H functionalization are discussed.

  10. Selective sp3 C-H Aerobic Oxidation enabled by Deca-tungstate Photocatalysis in Flow.

    Science.gov (United States)

    Laudadio, Gabriele; Govaerts, Sebastian; Wang, Ying; Ravelli, Davide; Koolman, Hannes; Fagnoni, Maurizio; Djuric, Stevan; Noel, Timothy

    2018-02-16

    A mild and selective sp3 C-H aerobic oxidation enabled by deca-tungstate photocatalysis has been developed. The reaction can be significantly improved in a microflow reactor enabling the safe use of oxygen and the enhanced irradiation of the reaction mixture. Our method allows for the oxidation of both activated and unactivated C-H bonds (30 examples). The ability to selectively oxidize natural scaffolds, such as (-)-ambroxide, pregnenolone acetate, (+)-sclareolide and artemisinin exemplifies the utility of this new method. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Electrochemical C-H amination: synthesis of aromatic primary amines via N-arylpyridinium ions.

    Science.gov (United States)

    Morofuji, Tatsuya; Shimizu, Akihiro; Yoshida, Jun-ichi

    2013-04-03

    We have developed a new method for C-H amination of aromatic compounds based on electrochemical oxidation of aromatic compounds in the presence of pyridine followed by the reaction of the resulting N-arylpyridinium ions with an alkylamine. This new transformation serves as a powerful method for synthesizing aromatic primary amines from aromatic compounds without using metal catalysts and harsh chemical reagents. High chemoselectivity of the present method is demonstrated by C-H amination of aromatic compounds bearing a nitro group to give a key intermediate for the synthesis of VLA-4 antagonist.

  12. Difluoroacetic Acid as a New Reagent for Direct C-H Difluoromethylation of Heteroaromatic Compounds

    DEFF Research Database (Denmark)

    Thanh Tung, Truong; Christensen, Søren Brøgger; Nielsen, John

    2017-01-01

    A technically simple procedure for direct C-H difluoromethylation of heteroaromatic compounds using off-the-shelf difluoroacetic acid as the difluoromethylating reagent has been developed. Mono-difluoromethylation versus bis-difluoromethylation is controlled as the result of the reaction temperat......A technically simple procedure for direct C-H difluoromethylation of heteroaromatic compounds using off-the-shelf difluoroacetic acid as the difluoromethylating reagent has been developed. Mono-difluoromethylation versus bis-difluoromethylation is controlled as the result of the reaction...

  13. Cavity ring-down spectroscopy of CO2 overtone bands near 830 nm

    Science.gov (United States)

    Tan, Y.; Zhao, X.-Q.; Liu, A.-W.; Hu, S.-M.; Lyulin, O. M.; Tashkun, S. A.; Perevalov, V. I.

    2015-11-01

    Three bands 4003i-00001 (i=2, 3, 4) of the Fermi pentad of 12C16O2 near 830 nm have been recorded with a continuous-wave cavity ring down spectrometer. A sensitivity at the 5×10-11 cm-1 level allowed us to obtain line positions and intensities of these very weak bands. The measured line intensities of these three bands together with those published for the 10051-00001 and 10052-00001 bands were used to obtain the effective dipole moment parameters of 12C16O2 for the ΔP=17 series of transitions, where P=2V1+V2+3V3 is a polyad number (Vi (i=1, 2, 3) are vibrational quantum numbers). Comparisons of the measured line positions and intensities of the 4003i-00001 (i=2, 3, 4) bands to those from the AMES and GEISA line lists are given.

  14. Fourth-Order Vibrational Transition State Theory and Chemical Kinetics

    Science.gov (United States)

    Stanton, John F.; Matthews, Devin A.; Gong, Justin Z.

    2015-06-01

    Second-order vibrational perturbation theory (VPT2) is an enormously successful and well-established theory for treating anharmonic effects on the vibrational levels of semi-rigid molecules. Partially as a consequence of the fact that the theory is exact for the Morse potential (which provides an appropriate qualitative model for stretching anharmonicity), VPT2 calculations for such systems with appropriate ab initio potential functions tend to give fundamental and overtone levels that fall within a handful of wavenumbers of experimentally measured positions. As a consequence, the next non-vanishing level of perturbation theory -- VPT4 -- offers only slight improvements over VPT2 and is not practical for most calculations since it requires information about force constants up through sextic. However, VPT4 (as well as VPT2) can be used for other applications such as the next vibrational correction to rotational constants (the ``gammas'') and other spectroscopic parameters. In addition, the marriage of VPT with the semi-classical transition state theory of Miller (SCTST) has recently proven to be a powerful and accurate treatment for chemical kinetics. In this talk, VPT4-based SCTST tunneling probabilities and cumulative reaction probabilities are give for the first time for selected low-dimensional model systems. The prospects for VPT4, both practical and intrinsic, will also be discussed.

  15. Efficient Vibrational Energy Transfer through Covalent Bond in Indigo Carmine Revealed by Nonlinear IR Spectroscopy.

    Science.gov (United States)

    He, Xuemei; Yu, Pengyun; Zhao, Juan; Wang, Jianping

    2017-10-12

    Ultrafast vibrational relaxation and structural dynamics of indigo carmine in dimethyl sulfoxide were examined using femtosecond pump-probe infrared and two-dimensional infrared (2D IR) spectroscopies. Using the intramolecularly hydrogen-bonded C═O and delocalized C═C stretching modes as infrared probes, local structural and dynamical variations of this blue dye molecule were observed. Energy relaxation of the vibrationally excited C═O stretching mode was found to occur through covalent bond to the delocalized aromatic vibrational modes on the time scale of a few picoseconds or less. Vibrational quantum beating was observed in magic-angle pump-probe, anisotropy, and 2D IR cross-peak dynamics, showing an oscillation period of ca. 1010 fs, which corresponds to the energy difference between the C═O and C═C transition frequency (33 cm-1). This confirms a resonant vibrational energy transfer happened between the two vibrators. However, a more efficient energy-accepting mode of the excited C═O stretching was believed to be a nearby combination and/or overtone mode that is more tightly connected to the C═O species. On the structural aspect, dynamical-time-dependent 2D IR spectra reveal an insignificant inhomogeneous contribution to time-correlation relaxation for both the C═O and C═C stretching modes, which is in agreement with the generally believed structural rigidity of such conjugated molecules.

  16. Relating normal vibrational modes to local vibrational modes: benzene and naphthalene.

    Science.gov (United States)

    Zou, Wenli; Kalescky, Robert; Kraka, Elfi; Cremer, Dieter

    2013-07-01

    Local vibrational modes can be directly derived from normal vibrational modes using the method of Konkoli and Cremer (Int J Quant Chem 67:29, 1998). This implies the calculation of the harmonic force constant matrix F (q) (expressed in internal coordinates q) from the corresponding Cartesian force constant matrix f (x) with the help of the transformation matrix U = WB (†)(BWB (†))(-1) (B: Wilson's B-matrix). It is proven that the local vibrational modes are independent of the choice of the matrix W. However, the choice W = M (-1) (M: mass matrix) has numerical advantages with regard to the choice W = I (I: identity matrix), where the latter is frequently used in spectroscopy. The local vibrational modes can be related to the normal vibrational modes in the form of an adiabatic connection scheme (ACS) after rewriting the Wilson equation with the help of the compliance matrix. The ACSs of benzene and naphthalene based on experimental vibrational frequencies are discussed as nontrivial examples. It is demonstrated that the local-mode stretching force constants provide a quantitative measure for the C-H and C-C bond strength.

  17. High growth rate of a-SiC: H films using ethane carbon source by ...

    Indian Academy of Sciences (India)

    Home; Journals; Bulletin of Materials Science; Volume 36; Issue 7. High growth rate of a-SiC:H films using ethane carbon source by HW-CVD method. Mahesh M Kamble Vaishali S Waman Sanjay S Ghosh Azam Mayabadi Vasant G Sathe T Shripathi Habib M Pathan Sandesh R Jadkar. Volume 36 Issue 7 December 2013 ...

  18. Penicillin resistant gonococci at Q.E.C.H. | Ward | Malawi Medical ...

    African Journals Online (AJOL)

    Penicillin resistant gonococci at Q.E.C.H.. JC Ward, JS Cheesebrough. Abstract. No Abstract. Full Text: EMAIL FREE FULL TEXT EMAIL FREE FULL TEXT · DOWNLOAD FULL TEXT DOWNLOAD FULL TEXT · AJOL African Journals Online. HOW TO USE AJOL... for Researchers · for Librarians · for Authors · FAQ's · More ...

  19. Type-studies in the Polyporaceae—I. Tropical species described by C. H. Persoon

    NARCIS (Netherlands)

    Ryvarden, Leif

    1973-01-01

    The type specimens of 20 tropical polypores described by C. H. Persoon have been examined. Eleven species are accepted, seven are reduced to synonymy, while one name is a nomen nudum. One type is so poorly developed that no conclusive determination is possible. The combination Trametes marianna

  20. Time resolved infrared studies of C-H bond activation by organometallics

    Energy Technology Data Exchange (ETDEWEB)

    Asplund, M.C. [Univ. of California, Berkeley, CA (United States). Dept. of Chemistry]|[Lawrence Berkeley National Lab., CA (United States). Chemical Sciences Div.

    1998-06-01

    This work describes how step-scan Fourier Transform Infrared spectroscopy and visible and near infrared ultrafast lasers have been applied to the study of the photochemical activation of C-H bonds in organometallic systems, which allow for the selective breaking of C-H bonds in alkanes. The author has established the photochemical mechanism of C-H activation by Tp{sup *}Rh(CO){sub 2}(Tp{sup *} = HB-Pz{sup *}{sub 3}, Pz = 3,5-dimethylpyrazolyl) in alkane solution. The initially formed monocarbonyl forms a weak solvent complex, which undergoes a change in Tp{sup *} ligand connectivity. The final C-H bond breaking step occurs at different time scales depending on the structure of the alkane. In linear solvents, the time scale is <50 ns and cyclic alkanes is {approximately}200 ps. The reactivity of the Tp{sup *}Rh(CO){sub 2} system has also been studied in aromatic solvents. Here the reaction proceeds through two different pathways, with very different time scales. The first proceeds in a manner analogous to alkanes and takes <50 ns. The second proceeds through a Rh-C-C complex, and takes place on a time scale of 1.8 {micro}s.

  1. Carboxylic Acids as Directing Groups for C-H Bond Functionalization.

    Science.gov (United States)

    Pichette Drapeau, Martin; Gooßen, Lukas J

    2016-12-23

    The selective transformation of C-H bonds is one of the most desirable approaches to creating complexity from simple building blocks. Several directing groups are efficient in controlling the regioselectivity of catalytic C-H bond functionalizations. Among them, carboxylic acids are particularly advantageous, since they are widely available in great structural diversity and at low cost. The carboxylate directing groups can be tracelessly cleaved or may serve as the anchor point for further functionalization through decarboxylative couplings. This Minireview summarizes the substantial progress made in the last few years in the development of reactions in which carboxylate groups direct C-H bond functionalizations with formation of C-C, C-O, C-N, or C-halogen bonds at specific positions. It is divided into sections on C-C, C-O, C-N, and C-halogen bond formation, each of which is subdivided by reactions and product classes. Particular emphasis is placed on methods that enable multiple derivatizations by combining carboxylate-directed C-H functionalization with decarboxylative couplings. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Cyclometallation of Aryl-Substituted Phosphinines through C-H-Bond Activation: A Mechanistic Investigation

    NARCIS (Netherlands)

    Broeckx, L.E.E.; Güven, S.; Heutz, F.J.L.; Lutz, M.; Vogt, D.; Müller, Christian

    2013-01-01

    A series of 2,4,6-triarylphosphinines were prepared and investigated in the base-assisted cyclometalation reaction using [Cp*IrCl2]2 (Cp*= 1,2,3,4,5-pentamethylcyclopentadienyl) as the metal precursor. Insight in the mechanism of the C H bond activation of phosphinines as well as in the

  3. Cobalt-Catalyzed Bis-alkynylation of Amides via Double C-H Bond Activation.

    Science.gov (United States)

    Landge, Vinod G; Jaiswal, Garima; Balaraman, Ekambaram

    2016-02-19

    The first example of cobalt-catalyzed selective bis-alkynylation of amides via double C-H bond activation with the directing assistance of a removable bidentate auxiliary is reported. The developed alkynylation strategy is simple, efficient, and tolerant of various functional groups including ether, amine, halides, and heterocyclic motifs. The reaction can be scaled up under mild conditions.

  4. Efficient photolytic C-H bond functionalization of alkylbenzene with hypervalent iodine(iii) reagent.

    Science.gov (United States)

    Sakamoto, Ryu; Inada, Tsubasa; Selvakumar, Sermadurai; Moteki, Shin A; Maruoka, Keiji

    2016-03-07

    A practical approach to radical C-H bond functionalization by the photolysis of a hypervalent iodine(iii) reagent is presented. The photolysis of [bis(trifluoroacetoxy)iodo]benzene (PIFA) leads to the generation of trifluoroacetoxy radicals, which allows the smooth transformation of various alkylbenzenes to the corresponding benzyl ester compounds under mild reaction conditions.

  5. Facile P-C/C-H Bond-Cleavage Reactivity of Nickel Bis(diphosphine) Complexes

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Shaoguang [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Li, Haixia [Texas A & M Univ., College Station, TX (United States). Dept. of Chemistry; Appel, Aaron M. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Hall, Michael B. [Texas A & M Univ., College Station, TX (United States). Dept. of Chemistry; Bullock, R. Morris [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

    2016-06-07

    Unusual cleavage of P-C and C-H bonds of the P2N2 ligand in heteroleptic [Ni(P2N2)(diphosphine)]2+ complexes results in the formation of an iminium formyl nickelate featuring a C,P,P-tridentate coordination mode.

  6. The C-H bond dissociation enthalpies in fused N-heterocyclic compounds

    Science.gov (United States)

    Wang, Ying-Xing; Zheng, Wen-Rui; Ding, Lan-Lan

    2016-03-01

    The C-H bond dissociation enthalpies (BDEs) of the 26 N, O, S-containing mono-heterocyclic compounds were evaluated using the composite high-level ab initio methods G3 and G4. The C-H BDEs for 32 heterocyclic compounds were calculated using 8 types of density functional theory (DFT) methods. Comparing with the experimental values, the BMK method gave the lowest root mean square error (RMSE) of 7.2 kJ/mol. Therefore, the C-H BDEs of N-fused-heterocyclic compounds at different positions were investigated by the BMK method. By NBO analysis two linear relationships between the C-H BDEs of quinoline and isoquinoline with natural charges qC/ e in molecules and with natural charges qC/ e in radicals were found. The substituent effects on C(α)-H BDEs in N-fused-heterocyclic compounds were also discussed. It was found that there are two linear relationships between the C(α)-H BDEs of quinoline and isoquinoline derivatives with natural charges qC(α)/ e for the EDGs and CEGs substituents.

  7. Divergent copper-mediated dimerization and hydroxylation of benzamides involving C-H bond functionalization.

    Science.gov (United States)

    Wang, Mingliang; Hu, Yimin; Jiang, Zhe; Shen, Hong C; Sun, Xun

    2016-05-04

    Convenient methods were developed for copper-mediated oxidative C-H activation of aminoquinoline benzamides. The reaction conditions can be tuned to give either hydroxylation or dimerization compounds as the major products efficiently. Preliminary mechanistic studies suggested that different coordination states of copper may lead to different reaction outcomes.

  8. Synthesis of all eight L-glycopyranosyl donors using C-H activation

    DEFF Research Database (Denmark)

    Frihed, Tobias; Pedersen, Christian Marcus; Bols, Mikael

    2014-01-01

    by an intramolecular C-H activation of the methyl group in g-position; both steps were catalyzed by iridium. The following Fleming-Tamao oxidation and acetylation gave the suitably protected L-hexoses. This is the first general method for the preparation of all eight L-hexoses as their thioglycosyl donors ready...

  9. Cobalt-catalysed C-H carbonylative cyclisation of aliphatic amides.

    Science.gov (United States)

    Williamson, Patrick; Galván, Alicia; Gaunt, Matthew J

    2017-04-01

    A cobalt-catalysed C-H carbonylation of aliphatic carboxamide derivatives is described, employing commercially available Co(ii)-salts in the presence of a silver oxidant. This operationally simple process utilises an atmospheric pressure of CO and generates a range of substituted succinimide products bearing diverse functional groups that can be successfully accessed via this methodology.

  10. Metal-catalysed azidation of tertiary C-H bonds suitable for late-stage functionalization

    Science.gov (United States)

    Sharma, Ankit; Hartwig, John F.

    2015-01-01

    Many enzymes oxidize unactivated aliphatic C-H bonds selectively to form alcohols; however, biological systems do not possess enzymes that catalyse the analogous aminations of C-H bonds. The absence of such enzymes limits the discovery of potential medicinal candidates because nitrogen-containing groups are crucial to the biological activity of therapeutic agents and clinically useful natural products. In one prominent example illustrating the importance of incorporating nitrogen-based functionality, the conversion of the ketone of erythromycin to the -N(Me)CH2- group in azithromycin leads to a compound that can be dosed once daily with a shorter treatment time. For such reasons, synthetic chemists have sought catalysts that directly convert C-H bonds to C-N bonds. Most currently used catalysts for C-H bond amination are ill suited to the intermolecular functionalization of complex molecules because they require excess substrate or directing groups, harsh reaction conditions, weak or acidic C-H bonds, or reagents containing specialized groups on the nitrogen atom. Among C-H bond amination reactions, those forming a C-N bond at a tertiary alkyl group would be particularly valuable, because this linkage is difficult to form from ketones or alcohols that might be created in a biosynthetic pathway by oxidation. Here we report a mild, selective, iron-catalysed azidation of tertiary C-H bonds that occurs without excess of the valuable substrate. The reaction tolerates aqueous environments and is suitable for the functionalization of complex structures in the late stages of a multistep synthesis. Moreover, this azidation makes it possible to install a range of nitrogen-based functional groups, including those from Huisgen `click' cycloadditions and the Staudinger ligation. We anticipate that these reactions will create opportunities to modify natural products, their precursors and their derivatives to produce analogues that contain different polarity and charge as a

  11. Mechanism of Rhodium-Catalyzed C-H Functionalization: Advances in Theoretical Investigation.

    Science.gov (United States)

    Qi, Xiaotian; Li, Yingzi; Bai, Ruopeng; Lan, Yu

    2017-11-07

    Transition-metal-catalyzed cross-coupling has emerged as an effective strategy for chemical synthesis. Within this area, direct C-H bond transformation is one of the most efficient and environmentally friendly processes for the construction of new C-C or C-heteroatom bonds. Over the past decades, rhodium-catalyzed C-H functionalization has attracted considerable attention because of the versatility and wide use of rhodium catalysts in chemistry. A series of C-X (X = C, N, or O) bond formation reactions could be realized from corresponding C-H bonds using rhodium catalysts. Various experimental studies on rhodium-catalyzed C-H functionalization reactions have been reported, and in tandem, mechanistic and computational studies have also progressed significantly. Since 2012, our group has performed theoretical studies to reveal the mechanism of rhodium-catalyzed C-H functionalization reactions. We have studied the changes in the oxidation state of rhodium and compared the Rh(I)/Rh(III) catalytic cycle to the Rh(III)/Rh(V) catalytic cycle using density functional theory calculation. The development of advanced computational methods and improvements in computing power make theoretical calculation a powerful tool for the mechanistic study of rhodium chemistry. Computational study is able to not only provide mechanistic insights but also explain the origin of regioselectivity, enantioselectivity, and stereoselectivity in rhodium-catalyzed C-H functionalization reactions. This Account summarizes our computational work on rhodium-catalyzed C-H functionalization reactions. The mechanistic study under discussion is divided into three main parts: C-H bond cleavage step, transformation of the C-Rh bond, and regeneration of the active catalyst. In the C-H bond cleavage step, computational results of four possible mechanisms, including concerted metalation-deprotonation (CMD), oxidative addition (OA), Friedel-Crafts-type electrophilic aromatic substitution (SEAr), and

  12. Rovibrational interaction and vibrational constants of the symmetric top molecule 14NF3.

    Science.gov (United States)

    Najib, Hamid

    2013-01-01

    Several accurate experimental values of the α(C) and α(B) rotation-vibration interaction parameters and ω(i), x(ij), and g(ij) vibrational constants have been extracted from the most recent high-resolution Fourier transform infrared, millimeter wave, and centimeter wave investigations in the spectra of the oblate symmetric top molecule (14)NF3. The band-centres used are those of the four fundamental, the overtones, the combination, and hot bands identified in the region between 400 cm(-1) and 2000 cm(-1). Comparison of our constants with the ones measured previously, by infrared spectroscopy at low resolution, reveals orders of magnitude higher accuracy of the new values. The agreement between our values and those determined by ab initio calculations employing the TZ2Pf basis is excellent.

  13. Pd/Norbornene: A Winning Combination for Selective Aromatic Functionalization via C-H Bond Activation.

    Science.gov (United States)

    Della Ca', Nicola; Fontana, Marco; Motti, Elena; Catellani, Marta

    2016-07-19

    Direct C-H bond activation is an important reaction in synthetic organic chemistry. This methodology has the potential to simplify reactions by avoiding the use of prefunctionalized reagents. However, selectivity, especially site selectivity, remains challenging. Sequential reactions, in which different molecules or groups are combined in an ordered sequence, represent a powerful tool for the construction of complex molecules in a single operation. We have discovered and developed a synthetic methodology that combines selective C-H bond activation with sequential reactions. This procedure, which is now known as the "Catellani reaction", enables the selective functionalization of both the ortho and ipso positions of aryl halides. The desired molecules are obtained with high selectivity from a pool of simple precursors. These molecules are assembled under the control of a palladacycle, which is formed through the joint action of a metal (Pd) and an olefin such as norbornene. These two species act cooperatively with an aryl halide to construct the palladacycle, which is formed through ortho-C-H activation of the original aryl halide. The resulting complex acts as a scaffold to direct the reaction (via Pd(IV)) of other species, such as alkyl or aryl halides and amination or acylation agents, toward the sp(2) C-Pd bond. At the end of this process, because of steric hindrance, the scaffold is dismantled by norbornene extrusion. Pd(0) is cleaved from the organic product through C-C, C-H, C-N, C-O, or C-B coupling, in agreement with the well-known reactivity of aryl-Pd complexes. The cycle involves Pd(0), Pd(II), and Pd(IV) species. In particular, our discovery relates to alkylation and arylation reactions. Recently, remarkable progress has been made in the following areas: (a) the installation of an amino or an acyl group at the ortho position of aryl halides, (b) the formation of a C-B bond at the ipso position, (c) the achievement of meta-C-H bond activation of aryl

  14. Cp*Rh(III)/Bicyclic Olefin Cocatalyzed C-H Bond Amidation by Intramolecular Amide Transfer.

    Science.gov (United States)

    Wang, Xiaoming; Gensch, Tobias; Lerchen, Andreas; Daniliuc, Constantin G; Glorius, Frank

    2017-05-10

    A bicyclic olefin was discovered as a cocatalyst in a Cp*Rh(III)-catalyzed C-H bond amidation proceeding by an intramolecular amide transfer in N-phenoxyacetamide derivatives. Combining experimental and theoretical studies, we propose that the olefin promotes a Rh(III) intermediate to undergo oxidative addition into the O-N bond to form a Rh(V) nitrenoid species and subsequently direct the nitrenoid to add to the ortho position. The amide directing group plays a dual role as a cleavable coordinating moiety as well as an essential coupling partner for the C-H amidation. This methodology was successfully applied to the late-stage diversification of natural products and a marketed drug under mild conditions.

  15. Recent advances in C-S bond formation via C-H bond functionalization and decarboxylation.

    Science.gov (United States)

    Shen, Chao; Zhang, Pengfei; Sun, Qiang; Bai, Shiqiang; Hor, T S Andy; Liu, Xiaogang

    2015-01-07

    The development of mild and general methods for C-S bond formation has received significant attention because the C-S bond is indispensable in many important biological and pharmaceutical compounds. Early examples for the synthesis of C-S bonds are generally limited to the condensation reaction between a metal thiolate and an organic halide. Recent chemical approaches for C-S bond formation, based upon direct C-H bond functionalization and decarboxylative reactions, not only provide new insights into the mechanistic understanding of C-S coupling reactions but also allow the synthesis of sulfur-containing compounds from more effective synthetic routes with high atom economy. This review intends to explore recent advances in C-S bond formation via C-H functionalization and decarboxylation, and the growing opportunities they present to the construction of complex chemical scaffolds for applications encompassing natural product synthesis, synthetic methodology development, and functional materials as well as nanotechnology.

  16. Binuclear Aromatic C-H Bond Activation at a Dirhenium Site.

    Science.gov (United States)

    Adams, Richard D; Rassolov, Vitaly; Wong, Yuen Onn

    2016-01-22

    The electronically unsaturated dirhenium complex [Re2(CO)8(μ-H)(μ-Ph)] (1) has been found to exhibit aromatic C-H activation upon reaction with N,N-diethylaniline, naphthalene, and even [D6]benzene to yield the compounds [Re2(CO)8(μ-H)(μ-η(1)-NEt2C6H4)] (2), [Re2(CO)8(μ-H)(μ-η(2)-1,2-C10H7)] (3), and [D6]-1, respectively, in good yields. The mechanism has been elucidated by using DFT computational analyses, and involves a binuclear C-H bond-activation process. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Pd-Catalyzed regioselective C-H halogenation of quinazolinones and benzoxazinones.

    Science.gov (United States)

    Dabiri, Minoo; Farajinia Lehi, Noushin; Kazemi Movahed, Siyavash; Khavasi, Hamid Reza

    2017-08-07

    A Pd-catalyzed ortho-selective halogenation of benzoxazinone and quinazolinone scaffolds has been described employing N-halosuccinimide as both a halogen source and an oxidant reagent via C-H bond activation. This transformation shows high chemo- and regioselectivities and demonstrates a broad range of benzoxazinone and quinazolinone substrates with different functional groups and has been scaled up to the gram level.

  18. Remote meta-C-H Cyanation of Arenes Enabled by a Pyrimidine-Based Auxiliary.

    Science.gov (United States)

    Bag, Sukdev; Jayarajan, Ramasamy; Dutta, Uttam; Chowdhury, Rajdip; Mondal, Rahul; Maiti, Debabrata

    2017-10-02

    An easily removable pyrimidine-based auxiliary has been employed for the remote meta-C-H cyanation of arenes. The scope of this Pd-catalyzed cyanation reaction using copper(I) cyanide as the cyanating agent was demonstrated with benzylsilanes, benzylsulfonates, benzylphophonates, phenethylsulfonates, and phenethyl ether derivatives. The method was utilized for the synthesis of pharmaceutically valuable precursors. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Theoretical study of the C-H bond dissociation energy of acetylene

    Science.gov (United States)

    Taylor, Peter R.; Bauschlicher, Charles W., Jr.; Langhoff, Stephen R.

    1990-01-01

    The authors present a theoretical study of the convergence of the C-H bond dissociation energy (D sub o) of acetylene with respect to both the one- and n-particle spaces. Their best estimate for D sub o of 130.1 plus or minus 1.0 kcal/mole is slightly below previous theoretical estimates, but substantially above the value determined using Stark anticrossing spectroscopy that is asserted to be an upper bound.

  20. Carbon dioxide utilization via carbonate-promoted C-H carboxylation

    Science.gov (United States)

    Banerjee, Aanindeeta; Dick, Graham R.; Yoshino, Tatsuhiko; Kanan, Matthew W.

    2016-03-01

    Using carbon dioxide (CO2) as a feedstock for commodity synthesis is an attractive means of reducing greenhouse gas emissions and a possible stepping-stone towards renewable synthetic fuels. A major impediment to synthesizing compounds from CO2 is the difficulty of forming carbon-carbon (C-C) bonds efficiently: although CO2 reacts readily with carbon-centred nucleophiles, generating these intermediates requires high-energy reagents (such as highly reducing metals or strong organic bases), carbon-heteroatom bonds or relatively acidic carbon-hydrogen (C-H) bonds. These requirements negate the environmental benefit of using CO2 as a substrate and limit the chemistry to low-volume targets. Here we show that intermediate-temperature (200 to 350 degrees Celsius) molten salts containing caesium or potassium cations enable carbonate ions (CO32-) to deprotonate very weakly acidic C-H bonds (pKa > 40), generating carbon-centred nucleophiles that react with CO2 to form carboxylates. To illustrate a potential application, we use C-H carboxylation followed by protonation to convert 2-furoic acid into furan-2,5-dicarboxylic acid (FDCA)—a highly desirable bio-based feedstock with numerous applications, including the synthesis of polyethylene furandicarboxylate (PEF), which is a potential large-scale substitute for petroleum-derived polyethylene terephthalate (PET). Since 2-furoic acid can readily be made from lignocellulose, CO32--promoted C-H carboxylation thus reveals a way to transform inedible biomass and CO2 into a valuable feedstock chemical. Our results provide a new strategy for using CO2 in the synthesis of multi-carbon compounds.

  1. Triple-Stranded Cluster Helicates for the Selective Catalytic Oxidation of C-H Bonds.

    Science.gov (United States)

    Fang, Yu; Gong, Wei; Liu, Lujia; Liu, Yan; Cui, Yong

    2016-10-17

    Triple-stranded cluster helicates with heptametallic dicubane cores are synthesized by entrapping metals in the cavities of linear triple helicates based on a C2-symmetrical hexadentate Schiff-base ligand of ortho-substitued biphenol. The helicates are stable in both the solution and solid states, and the copper species could selectively catalyze the oxidation of C-H bonds of alkanes to ketones.

  2. A Mild, Ferrocene-Catalyzed C?H Imidation of (Hetero)Arenes

    OpenAIRE

    Foo, Klement; Sella, Eran; Thom?, Isabelle; Eastgate, Martin D.; Baran, Phil S.

    2014-01-01

    A simple method for direct C?H imidation is reported using a new perester-based self-immolating reagent and a base-metal catalyst. The succinimide products obtained can be easily deprotected in situ (if desired) to reveal the corresponding anilines directly. The scope of the reaction is broad, the conditions are extremely mild, and the reaction is tolerant of oxidizable and acid-labile functionality, multiple heteroatoms, and aryl iodides. Mechanistic studies indicate that ferrocene (Cp2Fe) p...

  3. Cupric-Superoxo Mediated Inter-Molecular C-H Activation Chemistry

    Science.gov (United States)

    Peterson, Ryan L.; Himes, Richard A.; Kotani, Hiroaki; Suenobu, Tomoyoshi; Tian, Li; Siegler, Maxime A.; Solomon, Edward I.; Fukuzumi, Shunichi; Karlin, Kenneth D.

    2011-01-01

    A new cupric-superoxo complex [LCuII(O2•−)]+, which possesses particularly strong O–O and Cu–O bonding, is capable of intermolecular C-H activation of the NADH analogue 1-benzyl-1,4-dihydronicotinamide (BNAH). Kinetic studies indicate a first-order dependence on both the Cu-complex and BNAH with a deuterium kinetic isotope effect (KIE) of 12.1, similar to that observed for certain copper monooxygenases. PMID:21265534

  4. Synthesis of oxindole from acetanilide via Ir(iii)-catalyzed C-H carbenoid functionalization.

    Science.gov (United States)

    Patel, Pitambar; Borah, Gongutri

    2016-12-22

    Herein we disclose the first report on the synthesis of oxindole derivatives from acetanilide via Ir(iii)-catalyzed intermolecular C-H functionalization with diazotized Meldrum's acid. A broad range of substituted anilides were found to react smoothly under the Ir(iii)-catalytic system to afford the corresponding N-protected oxindoles. The N-protecting groups, such as Ac, Bz or Piv, can be easily removed to furnish the oxindole. Various synthetic applications of the synthesized oxindole were also demonstrated.

  5. Properties of a-C:H:Si thin films deposited by middle-frequency magnetron sputtering

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, Jinlong, E-mail: golden_dragon@126.com [State Key Laboratory of Advanced Processing and Recycling of Nonferrous Metals, Lanzhou University of Technology, Lanzhou 730050 (China); School of Science, Lanzhou University of Technology, Lanzhou 730050 (China); Wang, Yubao; Du, Jinfang; Yang, Hua [State Key Laboratory of Advanced Processing and Recycling of Nonferrous Metals, Lanzhou University of Technology, Lanzhou 730050 (China); Hao, Junying, E-mail: jyhao@licp.cas.cn [State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000 (China)

    2016-08-30

    Highlights: • The a-C:H:Si films were deposited by magnetron sputtering Si target in argon and methane gas mixture atmosphere. • The growth of a-C:H:Si films is classified into three modes with increasing of methane flow rate. • The a-C:H:Si films at moderate methane flow rate exhibit low stress, high hardness and superior tribological properties. - Abstract: The silicon doped hydrogenated amorphous carbon (a-C:H:Si) films were prepared on silicon substrates by middle-frequency magnetron sputtering silicon target in an argon and methane gas mixture atmosphere. The deposition rate, chemical composition, structure, surface properties, stress, hardness and tribological properties in the ambient air of the films were systemically investigated using X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM), atomic force microscopy (AFM), nanoindentation and tribological tester. The results show that doped silicon content in the films is controlled in the wide range from 39.7 at.% to 0.2 at.% by various methane gas flow rate, and methane flow rate affects not only the silicon content but also its chemical bonding structure in the films due to the transformation of sputtering modes. Meanwhile, the sp{sup 3} carbon component in the films linearly increases with increasing of methane flow rate. The film deposited at moderate methane flow rate of 40–60 sccm exhibits the very smooth surface (RMS roughness 0.4 nm), low stress (0.42 GPa), high hardness (21.1 GPa), as well as low friction coefficient (0.038) and wear rate (1.6 × 10{sup −7} mm{sup 3}/Nm). The superior tribological performance of the films could be attributed to the formation and integral covering of the transfer materials on the sliding surface and their high hardness.

  6. Aromatic C-H bond activation revealed by infrared multiphoton dissociation spectroscopy

    Czech Academy of Sciences Publication Activity Database

    Jašíková, L.; Hanikýřová, E.; Schröder, Detlef; Roithová, J.

    2012-01-01

    Roč. 47, č. 4 (2012), s. 460-465 ISSN 1076-5174 Grant - others:GA ČR(CZ) GAP207/11/0338; Seventh Framework Program(XE) 226716 Institutional research plan: CEZ:AV0Z40550506 Keywords : C-H activation * density functional theory calculations * ion spectroscopy * metal oxides * rearrangements Subject RIV: CC - Organic Chemistry Impact factor: 3.214, year: 2012

  7. Regioselective β-silylation of porphyrins via iridium-catalyzed C-H bond activation.

    Science.gov (United States)

    Sugita, Noriaki; Hayashi, Satoshi; Shibata, Masashi; Endo, Taiga; Noji, Masahiro; Takatori, Kazuhiko; Takanami, Toshikatsu

    2016-11-02

    An efficient approach to meso-unsubstituted β-silylporphyrins was developed through highly regioselective Ir-catalyzed C-H activation, in the presence of HSiMe(OSiMe3)2 as the Si source, from meso-unsubstituted porphyrins. Further transformations of the silyl group, such as oxidation, halogenation, and cross-coupling reactions, could be achieved under mild conditions, demonstrating the synthetic utility of β-silylporphyrins as a multipurpose synthon for fabricating porphyrin derivatives.

  8. Boron-Catalyzed Aromatic C-H Bond Silylation with Hydrosilanes.

    Science.gov (United States)

    Ma, Yuanhong; Wang, Baoli; Zhang, Liang; Hou, Zhaomin

    2016-03-23

    Metal-free catalytic C-H silylation of a series of aromatic compounds such as N,N-disubstituted anilines with various hydrosilanes has been achieved for the first time using commercially available B(C6F5)3 as a catalyst. This protocol features simple and neutral reaction conditions, high regioselectivity, wide substrate scope (up to 40 examples), Si-Cl bond compatibility, and no requirement for a hydrogen acceptor.

  9. The synthesis of functionalized bridged polycycles via C-H bond insertion.

    Science.gov (United States)

    Shih, Jiun-Le; Chen, Po-An; May, Jeremy A

    2016-01-01

    This review presents examples from the chemical literature of syntheses of bridged-polycyclic products via C-H bond insertion by carbenes and nitrenes. Applications to natural product synthesis, a description of the essential elements in substrate-controlled reactions, and mechanistic details of transformations are presented. Overall, these transformations allow the construction of important ring systems rapidly and efficiently, though additional catalyst development is needed.

  10. Recent advances in transition metal-catalyzed C-H bond functionalization of ferrocene derivatives

    OpenAIRE

    López, L.Á. (Luis); López, Enol

    2016-01-01

    Transition metal-catalyzed C-H bond functionalizations of ferrocene derivatives have emerged in the last few years as a versatile tool in synthetic organometallic chemistry. These protocols offer significant advantages over more traditional approaches for the synthesis of functionalized ferrocene derivatives in terms of both atom- and step-economy. In this Perspective, we aim to showcase the state of the art in this 10 field, with special emphasis on recent asymmetric methodologie...

  11. Ruthenium-Catalyzed Regioselective C-H Bond Acetoxylation on Carbazole and Indole Frameworks.

    Science.gov (United States)

    Okada, Takeshi; Nobushige, Kazunori; Satoh, Tetsuya; Miura, Masahiro

    2016-03-04

    The regioselective C-H bond cleavage/C-O bond formation takes place smoothly upon treatment of 9-(pyridin-2-yl)carbazoles with acetic acid in the presence of a silver salt oxidant under ruthenium catalysis to afford the corresponding C1- and C8-diacetoxylated products. Under similar conditions, the acetoxylation of 2-aryl-1-(pyridin-2-yl)indoles as well as 1-aryl-7-azaindoles can also be conducted efficiently.

  12. The synthesis of functionalized bridged polycycles via C?H bond insertion

    OpenAIRE

    Jiun-Le Shih; Po-An Chen; May, Jeremy A

    2016-01-01

    Summary This review presents examples from the chemical literature of syntheses of bridged-polycyclic products via C?H bond insertion by carbenes and nitrenes. Applications to natural product synthesis, a description of the essential elements in substrate-controlled reactions, and mechanistic details of transformations are presented. Overall, these transformations allow the construction of important ring systems rapidly and efficiently, though additional catalyst development is needed.

  13. Structure and phase composition of thin a-C:H films modified by Ag and Ti

    Science.gov (United States)

    Prikhodko, O. Yu.; Mikhailova, S. L.; Mukhametkarimov, Ye. S.; Dauthan, K.; Maksimova, S. Ya.

    2017-09-01

    The structure and phase composition of thin a-C:H and a-C:H〈 M〉 films ( M = Ag, Ti, or Ag + Ti) have been studied by Raman and X-ray photoelectron spectroscopy. The a-C:H〈 M〉 films were prepared by ion-plasma magnetron sputtering of a combined target of graphite and metal in an Ar-CH4 gas mixture. The Raman spectra of these films indicate that their structure is amorphous. The a-C:H〈Ag + Ti〉 films have a more graphitized structure in comparison with pure a-C:H films and films containing only one metal. It is established that carbon in the a-C:H〈Ag + Ti〉 films is in the sp 2, sp 3, and C=O states, which are characteristic of the a-C:H, a-C:H〈Ag〉, and a-C:H〈Ti〉 films. In addition, there are also ether (-C-O-C-) or epoxy (‒C‒O-) carbon groups in the a-C:H〈Ag + Ti〉 films. It has been revealed that silver atoms in the a-C:H〈Ag〉 and a-C:H〈Ag + Ti〉 films form no chemical bonds with carbon, oxygen, and titanium. Titanium in the a-C:H〈Ti〉 and a-C:H〈Ag + Ti〉 films exists in the form of titanium IV oxide (TiO2).

  14. Atomic and electronic structures of a-SiC:H from tight-binding molecular dynamics

    CERN Document Server

    Ivashchenko, V I; Shevchenko, V I; Ivashchenko, L A; Rusakov, G V

    2003-01-01

    The atomic and electronic properties of amorphous unhydrogenated (a-SiC) and hydrogenated (a-SiC:H) silicon carbides are studied using an sp sup 3 s sup * tight-binding force model with molecular dynamics simulations. The parameters of a repulsive pairwise potential are determined from ab initio pseudopotential calculations. Both carbides are generated from dilute vapours condensed from high temperature, with post-annealing at low temperature for a-SiC:H. A plausible model for the inter-atomic correlations and electronic states in a-SiC:H is suggested. According to this model, the formation of the amorphous network is weakly sensitive to the presence of hydrogen. Hydrogen passivates effectively only the weak bonds of threefold-coordinated atoms. Chemical ordering is very much affected by the cooling rate and the structure of the high-temperature vapour. The as-computed characteristics are in rather good agreement with the results for a-SiC and a-Si:H from ab initio calculations.

  15. Highly Stereoselective Cobalt(III)-Catalyzed Three-Component C-H Bond Addition Cascade.

    Science.gov (United States)

    Boerth, Jeffrey A; Hummel, Joshua R; Ellman, Jonathan A

    2016-10-04

    A highly stereoselective three-component C(sp(2) )-H bond addition across alkene and polarized π-bonds is reported for which Co(III) catalysis was shown to be much more effective than Rh(III) . The reaction proceeds at ambient temperature with both aryl and alkyl enones employed as efficient coupling partners. Moreover, the reaction exhibits extremely broad scope with respect to the aldehyde input; electron rich and poor aromatic, alkenyl, and branched and unbranched alkyl aldehydes all couple in good yield and with high diastereoselectivity. Multiple directing groups participate in this transformation, including pyrazole, pyridine, and imine functional groups. Both aromatic and alkenyl C(sp(2) )-H bonds undergo the three-component addition cascade, and the alkenyl addition product can readily be converted into diastereomerically pure five-membered lactones. Additionally, the first asymmetric reactions with Co(III) -catalyzed C-H functionalization are demonstrated with three-component C-H bond addition cascades employing N-tert-butanesulfinyl imines. These examples represent the first transition metal catalyzed C-H bond additions to N-tert-butanesulfinyl imines, which are versatile and extensively used intermediates for the asymmetric synthesis of amines. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Rh(III)-Catalyzed C-H Bond Addition/Amine-Mediated Cyclization of Bis-Michael Acceptors.

    Science.gov (United States)

    Potter, Tyler J; Ellman, Jonathan A

    2016-08-05

    A Rh(III)-catalyzed C-H bond addition/primary amine-promoted cyclization of bis-Michael acceptors is reported. The C-H bond addition step occurs with high chemoselectivity, and the subsequent intramolecular Michael addition, mediated by a primary amine catalyst, sets three contiguous stereocenters with high diastereoselectivity. A broad range of directing groups and both aromatic and alkenyl C-H bonds were shown to be effective in this transformation, affording functionalized piperidines, tetrahydropyrans, and cyclohexanes.

  17. Subfemtosecond steering of hydrocarbon deprotonation through superposition of vibrational modes

    Science.gov (United States)

    Alnaser, A. S.; Kübel, M.; Siemering, R.; Bergues, B.; Kling, Nora G.; Betsch, K. J.; Deng, Y.; Schmidt, J.; Alahmed, Z. A.; Azzeer, A. M.; Ullrich, J.; Ben-Itzhak, I.; Moshammer, R.; Kleineberg, U.; Krausz, F.; de Vivie-Riedle, R.; Kling, M. F.

    2014-05-01

    Subfemtosecond control of the breaking and making of chemical bonds in polyatomic molecules is poised to open new pathways for the laser-driven synthesis of chemical products. The break-up of the C-H bond in hydrocarbons is an ubiquitous process during laser-induced dissociation. While the yield of the deprotonation of hydrocarbons has been successfully manipulated in recent studies, full control of the reaction would also require a directional control (that is, which C-H bond is broken). Here, we demonstrate steering of deprotonation from symmetric acetylene molecules on subfemtosecond timescales before the break-up of the molecular dication. On the basis of quantum mechanical calculations, the experimental results are interpreted in terms of a novel subfemtosecond control mechanism involving non-resonant excitation and superposition of vibrational degrees of freedom. This mechanism permits control over the directionality of chemical reactions via vibrational excitation on timescales defined by the subcycle evolution of the laser waveform.

  18. First-principles calculations on anharmonic vibrational frequencies of polyethylene and polyacetylene in the Gamma approximation.

    Science.gov (United States)

    Keçeli, Murat; Hirata, So; Yagi, Kiyoshi

    2010-07-21

    The frequencies of the infrared- and/or Raman-active (k=0) vibrations of polyethylene and polyacetylene are computed by taking account of the anharmonicity in the potential energy surfaces (PESs) and the resulting phonon-phonon couplings explicitly. The electronic part of the calculations is based on Gaussian-basis-set crystalline orbital theory at the Hartree-Fock and second-order Møller-Plesset (MP2) perturbation levels, providing one-, two-, and/or three-dimensional slices of the PES (namely, using the so-called n-mode coupling approximation with n=3), which are in turn expanded in the fourth-order Taylor series with respect to the normal coordinates. The vibrational part uses the vibrational self-consistent field, vibrational MP2, and vibrational truncated configuration-interaction (VCI) methods within the Gamma approximation, which amounts to including only k=0 phonons. It is shown that accounting for both electron correlation and anharmonicity is essential in achieving good agreement (the mean and maximum absolute deviations less than 50 and 90 cm(-1), respectively, for polyethylene and polyacetylene) between computed and observed frequencies. The corresponding values for the calculations including only one of such effects are in excess of 120 and 300 cm(-1), respectively. The VCI calculations also reproduce semiquantitatively the frequency separation and intensity ratio of the Fermi doublet involving the nu(2)(0) fundamental and nu(8)(pi) first overtone in polyethylene.

  19. C-H nickellation of phenol-derived phosphinites: regioselectivity and structures of cyclonickellated complexes.

    Science.gov (United States)

    Mangin, Loïc P; Zargarian, Davit

    2017-11-13

    This report describes the results of a study on the ortho-C-H nickellation of the aryl phosphinites i-Pr2P(OAr) derived from the following four groups of substituted phenols: 3-R-C6H4OH (R = F (b), Me (c), MeO (d), Cl (e)); 3,5-R2-C6H3OH (R = F (f), Me (g), Cl (h), OMe (i)); 2-R-C6H4OH (R = Me (j), Ph(k)); and 2,6-R2-C6H3OH (R = Me (l), Ph (m)). No nickellation was observed with the phosphinites derived from the 3,5-disubstituted phenols g and h, and the 2,6-disubstituted phenols l and m; in all other cases nickellation occurred at an ortho-C-H to generate either the Br-bridged dimers [{κ(P),κ(C)-(i-Pr)2POAr}Ni(μ-Br)]2 (1b-1f, 1j, and 1k) or the monomeric acetonitrile adduct {κ(P),κ(C)-ArOP(i-Pr)2}Ni(Br)(NCMe) (1i-NCMe). Analysis of C-H nickellation regioselectivity with 3-R-C6H4OH pointed to the importance of substituent sterics, not electronics: nickellation occurred at the least hindered position either exclusively (for R = Me (c), MeO(d), and Cl (e)) or predominantly (for R = F (b); 6 : 1). This conclusion is also consistent with the observation that C-H nickellation is possible with the 3,5-disubstituted aryl phosphinites bearing F and OMe, but not with the more bulky substituents Me or Cl. For the 2-substituted aryl phosphinites, C-H nickellation occurs at the unsubstituted ortho-C-H and not on the R substituent, regardless of whether the alternative C-H moiety of the substituent is sp(3) (R = Me (j)) or sp(2) (R = Ph (k)). The system thus reveals a strong preference for formation of 5-membered metallacycles. Consistent with this reactivity, no nickellation occurs with (2,6-R2-C6H3O)P(i-Pr)2. Tests with the parent dimer derived from i-Pr2P(OPh) showed that conversion to the monomeric acetonitrile adduct is highly favored, going to completion with only a small excess of MeCN. All new cyclonickellated complexes reported in this study were fully characterized, including by single crystal X-ray diffraction studies. The solid state structures of the

  20. Electrostatics determine vibrational frequency shifts in hydrogen bonded complexes.

    Science.gov (United States)

    Dey, Arghya; Mondal, Sohidul Islam; Sen, Saumik; Ghosh, Debashree; Patwari, G Naresh

    2014-12-14

    The red-shifts in the acetylenic C-H stretching vibration of C-H∙∙∙X (X = O, N) hydrogen-bonded complexes increase with an increase in the basicity of the Lewis base. Analysis of various components of stabilization energy suggests that the observed red-shifts are correlated with the electrostatic component of the stabilization energy, while the dispersion modulates the stabilization energy.

  1. Microstructure characterization of advanced protective Cr/CrN+a-C:H/a-C:H:Cr multilayer coatings on carbon fibre composite (CFC).

    Science.gov (United States)

    Major, L; Janusz, M; Lackner, J M; Kot, M; Major, B

    2016-06-01

    Studies of advanced protective chromium-based coatings on the carbon fibre composite (CFC) were performed. Multidisciplinary examinations were carried out comprising: microstructure transmission electron microscopy (TEM, HREM) studies, micromechanical analysis and wear resistance. Coatings were prepared using a magnetron sputtering technique with application of high-purity chromium and carbon (graphite) targets deposited on the CFC substrate. Selection of the CFC for surface modification in respect to irregularities on the surface making the CFC surface more smooth was performed. Deposited coatings consisted of two parts. The inner part was responsible for the residual stress compensation and cracking initiation as well as resistance at elevated temperatures occurring namely during surgical tools sterilization process. The outer part was responsible for wear resistance properties and biocompatibility. Experimental studies revealed that irregularities on the substrate surface had a negative influence on the crystallites growth direction. Chromium implanted into the a-C:H structure reacted with carbon forming the cubic nanocrystal chromium carbides of the Cr23 C6 type. The cracking was initiated at the coating/substrate interface and the energy of brittle cracking was reduced because of the plastic deformation at each Cr interlayer interface. The wear mechanism and cracking process was described in micro- and nanoscale by means of transmission electron microscope studies. Examined materials of coated CFC type would find applications in advanced surgical tools. © 2016 The Authors Journal of Microscopy © 2016 Royal Microscopical Society.

  2. Stochastic many-body perturbation theory for anharmonic molecular vibrations

    Energy Technology Data Exchange (ETDEWEB)

    Hermes, Matthew R. [Department of Chemistry, University of Illinois at Urbana-Champaign, 600 South Mathews Avenue, Urbana, Illinois 61801 (United States); Hirata, So, E-mail: sohirata@illinois.edu [Department of Chemistry, University of Illinois at Urbana-Champaign, 600 South Mathews Avenue, Urbana, Illinois 61801 (United States); CREST, Japan Science and Technology Agency, 4-1-8 Honcho, Kawaguchi, Saitama 332-0012 (Japan)

    2014-08-28

    A new quantum Monte Carlo (QMC) method for anharmonic vibrational zero-point energies and transition frequencies is developed, which combines the diagrammatic vibrational many-body perturbation theory based on the Dyson equation with Monte Carlo integration. The infinite sums of the diagrammatic and thus size-consistent first- and second-order anharmonic corrections to the energy and self-energy are expressed as sums of a few m- or 2m-dimensional integrals of wave functions and a potential energy surface (PES) (m is the vibrational degrees of freedom). Each of these integrals is computed as the integrand (including the value of the PES) divided by the value of a judiciously chosen weight function evaluated on demand at geometries distributed randomly but according to the weight function via the Metropolis algorithm. In this way, the method completely avoids cumbersome evaluation and storage of high-order force constants necessary in the original formulation of the vibrational perturbation theory; it furthermore allows even higher-order force constants essentially up to an infinite order to be taken into account in a scalable, memory-efficient algorithm. The diagrammatic contributions to the frequency-dependent self-energies that are stochastically evaluated at discrete frequencies can be reliably interpolated, allowing the self-consistent solutions to the Dyson equation to be obtained. This method, therefore, can compute directly and stochastically the transition frequencies of fundamentals and overtones as well as their relative intensities as pole strengths, without fixed-node errors that plague some QMC. It is shown that, for an identical PES, the new method reproduces the correct deterministic values of the energies and frequencies within a few cm{sup −1} and pole strengths within a few thousandths. With the values of a PES evaluated on the fly at random geometries, the new method captures a noticeably greater proportion of anharmonic effects.

  3. Tunable Passive Vibration Suppressor

    Science.gov (United States)

    Boechler, Nicholas (Inventor); Dillon, Robert Peter (Inventor); Daraio, Chiara (Inventor); Davis, Gregory L. (Inventor); Shapiro, Andrew A. (Inventor); Borgonia, John Paul C. (Inventor); Kahn, Daniel Louis (Inventor)

    2016-01-01

    An apparatus and method for vibration suppression using a granular particle chain. The granular particle chain is statically compressed and the end particles of the chain are attached to a payload and vibration source. The properties of the granular particles along with the amount of static compression are chosen to provide desired filtering of vibrations.

  4. Vibrations and Eigenvalues

    Indian Academy of Sciences (India)

    We make music by causing strings, membranes, or air columns to vibrate. Engineers design safe structures by control- ling vibrations. I will describe to you a very simple vibrating system and the mathematics needed to analyse it. The ideas were born in the work of Joseph-Louis Lagrange (1736–1813), and I begin by quot-.

  5. Near-threshold vibrational excitation of acetylene by positron impact

    Science.gov (United States)

    de Oliveira, Eliane M.; Lima, Marco A. P.; Sanchez, Sergio D.'A.; Varella, Márcio T. Do N.

    2010-01-01

    We report vibrational excitation cross sections for C-C and C-H symmetric stretch modes of acetylene by positron impact. The contribution of these infrared inactive modes to the annihilation parameter is also addressed. The Feshbach projection operator approach was employed to vibrationally resolve e+-acetylene scattering phase shifts obtained with the Schwinger multichannel method. The present results point out a virtual state pole at the equilibrium geometry of acetylene that becomes a bound state as either bond is stretched, in qualitative agreement with previous calculations for small hydrocarbons. The vibrational couplings are stronger for the C-C mode, giving rise to a bound state pole within the Franck-Condon region of the vibrational ground state. These bound and virtual states give rise to sharp threshold structures (vibrational resonances) in both the vibrational excitation cross sections and the annihilation parameter (Zeff). We found fair agreement between the present calculations and previously reported e+-acetylene vibrational excitation cross sections.

  6. Recent Advances in the Selective Oxidation of Alkyl C-H Bonds Catalyzed by Iron Coordination Complexes.

    Science.gov (United States)

    Canta, Mercè; Rodríguez, Mònica; Costas, Miquel

    2016-01-01

    Selective and stereoretentive oxidation of alkyl C-H bonds has been described over the last decade by employing biologically inspired iron coordination complexes as catalysts and hydrogen peroxide as oxidant. Examples of catalyst dependent C-H site selectivity have started to appear. The current paper describes an account of these findings.

  7. Pd-Catalyzed C-H activation/oxidative cyclization of acetanilide with norbornene: concise access to functionalized indolines.

    Science.gov (United States)

    Gao, Yang; Huang, Yubing; Wu, Wanqing; Huang, Kefan; Jiang, Huanfeng

    2014-08-07

    An efficient Pd-catalyzed oxidative cyclization reaction for the synthesis of functionalized indolines by direct C-H activation of acetanilide has been developed. The norbornylpalladium species formed via direct ortho C-H activation of acetanilides is supposed to be a key intermediate in this transformation.

  8. Properties of a-C:H:O plasma polymer films deposited from acetone vapors

    Energy Technology Data Exchange (ETDEWEB)

    Drabik, M., E-mail: martin.drabik@gmail.com [Empa, Swiss Federal Laboratories for Materials Science and Technology, Lerchenfeldstrasse 5, 9014 St. Gallen (Switzerland); Celma, C. [Empa, Swiss Federal Laboratories for Materials Science and Technology, Lerchenfeldstrasse 5, 9014 St. Gallen (Switzerland); Kousal, J.; Biederman, H. [Charles University in Prague, Faculty of Mathematics and Physics, Department of Macromolecular Physics, V Holešovičkách 2, 180 00 Prague 8 (Czech Republic); Hegemann, D. [Empa, Swiss Federal Laboratories for Materials Science and Technology, Lerchenfeldstrasse 5, 9014 St. Gallen (Switzerland)

    2014-12-31

    To gain insight into the deposition and stability of oxygen-containing plasma polymer films, the properties of amorphous oxygenated hydrocarbon (a-C:H:O) plasma polymer coatings deposited from acetone vapors under various experimental conditions are investigated. Apart from the discharge power, the influence of the reactive carbon dioxide (CO{sub 2}) gas on the structure of the resulting films is studied. It is found by characterization using X-ray Photoelectron Spectroscopy and Fourier-Transform Infrared Spectroscopy that the experimental conditions particularly influence the amount of oxygen in the deposited a-C:H:O plasma polymer films. The O/C elemental ratio increases with increasing amount of CO{sub 2} in the working gas mixture (up to 0.2 for 24 sccm of CO{sub 2} at 30 W) and decreases with increasing RF discharge power (down to 0.17 for 50 W). Furthermore, the nature of bonds between the oxygen and carbon atoms has been examined. Only low amounts of double and triple bonded carbon are observed. This has a particular influence on the aging of the plasma polymer films which is studied both in ambient air and in distilled water for up to 4 months. Overall, stable a-C:H:O plasma polymer films are deposited comprising low amounts (up to about 5%) of ester/carboxyl groups. - Highlights: • Hydrocarbon plasma polymer films with variable oxygen content can be prepared. • Stable oxygenated hydrocarbon plasma polymers contain max 5% of ester/carboxyl groups. • Acetone-derived plasma polymer films can be used as permanent hydrophilic surfaces.

  9. Trapping a Highly Reactive Nonheme Iron Intermediate That Oxygenates Strong C-H Bonds with Stereoretention.

    Science.gov (United States)

    Serrano-Plana, Joan; Oloo, Williamson N; Acosta-Rueda, Laura; Meier, Katlyn K; Verdejo, Begoña; García-España, Enrique; Basallote, Manuel G; Münck, Eckard; Que, Lawrence; Company, Anna; Costas, Miquel

    2015-12-23

    An unprecedentedly reactive iron species (2) has been generated by reaction of excess peracetic acid with a mononuclear iron complex [Fe(II)(CF3SO3)2(PyNMe3)] (1) at cryogenic temperatures, and characterized spectroscopically. Compound 2 is kinetically competent for breaking strong C-H bonds of alkanes (BDE ≈ 100 kcal·mol(-1)) through a hydrogen-atom transfer mechanism, and the transformations proceed with stereoretention and regioselectively, responding to bond strength, as well as to steric and polar effects. Bimolecular reaction rates are at least an order of magnitude faster than those of the most reactive synthetic high-valent nonheme oxoiron species described to date. EPR studies in tandem with kinetic analysis show that the 490 nm chromophore of 2 is associated with two S = 1/2 species in rapid equilibrium. The minor component 2a (∼5% iron) has g-values at 2.20, 2.19, and 1.99 characteristic of a low-spin iron(III) center, and it is assigned as [Fe(III)(OOAc)(PyNMe3)](2+), also by comparison with the EPR parameters of the structurally characterized hydroxamate analogue [Fe(III)(tBuCON(H)O)(PyNMe3)](2+) (4). The major component 2b (∼40% iron, g-values = 2.07, 2.01, 1.95) has unusual EPR parameters, and it is proposed to be [Fe(V)(O)(OAc)(PyNMe3)](2+), where the O-O bond in 2a has been broken. Consistent with this assignment, 2b undergoes exchange of its acetate ligand with CD3CO2D and very rapidly reacts with olefins to produce the corresponding cis-1,2-hydroxoacetate product. Therefore, this work constitutes the first example where a synthetic nonheme iron species responsible for stereospecific and site selective C-H hydroxylation is spectroscopically trapped, and its catalytic reactivity against C-H bonds can be directly interrogated by kinetic methods. The accumulated evidence indicates that 2 consists mainly of an extraordinarily reactive [Fe(V)(O)(OAc)(PyNMe3)](2+) (2b) species capable of hydroxylating unactivated alkyl C-H bonds with

  10. A mild, ferrocene-catalyzed C-H imidation of (hetero)arenes.

    Science.gov (United States)

    Foo, Klement; Sella, Eran; Thomé, Isabelle; Eastgate, Martin D; Baran, Phil S

    2014-04-09

    A simple method for direct C-H imidation is reported using a new perester-based self-immolating reagent and a base-metal catalyst. The succinimide products obtained can be easily deprotected in situ (if desired) to reveal the corresponding anilines directly. The scope of the reaction is broad, the conditions are extremely mild, and the reaction is tolerant of oxidizable and acid-labile functionality, multiple heteroatoms, and aryl iodides. Mechanistic studies indicate that ferrocene (Cp2Fe) plays the role of an electron shuttle in the decomposition of the perester reagent, delivering a succinimidyl radical ready to add to an aromatic system.

  11. Selective molecular recognition, C-H bond activation, and catalysis in nanoscale reaction vessels

    Energy Technology Data Exchange (ETDEWEB)

    Fiedler, Dorothea; Leung, Dennis H.; Raymond, Kenneth N.; Bergman, Robert G.

    2004-11-27

    Supramolecular chemistry represents a way to mimic enzyme reactivity by using specially designed container molecules. We have shown that a chiral self-assembled M{sub 4}L{sub 6} supramolecular tetrahedron can encapsulate a variety of cationic guests, with varying degrees of stereoselectivity. Reactive iridium guests can be encapsulated and the C-H bond activation of aldehydes occurs, with the host cavity controlling the ability of substrates to interact with the metal center based upon size and shape. In addition, the host container can act as a catalyst by itself. By restricting reaction space and preorganizing the substrates into reactive conformations, it accelerates the sigmatropic rearrangement of enammonium cations.

  12. C-H Bond Oxidation Catalyzed by an Imine-Based Iron Complex: A Mechanistic Insight.

    Science.gov (United States)

    Olivo, Giorgio; Nardi, Martina; Vìdal, Diego; Barbieri, Alessia; Lapi, Andrea; Gómez, Laura; Lanzalunga, Osvaldo; Costas, Miquel; Di Stefano, Stefano

    2015-11-02

    A family of imine-based nonheme iron(II) complexes (LX)2Fe(OTf)2 has been prepared, characterized, and employed as C-H oxidation catalysts. Ligands LX (X = 1, 2, 3, and 4) stand for tridentate imine ligands resulting from spontaneous condensation of 2-pycolyl-amine and 4-substituted-2-picolyl aldehydes. Fast and quantitative formation of the complex occurs just upon mixing aldehyde, amine, and Fe(OTf)2 in a 2:2:1 ratio in acetonitrile solution. The solid-state structures of (L1)2Fe(OTf)(ClO4) and (L3)2Fe(OTf)2 are reported, showing a low-spin octahedral iron center, with the ligands arranged in a meridional fashion. (1)H NMR analyses indicate that the solid-state structure and spin state is retained in solution. These analyses also show the presence of an amine-imine tautomeric equilibrium. (LX)2Fe(OTf)2 efficiently catalyze the oxidation of alkyl C-H bonds employing H2O2 as a terminal oxidant. Manipulation of the electronic properties of the imine ligand has only a minor impact on efficiency and selectivity of the oxidative process. A mechanistic study is presented, providing evidence that C-H oxidations are metal-based. Reactions occur with stereoretention at the hydroxylated carbon and selectively at tertiary over secondary C-H bonds. Isotopic labeling analyses show that H2O2 is the dominant origin of the oxygen atoms inserted in the oxygenated product. Experimental evidence is provided that reactions involve initial oxidation of the complexes to the ferric state, and it is proposed that a ligand arm dissociates to enable hydrogen peroxide binding and activation. Selectivity patterns and isotopic labeling studies strongly suggest that activation of hydrogen peroxide occurs by heterolytic O-O cleavage, without the assistance of a cis-binding water or alkyl carboxylic acid. The sum of these observations provides sound evidence that controlled activation of H2O2 at (LX)2Fe(OTf)2 differs from that occurring in biomimetic iron catalysts described to date.

  13. C-H bond oxidation catalyzed by an imine-based iron complex: A mechanistic insight

    OpenAIRE

    Olivo, Giorgio; Nardi, Martina; Vidal Sánchez, Diego; Barbieri, Alessia; Lapi, Andrea; Gómez Martín, Laura; Lanzalunga, Osvaldo; Costas Salgueiro, Miquel; Di Stefano, Stefano

    2015-01-01

    A family of imine-based nonheme iron(II) complexes (LX)2Fe(OTf)2 has been prepared, characterized, and employed as C-H oxidation catalysts. Ligands LX (X = 1, 2, 3, and 4) stand for tridentate imine ligands resulting from spontaneous condensation of 2-pycolyl-amine and 4-substituted-2-picolyl aldehydes. Fast and quantitative formation of the complex occurs just upon mixing aldehyde, amine, and Fe(OTf)2 in a 2:2:1 ratio in acetonitrile solution. The solid-state structures of (L1)2Fe(OTf)(ClO4)...

  14. Photocatalytic C??H Activation of Hydrocarbons over VO@g??C3N4

    Science.gov (United States)

    A highly selective and sustainable method has been developed for the oxidation of methyl arenes and their analogues. The VO@g-C3N4 catalyst is very efficient in the C??H activation and oxygen insertion reaction resulting in formation of the corresponding carbonyl compounds and phenols.This dataset is associated with the following publication:Verma, S., R.B. Nasir Baig, M. Nadagouda , and R. Varma. Photocatalytic C−H Activation of Hydrocarbons over VO@g‑C3N4. ACS Sustainable Chemistry & Engineering. American Chemical Society, Washington, DC, USA, 4(4): 2333-2336, (2016).

  15. Palladium-Catalyzed Deaminative Phenanthridinone Synthesis from Aniline via C-H Bond Activation.

    Science.gov (United States)

    Yedage, Subhash L; Bhanage, Bhalchandra M

    2016-05-20

    This work reports palladium-catalyzed phenanthridinone synthesis using the coupling of aniline and amide by formation of C-C and C-N bonds in a one-pot fashion via dual C-H bond activation. It involves simultaneous cleavage of four bonds and the formation of two new bonds. The present protocol is ligand-free, takes place under mild reaction conditions, and is environmentally benign as nitrogen gas and water are the only side products. This transformation demonstrates a broad range of aniline and amide substrates with different functional groups and has been scaled up to gram level.

  16. Vibration analysis of cryocoolers

    Science.gov (United States)

    Tomaru, Takayuki; Suzuki, Toshikazu; Haruyama, Tomiyoshi; Shintomi, Takakazu; Yamamoto, Akira; Koyama, Tomohiro; Li, Rui

    2004-05-01

    The vibrations of Gifford-McMahon (GM) and pulse-tube (PT) cryocoolers were measured and analyzed. The vibrations of the cold-stage and cold-head were measured separately to investigate their vibration mechanisms. The measurements were performed while maintaining the thermal conditions of the cryocoolers at a steady state. We found that the vibration of the cold-head for the 4 K PT cryocooler was two orders of magnitude smaller than that of the 4 K GM cryocooler. On the other hand, the vibration of the cold-stages for both cryocoolers was of the same order of magnitude. From a spectral analysis of the vibrations and a simulation, we concluded that the vibration of the cold-stage is caused by an elastic deformation of the pulse tubes (or cylinders) due to the pressure oscillation of the working gas.

  17. Vibration analysis of cryocoolers

    Energy Technology Data Exchange (ETDEWEB)

    Tomaru, Takayuki; Suzuki, Toshikazu; Haruyama, Tomiyoshi; Shintomi, Takakazu; Yamamoto, Akira [High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki (Japan); Koyama, Tomohiro; Rui Li [Sumitomo Heavy Industries Ltd., Tokyo (Japan)

    2004-05-01

    The vibrations of Gifford-McMahon (GM) and pulse-tube (PT) cryocoolers were measured and analyzed. The vibrations of the cold-stage and cold-head were measured separately to investigate their vibration mechanisms. The measurements were performed while maintaining the thermal conditions of the cryocoolers at a steady state. We found that the vibration of the cold-head for the 4 K PT cryocooler was two orders of magnitude smaller than that of the 4 K GM cryocooler. On the other hand, the vibration of the cold-stages for both cryocoolers was of the same order of magnitude. From a spectral analysis of the vibrations and a simulation, we concluded that the vibration of the cold-stage is caused by an elastic deformation of the pulse tubes (or cylinders) due to the pressure oscillation of the working gas. (Author)

  18. Vibration of hydraulic machinery

    CERN Document Server

    Wu, Yulin; Liu, Shuhong; Dou, Hua-Shu; Qian, Zhongdong

    2013-01-01

    Vibration of Hydraulic Machinery deals with the vibration problem which has significant influence on the safety and reliable operation of hydraulic machinery. It provides new achievements and the latest developments in these areas, even in the basic areas of this subject. The present book covers the fundamentals of mechanical vibration and rotordynamics as well as their main numerical models and analysis methods for the vibration prediction. The mechanical and hydraulic excitations to the vibration are analyzed, and the pressure fluctuations induced by the unsteady turbulent flow is predicted in order to obtain the unsteady loads. This book also discusses the loads, constraint conditions and the elastic and damping characters of the mechanical system, the structure dynamic analysis, the rotor dynamic analysis and the system instability of hydraulic machines, including the illustration of monitoring system for the instability and the vibration in hydraulic units. All the problems are necessary for vibration pr...

  19. Spontaneous reduction and C-H borylation of arenes mediated by uranium(III) disproportionation

    Science.gov (United States)

    Arnold, Polly L.; Mansell, Stephen M.; Maron, Laurent; McKay, David

    2012-08-01

    Transition-metal-arene complexes such as bis(benzene)chromium Cr(η6-C6H6)2 are historically important to d-orbital bonding theory and have modern importance in organic synthesis, catalysis and organic spintronics. In investigations of f-block chemistry, however, arenes are invariably used as solvents rather than ligands. Here, we show that simple uranium complexes UX3 (X = aryloxide, amide) spontaneously disproportionate, transferring an electron and X-ligand, allowing the resulting UX2 to bind and reduce arenes, forming inverse sandwich molecules [X2U(µ-η6:η6-arene)UX2] and a UX4 by-product. Calculations and kinetic studies suggest a ‘cooperative small-molecule activation’ mechanism involving spontaneous arene reduction as an X-ligand is transferred. These mild reaction conditions allow functionalized arenes such as arylsilanes to be incorporated. The bulky UX3 are also inert to reagents such as boranes that would react with the traditional harsh reaction conditions, allowing the development of a new in situ arene C-H bond functionalization methodology converting C-H to C-B bonds.

  20. C-H Bond Activation/Arylation Catalyzed by Arene-Ruthenium-Aniline Complexes in Water.

    Science.gov (United States)

    Binnani, Chinky; Tyagi, Deepika; Rai, Rohit K; Mobin, Shaikh M; Singh, Sanjay K

    2016-11-07

    Water-soluble arene-ruthenium complexes coordinated with readily available aniline-based ligands were successfully employed as highly active catalysts in the C-H bond activation and arylation of 2-phenylpyridine with aryl halides in water. A variety of (hetero)aryl halides were also used for the ortho-C-H bond arylation of 2-phenylpyridine to afford the corresponding ortho- monoarylated products as major products in moderate to good yields. Our investigations, including time-scaled NMR spectroscopy and mass spectrometry studies, evidenced that the coordinating aniline-based ligands, having varying electronic and steric properties, had a significant influence on the catalytic activity of the resulting arene-ruthenium-aniline-based complexes. Moreover, mass spectrometry identification of the cycloruthenated species, {(η6 -arene)Ru(κ2 -C,N-phenylpyridine)}+ , and several ligand-coordinated cycloruthenated species, such as [(η6 -arene)Ru(4-methylaniline)(κ2 -C,N-phenylpyridine)]+ , found during the reaction of 2-phenylpyridine with the arene-ruthenium-aniline complexes further authenticated the crucial roles of these species in the observed highly active and tuned catalyst. At last, the structures of a few of the active catalysts were also confirmed by single-crystal X-ray diffraction studies. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Biocompatible Silver-containing a-C:H and a-C coatings: AComparative Study

    Energy Technology Data Exchange (ETDEWEB)

    Endrino, Jose Luis; Allen, Matthew; Escobar Galindo, Ramon; Zhang, Hanshen; Anders, Andre; Albella, Jose Maria

    2007-04-01

    Hydrogenated diamond-like-carbon (a-C:H) and hydrogen-free amorphous carbon (a-C) coatings are known to be biocompatible and have good chemical inertness. For this reason, both of these materials are strong candidates to be used as a matrix that embeds metallic elements with antimicrobial effect. In this comparative study, we have incorporated silver into diamond-like carbon (DLC) coatings by plasma based ion implantation and deposition (PBII&D) using methane (CH4) plasma and simultaneously depositing Ag from a pulsed cathodic arc source. In addition, we have grown amorphous carbon - silver composite coatings using a dual-cathode pulsed filtered cathodic-arc (FCA) source. The silver atomic content of the deposited samples was analyzed using glow discharge optical spectroscopy (GDOES). In both cases, the arc pulse frequency of the silver cathode was adjusted in order to obtain samples with approximately 5 at.% of Ag. Surface hardness of the deposited films was analyzed using the nanoindentation technique. Cell viability for both a-C:H/Ag and a-C:/Ag samples deposited on 24-well tissue culture plates has been evaluated.

  2. Vibrational Fingerprints of Low-Lying PtnP2n (n = 1–5) Cluster Structures from Global Optimization Based on Density Functional Theory Potential Energy Surfaces

    KAUST Repository

    Jedidi, Abdesslem

    2015-11-13

    Vibrational fingerprints of small PtnP2n (n = 1–5) clusters were computed from their low-lying structures located from a global exploration of their DFT potential energy surfaces with the GSAM code. Five DFT methods were assessed from the CCSD(T) wavenumbers of PtP2 species and CCSD relative energies of Pt2P4 structures. The eight first PtnP2n isomers found are reported. The vibrational computations reveal (i) the absence of clear signatures made by overtone or combination bands due to very weak mechanical and electrical anharmonicities and (ii) some significant and recurrent vibrational fingerprints in correlation with the different PP bonding situations in the PtnP2n structures.

  3. Chemoselective, Enzymatic C-H Bond Amination Catalyzed by a Cytochrome P450 Containing an Ir(Me)-PIX Cofactor.

    Science.gov (United States)

    Dydio, Paweł; Key, Hanna M; Hayashi, Hiroki; Clark, Douglas S; Hartwig, John F

    2017-02-08

    Cytochrome P450 enzymes have been engineered to catalyze abiological C-H bond amination reactions, but the yields of these reactions have been limited by low chemoselectivity for the amination of C-H bonds over competing reduction of the azide substrate to a sulfonamide. Here we report that P450s derived from a thermophilic organism and containing an iridium porphyrin cofactor (Ir(Me)-PIX) in place of the heme catalyze enantioselective intramolecular C-H bond amination reactions of sulfonyl azides. These reactions occur with chemoselectivity for insertion of the nitrene units into C-H bonds over reduction of the azides to the sulfonamides that is higher and with substrate scope that is broader than those of enzymes containing iron porphyrins. The products from C-H amination are formed in up to 98% yield and ∼300 TON. In one case, the enantiomeric excess reaches 95:5 er, and the reactions can occur with divergent site selectivity. The chemoselectivity for C-H bond amination is greater than 20:1 in all cases. Variants of the Ir(Me)-PIX CYP119 displaying these properties were identified rapidly by evaluating CYP119 mutants containing Ir(Me)-PIX in cell lysates, rather than as purified enzymes. This study sets the stage to discover suitable enzymes to catalyze challenging C-H amination reactions.

  4. Manganese- and Borane-Mediated Synthesis of Isobenzofuranones from Aromatic Esters and Oxiranes via C-H Bond Activation.

    Science.gov (United States)

    Sueki, Shunsuke; Wang, Zijia; Kuninobu, Yoichiro

    2016-01-15

    A manganese- and borane-mediated synthesis of isobenzofuranones from esters and oxiranes is developed. The reaction proceeded at aromatic, heteroaromatic, and olefinic C-H bonds with high functional group tolerance. This is the first example of a manganese-catalyzed C-H transformation using an oxygen-directing group. Triphenylborane played an important role in this reaction to cooperatively promote the annulation reaction. Kinetic isotope effect experiments revealed that C-H bond activation of the aromatic rings was the rate-determining step.

  5. Rh(III)-catalyzed direct C-H/C-H cross-coupling of quinones with arenes assisted by a directing group: identification of carbazole quinones as GSKβ inhibitors.

    Science.gov (United States)

    Moon, Youngtaek; Jeong, Yujeong; Kook, Daehyuk; Hong, Sungwoo

    2015-04-07

    Rh-catalyzed direct C-H/C-H cross-coupling reaction of various (hetero)arenes with quinones is developed. This protocol is effective for a broad range of both quinone and arene substrates and a wide range of directing groups for this reaction, affording structurally diverse aryl-substituted quinones with high synthetic utility. Moreover, the present synthetic route allowed for the rapid construction of the carbazole quinone moiety that was identified as a new inhibitor scaffold for GSKβ.

  6. A Base-Resistant Metalloporphyrin Metal-Organic Framework for C-H Bond Halogenation.

    Science.gov (United States)

    Lv, Xiu-Liang; Wang, Kecheng; Wang, Bin; Su, Jie; Zou, Xiaodong; Xie, Yabo; Li, Jian-Rong; Zhou, Hong-Cai

    2017-01-11

    A base-resistant porphyrin metal-organic framework (MOF), namely PCN-602 has been constructed with 12-connected [Ni8(OH)4(H2O)2Pz12] (Pz = pyrazolate) cluster and a newly designed pyrazolate-based porphyrin ligand, 5,10,15,20-tetrakis(4-(pyrazolate-4-yl)phenyl)porphyrin under the guidance of the reticular synthesis strategy. Besides its robustness in hydroxide solution, PCN-602 also shows excellent stability in aqueous solutions of F(-), CO3(2-), and PO4(3-) ions. Interestingly, the Mn(3+)-porphyrinic PCN-602, as a recyclable MOF catalyst, presents high catalytic activity for the C-H bond halogenation reaction in a basic system, significantly outperforming its homogeneous counterpart. For the first time, a porphyrinic MOF was thus used as an efficient catalyst in a basic solution with coordinating anions, to the best of our knowledge.

  7. Enzymatic Halogenation: A Timely Strategy for Regioselective C-H Activation.

    Science.gov (United States)

    Schnepel, Christian; Sewald, Norbert

    2017-09-07

    Halogenating enzymes are increasingly attracting attention for biocatalytic C-H functionalization. Despite its importance for synthetic chemistry, selective introduction of halogens using conventional approaches often remains challenging, whereas biocatalysis offers excellent catalyst-controlled selectivity without requiring protecting groups or hazardous reagents. Owing to the high prevalence of halogenated secondary metabolites, a still growing repertoire of halogenases has been identified. Recently, flavin-dependent tryptophan halogenases came into focus for synthetic use. Nevertheless, these enzymes still suffer from severe deficiencies. Herein, current attempts in optimizing tryptophan halogenases have been compiled. Enzyme discovery, structure elucidation and mechanisms are reviewed with focus on biosynthesis of halogenated arenes. Emphasis is also given to random and rational engineering, high-throughput screening and implementation of halogenases into one-pot processes. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. 2008 C. H. McCloy lecture. Social psychology and physical activity: back to the future.

    Science.gov (United States)

    Gill, Diane L

    2009-12-01

    In the early 1970s, both my academic career and the psychology subdiscipline within kinesiology began as "social psychology and physical activity. "Since then, sport and exercise psychology research has shifted away from the social to a narrower biopsycho-(no social) approach, and professional practice has focused on the elite rather than the larger public. Psychology can contribute to an integrative and relevant professional discipline by going back to the future as social psychology and physical activity and by incorporating three of C. H. McCloy's themes (a) evidence-based practice, (b) beyond dualisms, and (c) commitment to public service. Our scholarship must move beyond dualisms to recognize complexities and connections and be truly scholarship for practice. Social psychology and physical activity can serve the public by advocating for inclusive, empowering physical activity programs that promote health and well being for all.

  9. Modeling a-SiC:H tandem pinpin and pinip photodiodes for color sensor application.

    Science.gov (United States)

    Fantoni, A; Martins, J; Fernandes, M; Louro, P; Vygranenko, Y; Vieira, M

    2009-07-01

    The present paper reports the optical properties of multilayer structures composed by p-i-n cells based on a-SiC:H or a-Si:H material. Different structures are studied in order to obtain image sensors that accomplish color filtering in addition to image pattern recognition. A simple theoretical model is developed to explain sensors behavior and to derive the optical-readout experimental procedure. Electrical models for the sensors are established for simulation purposes and to compare photocurrent signals with experimental data. A numerical simulation of the JV characteristic and of the spectral response is also presented in order to show possible future optimization of the device. Two main structures are studied, namely p-i-n/p-i-n and p-i-n/n-i-p tandem cells.

  10. Triiodide-Mediated δ-Amination of Secondary C-H Bonds.

    Science.gov (United States)

    Wappes, Ethan A; Fosu, Stacy C; Chopko, Trevor C; Nagib, David A

    2016-08-16

    The Cδ -H amination of unactivated, secondary C-H bonds to form a broad range of functionalized pyrrolidines has been developed by a triiodide (I3 (-) )-mediated strategy. By in situ 1) oxidation of sodium iodide and 2) sequestration of the transiently generated iodine (I2 ) as I3 (-) , this approach precludes undesired I2 -mediated decomposition which can otherwise limit synthetic utility to only weak C(sp(3) )-H bonds. The mechanism of this triiodide-mediated cyclization of unbiased, secondary C(sp(3) )-H bonds, by either thermal or photolytic initiation, is supported by NMR and UV/Vis data, as well as intercepted intermediates. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Studies of beauty baryon decays to $D^0 ph^-$ and $\\Lambda_c^+ h^-$ final states

    CERN Document Server

    Aaij, Roel; Adinolfi, Marco; Adrover, Cosme; Affolder, Anthony; Ajaltouni, Ziad; Albrecht, Johannes; Alessio, Federico; Alexander, Michael; Ali, Suvayu; Alkhazov, Georgy; Alvarez Cartelle, Paula; Alves Jr, Antonio; Amato, Sandra; Amerio, Silvia; Amhis, Yasmine; Anderlini, Lucio; Anderson, Jonathan; Andreassen, Rolf; Andreotti, Mirco; Andrews, Jason; Appleby, Robert; Aquines Gutierrez, Osvaldo; Archilli, Flavio; Artamonov, Alexander; Artuso, Marina; Aslanides, Elie; Auriemma, Giulio; Baalouch, Marouen; Bachmann, Sebastian; Back, John; Badalov, Alexey; Balagura, Vladislav; Baldini, Wander; Barlow, Roger; Barschel, Colin; Barsuk, Sergey; Barter, William; Batozskaya, Varvara; Bauer, Thomas; Bay, Aurelio; Beddow, John; Bedeschi, Franco; Bediaga, Ignacio; Belogurov, Sergey; Belous, Konstantin; Belyaev, Ivan; Ben-Haim, Eli; Bencivenni, Giovanni; Benson, Sean; Benton, Jack; Berezhnoy, Alexander; Bernet, Roland; Bettler, Marc-Olivier; van Beuzekom, Martinus; Bien, Alexander; Bifani, Simone; Bird, Thomas; Bizzeti, Andrea; Bjørnstad, Pål Marius; Blake, Thomas; Blanc, Frédéric; Blouw, Johan; Blusk, Steven; Bocci, Valerio; Bondar, Alexander; Bondar, Nikolay; Bonivento, Walter; Borghi, Silvia; Borgia, Alessandra; Bowcock, Themistocles; Bowen, Espen Eie; Bozzi, Concezio; Brambach, Tobias; van den Brand, Johannes; Bressieux, Joël; Brett, David; Britsch, Markward; Britton, Thomas; Brook, Nicholas; Brown, Henry; Bursche, Albert; Busetto, Giovanni; Buytaert, Jan; Cadeddu, Sandro; Calabrese, Roberto; Callot, Olivier; Calvi, Marta; Calvo Gomez, Miriam; Camboni, Alessandro; Campana, Pierluigi; Campora Perez, Daniel; Carbone, Angelo; Carboni, Giovanni; Cardinale, Roberta; Cardini, Alessandro; Carranza-Mejia, Hector; Carson, Laurence; Carvalho Akiba, Kazuyoshi; Casse, Gianluigi; Castillo Garcia, Lucia; Cattaneo, Marco; Cauet, Christophe; Cenci, Riccardo; Charles, Matthew; Charpentier, Philippe; Cheung, Shu-Faye; Chiapolini, Nicola; Chrzaszcz, Marcin; Ciba, Krzystof; Cid Vidal, Xabier; Ciezarek, Gregory; Clarke, Peter; Clemencic, Marco; Cliff, Harry; Closier, Joel; Coca, Cornelia; Coco, Victor; Cogan, Julien; Cogneras, Eric; Collins, Paula; Comerma-Montells, Albert; Contu, Andrea; Cook, Andrew; Coombes, Matthew; Coquereau, Samuel; Corti, Gloria; Couturier, Benjamin; Cowan, Greig; Craik, Daniel Charles; Cruz Torres, Melissa Maria; Cunliffe, Samuel; Currie, Robert; D'Ambrosio, Carmelo; Dalseno, Jeremy; David, Pascal; David, Pieter; Davis, Adam; De Bonis, Isabelle; De Bruyn, Kristof; De Capua, Stefano; De Cian, Michel; De Miranda, Jussara; De Paula, Leandro; De Silva, Weeraddana; De Simone, Patrizia; Decamp, Daniel; Deckenhoff, Mirko; Del Buono, Luigi; Déléage, Nicolas; Derkach, Denis; Deschamps, Olivier; Dettori, Francesco; Di Canto, Angelo; Dijkstra, Hans; Dogaru, Marius; Donleavy, Stephanie; Dordei, Francesca; Dorosz, Piotr; Dosil Suárez, Alvaro; Dossett, David; Dovbnya, Anatoliy; Dupertuis, Frederic; Durante, Paolo; Dzhelyadin, Rustem; Dziurda, Agnieszka; Dzyuba, Alexey; Easo, Sajan; Egede, Ulrik; Egorychev, Victor; Eidelman, Semen; van Eijk, Daan; Eisenhardt, Stephan; Eitschberger, Ulrich; Ekelhof, Robert; Eklund, Lars; El Rifai, Ibrahim; Elsasser, Christian; Falabella, Antonio; Färber, Christian; Farinelli, Chiara; Farry, Stephen; Ferguson, Dianne; Fernandez Albor, Victor; Ferreira Rodrigues, Fernando; Ferro-Luzzi, Massimiliano; Filippov, Sergey; Fiore, Marco; Fiorini, Massimiliano; Fitzpatrick, Conor; Fontana, Marianna; Fontanelli, Flavio; Forty, Roger; Francisco, Oscar; Frank, Markus; Frei, Christoph; Frosini, Maddalena; Furfaro, Emiliano; Gallas Torreira, Abraham; Galli, Domenico; Gandelman, Miriam; Gandini, Paolo; Gao, Yuanning; Garofoli, Justin; Garosi, Paola; Garra Tico, Jordi; Garrido, Lluis; Gaspar, Clara; Gauld, Rhorry; Gersabeck, Evelina; Gersabeck, Marco; Gershon, Timothy; Ghez, Philippe; Gibson, Valerie; Giubega, Lavinia-Helena; Gligorov, V.V.; Göbel, Carla; Golubkov, Dmitry; Golutvin, Andrey; Gomes, Alvaro; Gordon, Hamish; Grabalosa Gándara, Marc; Graciani Diaz, Ricardo; Granado Cardoso, Luis Alberto; Graugés, Eugeni; Graziani, Giacomo; Grecu, Alexandru; Greening, Edward; Gregson, Sam; Griffith, Peter; Grillo, Lucia; Grünberg, Oliver; Gui, Bin; Gushchin, Evgeny; Guz, Yury; Gys, Thierry; Hadjivasiliou, Christos; Haefeli, Guido; Haen, Christophe; Hafkenscheid, Tom; Haines, Susan; Hall, Samuel; Hamilton, Brian; Hampson, Thomas; Hansmann-Menzemer, Stephanie; Harnew, Neville; Harnew, Samuel; Harrison, Jonathan; Hartmann, Thomas; He, Jibo; Head, Timothy; Heijne, Veerle; Hennessy, Karol; Henrard, Pierre; Hernando Morata, Jose Angel; van Herwijnen, Eric; Heß, Miriam; Hicheur, Adlène; Hicks, Emma; Hill, Donal; Hoballah, Mostafa; Hombach, Christoph; Hulsbergen, Wouter; Hunt, Philip; Huse, Torkjell; Hussain, Nazim; Hutchcroft, David; Hynds, Daniel; Iakovenko, Viktor; Idzik, Marek; Ilten, Philip; Jacobsson, Richard; Jaeger, Andreas; Jans, Eddy; Jaton, Pierre; Jawahery, Abolhassan; Jing, Fanfan; John, Malcolm; Johnson, Daniel; Jones, Christopher; Joram, Christian; Jost, Beat; Jurik, Nathan; Kaballo, Michael; Kandybei, Sergii; Kanso, Wallaa; Karacson, Matthias; Karbach, Moritz; Kenyon, Ian; Ketel, Tjeerd; Khanji, Basem; Klaver, Suzanne; Kochebina, Olga; Komarov, Ilya; Koopman, Rose; Koppenburg, Patrick; Korolev, Mikhail; Kozlinskiy, Alexandr; Kravchuk, Leonid; Kreplin, Katharina; Kreps, Michal; Krocker, Georg; Krokovny, Pavel; Kruse, Florian; Kucharczyk, Marcin; Kudryavtsev, Vasily; Kurek, Krzysztof; Kvaratskheliya, Tengiz; La Thi, Viet Nga; Lacarrere, Daniel; Lafferty, George; Lai, Adriano; Lambert, Dean; Lambert, Robert W; Lanciotti, Elisa; Lanfranchi, Gaia; Langenbruch, Christoph; Latham, Thomas; Lazzeroni, Cristina; Le Gac, Renaud; van Leerdam, Jeroen; Lees, Jean-Pierre; Lefèvre, Regis; Leflat, Alexander; Lefrançois, Jacques; Leo, Sabato; Leroy, Olivier; Lesiak, Tadeusz; Leverington, Blake; Li, Yiming; Li Gioi, Luigi; Liles, Myfanwy; Lindner, Rolf; Linn, Christian; Lionetto, Federica; Liu, Bo; Liu, Guoming; Lohn, Stefan; Longstaff, Ian; Lopes, Jose; Lopez-March, Neus; Lu, Haiting; Lucchesi, Donatella; Luisier, Johan; Luo, Haofei; Luppi, Eleonora; Lupton, Oliver; Machefert, Frederic; Machikhiliyan, Irina V; Maciuc, Florin; Maev, Oleg; Malde, Sneha; Manca, Giulia; Mancinelli, Giampiero; Maratas, Jan; Marconi, Umberto; Marino, Pietro; Märki, Raphael; Marks, Jörg; Martellotti, Giuseppe; Martens, Aurelien; Martín Sánchez, Alexandra; Martinelli, Maurizio; Martinez Santos, Diego; Martins Tostes, Danielle; Martynov, Aleksandr; Massafferri, André; Matev, Rosen; Mathe, Zoltan; Matteuzzi, Clara; Maurice, Emilie; Mazurov, Alexander; McCann, Michael; McCarthy, James; McNab, Andrew; McNulty, Ronan; McSkelly, Ben; Meadows, Brian; Meier, Frank; Meissner, Marco; Merk, Marcel; Milanes, Diego Alejandro; Minard, Marie-Noelle; Molina Rodriguez, Josue; Monteil, Stephane; Moran, Dermot; Morawski, Piotr; Mordà, Alessandro; Morello, Michael Joseph; Mountain, Raymond; Mous, Ivan; Muheim, Franz; Müller, Katharina; Muresan, Raluca; Muryn, Bogdan; Muster, Bastien; Naik, Paras; Nakada, Tatsuya; Nandakumar, Raja; Nasteva, Irina; Needham, Matthew; Neubert, Sebastian; Neufeld, Niko; Nguyen, Anh Duc; Nguyen, Thi-Dung; Nguyen-Mau, Chung; Nicol, Michelle; Niess, Valentin; Niet, Ramon; Nikitin, Nikolay; Nikodem, Thomas; Nomerotski, Andrey; Novoselov, Alexey; Oblakowska-Mucha, Agnieszka; Obraztsov, Vladimir; Oggero, Serena; Ogilvy, Stephen; Okhrimenko, Oleksandr; Oldeman, Rudolf; Onderwater, Gerco; Orlandea, Marius; Otalora Goicochea, Juan Martin; Owen, Patrick; Oyanguren, Maria Arantza; Pal, Bilas Kanti; Palano, Antimo; Palutan, Matteo; Panman, Jacob; Papanestis, Antonios; Pappagallo, Marco; Pappalardo, Luciano; Parkes, Christopher; Parkinson, Christopher John; Passaleva, Giovanni; Patel, Girish; Patel, Mitesh; Patrignani, Claudia; Pavel-Nicorescu, Carmen; Pazos Alvarez, Antonio; Pearce, Alex; Pellegrino, Antonio; Penso, Gianni; Pepe Altarelli, Monica; Perazzini, Stefano; Perez Trigo, Eliseo; Pérez-Calero Yzquierdo, Antonio; Perret, Pascal; Perrin-Terrin, Mathieu; Pescatore, Luca; Pesen, Erhan; Pessina, Gianluigi; Petridis, Konstantin; Petrolini, Alessandro; Picatoste Olloqui, Eduardo; Pietrzyk, Boleslaw; Pilař, Tomas; Pinci, Davide; Playfer, Stephen; Plo Casasus, Maximo; Polci, Francesco; Polok, Grzegorz; Poluektov, Anton; Polycarpo, Erica; Popov, Alexander; Popov, Dmitry; Popovici, Bogdan; Potterat, Cédric; Powell, Andrew; Prisciandaro, Jessica; Pritchard, Adrian; Prouve, Claire; Pugatch, Valery; Puig Navarro, Albert; Punzi, Giovanni; Qian, Wenbin; Rachwal, Bartolomiej; Rademacker, Jonas; Rakotomiaramanana, Barinjaka; Rangel, Murilo; Raniuk, Iurii; Rauschmayr, Nathalie; Raven, Gerhard; Redford, Sophie; Reichert, Stefanie; Reid, Matthew; dos Reis, Alberto; Ricciardi, Stefania; Richards, Alexander; Rinnert, Kurt; Rives Molina, Vincente; Roa Romero, Diego; Robbe, Patrick; Roberts, Douglas; Rodrigues, Ana Barbara; Rodrigues, Eduardo; Rodriguez Perez, Pablo; Roiser, Stefan; Romanovsky, Vladimir; Romero Vidal, Antonio; Rotondo, Marcello; Rouvinet, Julien; Ruf, Thomas; Ruffini, Fabrizio; Ruiz, Hugo; Ruiz Valls, Pablo; Sabatino, Giovanni; Saborido Silva, Juan Jose; Sagidova, Naylya; Sail, Paul; Saitta, Biagio; Salustino Guimaraes, Valdir; Sanmartin Sedes, Brais; Santacesaria, Roberta; Santamarina Rios, Cibran; Santovetti, Emanuele; Sapunov, Matvey; Sarti, Alessio; Satriano, Celestina; Satta, Alessia; Savrie, Mauro; Savrina, Darya; Schiller, Manuel; Schindler, Heinrich; Schlupp, Maximilian; Schmelling, Michael; Schmidt, Burkhard; Schneider, Olivier; Schopper, Andreas; Schune, Marie Helene; Schwemmer, Rainer; Sciascia, Barbara; Sciubba, Adalberto; Seco, Marcos; Semennikov, Alexander; Senderowska, Katarzyna; Sepp, Indrek; Serra, Nicola; Serrano, Justine; Seyfert, Paul; Shapkin, Mikhail; Shapoval, Illya; Shcheglov, Yury; Shears, Tara; Shekhtman, Lev; Shevchenko, Oksana; Shevchenko, Vladimir; Shires, Alexander; Silva Coutinho, Rafael; Sirendi, Marek; Skidmore, Nicola; Skwarnicki, Tomasz; Smith, Anthony; Smith, Edmund; Smith, Eluned; Smith, Jackson; Smith, Mark; Sokoloff, Michael; Soler, Paul; Soomro, Fatima; Souza, Daniel; Souza De Paula, Bruno; Spaan, Bernhard; Sparkes, Ailsa; Spradlin, Patrick; Stagni, Federico; Stahl, Sascha; Steinkamp, Olaf; Stevenson, Scott; Stoica, Sabin; Stone, Sheldon; Storaci, Barbara; Stracka, Simone; Straticiuc, Mihai; Straumann, Ulrich; Subbiah, Vijay Kartik; Sun, Liang; Sutcliffe, William; Swientek, Stefan; Syropoulos, Vasileios; Szczekowski, Marek; Szczypka, Paul; Szilard, Daniela; Szumlak, Tomasz; T'Jampens, Stephane; Teklishyn, Maksym; Tellarini, Giulia; Teodorescu, Eliza; Teubert, Frederic; Thomas, Christopher; Thomas, Eric; van Tilburg, Jeroen; Tisserand, Vincent; Tobin, Mark; Tolk, Siim; Tomassetti, Luca; Tonelli, Diego; Topp-Joergensen, Stig; Torr, Nicholas; Tournefier, Edwige; Tourneur, Stephane; Tran, Minh Tâm; Tresch, Marco; Tsaregorodtsev, Andrei; Tsopelas, Panagiotis; Tuning, Niels; Ubeda Garcia, Mario; Ukleja, Artur; Ustyuzhanin, Andrey; Uwer, Ulrich; Vagnoni, Vincenzo; Valenti, Giovanni; Vallier, Alexis; Vazquez Gomez, Ricardo; Vazquez Regueiro, Pablo; Vázquez Sierra, Carlos; Vecchi, Stefania; Velthuis, Jaap; Veltri, Michele; Veneziano, Giovanni; Vesterinen, Mika; Viaud, Benoit; Vieira, Daniel; Vilasis-Cardona, Xavier; Vollhardt, Achim; Volyanskyy, Dmytro; Voong, David; Vorobyev, Alexey; Vorobyev, Vitaly; Voß, Christian; Voss, Helge; de Vries, Jacco; Waldi, Roland; Wallace, Charlotte; Wallace, Ronan; Wandernoth, Sebastian; Wang, Jianchun; Ward, David; Watson, Nigel; Webber, Adam Dane; Websdale, David; Whitehead, Mark; Wicht, Jean; Wiechczynski, Jaroslaw; Wiedner, Dirk; Wiggers, Leo; Wilkinson, Guy; Williams, Matthew; Williams, Mike; Wilson, Fergus; Wimberley, Jack; Wishahi, Julian; Wislicki, Wojciech; Witek, Mariusz; Wormser, Guy; Wotton, Stephen; Wright, Simon; Wu, Suzhi; Wyllie, Kenneth; Xie, Yuehong; Xing, Zhou; Yang, Zhenwei; Yuan, Xuhao; Yushchenko, Oleg; Zangoli, Maria; Zavertyaev, Mikhail; Zhang, Feng; Zhang, Liming; Zhang, Wen Chao; Zhang, Yanxi; Zhelezov, Alexey; Zhokhov, Anatoly; Zhong, Liang; Zvyagin, Alexander

    2014-01-01

    Decays of beauty baryons to the $D^0 p h^-$ and $\\Lambda_c^+ h^-$ final states (where $h$ indicates a pion or a kaon) are studied using a data sample of $pp$ collisions, corresponding to an integrated luminosity of 1.0 fb$^{-1}$, collected by the LHCb detector. The Cabibbo-suppressed decays $\\Lambda_b^0\\to D^0 p K^-$ and $\\Lambda_b^0\\to \\Lambda_c^+ K^-$ are observed and their branching fractions are measured with respect to the decays $\\Lambda_b^0\\to D^0 p \\pi^-$ and $\\Lambda_b^0\\to \\Lambda_c^+ \\pi^-$. In addition, the first observation is reported of the decay of the neutral beauty-strange baryon $\\Xi_b^0$ to the $D^0 p K^-$ final state, and a measurement of the $\\Xi_b^0$ mass is performed. Evidence of the $\\Xi_b^0\\to \\Lambda_c^+ K^-$ decay is also reported.

  12. Resolving a Reactive Organometallic Intermediate from Dynamic Directing Group Systems by Selective C-H Activation.

    Science.gov (United States)

    Schaufelberger, Fredrik; Timmer, Brian J J; Ramström, Olof

    2017-11-17

    Catalyst discovery from systems of potential precursors is a challenging endeavor. Herein, a new strategy applying dynamic chemistry to the identification of catalyst precursors from C-H activation of imines is proposed and evaluated. Using hydroacylation of imines as a model reaction, the selection of an organometallic reactive intermediate from a dynamic imine system, involving many potential directing group/metal entities, is demonstrated. The identity of the amplified reaction intermediate with the best directing group could be resolved in situ via ESI-MS, and coupling of the procedure to an iterative deconvolution protocol generated a system with high screening efficiency. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Carbene-mediated functionalization of the anomeric C-H bond of carbohydrates: scope and limitations.

    Science.gov (United States)

    Boultadakis-Arapinis, Mélissa; Prost, Elise; Gandon, Vincent; Lemoine, Pascale; Turcaud, Serge; Micouin, Laurent; Lecourt, Thomas

    2013-05-03

    Herein we investigate the scope and limitations of a new synthetic approach towards α- and β-ketopyranosides relying on the functionalization of the anomeric C-H bond of carbohydrates by insertion of a metal carbene. A key bromoacetate grafted at the 2-position is the cornerstone of a stereoselective glycosylation/diazotransfer/quaternarization sequence that makes possible the construction of a quaternary center with complete control of the stereochemistry. This sequence shows a good tolerance toward protecting groups commonly used in carbohydrate chemistry and gives rise to quaternary disaccharides with good efficiency. In the case of a disaccharide with a more restricted conformation, this functionalization process can be hampered by the steric demand next to the targeted anomeric position. In addition, the formation of transient orthoesters during the glycosylation step may also reduce the overall efficiency of the synthetic sequence. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Direct α-C-H bond functionalization of unprotected cyclic amines

    Science.gov (United States)

    Chen, Weijie; Ma, Longle; Paul, Anirudra; Seidel, Daniel

    2018-02-01

    Cyclic amines are ubiquitous core structures of bioactive natural products and pharmaceutical drugs. Although the site-selective abstraction of C-H bonds is an attractive strategy for preparing valuable functionalized amines from their readily available parent heterocycles, this approach has largely been limited to substrates that require protection of the amine nitrogen atom. In addition, most methods rely on transition metals and are incompatible with the presence of amine N-H bonds. Here we introduce a protecting-group-free approach for the α-functionalization of cyclic secondary amines. An operationally simple one-pot procedure generates products via a process that involves intermolecular hydride transfer to generate an imine intermediate that is subsequently captured by a nucleophile, such as an alkyl or aryl lithium compound. Reactions are regioselective and stereospecific and enable the rapid preparation of bioactive amines, as exemplified by the facile synthesis of anabasine and (-)-solenopsin A.

  15. Modification of Purine and Pyrimidine Nucleosides by Direct C-H Bond Activation

    Directory of Open Access Journals (Sweden)

    Yong Liang

    2015-03-01

    Full Text Available Transition metal-catalyzed modifications of the activated heterocyclic bases of nucleosides as well as DNA or RNA fragments employing traditional cross-coupling methods have been well-established in nucleic acid chemistry. This review covers advances in the area of cross-coupling reactions in which nucleosides are functionalized via direct activation of the C8-H bond in purine and the C5-H or C6-H bond in uracil bases. The review focuses on Pd/Cu-catalyzed couplings between unactivated nucleoside bases with aryl halides. It also discusses cross-dehydrogenative arylations and alkenylations as well as other reactions used for modification of nucleoside bases that avoid the use of organometallic precursors and involve direct C-H bond activation in at least one substrate. The scope and efficiency of these coupling reactions along with some mechanistic considerations are discussed.

  16. Silylation of C-H bonds in aromatic heterocycles by an Earth-abundant metal catalyst

    Science.gov (United States)

    Toutov, Anton A.; Liu, Wen-Bo; Betz, Kerry N.; Fedorov, Alexey; Stoltz, Brian M.; Grubbs, Robert H.

    2015-02-01

    Heteroaromatic compounds containing carbon-silicon (C-Si) bonds are of great interest in the fields of organic electronics and photonics, drug discovery, nuclear medicine and complex molecule synthesis, because these compounds have very useful physicochemical properties. Many of the methods now used to construct heteroaromatic C-Si bonds involve stoichiometric reactions between heteroaryl organometallic species and silicon electrophiles or direct, transition-metal-catalysed intermolecular carbon-hydrogen (C-H) silylation using rhodium or iridium complexes in the presence of excess hydrogen acceptors. Both approaches are useful, but their limitations include functional group incompatibility, narrow scope of application, high cost and low availability of the catalysts, and unproven scalability. For this reason, a new and general catalytic approach to heteroaromatic C-Si bond construction that avoids such limitations is highly desirable. Here we report an example of cross-dehydrogenative heteroaromatic C-H functionalization catalysed by an Earth-abundant alkali metal species. We found that readily available and inexpensive potassium tert-butoxide catalyses the direct silylation of aromatic heterocycles with hydrosilanes, furnishing heteroarylsilanes in a single step. The silylation proceeds under mild conditions, in the absence of hydrogen acceptors, ligands or additives, and is scalable to greater than 100 grams under optionally solvent-free conditions. Substrate classes that are difficult to activate with precious metal catalysts are silylated in good yield and with excellent regioselectivity. The derived heteroarylsilane products readily engage in versatile transformations enabling new synthetic strategies for heteroaromatic elaboration, and are useful in their own right in pharmaceutical and materials science applications.

  17. Iron Mineral Catalyzed C-H Activation As a Potential Pathway for Halogenation Processes

    Science.gov (United States)

    Tubbesing, C.; Schoeler, H. F.; Benzing, K.; Krause, T.; Lippe, S.; Rudloff, M.

    2014-12-01

    Due to increasing drinking water demand of mankind and an expected climate change the impact of salt lakes and salt deserts will increase within the next decades. Furthermore, a rising sea level influences coastal areas like salt marshes and abets processes which will lead to elevated organohalogen formation. An additional increase of the global warming potential, of particle formation and stratospheric ozone depletion is expected. Understanding these multifaceted processes is essential for mankind to be prepared for these alterations of the atmosphere. For example, Keppler et al. (2000) described the production of volatile halogenated organic compounds via oxidation of organic matter driven by ferric iron. However, the formation of long-chained alkyl halides in salt lakes is yet undisclosed. Despite the relative "inertness" of alkanes a direct halogenation of these compounds might be envisaged. In 2005 Vaillancourt et al. discovered a nonheme iron enzyme which is able to halogenate organic compounds via generating the high valent ferryl cation as reaction center. Based on various publications about C-H activation (Bergman, 2007) we postulate a halogenation process in which an iron containing minerals catalyse the C-H bond cleavage of organic compounds in soils. The generated organic radicals are highly reactive towards halides connected to the iron complex. We suggest that next to diagenetically altered iron containing enzymes, minerals such as oxides, hydroxides and sulfides are involved in abiotic halogenation processes. We applied the amino acid methionine as organic model compound and soluble iron species as reactants. All samples were incubated in aqueous phases containing various NaCl concentrations. As a result various halogenated ethanes and ethenes were identified as reaction products. References Bergman, R. G. (2007) Nature, 446(7134) 391-393 Keppler, F., et al. (2000) Nature, 403(6767) 298-301 Vaillancourt, F. H., et al. (2005) Nature, 436(7054) 1191-1194

  18. Higher-order diagrammatic vibrational coupled-cluster theory.

    Science.gov (United States)

    Faucheaux, Jacob A; Hirata, So

    2015-10-07

    Diagrammatically size-consistent and basis-set-free vibrational coupled-cluster (XVCC) theory for both zero-point energies and transition frequencies of a molecule, the latter through the equation-of-motion (EOM) formalism, is defined for an nth-order Taylor-series potential energy surface (PES). Quantum-field-theoretical tools (the rules of normal-ordered second quantization and Feynman-Goldstone diagrams) for deriving their working equations are established. The equations of XVCC and EOM-XVCC including up to the mth-order excitation operators are derived and implemented with the aid of computer algebra in the range of 1 ≤ m ≤ 8. Algorithm optimizations known as strength reduction, intermediate reuse, and factorization are carried out before code generation, reducing the cost scaling of the mth-order XVCC and EOM-XVCC in an nth-order Taylor-series PES (m ≥ n) to the optimal value of O(N(m+⌊n/2⌋)), where N is the number of modes. The calculated zero-point energies and frequencies of fundamentals, overtones, and combinations as well as Fermi-resonant modes display rapid and nearly monotonic convergence with m towards the exact values for the PES. The theory with the same excitation rank as the truncation order of the Taylor-series PES (m = n) seems to strike the best cost-accuracy balance, achieving the accuracy of a few tenths of cm(-1) for transitions involving (m - 3) modes and of a few cm(-1) for those involving (m - 2) modes. The relationships between XVCC and the vibrational coupled-cluster theories of Prasad and coworkers and of Christiansen and coworkers as well as the size-extensive vibrational self-consistent-field and many-body perturbation theories are also elucidated.

  19. Mechanistic elucidation of C-H oxidation by electron rich non-heme iron(IV)-oxo at room temperature.

    Science.gov (United States)

    Rana, Sujoy; Dey, Aniruddha; Maiti, Debabrata

    2015-10-04

    Non-heme iron(IV)-oxo species form iron(III) intermediates during hydrogen atom abstraction (HAA) from the C-H bond. While synthesizing a room temperature stable, electron rich, non-heme iron(IV)-oxo compound, we obtained iron(III)-hydroxide, iron(III)-alkoxide and hydroxylated-substrate-bound iron(II) as the detectable intermediates. The present study revealed that a radical rebound pathway was operative for benzylic C-H oxidation of ethylbenzene and cumene. A dissociative pathway for cyclohexane oxidation was established based on UV-vis and radical trap experiments. Interestingly, experimental evidence including O-18 labeling and mechanistic study suggested an electron transfer mechanism to be operative during C-H oxidation of alcohols (e.g. benzyl alcohol and cyclobutanol). The present report, therefore, unveils non-heme iron(IV)-oxo promoted substrate-dependent C-H oxidation pathways which are of synthetic as well as biological significance.

  20. Transition metal-catalyzed C-H bond functionalization in multicomponent reactions: a tool toward molecular diversity.

    Science.gov (United States)

    Wan, Jie-Ping; Gan, Lu; Liu, Yunyun

    2017-11-07

    Transition metal-catalyzed C-H bond functionalization has numerous applications in organic synthesis as a powerful type of bond transformation. In particular, the combination of C-H functionalization with other types of chemical transformations in the manner of multicomponent reactions is an even more beneficial tool in the synthesis of small organic molecules because such reactions provide a platform for the rapid generation of high molecular diversity and complexity by making use of the advantages of both latent C-H bond transformation and the multicomponent reaction. Herein, we provide a review highlighting the research advances in the multicomponent reactions built upon transition metal-catalyzed C-H bond functionalization. The content spans from the reactions featuring the functionalization of C(sp(3))-H, C(sp(2))-H and C(sp)-H bonds over the last decade.

  1. Thermochemistry of C7H16 to C10H22 alkane isomers: primary, secondary, and tertiary C-H bond dissociation energies and effects of branching.

    Science.gov (United States)

    Hudzik, Jason M; Bozzelli, Joseph W; Simmie, John M

    2014-10-09

    Standard enthalpies of formation (ΔH°f 298) of methyl, ethyl, primary and secondary propyl, and n-butyl radicals are evaluated and used in work reactions to determine internal consistency. They are then used to calculate the enthalpy of formation for the tert-butyl radical. Other thermochemical properties including standard entropies (S°(T)), heat capacities (Cp(T)), and carbon-hydrogen bond dissociation energies (C-H BDEs) are reported for n-pentane, n-heptane, 2-methylhexane, 2,3-dimethylpentane, and several branched higher carbon number alkanes and their radicals. ΔH°f 298 and C-H BDEs are calculated using isodesmic work reactions at the B3LYP (6-31G(d,p) and 6-311G(2d,2p) basis sets), CBS-QB3, CBS-APNO, and G3MP2B3 levels of theory. Structures, moments of inertia, vibrational frequencies, and internal rotor potentials are calculated at the B3LYP/6-31G(d,p) level for contributions to entropy and heat capacities. Enthalpy calculations for these hydrocarbon radical species are shown to have consistency with the CBS-QB3 and CBS-APNO methods using all work reactions. Our recommended ideal gas phase ΔH°f 298 values are from the average of all CBS-QB3, CBS-APNO, and for G3MP2B3, only where the reference and target radical are identical types, and are compared with literature values. Calculated values show agreement between the composite calculation methods and the different work reactions. Secondary and tertiary C-H bonds in the more highly branched alkanes are shown to have bond energies that are several kcal mol(-1) lower than the BDEs in corresponding smaller molecules often used as reference species. Entropies and heat capacities are calculated and compared to literature values (when available) when all internal rotors are considered.

  2. Study of optical sensors of the form Al/a-SiC:H/c-Si(n with high sensitivity.

    Directory of Open Access Journals (Sweden)

    L. Magafas

    2008-06-01

    Full Text Available In the present work optical sensors of the form Al/a-SiC:H/c-Si(n, for different thickness of a-SiC:H thin films are stud-ied. More specifically, a-SiC:H thin films were deposited by rf sputtering technique on c-Si(n substrates for different thickness of the amorphous semiconductor and, subsequently, the samples were annealed in the temperature range from 300oC up to 675 oC. Experimental measurements of the optical response of these sensors showed that for thicknesses of a-SiC:H greater than a critical value, which depends on annealing temperature, a mechanism of losses is appeared in the region of wavelengths from 525nm up to 625nm. This behaviour is attributed to the recombination of photo-generated electrons-hole pairs in the neutral region of a-SiC:H, when this exceeds the diffusion length of minority carries, Lp. Also, the value of the reverse bias voltage appears to influence considerably the optical response of these sensors when d > Lp in the case where the a-SiC: H thin films were annealed at 600oC.

  3. Direct Functionalization of Nitrogen Heterocycles via Rh-Catalyzed C-H Bond Activation

    Science.gov (United States)

    Lewis, Jared C.; Bergman, Robert G.; Ellman, Jonathan A.

    2008-01-01

    Conspectus Nitrogen heterocycles are present in many compounds of enormous practical importance, ranging from pharmaceutical agents and biological probes to electroactive materials. Direct functionalization of nitrogen heterocycles through C-H bond activation constitutes a powerful means of regioselectively introducing a variety of substituents with diverse functional groups onto the heterocycle scaffold. Working together, our two groups have developed a family of Rh-catalyzed heterocycle alkylation and arylation reactions that are notable for their high level of functional-group compatibility. This Account describes our work in this area, emphasizing the relevant mechanistic insights that enabled synthetic advances and distinguished the resulting transformations from other methods. We initially discovered an intramolecular Rh-catalyzed C-2-alkylation of azoles by alkenyl groups. That reaction provided access to a number of di-, tri-, and tetracyclic azole derivatives. We then developed conditions that exploited microwave heating to expedite these reactions. While investigating the mechanism of this transformation, we discovered that a novel substrate-derived Rh-N-heterocyclic carbene (NHC) complex was involved as an intermediate. We then synthesized analogous Rh–NHC complexes directly by treating precursors to the intermediate [RhCl(PCy3)2] with N-methylbenzimidazole, 3-methyl-3,4-dihydroquinazoline, and 1-methyl-1,4-benzodiazepine-2-one. Extensive kinetic analysis and DFT calculations supported a mechanism for carbene formation in which the catalytically active RhCl(PCy3)2 fragment coordinates to the heterocycle before intramolecular activation of the C-H bond occurs. The resulting Rh-H intermediate ultimately tautomerizes to the observed carbene complex. With this mechanistic information and the discovery that acid co-catalysts accelerate the alkylation, we developed conditions that efficiently and intermolecularly alkylate a variety of heterocycles, including

  4. Direct Functionalization of Nitrogen Heterocycles via Rh-Catalyzed C-H Bond Activation

    Energy Technology Data Exchange (ETDEWEB)

    Lewis, Jared; Bergman, Robert; Ellman, Jonathan

    2008-02-04

    Nitrogen heterocycles are present in many compounds of enormous practical importance, ranging from pharmaceutical agents and biological probes to electroactive materials. Direct funtionalization of nitrogen heterocycles through C-H bond activation constitutes a powerful means of regioselectively introducing a variety of substituents with diverse functional groups onto the heterocycle scaffold. Working together, our two groups have developed a family of Rh-catalyzed heterocycle alkylation and arylation reactions that are notable for their high level of functional-group compatibility. This Account describes their work in this area, emphasizing the relevant mechanistic insights that enabled synthetic advances and distinguished the resulting transformations from other methods. They initially discovered an intramolecular Rh-catalyzed C-2-alkylation of azoles by alkenyl groups. That reaction provided access to a number of di-, tri-, and tetracyclic azole derivatives. They then developed conditions that exploited microwave heating to expedite these reactions. While investigating the mechanism of this transformation, they discovered that a novel substrate-derived Rh-N-heterocyclic carbene (NHC) complex was involved as an intermediate. They then synthesized analogous Rh-NHC complexes directly by treating precursors to the intermediate [RhCl(PCy{sub 3}){sub 2}] with N-methylbenzimidazole, 3-methyl-3,4-dihydroquinazolein, and 1-methyl-1,4-benzodiazepine-2-one. Extensive kinetic analysis and DFT calculations supported a mechanism for carbene formation in which the catalytically active RhCl(PCy{sub 3}){sub 2} fragment coordinates to the heterocycle before intramolecular activation of the C-H bond occurs. The resulting Rh-H intermediate ultimately tautomerizes to the observed carbene complex. With this mechanistic information and the discovery that acid co-catalysts accelerate the alkylation, they developed conditions that efficiently and intermolecularly alkylate a variety of

  5. Model Indepedent Vibration Control

    OpenAIRE

    Yuan, Jing

    2010-01-01

    A NMIFC system is proposed for broadband vibration control. It has two important features. Feature F1 is that the NMIFC is stable without introducing any invasive effects, such as probing signals or controller perturbations, into the vibration system; feature F2 is

  6. Vibration Theory, Vol. 3

    DEFF Research Database (Denmark)

    Nielsen, Søren R. K.

    The present textbook has been written based on previous lecture notes for a course on stochastic vibration theory that is being given on the 9th semester at Aalborg University for M. Sc. students in structural engineering. The present 4th edition of this textbook on linear stochastic vibration...

  7. Vibration Theory, Vol. 3

    DEFF Research Database (Denmark)

    Nielsen, Søren R. K.

    The present textbook has been written based on previous lecture notes for a course on stochastic vibration theory that is being given on the 9th semester at Aalborg University for M. Sc. students in structural engineering. The present 2nd edition of this textbook on linear stochastic vibration...

  8. Hydroelastic Vibrations of Ships

    DEFF Research Database (Denmark)

    Jensen, Jørgen Juncher; Folsø, Rasmus

    2002-01-01

    A formula for the necessary hull girder bending stiffness required to avoid serious springing vibrations is derived. The expression takes into account the zero crossing period of the waves, the ship speed and main dimensions. For whipping vibrations the probability of exceedance for the combined...

  9. Gearbox vibration diagnostic analyzer

    Science.gov (United States)

    1992-01-01

    This report describes the Gearbox Vibration Diagnostic Analyzer installed in the NASA Lewis Research Center's 500 HP Helicopter Transmission Test Stand to monitor gearbox testing. The vibration of the gearbox is analyzed using diagnostic algorithms to calculate a parameter indicating damaged components.

  10. Mechanical vibration and shock analysis, sinusoidal vibration

    CERN Document Server

    Lalanne, Christian

    2014-01-01

    Everything engineers need to know about mechanical vibration and shock...in one authoritative reference work! This fully updated and revised 3rd edition addresses the entire field of mechanical vibration and shock as one of the most important types of load and stress applied to structures, machines and components in the real world. Examples include everything from the regular and predictable loads applied to turbines, motors or helicopters by the spinning of their constituent parts to the ability of buildings to withstand damage from wind loads or explosions, and the need for cars to m

  11. 2005: The Overtone Violin

    DEFF Research Database (Denmark)

    Overholt, Daniel

    2017-01-01

    The pursuit of novel interfaces for new music performance is a very interesting angle from which to approach the design of a musical instrument, but without the proper perspective the result can be hard to differentiate between a musically useful device and a simple gadget. There is of course...

  12. Copper-promoted methylene C-H oxidation to a ketone derivative by O2.

    Science.gov (United States)

    Deville, Claire; McKee, Vickie; McKenzie, Christine J

    2017-01-17

    The methylene group of the ligand 1,2-di(pyridin-2-yl)-ethanone oxime (dpeo) is slowly oxygenated by the O2 in air under ambient conditions when [Cu(dpeo)2](ClO4)2 is dissolved in ethanol or acetonitrile. An initial transient ketone product, 2-(hydroxyimino)-1,2-di(pyridine-2-yl)ethanone, (hidpe) was characterized in the heteroleptic copper(ii) complex [Cu(bpca)(hidpe)](ClO4). The co-ligand in this complex, N-(2'-pyridylcarbonyl)pyridine-2-carboximidate (bpca(-)), is derived from a copper-promoted Beckmann rearrangement of hidpe. In the presence of bromide only [Cu(bpca)Br] is isolated. When significant water is present in reaction mixtures copper complexes of dpeo, hidpe and bpca(-) are not recovered and [Cu(pic)2H2O] is isolated. This occurs since two equivalents of picolinate are ultimately generated from one equivalent of oxidized and hydrolysed dpeo. The copper-dependent O2 activation and consequent stoichiometric dpeo C-H oxidation is reminiscent of the previously observed catalysis of dpeo oxidation by Mn(ii) [C. Deville, S. K. Padamati, J. Sundberg, V. McKee, W. R. Browne, C. J. McKenzie, Angew. Chem., Int. Ed., 2016, 55, 545-549]. By contrast dpeo oxidation is not observed during complexation reactions with other late transition metal(ii) ions (M = Fe, Co, Ni, Zn) under aerobic conditions. In these cases bis and tris complexes of bidentate dpeo are isolated in good yields. It is interesting to note that dpeo is not oxidised by H2O2 in the absence of Cu or Mn, suggesting that metal-based oxidants capable of C-H activation are produced from the dpeo-Cu/Mn systems and specifically O2. The metastable copper complexes [Cu(dpeo)2](ClO4)2 and [Cu(bpca)(hidpe)](ClO4), along with [NiX2(dpeo)2] (X = Cl, Br), [Ni(dpeo)3](ClO4)2, [Co(dpeo)3](ClO4)3 and the mixed valence complex [Fe(III)Fe(dpeo-H)3(dpeo)3](PF6)4, have been structurally characterized.

  13. Tuning the Reactivity of Terminal Nickel(III)-Oxygen Adducts for C-H Bond Activation.

    Science.gov (United States)

    Pirovano, Paolo; Farquhar, Erik R; Swart, Marcel; McDonald, Aidan R

    2016-11-02

    Two metastable NiIII complexes, [NiIII(OAc)(L)] and [NiIII(ONO2)(L)] (L = N,N'-(2,6-dimethylphenyl)-2,6-pyridinedicarboxamidate, OAc = acetate), were prepared, adding to the previously prepared [NiIII(OCO2H)(L)], with the purpose of probing the properties of terminal late-transition metal oxidants. These high-valent oxidants were prepared by the one-electron oxidation of their NiII precursors ([NiII(OAc)(L)]- and [NiII(ONO2)(L)]-) with tris(4-bromophenyl)ammoniumyl hexachloroantimonate. Fascinatingly, the reaction between any [NiII(X)(L)]- and NaOCl/acetic acid (AcOH) or cerium ammonium nitrate ((NH4)2[CeIV(NO3)6], CAN), yielded [NiIII(OAc)(L)] and [NiIII(ONO2)(L)], respectively. An array of spectroscopic characterizations (electronic absorption, electron paramagnetic resonance, X-ray absorption spectroscopies), electrochemical methods, and computational predictions (density functional theory) have been used to determine the structural, electronic, and magnetic properties of these highly reactive metastable oxidants. The NiIII-oxidants proved competent in the oxidation of phenols (weak O-H bonds) and a series of hydrocarbon substrates (some with strong C-H bonds). Kinetic investigation of the reactions with di-tert-butylphenols showed a 15-fold enhanced reaction rate for [NiIII(ONO2)(L)] compared to [NiIII(OCO2H)(L)] and [NiIII(OAc)(L)], demonstrating the effect of electron-deficiency of the O-ligand on oxidizing power. The oxidation of a series of hydrocarbons by [NiIII(OAc)(L)] was further examined. A linear correlation between the rate constant and the bond dissociation energy of the C-H bonds in the substrates was indicative of a hydrogen atom transfer mechanism. The reaction rate with dihydroanthracene (k2 = 8.1 M-1 s-1) compared favorably with the most reactive high-valent metal-oxidants, and showcases the exceptional reactivity of late transition metal-oxygen adducts.

  14. Vibrations of rotating machinery

    CERN Document Server

    Matsushita, Osami; Kanki, Hiroshi; Kobayashi, Masao; Keogh, Patrick

    2017-01-01

    This book opens with an explanation of the vibrations of a single degree-of-freedom (dof) system for all beginners. Subsequently, vibration analysis of multi-dof systems is explained by modal analysis. Mode synthesis modeling is then introduced for system reduction, which aids understanding in a simplified manner of how complicated rotors behave. Rotor balancing techniques are offered for rigid and flexible rotors through several examples. Consideration of gyroscopic influences on the rotordynamics is then provided and vibration evaluation of a rotor-bearing system is emphasized in terms of forward and backward whirl rotor motions through eigenvalue (natural frequency and damping ratio) analysis. In addition to these rotordynamics concerning rotating shaft vibration measured in a stationary reference frame, blade vibrations are analyzed with Coriolis forces expressed in a rotating reference frame. Other phenomena that may be assessed in stationary and rotating reference frames include stability characteristic...

  15. Vibrational relaxation of matrix-isolated CH/sub 3/F and HCl

    Energy Technology Data Exchange (ETDEWEB)

    Young, L.

    1981-08-01

    Kinetic and spectroscopic studies have been performed on CH/sub 3/F and HCl as a function of host matrix and temperature. Temporally and spectrally resolved infrared fluorescence was used to monitor the populations of both the initially excited state and the lower lying levels which participate in the relaxation process. For CH/sub 3/F, relaxation from any of the levels near 3.5 ..mu.., i.e. the CH stretching fundamentals or bend overtones, occurs via rapid (< 5 ns) V ..-->.. V transfer to 2..nu../sub 3/ with subsequent relaxation of the ..nu../sub 3/ (CF stretch) manifold. Lifetimes of 2..nu../sub 3/ and ..nu../sub 3/ were determined through overtone, ..delta..V = 2, and fundamental fluorescence. These lifetimes show a dramatic dependence on host lattice, an increase of two orders of magnitude in going from Xe and Ar matrices. Lifetimes depend only weakly on temperature. The relaxation of 2..nu../sub 3/ and ..nu../sub 3/ is consistent with a model in which production of a highly rotationally excited guest via collisions with the repulsive wall of the host is the rate limiting step. For HCl, lifetimes of v = 1,2,3 have been determined. In all hosts, the relaxation is non-radiative. For a given vibrational state, v, the relaxation rate increases in the series k(Ar) < k(Kr) < k(Xe). The dependence of the relaxation rate; on v is superlinear in all matrices, the deviation from linearity increasng in the order Ar < Kr < Xe. The relaxation rates become more strongly temperature dependent with increasing vibrational excitation. The results are consistent with a mechanism in which complex formation introduces the anisotropy necessary to induce a near resonant V ..-->.. R transition in the rate limiting step.

  16. Engineering Biological C-H Functionalization Leads to Allele-Specific Regulation of Histone Demethylases.

    Science.gov (United States)

    Breski, Megan; Dey, Debasis; Obringer, Sara; Sudhamalla, Babu; Islam, Kabirul

    2016-10-06

    Oxidative C-H hydroxylation of methyl groups, followed by their removal from DNA, RNA or histones, is an epigenetic process critical to transcriptional reprogramming and cell fate determination. This reaction is catalyzed by Fe(II)-dependent dioxygenases using the essential metabolite 2-ketoglutarate (2KG) as a cofactor. Given that the human genome encodes for more than 60 2KG-dependent dioxygenases, assigning their individual functions remains a significant challenge. Here we describe a protein-ligand interface engineering approach to break the biochemical degeneracy of these enzymes. Using histone lysine demethylase 4 (KDM4) as a proof-of-concept, we show that the enzyme active site can be expanded to employ bulky 2KG analogues that do not sensitize wild type demethylases. We establish the orthogonality, substrate specificity and catalytic competency of the engineered demethylation apparatus in biochemical assays. We further demonstrate demethylation of cognate substrates in physiologically relevant settings. Our results provide a para-digm for rapid and conditional manipulation of histone deme-thylases to uncloak their isoform-specific functions.

  17. Use of VLC for indoors navigation with RGB LEDs and a-SiC:H photodetector

    Science.gov (United States)

    Louro, P.; Costa, J.; Vieira, M.; Vieira, M. A.; Vygranenko, Y.

    2017-05-01

    In this research we present a Visible Light Communication (VLC) system for indoor positioning and navigation. The viability of this methodology was demonstrated in previous work for indoor positioning within the unit navigation cell. In this paper it is proposed to extend this concept for navigation in wider spaces that demand more than one navigation unit. The proposed system uses white RGB LEDs of wide divergence angle and a specific photodetector dedicated to the selective wavelengths detection of red, green and blue light. The photodetector is a multilayered pin-pin heterostructure based on a-SiC:H/a-Si:H, such that the spectral sensitivity can be controlled externally by steady state background light. The RGB emitters of the white LED were modulated with specific bit sequences and frequency to assign different optical excitations to each spatial region. The measurement of the induced photocurrent signal by the detector allows the identification of the position. For this purpose the decoding algorithm for the photocurrent signal processing uses the filtering properties of the photodetector for the recognition of the navigation cell word code, and detection of the wavelength and Fourier analysis for recognition of the signal frequency.

  18. Influence of modulation periods on the tribological behavior of Si/a-C: H multilayer film

    Science.gov (United States)

    Zhu, Linan; Wu, Yanxia; Zhang, Shujiao; Yu, Shengwang; Tang, Bin; Liu, Ying; Zhou, Bing; Shen, Yanyan

    2018-01-01

    A series of Si/a-C: H multilayer films with different modulation periods were fabricated on stainless steel and silicon substrates by radio-frequency magnetron sputtering. The influence of the modulation period on the structure, morphology, mechanical properties and tribological behaviors in different environments (air, simulated acid rain, and NaCl solution) was investigated. The results show that the content of the sp2 hybrid carbon, surface roughness and hardness of the multilayer film increased firstly and then decreased with the decreased modulation period. Furthermore, the combination of the sublayer agrees well with the formation of the SiC crystal at the interface. Interestingly, the films show quite substantially different tribological properties in various test environments. The lowest friction coefficient is 0.2 for the S1 film in air. However, the lowest friction coefficient can reach 0.13 in solution. Importantly, the tribological behavior of the multilayer film is mainly determined by its hardness, as well as surface roughness in air while it is closely related with modulation period and interface structure in solution.

  19. Indoors positioning through VLC technology using an a-SiC:H photodetector

    Science.gov (United States)

    Louro, P.; Costa, J.; Vieira, M.; Vieira, M. A.

    2017-08-01

    The work presented in this paper supports the viability of a navigation system based on Visible Light Communication (VLC) for indoors applications. The system design uses RGB LEDs and an a:SiC:H photodetector. An optoelectronic characterization of the devices used in the integrated system is presented to support the main results, namely the decoding strategy. The photodetector is a pin-pin heterostructure that works as an optical filter, presenting a selective spectral sensitivity dependent on the external optical bias. The red and blue light emitted from the white RGB LEDs were modulated at different frequencies. With this configuration each cardinal direction becomes assigned to a specific set of optical excitation (wavelength and frequency). The decoding of the output photocurrent allows the identification of the input optical signals and the determination of the correspondent spatial direction. The localization algorithm makes use of the Fourier transform to identify the frequencies present in the photocurrent signal and the wavelength filtering properties of the sensor under front and back optical bias to detect the existing red and blue signals. The viability of the system is demonstrated through the implementation of an automatic algorithm to infer the photodetector cardinal direction. Additional research on the light intensity is presented to investigate the accuracy of the spatial position along a cardinal direction.

  20. Graphene Oxide Catalyzed C-H Bond Activation: The Importance Oxygen Functional Groups for Biaryl Construction

    Energy Technology Data Exchange (ETDEWEB)

    Gao, Yongjun; Tang, Pei; Zhou, Hu; Zhang, Wei; Yang, Hanjun; Yan, Ning; Hu, Gang; Mei, Donghai; Wang, Jianguo; Ma, Ding

    2016-02-24

    A heterogeneous, inexpensive and environment-friendly carbon catalytic system was developed for the C-H bond arylation of benzene resulting in the subsequent formation of biaryl compounds. The oxygen-containing groups on these graphene oxide sheets play an essential role in the observed catalytic activity. The catalytic results of model compounds and DFT calculations show that these functional groups promote this reaction by stabilization and activation of K ions at the same time of facilitating the leaving of I. And further mechanisms studies show that it is the charge induced capabilities of oxygen groups connected to specific carbon skeleton together with the giant π-reaction platform provided by the π-domain of graphene that played the vital roles in the observed excellent catalytic activity. D. Mei acknowledges the support from the US Department of Energy (DOE), Office of Science, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences & Biosciences. Pacific Northwest National Laboratory (PNNL) is a multiprogram national laboratory operated for DOE by Battelle. Computing time was granted by the grand challenge of computational catalysis of the William R. Wiley Environmental Molecular Sciences Laboratory.

  1. N-heterocyclic carbene gold(I) and copper(I) complexes in C-H bond activation.

    Science.gov (United States)

    Gaillard, Sylvain; Cazin, Catherine S J; Nolan, Steven P

    2012-06-19

    Environmental concerns have and will continue to have a significant role in determining how chemistry is carried out. Chemists will be challenged to develop new, efficient synthetic processes that have the fewest possible steps leading to a target molecule, the goal being to decrease the amount of waste generated and reduce energy use. Along this path, chemists will need to develop highly selective reactions with atom-economical pathways producing nontoxic byproduct. In this context, C-H bond activation and functionalization is an extremely attractive method. Indeed, for most organic transformations, the presence of a reactive functionality is required. In Total Synthesis, the "protection and deprotection" approach with such reactive groups limits the overall yield of the synthesis, involves the generation of significant chemical waste, costs energy, and in the end is not as green as one would hope. In turn, if a C-H bond functionalization were possible, instead of the use of a prefunctionalized version of the said C-H bond, the number of steps in a synthesis would obviously be reduced. In this case, the C-H bond can be viewed as a dormant functional group that can be activated when necessary during the synthetic strategy. One issue increasing the challenge of such a desired reaction is selectivity. The cleavage of a C-H bond (bond dissociation requires between 85 and 105 kcal/mol) necessitates a high-energy species, which could quickly become a drawback for the control of chemo-, regio-, and stereoselectivity. Transition metal catalysts are useful reagents for surmounting this problem; they can decrease the kinetic barrier of the reaction yet retain control over selectivity. Transition metal complexes also offer important versatility in having distinct pathways that can lead to activation of the C-H bond. An oxidative addition of the metal in the C-H bond, and a base-assisted metal-carbon bond formation in which the base can be coordinated (or not) to the metal

  2. Hydrogen-bond-assisted controlled C-H functionalization via adaptive recognition of a purine directing group.

    Science.gov (United States)

    Kim, Hyun Jin; Ajitha, Manjaly J; Lee, Yongjae; Ryu, Jaeyune; Kim, Jin; Lee, Yunho; Jung, Yousung; Chang, Sukbok

    2014-01-22

    We have developed the Rh-catalyzed selective C-H functionalization of 6-arylpurines, in which the purine moiety directs the C-H bond activation of the aryl pendant. While the first C-H amination proceeds via the N1-chelation assistance, the subsequent second C-H bond activation takes advantage of an intramolecular hydrogen-bonding interaction between the initially formed amino group and one nitrogen atom, either N1 or N7, of the purinyl part. Isolation of a rhodacycle intermediate and the substrate variation studies suggest that N1 is the main active site for the C-H functionalization of both the first and second amination in 6-arylpurines, while N7 plays an essential role in controlling the degree of functionalization serving as an intramolecular hydrogen-bonding site in the second amination process. This pseudo-Curtin-Hammett situation was supported by density functional calculations, which suggest that the intramolecular hydrogen-bonding capability helps second amination by reducing the steric repulsion between the first installed ArNH and the directing group.

  3. C-H Bond Cleavage by Bioinspired Nonheme Oxoiron(IV) Complexes, Including Hydroxylation of n-Butane.

    Science.gov (United States)

    Kleespies, Scott T; Oloo, Williamson N; Mukherjee, Anusree; Que, Lawrence

    2015-06-01

    The development of efficient and selective hydrocarbon oxidation processes with low environmental impact remains a major challenge of the 21st century because of the strong and apolar nature of the C-H bond. Naturally occurring iron-containing metalloenzymes can, however, selectively functionalize strong C-H bonds on substrates under mild and environmentally benign conditions. The key oxidant in a number of these transformations is postulated to possess an S = 2 Fe(IV)═O unit in a nonheme ligand environment. This oxidant has been trapped and spectroscopically characterized and its reactivity toward C-H bonds demonstrated for several nonheme iron enzyme classes. In order to obtain insight into the structure-activity relationships of these reactive intermediates, over 60 synthetic nonheme Fe(IV)(O) complexes have been prepared in various laboratories and their reactivities investigated. This Forum Article summarizes the current status of efforts in the characterization of the C-H bond cleavage reactivity of synthetic Fe(IV)(O) complexes and provides a snapshot of the current understanding of factors that control this reactivity, such as the properties of the supporting ligands and the spin state of the iron center. In addition, new results on the oxidation of strong C-H bonds such as those of cyclohexane and n-butane by a putative S = 2 synthetic Fe(IV)(O) species that is generated in situ using dioxygen at ambient conditions are presented.

  4. Structural Stability and Vibration

    DEFF Research Database (Denmark)

    Wiggers, Sine Leergaard; Pedersen, Pauli

    This book offers an integrated introduction to the topic of stability and vibration. Strikingly, it describes stability as a function of boundary conditions and eigenfrequency as a function of both boundary conditions and column force. Based on a post graduate course held by the author at the Uni......This book offers an integrated introduction to the topic of stability and vibration. Strikingly, it describes stability as a function of boundary conditions and eigenfrequency as a function of both boundary conditions and column force. Based on a post graduate course held by the author...... and their derivation, thus stimulating them to write interactive and dynamic programs to analyze instability and vibrational modes....

  5. Characterization of the visible photoluminescence from porous a-Si:H and porous a-Si:C:H thin films

    Energy Technology Data Exchange (ETDEWEB)

    Estes, M.J. [Wright Lab., Wright-Patterson AFB, OH (United States). Avionics Directorate; Hirsch, L.R.; Wichart, S.; Moddel, G. [Univ. of Colorado, Boulder, CO (United States)

    1996-12-31

    The authors report on the influence of doping, temperature, porosity, and bandgap on the visible photoluminescence properties of anodically-etched porous a-Si:H and a-Si:C:H thin films. Only boron-doped, p-type a-Si:H or a-Si:C:H samples exhibited any visible photoluminescence. The authors see evidence of discrete defect or impurity levels in temperature-dependent luminescence measurements. Unlike in porous crystalline silicon, they see no correlation of luminescence energy with porosity. The authors do, though, observe a correlation of luminescence energy with bandgap of the starting a-Si:C:H films. They discuss the implication of these observations on the nature of the luminescence mechanism.

  6. Correlation between a-C:H film properties and Ar/CH{sub 4} dielectric barrier discharge

    Energy Technology Data Exchange (ETDEWEB)

    Bratescu, M.A. [Graduate School of Information Science and Technology, Hokkaido University, N14 W9, Sapporo 060-0814 (Japan)]. E-mail: maria@plasma.numse.nagoya-u.ac.jp; Yoshizaki, Y. [Graduate School of Information Science and Technology, Hokkaido University, N14 W9, Sapporo 060-0814 (Japan); Suda, Y. [Graduate School of Information Science and Technology, Hokkaido University, N14 W9, Sapporo 060-0814 (Japan); Sakai, Y. [Graduate School of Information Science and Technology, Hokkaido University, N14 W9, Sapporo 060-0814 (Japan); Sugawara, H. [Graduate School of Information Science and Technology, Hokkaido University, N14 W9, Sapporo 060-0814 (Japan); Takai, O. [Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan)

    2006-05-26

    A dielectric barrier discharge (DBD) in Ar/CH{sub 4} gas mixtures used for amorphous hydrogenated carbon (a-C:H) film deposition was investigated. It was found that the a-C:H film properties (the ratios of sp {sup 3}/sp {sup 2} and CH{sub 3}/CH{sub 2}, the number density of hydrogen atoms in the film and the energy band gap) correlate with the number densities of Ar(1s {sub 5}) atom and CH(X {sup 2} {pi}) radical. A high value of the energy band gap, which corresponds to a high content of sp {sup 3} fraction in the film was obtained, when the CH radical number density in the plasma was relatively small ({approx} 10{sup 8} cm{sup -3}). The DBD breakdown voltage decreased when the a-C:H film was deposited on the dielectric surface of the electrode.

  7. Ruthenium(II)-catalysed remote C-H alkylations as a versatile platform to meta-decorated arenes

    Science.gov (United States)

    Li, Jie; Korvorapun, Korkit; de Sarkar, Suman; Rogge, Torben; Burns, David J.; Warratz, Svenja; Ackermann, Lutz

    2017-06-01

    The full control of positional selectivity is of prime importance in C-H activation technology. Chelation assistance served as the stimulus for the development of a plethora of ortho-selective arene functionalizations. In sharp contrast, meta-selective C-H functionalizations continue to be scarce, with all ruthenium-catalysed transformations currently requiring difficult to remove or modify nitrogen-containing heterocycles. Herein, we describe a unifying concept to access a wealth of meta-decorated arenes by a unique arene ligand effect in proximity-induced ruthenium(II) C-H activation catalysis. The transformative nature of our strategy is mirrored by providing a step-economical entry to a range of meta-substituted arenes, including ketones, acids, amines and phenols--key structural motifs in crop protection, material sciences, medicinal chemistry and pharmaceutical industries.

  8. Vibration Analysis and the Accelerometer

    Science.gov (United States)

    Hammer, Paul

    2011-01-01

    Have you ever put your hand on an electric motor or motor-driven electric appliance and felt it vibrate? Ever wonder why it vibrates? What is there about the operation of the motor, or the object to which it is attached, that causes the vibrations? Is there anything "regular" about the vibrations, or are they the result of random causes? In this…

  9. Selectivity in the initial C-H bond cleavage of n-butane on PdO(101).

    Science.gov (United States)

    Hakanoglu, Can; Zhang, Feng; Antony, Abbin; Asthagiri, Aravind; Weaver, Jason F

    2013-08-07

    We used temperature programmed reaction spectroscopy (TPRS) and molecular beam reflectivity measurements to investigate the initial dissociation of n-butane isotopologues on PdO(101) and determine kinetic parameters governing the selectivity of initial C-H(D) bond cleavage. We observe differences in the reactivity of the n-butane isotopologues on PdO(101) due to kinetic isotope effects, and find that the initial dissociation probability decreases with increasing surface temperature for each isotopologue. We performed an analysis of the dissociation kinetics using a model that is based on a precursor-mediated mechanism for n-butane dissociation and enables quantification of kinetic parameters for selective C-H bond cleavage by considering differences in the reactivity among the n-butane isotopologues. From the analysis, we estimate that 49% of the n-butane molecules which react during TPRS do so through 1° C-H bond cleavage when the initial coverage of n-butane lies between ∼40% and 100% of the saturation coverage of the molecular precursor state. For dissociation in the limit of zero coverage, we estimate that the conditional probability for 1° C-H bond cleavage is equal to ∼87% and varies only weakly with surface temperature from 300 K to 400 K. Analysis of the temperature dependent rate data further predicts that the barrier for 1° C-H bond cleavage is 3.5 kJ mol(-1) lower than that for 2° C-H bond cleavage for n-butane dissociation on PdO(101) in the limit of zero coverage. Our results provide evidence that the selectivity for 1° C-H bond cleavage on PdO(101) increases as the n-butane coverage decreases below ∼40% of the saturation value. We speculate that intermolecular interactions among the n-butane species are responsible for the apparent coverage dependence of the C-H bond selectivity for n-butane dissociation on PdO(101).

  10. Vibrations and Stability

    DEFF Research Database (Denmark)

    Thomsen, Jon Juel

    About this textbook An ideal text for students that ties together classical and modern topics of advanced vibration analysis in an interesting and lucid manner. It provides students with a background in elementary vibrations with the tools necessary for understanding and analyzing more complex...... dynamical phenomena that can be encountered in engineering and scientific practice. It progresses steadily from linear vibration theory over various levels of nonlinearity to bifurcation analysis, global dynamics and chaotic vibrations. It trains the student to analyze simple models, recognize nonlinear...... phenomena and work with advanced tools such as perturbation analysis and bifurcation analysis. Explaining theory in terms of relevant examples from real systems, this book is user-friendly and meets the increasing interest in non-linear dynamics in mechanical/structural engineering and applied mathematics...

  11. Rhodium-Catalyzed C-C Bond Formation via Heteroatom-Directed C-H Bond Activation

    Energy Technology Data Exchange (ETDEWEB)

    Colby, Denise; Bergman, Robert; Ellman, Jonathan

    2010-05-13

    Once considered the 'holy grail' of organometallic chemistry, synthetically useful reactions employing C-H bond activation have increasingly been developed and applied to natural product and drug synthesis over the past decade. The ubiquity and relative low cost of hydrocarbons makes C-H bond functionalization an attractive alternative to classical C-C bond forming reactions such as cross-coupling, which require organohalides and organometallic reagents. In addition to providing an atom economical alternative to standard cross - coupling strategies, C-H bond functionalization also reduces the production of toxic by-products, thereby contributing to the growing field of reactions with decreased environmental impact. In the area of C-C bond forming reactions that proceed via a C-H activation mechanism, rhodium catalysts stand out for their functional group tolerance and wide range of synthetic utility. Over the course of the last decade, many Rh-catalyzed methods for heteroatom-directed C-H bond functionalization have been reported and will be the focus of this review. Material appearing in the literature prior to 2001 has been reviewed previously and will only be introduced as background when necessary. The synthesis of complex molecules from relatively simple precursors has long been a goal for many organic chemists. The ability to selectively functionalize a molecule with minimal pre-activation can streamline syntheses and expand the opportunities to explore the utility of complex molecules in areas ranging from the pharmaceutical industry to materials science. Indeed, the issue of selectivity is paramount in the development of all C-H bond functionalization methods. Several groups have developed elegant approaches towards achieving selectivity in molecules that possess many sterically and electronically similar C-H bonds. Many of these approaches are discussed in detail in the accompanying articles in this special issue of Chemical Reviews. One approach

  12. Rhodium(III)-catalyzed C-H activation/annulation with vinyl esters as an acetylene equivalent.

    Science.gov (United States)

    Webb, Nicola J; Marsden, Stephen P; Raw, Steven A

    2014-09-19

    The behavior of electron-rich alkenes in rhodium-catalyzed C-H activation/annulation reactions is investigated. Vinyl acetate emerges as a convenient acetylene equivalent, facilitating the synthesis of sixteen 3,4-unsubstituted isoquinolones, as well as select heteroaryl-fused pyridones. The complementary regiochemical preferences of enol ethers versus enol esters/enamides is discussed.

  13. Influence of energetic ion bombardment on W-C : H coatings deposited with W and WC targets

    NARCIS (Netherlands)

    Strondl, C.; Carvalho, N.M.; de Hosson, J.T.M.; Krug, T.G.

    2005-01-01

    Tungsten containing diamond-like carbon (W-C:H) coatings have been produced by unbalanced magnetron sputtering using two different target materials. In the first series of coatings, W has been used as target material, and in the second series, WC has been used as target material. In both series of

  14. Transition-metal triflate catalyzed unprecedented formation of oxime ketals of tetrahydrofuran via C-H functionalization

    Science.gov (United States)

    Shafi, Syed

    2015-02-01

    Benzaldehyde O-tetrahydrofuran-2-yl oximes were formed through the C-H functionalization from the reaction between benzaldoximes and aqueous tetrahydrofuran catalyzed by water tolerant transition metal triflates (Lewis acids). The formation of oxime ketal has been confirmed from 2D NMR analysis (HMBC and HSQC studies).

  15. Tribological Performance of Hydrogenated Amorphous Carbon (a-C: H DLC Coating when Lubricated with Biodegradable Vegetal Canola Oil

    Directory of Open Access Journals (Sweden)

    H.M. Mobarak

    2014-06-01

    Full Text Available Increasing environmental awareness and demands for lowering energy consumptions are strong driving forces behind the development of the vehicles of tomorrow. Without the advances of lubricant chemistry and adequate lubricant formulation, expansion of modern engines would not have been possible. Considering environmental awareness factors as compared to mineral oils, vegetal oil based biolubricants are renewable, biodegradable, non-toxic and have a least amount of greenhouse gases. Furthermore, improvement in engine performance and transmission components, which were impossible to achieve by applying only lubricants design, is now possible through diamond like carbon (DLC coatings. DLC coatings exhibit brilliant tribological properties, such as good wear resistance and low friction. In this regard, tribological performance of a-C: H DLC coating when lubricated with Canola vegetal oil has been investigated by the help of a ball-on-flat geometry. Experimental results demonstrated that the a-C: H DLC coating exhibited better performance with Canola oil in terms of friction and wear as compared to the uncoated materials. Large amount of polar components in the Canola oil significantly improved the tribological properties of the a-C:H coating. Thus, usage of a-C: H DLC coating with Canola oil in the long run may have a positive impact on engine life.

  16. Direct sp(3)C-H acroleination of N-aryl-tetrahydroisoquinolines by merging photoredox catalysis with nucleophilic catalysis.

    Science.gov (United States)

    Feng, Zhu-Jia; Xuan, Jun; Xia, Xu-Dong; Ding, Wei; Guo, Wei; Chen, Jia-Rong; Zou, You-Quan; Lu, Liang-Qiu; Xiao, Wen-Jing

    2014-04-07

    Sequence catalysis merging photoredox catalysis (PC) and nucleophilic catalysis (NC) has been realized for the direct sp(3) C-H acroleination of N-aryl-tetrahydroisoquinoline (THIQ). The reaction was performed under very mild conditions and afforded products in 50-91% yields. A catalytic asymmetric variant was proved to be successful with moderate enantioselectivities (up to 83 : 17 er).

  17. Nickel-Catalyzed Site-Selective C-H Bond Difluoroalkylation of 8-Aminoquinolines on the C5-Position.

    Science.gov (United States)

    Chen, Hao; Li, Pinhua; Wang, Min; Wang, Lei

    2016-10-07

    A simple and efficient protocol for nickel-catalyzed regioselective C-H bond difluoroalkylation of 8-aminoquinoline scaffolds with functionalized difluoromethyl bromides was developed. The reaction has broad substrate scope and provides a facile and useful access to the corresponding C5-functionalized difluoromethylated quinolines in good to excellent yields.

  18. Rhodium-Catalyzed Oxidative Synthesis of Quinoline-Fused Sydnones via 2-fold C-H Bond Activation.

    Science.gov (United States)

    Li, Lei; Wang, He; Yang, Xifa; Kong, Lingheng; Wang, Fen; Li, Xingwei

    2016-12-02

    Rh(III)-catalyzed synthesis of mesoionic heterocycles has been achieved via C-H activation of sydnones and oxidative coupling with internal alkynes. This reaction occurred under mild conditions with high efficiency, broad substrate scope, and low catalyst loading. Moreover, synthetic applications of a coupled product have been demonstrated in the late-stage derivatization into a variety of highly functionalized scaffolds.

  19. Rhodium(iii)-catalyzed sp(2) C-H bond addition to CF3-substituted unsaturated ketones.

    Science.gov (United States)

    Jiang, Quanbin; Guo, Tenglong; Wu, Kaikai; Yu, Zhengkun

    2016-02-18

    Rhodium(iii)-catalyzed conjugate addition of aromatic and olefinic C-H bonds to CF3-substituted unsaturated ketones was efficiently achieved. Both arene and olefin substrates bearing a chelate assisted-directing group were coupled with a variety of β-trifluoromethyl-α,β-unsaturated ketones with excellent atom-economy, high yields, and broad substrate scopes.

  20. Control of the Chemoselectivity of Metal N-Aryl Nitrene Reactivity: C-H Bond Amination versus Electrocyclization.

    Science.gov (United States)

    Kong, Chen; Jana, Navendu; Jones, Crystalann; Driver, Tom G

    2016-10-04

    A mechanism study to identify the elements that control the chemoselectivity of metal-catalyzed N-atom transfer reactions of styryl azides is presented. Our studies show that the proclivity of the metal N-aryl nitrene to participate in sp3-C-H bond amination or electrocyclization reactions can be controlled by either the substrate or the catalyst. Electrocyclization is favored for mono-β-substituted and sterically noncongested styryl azides, whereas sp3-C-H bond amination through an H-atom abstraction-radical recombination mechanism is preferred when a tertiary allylic reaction center is present. Even when a weakened allylic C-H bond is present, our data suggest that the indole is still formed through an electrocyclization instead of a common allyl radical intermediate. The site selectivity of metal N-aryl nitrenes was found to be controlled by the choice of catalyst: Ir(I)-alkene complexes trigger electrocyclization processes while Fe(III) porphyrin complexes catalyze sp3-C-H bond amination in substrates where Rh2(II) carboxylate catalysts provide both products.

  1. Metal-Free Remote C-H Bond Amidation of 8-Amidoquinolines on the C5 Position under Mild Conditions.

    Science.gov (United States)

    Ji, Dezhong; He, Xin; Xu, Yizhu; Xu, Ziyue; Bian, Yuchen; Liu, Weixing; Zhu, Qihua; Xu, Yungen

    2016-09-16

    An efficient and facile process was developed for the remote C-H bond amidation of 8-aminoquinoline scaffolds on the C5 position which is geometric. The method only made use of PhI(OAc)2 as a mediator and showed good tolerance toward numerous dibenzenesulfonimides and amides, giving the corresponding products in moderate to excellent yield.

  2. Palladium-Catalyzed Enantioselective C-H Activation of Aliphatic Amines Using Chiral Anionic BINOL-Phosphoric Acid Ligands.

    Science.gov (United States)

    Smalley, Adam P; Cuthbertson, James D; Gaunt, Matthew J

    2017-02-01

    The design of an enantioselective Pd(II)-catalyzed C-H amination reaction is described. The use of a chiral BINOL phosphoric acid ligand enables the conversion of readily available amines into synthetically valuable aziridines in high enantiomeric ratios. The aziridines can be derivatized to afford a range of chiral amine building blocks incorporating motifs readily encountered in pharmaceutically relevant molecules.

  3. A study of aliphatic amino acids using simulated vibrational circular dichroism and Raman optical activity spectra

    CERN Document Server

    Ganesan, Aravindhan; Wang, Feng

    2013-01-01

    Vibrational optical activity (VOA) spectra, such as vibrational circular dichroism (VCD) and Raman optical activity (ROA) spectra, of aliphatic amino acids are simulated using density functional theory (DFT) methods in both gas phase (neutral form) and solution (zwitterionic form), together with their respective infrared (IR) and Raman spectra of the amino acids. The DFT models, which are validated by excellent agreements with the available experimental Raman and ROA spectra of alanine in solution, are employed to study other aliphatic amino acids. The inferred (IR) intensive region (below 2000 cm-1) reveals the signature of alkyl side chains, whereas the Raman intensive region (above 3000 cm-1) contains the information of the functional groups in the amino acids. Furthermore, the chiral carbons of the amino acids (except for glycine) dominate the VCD and ROA spectra in the gas phase, but the methyl group vibrations produce stronger VCD and ROA signals in solution. The C-H related asymmetric vibrations domina...

  4. Meyer-Overton reforged: The origins of alcohol and anesthetic potency in membranes as determined by a new NMR partitioning probe, benzyl alcohol

    Energy Technology Data Exchange (ETDEWEB)

    Janes, N.; Ma, L.; Hsu, J.W.; Rubin, E.; Taraschi, T.F. (Thomas Jefferson Univ., Philadelphia, PA (United States))

    1992-01-01

    The Meyer-Overton hypothesis--that anesthesia arises from the nonspecific action of solutes on membrane lipids--is reformulated using colligative thermodynamics. Configurational entropy, the randomness imparted by the solute through the partitioning process, is implicated as the energetic driving force that pertubs cooperative membrane equilibria. A proton NMR partitioning approach based on the anesthetic benzyl alcohol is developed to assess the reformulation. Ring resonances from the partitioned drug are shielded by 0.2 ppm and resolved from the free, aqueous drug. Free alcohol is quantitated in dilute lipid dispersions using an acetate internal standard. Cooperative equilibria in model dipalmitoyl lecithin membranes are examined with changes in temperature and alcohol concentration. The L[sub [beta][prime

  5. Combined UV-C/H2O2-VUV processes for the treatment of an actual slaughterhouse wastewater.

    Science.gov (United States)

    Naderi, Kambiz Vaezzadeh; Bustillo-Lecompte, Ciro Fernando; Mehrvar, Mehrab; Abdekhodaie, Mohammad Jafar

    2017-05-04

    In this study, a three-factor, three-level Box-Behnken design with response surface methodology were used to maximize the TOC removal and minimize the H2O2 residual in the effluent of the combined UV-C/H2O2-VUV system for the treatment of an actual slaughterhouse wastewater (SWW) collected from one of the meat processing plants in Ontario, Canada. The irradiation time and the initial concentrations of total organic carbon (TOCo) and hydrogen peroxide (H2O2o) were the three predictors, as independent variables, studied in the design of experiments. The multiple response approach was used to obtain desirability response surfaces at the optimum factor settings. Subsequently, the optimum conditions to achieve the maximum percentage TOC removal of 46.19% and minimum H2O2 residual of 1.05% were TOCo of 213 mg L-1, H2O2o of 450 mg L-1, and irradiation time of 9 min. The attained optimal operating conditions were validated with a complementary test. Consequently, the TOC removal of 45.68% and H2O2 residual of 1.03% were achieved experimentally, confirming the statistical model reliability. Three individual processes, VUV alone, VUV/H2O2, and UV-C/H2O2, were also evaluated to compare their performance for the treatment of the actual SWW using the optimum parameters obtained in combined UV-C/H2O2-VUV processes. Results confirmed that an adequate combination of the UV-C/H2O2-VUV processes is essential for an optimized TOC removal and H2O2 residual. Finally, respirometry analyses were also performed to evaluate the biodegradability of the SWW and the BOD removal efficiency of the combined UV-C/H2O2-VUV processes.

  6. Pathways and kinetics of methane and ethane C-H bond cleavage on PdO(101).

    Science.gov (United States)

    Antony, Abbin; Asthagiri, Aravind; Weaver, Jason F

    2013-09-14

    We used conventional density functional theory (DFT) and dispersion-corrected DFT (DFT-D3) calculations to investigate C-H bond activation pathways for methane and ethane σ-complexes adsorbed on the PdO(101) surface. The DFT-D3 calculations predict lower and more physically realistic values of the apparent C-H bond cleavage barriers, which are defined relative to the gas-phase energy level, while giving nearly the same energy differences between stationary states as predicted by conventional DFT for a given reaction pathway. For the stable CH4 η(2) complex on PdO(101), DFT-D3 predicts that the C-H bond cleavage barriers are 55.2 and 16.1 kJ∕mol relative to the initial molecularly adsorbed and gaseous states, respectively. We also predict that dehydrogenation of the resulting CH3 groups and conversion to CH3O species are significantly more energetically demanding than the initial C-H bond activation of CH4 on PdO(101). Using DFT-D3, we find that an η(2) and an η(1) ethane complex can undergo C-H bond cleavage on PdO(101) with intrinsic energy barriers that are similar to that of the methane complex, but with apparent barriers that are close to zero. We also investigated the dissociation kinetics of methane and ethane on PdO(101) using microkinetic models, with parameters derived from the DFT-D3 relaxed structures. We find that a so-called 3N - 2 model, in which two frustrated adsorbate motions are treated as free motions, predicts desorption pre-factors and alkane dissociation probabilities that agree well with estimates obtained from the literature. The microkinetic simulations demonstrate the importance of accurately describing entropic contributions in kinetic simulations of alkane dissociative chemisorption.

  7. High resolution overtone spectroscopy of the acetylene van der Waals dimer, ((12)C2H2)2.

    Science.gov (United States)

    Didriche, K; Lauzin, C; Földes, T; Golebiowski, D; Herman, M; Leforestier, C

    2011-08-21

    CW-cavity ring down spectroscopy was used to record in a free jet expansion the spectrum of the absorption band in ((12)C(2)H(2))(2) with origin at 6547.6 cm(-1). It is a perpendicular band and corresponds to 2CH excitation in the hat unit of the T-shaped dimer. Calibration (better than ±1 × 10(-3) cm(-1) accuracy) and ring-down time (130 μs) were improved compared to a previous contribution (Didriche et al. Mol. Phys., 2010, 108, 2158-2164). A line-by-line analysis was achieved. Three series of lines were identified involving levels with A(1)(+), E(+) and B(1)(+) ground state tunneling symmetries, confirming the spectral and symmetry analyses reported in the literature for the 1CH excitation band (Fraser et al. J. Chem. Phys., 1988, 89, 6028-6045). 164 vibration-rotation-tunneling lines were assigned in the K(a)' - K(a)'' = 2 - 3, 0 - 1, 2 - 1 and 4 - 3 sub-bands and effective rigid rotor vibration-rotation constants were obtained by simultaneously fitting 1CH and 2CH lines with the same symmetry series. Perturbations affecting the K(a) stacks, in particular, are reported. The tunneling frequency in 2CH is estimated to be ν(tunn)(2CH) = 270 MHz for the K(a) = 0 stack. The rotational temperature is determined to be 23 K from relative line intensities and the lifetime of the dimer in the 2CH hat state is estimated to be 1 ns from individual line widths.

  8. Vibrational Spectral Studies and Ab initio Computations of a Nonlinear Food Dye Carmoisine

    Science.gov (United States)

    Snehalatha, M.; Ravikumar, C.; Sekar, N.; Jayakumar, V. S.; Joe, I. Hubert

    2008-11-01

    FT-IR and Raman techniques were employed for the vibrational characterization of the food dye Carmoisine (E122). The equilibrium geometry, various bonding features, and harmonic vibrational wavenumbers have been investigated with the help of density functional theory (DFT) calculations. The first hyperpolarizability of the molecule is calculated. A good correlation was found between the computed and experimental wavenumbers. Azo stretching wavenumbers have been lowered due to conjugation and π-electron delocalization. The optimized structure indicates intramolecular C-H …O=S hydrogen bonding in the molecule. Intramolecular charge transfer (ICT) responsible for the optical nonlinearity of the dye molecule has been discussed theoretically and experimentally.

  9. Experimental-Computational Synergy for Selective Pd(II)-Catalyzed C-H Activation of Aryl and Alkyl Groups.

    Science.gov (United States)

    Yang, Yun-Fang; Hong, Xin; Yu, Jin-Quan; Houk, K N

    2017-11-08

    C-H activation and functionalization are on the forefront of modern synthetic chemistry. Imagine if any C-H bond of a molecule could be converted to a C-X bond, where X is the target functionality-this would alter the synthetic blueprints for complex target molecules since it would provide novel disconnections in retrosynthetic analysis. Collaborations between many experimental and computational groups have led to rapid developments of new C-H functionalization methods. Our groups represent an example of this; we were brought together as part of the NSF-supported Center for Selective C-H Functionalization. Many examples of experimental-computational synergy for selective Pd(II)-catalyzed C-H activation of aryl and alkyl groups are described in this Account. We describe computations by the Houk group made in response to experimental stimuli by the Yu group. The first section discusses the experimental and computational investigations of oxazoline-directed stereoselective Pd(II)-catalyzed C(sp(3))-H bond activation that occurs through the concerted metalation-deprotonation (CMD) pathway involving a monomeric Pd(II) complex. The second section involves two types of bidentate ligands, mono-N-protected amino acid (MPAA) and acetyl-protected aminoethyl quinoline (APAQ) ligands that promote the C-H activation reactions with the ligand as the internal base. In the MPAA-assisted remote C-H bond activation, the basic dianionic amidate ligand participates in the deprotonation of a specific C-H bond. This mechanism accounts for the improved reactivity and selectivity in C-H activation reactions with MPAA ligands. The chiral APAQ ligands enable asymmetric palladium insertion into prochiral C-H bonds on a single methylene carbon center. The dianionic amidate of the APAQ ligand acts as an intramolecular base to deprotonate the methylene C-H asymmetrically and facilitate chiral Pd-C bond formation. The origins of the dramatic differences of five-membered (relatively inactive) and

  10. Beyond local group modes in vibrational sum frequency generation.

    Science.gov (United States)

    Chase, Hilary M; Psciuk, Brian T; Strick, Benjamin L; Thomson, Regan J; Batista, Victor S; Geiger, Franz M

    2015-04-09

    We combine deuterium labeling, density functional theory calculations, and experimental vibrational sum frequency generation spectroscopy into a form of "counterfactual-enabled molecular spectroscopy" for producing reliable vibrational mode assignments in situations where local group mode approximations are insufficient for spectral interpretation and vibrational mode assignments. We demonstrate the method using trans-β-isoprene epoxydiol (trans-β-IEPOX), a first-generation product of isoprene relevant to atmospheric aerosol formation, and one of its deuterium-labeled isotopologues at the vapor/silica interface. We use our method to determine that the SFG responses that we obtain from trans-β-IEPOX are almost exclusively due to nonlocal modes involving multiple C-H groups oscillating at the same frequency as one vibrational mode. We verify our assignments using deuterium labeling and use DFT calculations to predict SFG spectra of additional isotopologues that have not yet been synthesized. Finally, we use our new insight to provide a viable alternative to molecular orientation analysis methods that rely on local mode approximations in cases where the local mode approximation is not applicable.

  11. Aging of oxygen and hydrogen plasma discharge treated a-C:H and ta-C coatings

    Energy Technology Data Exchange (ETDEWEB)

    Bachmann, Svenja [Physics of Surfaces, Institute of Materials Science, Technische Universität Darmstadt, Alarich-Weiss-Str. 16, 64287 Darmstadt (Germany); BMW Group, Hufelandstraße 4, 80788 Munich (Germany); Schulze, Marcus [Physics of Surfaces, Institute of Materials Science, Technische Universität Darmstadt, Alarich-Weiss-Str. 16, 64287 Darmstadt (Germany); Center of Smart Interfaces, Technische Universität Darmstadt, Alarich-Weiss-Str. 10, 64287 Darmstadt (Germany); Morasch, Jan [Institute of Materials Science, Technische Universität Darmstadt, Surface Science Division, Jovanka-Bonschits-Straße 2, 64287 Darmstadt (Germany); Hesse, Sabine [Physics of Surfaces, Institute of Materials Science, Technische Universität Darmstadt, Alarich-Weiss-Str. 16, 64287 Darmstadt (Germany); Center of Smart Interfaces, Technische Universität Darmstadt, Alarich-Weiss-Str. 10, 64287 Darmstadt (Germany); Hussein, Laith [Eduard-Zintl-Institut, Department of Chemistry, Technische Universität Darmstadt, Alarich-Weiss-Str. 12, 64287, Darmstadt (Germany); Krell, Lisa; Schnagl, Johann [BMW Group, Hufelandstraße 4, 80788 Munich (Germany); Stark, Robert W. [Physics of Surfaces, Institute of Materials Science, Technische Universität Darmstadt, Alarich-Weiss-Str. 16, 64287 Darmstadt (Germany); Center of Smart Interfaces, Technische Universität Darmstadt, Alarich-Weiss-Str. 10, 64287 Darmstadt (Germany); and others

    2016-05-15

    Highlights: • The water CA of O{sub 2} and H{sub 2} plasma treated a-C:H and ta-C changes from hydrophillic to hydrophobic on aging. • XPS study indicates that the decrease in surface energy of plasma treated a-C:H and ta-C could be due to adsorption of organic component from air. • The COFLFM of O{sub 2} and H{sub 2} plasma treated a-C:H and ta-C decreased upon aging. • The COF of glycerol lubricated ta-C showed no sign of change upon aging. - Abstract: Surface modification with gas plasma is an efficient and easy way to improve the surface energy and the tribological behavior of diamond-like carbon (DLC) coatings, e.g., in biomedical implants or as protective coatings. However, the long-term performance of the plasma treated DLC coatings is not fully clear. We thus studied the long-term stability of two kinds of DLC coatings, namely (a) hydrogenated amorphous carbon (a-C:H) and (b) tetrahedral amorphous carbon (ta-C) treated at different radio frequency (RF) power and time of oxygen (O{sub 2}) and hydrogen (H{sub 2}) plasma. Their surface properties, e.g. surface wettability, structure and tribological behavior, were studied at regular intervals for a period of two months using contact angle goniometer, Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), lateral force microscopy (LFM) and ball on disc apparatus. The surface energy of both the coatings decreased upon aging. The higher the RF power and time of treatment, the higher was the hydrophobicity upon aging. XPS analysis showed that the increase in hydrophobicity could be due to adsorption of unavoidable volatile organic components in the atmosphere. The H{sub 2} plasma treated ta-C was capable of rearranging its structural bonds upon aging. The nano-friction measurements by LFM showed that the coefficient of friction of plasma treated a-C:H and ta-C decreased upon aging. The results indicate that the surface properties of plasma treated a‐C:H and ta‐C are not stable on long-term and are

  12. Deposition and characterisation of multilayer hard coatings. Ti/TiN delta/TiC sub x N sub y /(TiC) a-C H/(Ti) a-C H

    CERN Document Server

    Burinprakhon, T

    2001-01-01

    mixture. The top layer (Ti) a-C:H was found to contain approximately 10 atomic % nitrogen, due to N sub 2 contamination during deposition caused by low conductance of N sub 2 through the nominally closed valve of the mass flow controller. The change of the CH sub 4 concentration during deposition of the top layer (Ti) a-C:H, however, showed a strong influence on the hydrogen content. The comparison of the fluorescence background of the Raman spectra revealed that hydrogen-less (Ti) a-C:H was deposited at a CH sub 4 concentration of less than 50 % flow rate in Ar. The hardness and adhesion of the multilayer coated titanium substrates were assessed by using microindentation hardness and scratch tests, respectively. A simple hardness model containing parameters that assess the contributions from the coating and the substrate to the measured hardness was developed to describe hardness variation as a function of indentation size. This model allowed the determination of a coating hardness and an effective substrate...

  13. Vibrational spectroscopy of resveratrol

    Science.gov (United States)

    Billes, Ferenc; Mohammed-Ziegler, Ildikó; Mikosch, Hans; Tyihák, Ernő

    2007-11-01

    In this article the authors deal with the experimental and theoretical interpretation of the vibrational spectra of trans-resveratrol (3,5,4'-trihydroxy- trans-stilbene) of diverse beneficial biological activity. Infrared and Raman spectra of the compound were recorded; density functional calculations were carried out resulting in the optimized geometry and several properties of the molecule. Based on the calculated force constants, a normal coordinate analysis yielded the character of the vibrational modes and the assignment of the measured spectral bands.

  14. Bumblebee vibration activated foraging

    OpenAIRE

    Su, Dan Kuan-Nien

    2009-01-01

    The ability use vibrational signals to activate nestmate foraging is found in the highly social bees, stingless bees and honey bees, and has been hypothesized to exist in the closely related, primitively eusocial bumble bees. We provide the first strong and direct evidence that this is correct. Inside the nest, bumble bee foragers produce brief bursts of vibration (foraging activation pulses) at 594.5 Hz for 63±26 ms (velocityRMS=0.46±0.02mm/s, forceRMS=0.8±0.2 mN. Production of these vibrati...

  15. Man-Induced Vibrations

    DEFF Research Database (Denmark)

    Jönsson, Jeppe; Hansen, Lars Pilegaard

    1994-01-01

    concerned with spectator-induced vertical vibrations on grandstands. The idea is to use impulse response analysis and base the load description on the load impulse. If the method is feasable, it could be used in connection with the formulation of requirements in building codes. During the last two decades...... work has been done on the measurement of the exact load functions and related reponse analysis. A recent work using a spectral description has been performed by Per-Erik Erikson and includes a good literature survey. Bachmann and Ammann give a good overview of vibrations caused by human activity. Other...

  16. Vibrations and waves

    CERN Document Server

    Kaliski, S

    2013-01-01

    This book gives a comprehensive overview of wave phenomena in different media with interacting mechanical, electromagnetic and other fields. Equations describing wave propagation in linear and non-linear elastic media are followed by equations of rheological models, models with internal rotational degrees of freedom and non-local interactions. Equations for coupled fields: thermal, elastic, electromagnetic, piezoelectric, and magneto-spin with adequate boundary conditions are also included. Together with its companion volume Vibrations and Waves. Part A: Vibrations this work provides a wealth

  17. Rotational spectra of vibrationally excited CCH and CCD.

    Science.gov (United States)

    Killian, T C; Gottlieb, C A; Thaddeus, P

    2007-09-21

    The millimeter-wave rotational spectra of the lowest bending and stretching vibrational levels of CCH and CCD were observed in a low pressure discharge through acetylene and helium. The rotational, centrifugal distortion, and fine structure constants were determined for the (02(0)0) and (02(2)0) bending states, the (100) and (001) stretching levels, and the (011) combination level of CCH. The same pure bending and stretching levels, and the (110) combination level were observed in CCD. Apparent anomalies in the spectroscopic constants in the bending states were shown to be due to l-type resonances. Hyperfine constants, which in CCH are sensitive to the degree of admixture of the A 2Pi excited electronic state, were determined in the excited vibrational levels of both isotopic species. Theoretical Fermi contact and dipole-dipole hyperfine constants calculated by Peric et al. [J. Mol. Spectrosc. 150, 70 (1991)] were found to be in excellent agreement with the measured constants. In CCD, new rotational lines tentatively assigned to the (100) level largely on the basis of the observed hyperfine structure support the assignment of the C-H stretching fundamental (nu1) by Stephens et al. [J. Mol. Struct. 190, 41 (1988)]. Rotational lines in the excited vibrational levels of CCH are fairly intense in our discharge source because the vibrational excitation temperatures of the bending vibrational levels and the (110) and (011) combination levels are only about 100 K higher than the gas kinetic temperature, unlike the higher frequency stretching vibrations, where the excitation temperatures are five to ten times higher.

  18. Heterogeneous Dynamics of Coupled Vibrations

    NARCIS (Netherlands)

    Cringus, Dan; Jansen, Thomas I. C.; Pshenichnikov, Maxim S.; Schoenlein, RW; Corkum, P; DeSilvestri, S; Nelson, KA; Riedle, E

    2009-01-01

    Frequency-dependent dynamics of coupled stretch vibrations of a water molecule are revealed by 2D IR correlation spectroscopy. These are caused by non-Gaussian fluctuations of the environment around the individual OH stretch vibrations.

  19. Mechanistic Investigations of C-H Activations on Silica-Supported Co(ii) Sites in Catalytic Propane Dehydrogenation.

    Science.gov (United States)

    Estes, Deven P

    2017-04-26

    Catalytic reactions involving C-H bond activations are central to the chemical industry. One such example, alkane dehydrogenation, has recently become very important due to shortfalls in propene production and a large supply of cheap propane. However, current technologies are inefficient and have only moderate selectivity. In order to understand how to improve currently used catalysts, we must know more about the mechanism by which propane is dehydrogenated. We show here that Co(ii) sites on silica are good catalysts for the dehydrogenation of propane, having high activity and selectivity that is reasonably stable over the course of 10 h. Mechanistic investigations of this catalyst show that the main activation mechanism is most likely C-H activation by 1,2 addition.

  20. The Breathing Orbital Valence Bond Method in Diffusion Monte Carlo: C-H Bond Dissociation ofAcetylene

    Energy Technology Data Exchange (ETDEWEB)

    Domin, D.; Braida, Benoit; Lester Jr., William A.

    2008-05-30

    This study explores the use of breathing orbital valence bond (BOVB) trial wave functions for diffusion Monte Carlo (DMC). The approach is applied to the computation of the carbon-hydrogen (C-H) bond dissociation energy (BDE) of acetylene. DMC with BOVB trial wave functions yields a C-H BDE of 132.4 {+-} 0.9 kcal/mol, which is in excellent accord with the recommended experimental value of 132.8 {+-} 0.7 kcal/mol. These values are to be compared with DMC results obtained with single determinant trial wave functions, using Hartree-Fock orbitals (137.5 {+-} 0.5 kcal/mol) and local spin density (LDA) Kohn-Sham orbitals (135.6 {+-} 0.5 kcal/mol).

  1. (NHC)Cu-Catalyzed Mild C-H Amidation of (Hetero)arenes with Deprotectable Carbamates: Scope and Mechanistic Studies.

    Science.gov (United States)

    Xie, Weilong; Yoon, Jung Hee; Chang, Sukbok

    2016-09-28

    Primary arylamines are an important unit broadly found in synthetic, biological, and materials science. Herein we describe the development of a (NHC)Cu system that mediates a direct C-H amidation of (hetero)arenes by using N-chlorocarbamates or their sodio derivatives as the practical amino sources. A facile stoichiometric reaction of reactive copper-aryl intermediates with the amidating reagent led us to isolate key copper arylcarbamate species with the formation of a C-N bond. The use of (t)BuONa base made this transformation catalytic under mild conditions. The present (NHC)Cu-catalyzed C-H amidation works efficiently and selectively on a large scale over a range of arenes including polyfluorobenzenes, azoles, and quinoline N-oxides. Deprotection of the newly installed carbamate groups such as Boc and Cbz was readily performed to afford the corresponding primary arylamines.

  2. Utilising Sodium-Mediated Ferration for Regioselective Functionalisation of Fluoroarenes via C-H and C-F Bond Activations.

    Science.gov (United States)

    Hevia, Eva; Maddock, Lewis C H; Nixon, Tracy; Kennedy, Alan R; Probert, Michael R; Clegg, William

    2017-10-25

    While Fe(II) complexes have shown little promise in deprotonative metallation chemistry, pairing iron bis(amide) Fe(HMDS)2 with Na(HMDS) to form new sodium ferrate base [(dioxane)0.5·NaFe(HMDS)3] (1) enables regioselective mono and di-ferration (via direct Fe-H exchange) of a wide range of fluoroaromatic substrates under mild reaction conditions. Trapping of several ferrated intermediates has provided key insight into how synchronised Na/Fe cooperation operates in these transformations. Furthermore using excess 1 at 80oC switches on a remarkable cascade process inducing the collective 2-fold C-H/3-fold C-F bond activation, where each C-H bond is transformed to C-Fe bonds whereas each C-F bond is transformed into a C-N bond. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. Supramolecular Recognition Allows Remote, Site-Selective C-H Oxidation of Methylenic Sites in Linear Amines.

    Science.gov (United States)

    Olivo, Giorgio; Farinelli, Giulio; Barbieri, Alessia; Lanzalunga, Osvaldo; Di Stefano, Stefano; Costas, Miquel

    2017-12-18

    Site-selective C-H functionalization of aliphatic alkyl chains is a longstanding challenge in oxidation catalysis, given the comparable relative reactivity of the different methylenes. A supramolecular, bioinspired approach is described to address this challenge. A Mn complex able to catalyze C(sp3 )-H hydroxylation with H2 O2 is equipped with 18-benzocrown-6 ether receptors that bind ammonium substrates via hydrogen bonding. Reversible pre-association of protonated primary aliphatic amines with the crown ether selectively exposes remote positions (C8 and C9) to the oxidizing unit, resulting in a site-selective oxidation. Remarkably, such control of selectivity retains its efficiency for a whole series of linear amines, overriding the intrinsic reactivity of C-H bonds, no matter the chain length. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Up-scaling the production of modified a-C:H coatings in the framework of plasma polymerization processes

    Science.gov (United States)

    Corbella, C.; Bialuch, I.; Kleinschmidt, M.; Bewilogua, K.

    2009-10-01

    Hydrogenated amorphous carbon (a-C:H) films with silicon and oxygen additions, which exhibit mechanical, tribological and wetting properties adequate for protective coating performance, have been synthesized at room temperature in a small- (0.1 m 3) and a large-scale (1 m 3) coaters by low-pressure Plasma-Activated Chemical Vapour Deposition (PACVD). Hence, a-C:H:Si and a-C:H:Si:O coatings were produced in atmospheres of tetramethylsilane (TMS) and hexamethyldisiloxane (HMDSO), respectively, excited either by radiofrequency (RF - small scale) or by pulsed-DC power (large scale). Argon was employed as a carrier gas to stabilize the glow discharge. Several series of 2-5 μm thick coatings have been prepared at different mass deposition rates, Rm, by varying total gas flow, F, and input power, W. Arrhenius-type plots of Rm/ F vs. ( W/ F) -1 show linear behaviours for both plasma reactors, as expected for plasma polymerization processes at moderated energies. The calculation of apparent activation energy, Ea, in each series permitted us to define the regimes of energy-deficient and monomer-deficient PACVD processes as a function of the key parameter W/ F. Moreover, surface properties of the modified a-C:H coatings, such as contact angle, abrasive wear rate and hardness, appear also correlated to this parameter. This work shows an efficient methodology to scale up PACVD processes from small, lab-scale plasma machines to industrial plants by the unique evaluation of macroscopic parameters of deposition.

  5. Pärt: Collage sur B-A-C-H für Kammerorschester / Hans-Christian Dadelsen

    Index Scriptorium Estoniae

    Dadelsen, Hans-Christian

    1993-01-01

    Uuest heliplaadist "Pärt: Collage sur B-A-C-H für Kammerorschester, Summa (1991) für Streichorchester, Fratres, Sinfonie Nr. 2, Festina lente, Wenn Bach Bienen gezüchtet hätte, Credo für Klavier, Chor und Orchester. Philharmonia Orchestra and Chorus, Neeme Järvi". Chandos/Koch CD 9134 (WD: 63'02")

  6. Ionic and Neutral Mechanisms for C-H Bond Silylation of Aromatic Heterocycles Catalyzed by Potassium tert-Butoxide.

    Science.gov (United States)

    Banerjee, Shibdas; Yang, Yun-Fang; Jenkins, Ian D; Liang, Yong; Toutov, Anton A; Liu, Wen-Bo; Schuman, David P; Grubbs, Robert H; Stoltz, Brian M; Krenske, Elizabeth H; Houk, Kendall N; Zare, Richard N

    2017-05-24

    Exploiting C-H bond activation is difficult, although some success has been achieved using precious metal catalysts. Recently, it was reported that C-H bonds in aromatic heterocycles were converted to C-Si bonds by reaction with hydrosilanes under the catalytic action of potassium tert-butoxide alone. The use of Earth-abundant potassium cation as a catalyst for C-H bond functionalization seems to be without precedent, and no mechanism for the process was established. Using ambient ionization mass spectrometry, we are able to identify crucial ionic intermediates present during the C-H silylation reaction. We propose a plausible catalytic cycle, which involves a pentacoordinate silicon intermediate consisting of silane reagent, substrate, and the tert-butoxide catalyst. Heterolysis of the Si-H bond, deprotonation of the heteroarene, addition of the heteroarene carbanion to the silyl ether, and dissociation of tert-butoxide from silicon lead to the silylated heteroarene product. The steps of the silylation mechanism may follow either an ionic route involving K+ and tBuO- ions or a neutral heterolytic route involving the [KOtBu]4 tetramer. Both mechanisms are consistent with the ionic intermediates detected experimentally. We also present reasons why KOtBu is an active catalyst whereas sodium tert-butoxide and lithium tert-butoxide are not, and we explain the relative reactivities of different (hetero)arenes in the silylation reaction. The unique role of KOtBu is traced, in part, to the stabilization of crucial intermediates through cation-π interactions.

  7. C-H oxidation and chelation of a dipyrromethane mediated rapid colorimetric naked-eye Cu(ii) chemosensor.

    Science.gov (United States)

    Rajmohan, Rajamani; Ayaz Ahmed, Khan Behlol; Sangeetha, Sampathkumar; Anbazhagan, Veerappan; Vairaprakash, Pothiappan

    2017-09-08

    Copper(ii) ion mediated C-H oxidation of dipyrromethanes (DPMs) to the corresponding dipyrrins followed by complexation invoked the selective sensing of copper(ii) ions in aqueous solutions. On the addition of copper, the colour of the DPM solution instantaneously changes from yellow to pink with the detection limit of 0.104 μM measured by absorption spectroscopy, whereas visible colour changes could be observed by the naked eye for concentrations as low as 3 μM.

  8. Aliphatic C-H bond oxidation of toluene using copper peroxo complexes that are stable at room temperature.

    Science.gov (United States)

    Würtele, Christian; Sander, Ole; Lutz, Volker; Waitz, Thomas; Tuczek, Felix; Schindler, Siegfried

    2009-06-10

    Dinuclear copper peroxo complexes obtained from mononuclear copper(I) complexes showed extremely high stabilities under ambient conditions in the solid state and could be heated above 100 degrees C without decomposition. The increased stability could be explained with regard to their molecular structures. Furthermore, the four complexes investigated showed a high potential for aliphatic C-H bond oxidations: for example, technical-grade toluene was oxidized to benzaldehyde in yields of up to 20%.

  9. Hydrocarbon plume discrimination using the C-H stretch region of the Infrared spectrum using OP-FTIR.

    Science.gov (United States)

    Crampton, R. S.; Pikelnaya, O.; Polidori, A.; Tisopulos, L.; Perry, S.

    2016-12-01

    Open path FTIR spectroscopy can measure many different gases including most gaseous hydrocarbons in the atmosphere. Individual Hydrocarbons can be identified in the fingerprint region (500 cm-1 to 1500 cm-1) due to unique bond absorption features. Often times the strongest absorption is not unique because it is a result of the C-H bonds stretching. These bonds and absorption features are in all hydrocarbons and overlap (2850 cm-1 to 3000 cm-1) so they are not ideal for identification of individual compounds. For this reason any FTIR investigations treat total hydrocarbons as hexane or pentane equivalent. This way the C-H stretch can be used to get real information about the total hydrocarbons when the individual compounds cannot be quantified. In the fall of 2015, KASSAY Field Services, Inc, participated in a program sponsored by the South Coast Air Quality Management District (SCAQMD) to conduct open path FTIR measurements downwind of oil wells located in the southern California basin. Most of the oil wells for this measurement study reside in the town of Signal Hill, CA. In a location such as Signal Hill (part of Long Beach, CA) there are always some Hydrocarbons in the air due to vehicles, gas stations, the oil and gas industry, and other sources mixed together. Each source has a different combination of hydrocarbons resulting in different shapes of absorption in the C-H stretch region. The final shape is a result of the ratio of all the absorber concentrations multiplied by the I.R. features of each. We investigated how the C-H stretch absorption feature shape changes over time and space in a complicated air shed and what the implications for possible source apportionment without needing highly accurate quantification of many gases.

  10. Vapour-induced solid-state C-H bond activation for the clean synthesis of an organopalladium biothiol sensor.

    Science.gov (United States)

    Monas, Andrea; Užarević, Krunoslav; Halasz, Ivan; Kulcsár, Marina Juribašić; Ćurić, Manda

    2016-10-27

    Room-temperature accelerated aging in the solid state has been applied for atom- and energy-efficient activation of either one or two C-H bonds of azobenzene and methyl orange by palladium(ii) acetate. Organopalladium complexes are prepared in quantitative reactions without potentially harmful side products. Dicyclopalladated methyl orange is water-soluble and is a selective chromogenic biothiol sensor at physiologically-relevant micromolar concentrations in buffered aqueous media.

  11. Rhodium-catalyzed ortho C-H bond activation of arylamines for the synthesis of quinoline carboxylates.

    Science.gov (United States)

    Gadakh, Sunita K; Dey, Soumen; Sudalai, A

    2016-03-14

    The rhodium catalyzed annulation of anilines with alkynic esters allowing for the high-yield synthesis of quinoline carboxylates with excellent regioselectivity is described. This unprecedented reaction employs either formic acid as the C1 source and reductant or copper(ii) as the oxidant and is proposed to proceed via rhodacycle of in situ generated amide and enamine ester followed by ortho C-H activation of arylamines with rhodium as the catalyst.

  12. Cooperative Lewis Acid/Cp*Co(III) Catalyzed C-H Bond Activation for the Synthesis of Isoquinolin-3-ones.

    Science.gov (United States)

    Kim, Ju Hyun; Greßies, Steffen; Glorius, Frank

    2016-04-25

    A facile route toward the synthesis of isoquinolin-3-ones through a cooperative B(C6 F5 )3 - and Cp*Co(III) -catalyzed C-H bond activation of imines with diazo compounds is presented. The inclusion of a catalytic amount of B(C6 F5 )3 results in a highly efficient reaction, thus enabling unstable NH imines to serve as substrates. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Incorporated W Roles on Microstructure and Properties of W-C:H Films by a Hybrid Linear Ion Beam Systems

    Directory of Open Access Journals (Sweden)

    Peng Guo

    2013-01-01

    Full Text Available W-incorporated diamond-like carbon (W-C:H films were fabricated by a hybrid beams system consisting of a DC magnetron sputtering and a linear ion source. The W concentration (1.08~31.74 at.% in the film was controlled by varying the sputtering current. The cross-sectional topography, composition, and microstructure of the W-C:H films were investigated by SEM, XPS, TEM, and Raman spectroscopy. The mechanical and tribological properties of the films as a function of W concentration were evaluated by a stress-tester, nanoindentation, and ball-on-disk tribometer, respectively. The results showed that films mainly exhibited the feature of amorphous carbon when W concentration of the films was less than 4.38 at.%, where the incorporated W atoms would be bonded with C atoms and resulted in the formation of WC1-x nanoparticles. The W-C:H film with 4.38 at.% W concentration showed a minimum value of residual compressive stress, a higher hardness, and better tribological properties. Beyond this W concentration range, both the residual stress and mechanical properties were deteriorated due to the growth of tungsten carbide nanoparticles in the carbon matrix.

  14. FT-IR analysis of high temperature annealing effects in a-SiC:H thin films

    Science.gov (United States)

    Frischmuth, Tobias; Schneider, Michael; Grille, Thomas; Schmid, U.

    2017-06-01

    Hydrogenated amorphous SiC (a-SiC:H) is an attractive material for MEMS applications where high robustness or operation in harsh environments is targeted. In previous publications, it was demonstrated, that the properties of a-SiC:H thin films can be tailored over a wide range by changing the auxiliary table excitation power of a dual plasma source deposition process using an inductively coupled plasma-enhanced chemical vapour deposition system. In this work, the annealing behavior of dual plasma source deposited a-SiC:H thin films under argon atmosphere is investigated by using Fourier transform infrared (FT-IR) spectroscopy for chemical analysis. All investigated layers show a decrease of hydrogen containing bonds (X-Hx) and an increase of Si-C bonds with increasing annealing temperature in the FT-IR spectrum. This behaviour is directly linked to the effusion of hydrogen from the thin films at elevated temperatures. In addition, films deposited at higher auxiliary plasma power show more X-Hx and less Si-C bonds, indicating a higher hydrogen amount in those films. All layers shrink with increasing annealing temperature due to the effusion of hydrogen with a stronger shrink at higher PT values caused by the increased hydrogen amount. This shrink also leads to a densification of the thin films.

  15. Non-coordinating-Anion-Directed Reversal of Activation Site: Selective C-H Bond Activation of N-Aryl Rings.

    Science.gov (United States)

    Wang, Dawei; Yu, Xiaoli; Xu, Xiang; Ge, Bingyang; Wang, Xiaoli; Zhang, Yaxuan

    2016-06-13

    An Rh-catalyzed selective C-H bond activation of diaryl-substituted anilides is described. In an attempt to achieve C-H activation of C-aryl rings, we unexpectedly obtained an N-aryl ring product under non-coordinating anion conditions, whereas the C-aryl ring product was obtained in the absence of a non-coordinating anion. This methodology has proved to be an excellent means of tuning and adjusting selective C-H bond activation of C-aryl and N-aryl rings. The approach has been rationalized by mechanistic studies and theoretical calculations. In addition, it has been found and verified that the catalytic activity of the rhodium catalyst is obviously improved by non-coordinating anions, which provides an efficient strategy for obtaining a highly chemoselective catalyst. Mechanistic experiments also unequivocally ruled out the possibility of a so-called "silver effect" in this transformation involving silver. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Composite Struts Would Damp Vibrations

    Science.gov (United States)

    Dolgin, Benjamin P.

    1991-01-01

    New design of composite-material (fiber/matrix laminate) struts increases damping of longitudinal vibrations without decreasing longitudinal stiffness or increasing weight significantly. Plies with opposing chevron patterns of fibers convert longitudinal vibrational stresses into shear stresses in intermediate viscoelastic layer, which dissipate vibrational energy. Composite strut stronger than aluminum strut of same weight and stiffness.

  17. Ship Vibration Design Guide

    Science.gov (United States)

    1989-07-01

    Frachtschiffen," Werft Reederie Hafen, 1925. 4-21 Noonan, E. F. "Vibration Considerations for 120,000 CM LNG Ships," NKF: Preliminary Report No. 7107, 25...Ship Response to Ice - A Second Season by C. Daley, J. W. St. John, R. Brown, J. Meyer , and I. Glen 1990 SSC-340 Ice Forces and Ship Response to Ice

  18. Compact Vibration Damper

    Science.gov (United States)

    Ivanco, Thomas G. (Inventor)

    2014-01-01

    A vibration damper includes a rigid base with a mass coupled thereto for linear movement thereon. Springs coupled to the mass compress in response to the linear movement along either of two opposing directions. A converter coupled to the mass converts the linear movement to a corresponding rotational movement. A rotary damper coupled to the converter damps the rotational movement.

  19. Vibrations and Eigenvalues

    Indian Academy of Sciences (India)

    The vibrating string problem is the source of much mathematicsand physics. This article describes Lagrange's formulationof a discretised version of the problem and its solution.This is also the first instance of an eigenvalue problem. Author Affiliations. Rajendra Bhatia1. Ashoka University, Rai, Haryana 131 029, India.

  20. Blade Vibration Measurement System

    Science.gov (United States)

    Platt, Michael J.

    2014-01-01

    The Phase I project successfully demonstrated that an advanced noncontacting stress measurement system (NSMS) could improve classification of blade vibration response in terms of mistuning and closely spaced modes. The Phase II work confirmed the microwave sensor design process, modified the sensor so it is compatible as an upgrade to existing NSMS, and improved and finalized the NSMS software. The result will be stand-alone radar/tip timing radar signal conditioning for current conventional NSMS users (as an upgrade) and new users. The hybrid system will use frequency data and relative mode vibration levels from the radar sensor to provide substantially superior capabilities over current blade-vibration measurement technology. This frequency data, coupled with a reduced number of tip timing probes, will result in a system capable of detecting complex blade vibrations that would confound traditional NSMS systems. The hardware and software package was validated on a compressor rig at Mechanical Solutions, Inc. (MSI). Finally, the hybrid radar/tip timing NSMS software package and associated sensor hardware will be installed for use in the NASA Glenn spin pit test facility.

  1. Vibration Sensitive Keystroke Analysis

    NARCIS (Netherlands)

    Lopatka, M.; Peetz, M.-H.; van Erp, M.; Stehouwer, H.; van Zaanen, M.

    2009-01-01

    We present a novel method for performing non-invasive biometric analysis on habitual keystroke patterns using a vibration-based feature space. With the increasing availability of 3-D accelerometer chips in laptop computers, conventional methods using time vectors may be augmented using a distinct

  2. Redox potential and C-H bond cleaving properties of a nonheme Fe(IV)=O complex in aqueous solution.

    Science.gov (United States)

    Wang, Dong; Zhang, Mo; Bühlmann, Philippe; Que, Lawrence

    2010-06-09

    High-valent iron-oxo intermediates have been identified as the key oxidants in the catalytic cycles of many nonheme enzymes. Among the large number of synthetic Fe(IV)=O complexes characterized to date, [Fe(IV)(O)(N4Py)](2+) (1) exhibits the unique combination of thermodynamic stability, allowing its structural characterization by X-ray crystallography, and oxidative reactivity sufficient to cleave C-H bonds as strong as those in cyclohexane (D(C-H) = 99.3 kcal mol(-1)). However, its redox properties are not yet well understood. In this work, the effect of protons on the redox properties of 1 has been investigated electrochemically in nonaqueous and aqueous solutions. While the cyclic voltammetry of 1 in CH(3)CN is complicated by coupling of several chemical and redox processes, the Fe(IV/III) couple is reversible in aqueous solution with E(1/2) = +0.41 V versus SCE at pH 4 and involves the transfer of one electron and one proton to give the Fe(III)-OH species. This is in fact the first example of reversible electrochemistry to be observed for this family of nonheme oxoiron (IV) complexes. C-H bond oxidations by 1 have been studied in H(2)O and found to have reaction rates that depend on the C-H bond strength but not on the solvent. Furthermore, our electrochemical results have allowed a D(O-H) value of 78(2) kcal mol(-1) to be calculated for the Fe(III)-OH unit derived from 1. Interestingly, although this D(O-H) value is 6-11 kcal mol(-1) lower than those corresponding to oxidants such as [Fe(IV)(O)(TMP)] (TMP = tetramesitylporphinate), [Ru(IV)(O)(bpy)(2)(py)](2+) (bpy = bipyridine, py = pyridine), and the tert-butylperoxyl radical, the oxidation of dihydroanthracene by 1 occurs at a rate comparable to rates for these other oxidants. This comparison suggests that the nonheme N4Py ligand environment confers a kinetic advantage over the others that enhances the C-H bond cleavage ability of 1.

  3. Animal Communications Through Seismic Vibrations

    Energy Technology Data Exchange (ETDEWEB)

    Hill, Peggy (University of Tulsa)

    2001-05-02

    Substrate vibration has been important to animals as a channel of communication for millions of years, but our literature on vibration in this context of biologically relevant information is only decades old. The jaw mechanism of the earliest land vertebrates allowed them to perceive substrate vibrations as their heads lay on the ground long before airborne sounds could be heard. Although the exact mechanism of vibration production and the precise nature of the wave produced are not always understood, recent development of affordable instrumentation to detect and measure vibrations has allowed researchers to answer increasingly sophisticated questions about how animals send and receive vibration signals. We now know that vibration provides information used in predator defense, prey detection, recruitment to food, mate choice, intrasexual competition, and maternal/brood social interactions in a variety of insect orders, spiders, crabs, scorpions, chameleons, frogs, golden moles, mole rats, kangaroos rats, wallabies, elephants and bison.

  4. Vibration Attenuation of Plate Using Multiple Vibration Absorbers

    Directory of Open Access Journals (Sweden)

    Zaman Izzuddin

    2014-07-01

    Full Text Available Vibrations are undesired phenomenon and it can cause harm, distress and unsettling influence to the systems or structures, for example, aircraft, automobile, machinery and building. One of the approach to limit this vibration by introducing passive vibration absorber attached to the structure. In this paper, the adequacy of utilizing passive vibration absorbers are investigated. The vibration absorber system is designed to minimize the vibration of a thin plate fixed along edges. The plate’s vibration characteristics, such as, natural frequency and mode shape are determined using three techniques: theoretical equations, finite element (FE analysis and experiment. The results demonstrate that the first four natural frequencies of fixed-fixed ends plate are 48, 121, 193 and 242 Hz, and these results are corroborated well with theoretical, FE simulation and experiment. The experiment work is further carried out with attached single and multiple vibration absorbers onto plate by tuning the absorber’s frequency to match with the excitation frequency. The outcomes depict that multiple vibration absorbers are more viable in lessening the global structural vibration.

  5. Spectrométrie ultrasensible par transformée de Fourier couplée à un montage laser intracavité: application à l'étude des niveaux de vibration-rotation de l'acétylène

    OpenAIRE

    Depiesse, Cédric

    2005-01-01

    Notre travail concerne l’étude par spectroscopie à haute résolution de molécules polyatomiques en phase gazeuse fortement excitées vibrationnellement. L’excitation de molécules dans leurs hauts niveaux de vibration est typiquement produite par absorption de lumière infrarouge proche, voire visible, d’où la dénomination de « vibrations colorées » ou « overtones ». L’excitation de degrés de liberté de vibration à des énergies aussi inhabituelles place la molécule dans un régime tellement anharm...

  6. Good vibrations. [Hydraulic turbines

    Energy Technology Data Exchange (ETDEWEB)

    Reynolds, P.

    1994-07-01

    The latest developments in the Voith Turbine Control and Automation System (VTLS), which couples digital control technology to hydropower plant equipment, are described. Prominent among these is the vibration diagnostics module for hydraulic turbines. It provides machine-specific diagnostic logic for a vibration monitoring and analysis system. Of the two other VTLS modules described, the operation module optimizes the control of a power plant with three or more turbines by considering the individual properties of each in turn, recommending which should be run, and how, in order to partition the load for a required power output. The cavitation module is a diagnostic system which enables the limits of operation of the turbines to be extended to bands just outside those determined by cavitation calculations. (3 figures). (UK)

  7. Investigation of structure and vibrational properties of cyclobutane pirimidine dimer

    Directory of Open Access Journals (Sweden)

    Petković Milena M.

    2013-01-01

    Full Text Available We performed a theoretical analysis of the structure and vibrational properties of cyclobutane pyrimidine dimer, which is the main product in a photochemical reaction involving two molecules of 1-methylthymine. Thymine is a pyrimidine base that has the highest yield of the dimerization photoproducts. Methylation in position one was chosen because in this position thymine is linked to sugar in DNA. The calculations were performed at the B3LYP/cc-pVTZ level with a Gaussian program package. All molecular geometries were optimized without symmetry constraints in vacuum and D2O. Vibrational frequencies were calculated in the harmonic approximation. It was shown that there are two stable isomers, CPD(cis-syn and CPD(trans-syn. CPD(trans-syn is more stable both in vacuum and in D2O. By dissolving these molecules in D2O, both structures become more stable, although the stabilization of the less stable isomer is more pronounced due to its larger dipole moment. Thus, the difference in stability of the two isomers in D2O is almost two times lower than in vacuum. Because of the similarity of the two isomers’ structures, the difference in their vibrational spectra is not pronounced. Within the harmonic approximation, there is only a slight difference in the C=O and C-H stretching region. The difference in the N-H stretching region is more pronounced; in the CPD(cis-syn molecule the two bonds vibrate separately, whereas in the CPD(trans-syn the two modes couple, and this coupling results in symmetric and asymmetric N-H stretching. The observation shows that a slight difference in geometry can be reflected in the shape of the infrared spectra. A more detailed analysis of the vibrational properties would involve computation of anharmonic coupling terms, which would enable a more precise determination of the peak positions.

  8. Pickin’ up good vibrations

    CERN Multimedia

    Katarina Anthony

    2015-01-01

    In preparation for the civil engineering work on the HL-LHC, vibration measurements were carried out at the LHC’s Point 1 last month. These measurements will help evaluate how civil engineering work could impact the beam, and will provide crucial details about the site’s geological make-up before construction begins.   A seismic truck at Point 1 generated wave-like vibrations measured by EN/MME. From carrying out R&D to produce state-of-the-art magnets to developing innovative, robust materials capable of withstanding beam impact, the HL-LHC is a multi-faceted project involving many groups and teams across CERN’s departments. It was in this framework that the project management mandated CERN's Mechanical and Materials Engineering (EN/MME) group to measure the propagation of vibrations around Point 1. Their question: can civil engineering work for the HL-LHC – the bulk of which is scheduled for LS2 – begin while the LHC is running? Alth...

  9. Vibrational stability of graphene

    Directory of Open Access Journals (Sweden)

    Yangfan Hu

    2013-05-01

    Full Text Available The mechanical stability of graphene as temperature rises is analyzed based on three different self-consistent phonon (SCP models. Compared with three-dimensional (3-D materials, the critical temperature Ti at which instability occurs for graphene is much closer to its melting temperature Tm obtained from Monte Carlo simulation (Ti ≃ 2Tm, K. V. Zakharchenko, A. Fasolino, J. H. Los, and M. I. Katsnelson, J. Phys. Condens. Matter 23, 202202. This suggests that thermal vibration plays a significant role in melting of graphene while melting for 3-D materials is often dominated by topologic defects. This peculiar property of graphene derives from its high structural anisotropy, which is characterized by the vibrational anisotropic coefficient (VAC, defined upon its Lindermann ratios in different directions. For any carbon based material with a graphene-like structure, the VAC value must be smaller than 5.4 to maintain its stability. It is also found that the high VAC value of graphene is responsible for its negative thermal expansion coefficient at low temperature range. We believe that the VAC can be regarded as a new criterion concerning the vibrational stability of any low-dimensional (low-D materials.

  10. Anharmonic vibrational and electronic spectral study of 2-amino-4-hydroxy-6-methylpyrimidine: A combined experimental (FTIR, FT-Raman, UV-Vis) and theoretical (DFT, MP2) approach

    Science.gov (United States)

    Faizan, Mohd; Bhat, Sheeraz Ahmad; Alam, Mohammad Jane; Afroz, Ziya; Ahmad, Shabbir

    2017-11-01

    A combined experimental and theoretical study of the structure, vibrational spectra and electronic spectra of 2-amino-4-hydroxy-6-methylpyrimidine in the ground electronic state are reported. Anharmonic frequencies for the most stable conformer have been simulated using GVPT2, VSCF and PT2-VSCF methods with potential energy surface calculated using MP2 and DFT level of theory with 6-311G(d,p) basis set. The vibrational spectra (FTIR and FT-Raman) are interpreted in terms of fundamental, combination and overtone bands. It is found that the experimental and the VPT2 computed frequencies are in well agreement. The experimental and the calculated UV-Vis spectrum in gas and ethanol solvent are found comparable. Furthermore, HOMO-LUMO analysis, NLO, MEP, and natural charges of the molecule are also reported.

  11. Palladium-Catalyzed, ortho-Selective C-H Halogenation of Benzyl Nitriles, Aryl Weinreb Amides, and Anilides.

    Science.gov (United States)

    Das, Riki; Kapur, Manmohan

    2017-01-20

    A palladium-catalyzed, ortho-selective C-H halogenation methodology is reported herein. The highlight of the work is the highly selective C(sp(2))-H functionalization of benzyl nitriles in the presence of activated C(sp(3))-H bond, which results in good yields of the halogenated products with excellent regioselectivity. Along with benzyl nitriles, aryl Weinreb amides and anilides have been evaluated for the transformation using aprotic conditions. Mechanistic studies yield interesting aspects with respect to the pathway of the reaction and the directing group abilities.

  12. Ruthenium-Catalyzed Remote C-H Sulfonylation of N-Aryl-2-aminopyridines with Aromatic Sulfonyl Chlorides.

    Science.gov (United States)

    Ramesh, Balu; Jeganmohan, Masilamani

    2017-10-23

    A ruthenium-catalyzed remote sulfonylation at the C5 position of the pyridine group of N-aryl-2-aminopyridines with aromatic sulfonyl chlorides is described. The mechanistic and deuterium labeling studies clearly reveal that the ruthenametallacycle is a key intermediate in the reaction, which forms via the C-H bond activation. The DFT calculation supports that the C5 position of the 2-aminopyridine group carries a more negative charge (-0.304) as compared with other carbons in the metalacycle intermediate.

  13. DEGRADATION OF NATURAL ORGANIC MATTER IN WATER BY USING UV-C/H2O2 PROCESS

    OpenAIRE

    Juretić, Hrvoje; Smoljanić, Goran; Barta, Marija

    2015-01-01

    This laboratory study evaluated the ultraviolet (UV) photolysis, H2O2 treatment and UV-C/H2O2 advanced oxidation for the degradation of natural organic matter (NOM) in raw groundwater having high alkalinity and elevated dissolved organic carbon (DOC) concentration. The treatment efficiency was evaluated in terms of the reduction of DOC and UV absorbance at 254 nm (A254). UV photolysis and H2O2 oxidation as standalone treatments were not effective at reducing DOC but the rate of DOC reduction ...

  14. C H Rautenbach, P S Dreyer en C K Oberholzer: Hulle nalatenskap en die pad vorentoe1

    Directory of Open Access Journals (Sweden)

    Johann Beukes

    2000-01-01

    Full Text Available C H Rautenbach, P S Dreyer and C K Oberholzer: Their legacy and the way ahead. This article explores the legacy of three early philosophers at the University of Pretoria (1939-1987, who contributed substantially to the Nederduitsch Hervormde Kerk's perspectives on the relation between (modern theology and (modern philosophy. The authors consider their legacy to be an essentially Kantian stabilisation of the complex and problematic relationship between reason and faith, church and society, and theology and philosophy. The article then proceeds to interpret the changes in these relationships that were brought about by the postmodern discourse.

  15. Direct ortho-C-H functionalization of aromatic alcohols masked by acetone oxime ether via exo-palladacycle.

    Science.gov (United States)

    Guo, Kun; Chen, Xiaolan; Guan, Mingyu; Zhao, Yingsheng

    2015-04-03

    A simple and practical exo-oxime ether auxilixary for ortho-C-H functionalization of aromatic alcohols has been developed. Selective olefination of aromatic alcohols were first achieved via a six- or seven-membered exo-acetone oxime ether palladacycle with broad substrate scope. In addition, the crystal of the exo-palladacycle intermediate was obtained for the first time, and the application of this method in total synthesis of 3-deoxyisoochracinic acid was accomplished via a novel retro-synthetic disconnection approach, thus demonstrating the utility of this transformation.

  16. Discovery of an α-amino C-H arylation reaction using the strategy of accelerated serendipity.

    Science.gov (United States)

    McNally, Andrew; Prier, Christopher K; MacMillan, David W C

    2011-11-25

    Serendipity has long been a welcome yet elusive phenomenon in the advancement of chemistry. We sought to exploit serendipity as a means of rapidly identifying unanticipated chemical transformations. By using a high-throughput, automated workflow and evaluating a large number of random reactions, we have discovered a photoredox-catalyzed C-H arylation reaction for the construction of benzylic amines, an important structural motif within pharmaceutical compounds that is not readily accessed via simple substrates. The mechanism directly couples tertiary amines with cyanoaromatics by using mild and operationally trivial conditions.

  17. Rhodium-Catalyzed Intramolecular C-H Bond Activation with Triazoles: Preparation of Stereodefined Pyrrolidines and Other Related Cyclic Compounds.

    Science.gov (United States)

    Senoo, Masato; Furukawa, Ayana; Hata, Takeshi; Urabe, Hirokazu

    2016-01-18

    On treatment of triazoles having an N-sulfonyl-protected benzylamine moiety with [Rh2 (C7 H15 CO2 )4 ], intramolecular C-H bond insertion takes place at the benzylic position to give cis-N-sulfonyl-2-aryl-3-[(sulfonylimino)methyl]pyrrolidines in good yields and with highly stereoselectivities. Analogously, the similar treatment of triazoles having an ether or even an alkyl moiety affords 2-alkyl- or 2-aryl-3-[(sulfonylimino)methyl]tetrahydrofurans or a 2-alkyl-3-[(sulfonylimino)methyl]cyclopentane in good yields. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Rh-Catalyzed, Regioselective, C-H Bond Functionalization: Access to Quinoline-Branched Amines and Dimers.

    Science.gov (United States)

    Reddy, M Damoder; Fronczek, Frank R; Watkins, E Blake

    2016-11-04

    Rh-catalyzed, chelation-induced, C-5 regioselective C-H functionalization of 8-amidoquinolines with a range of N-Boc aminals is reported for the first time. The addition of in situ generated imines to C(sp2)-H bonds afforded branched amines in good to excellent yields. Moreover, this transformation features good functional group compatibility, broad substrate scope, and mild reaction conditions and is suitable for gram-scale synthesis. In addition, an unprecedented, chelation-induced, site-selective, remote dimerization of quinolines led to the formation of dimer frameworks in moderate yields under Rh-catalyzed conditions.

  19. Indole Synthesis through Sequential Electrophilic N-H and C-H Bond Activation Using Iodine(III) Reactivity.

    Science.gov (United States)

    Fra, Laura; Muñiz, Kilian

    2016-03-18

    An intramolecular approach towards the regioselective construction of 2,3-diarylated indoles is reported. The reaction follows an intramolecular electrophilic N-H and C-H bond functionalization between the aniline and acetylene. This methodology employs the concept of a traceless tether to provide access to the free 2,3-diarylated indole products comprising a total of 18 examples. Hypervalent iodine reagents were identified as suitable promoters and four different protocols are provided, including stoichiometric and catalytic transformations. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Quantum reaction dynamics study of vibrational excitation effects on the Cl + CHD3/CD4 → HCl/DCl + CD3 reactions

    Science.gov (United States)

    Yan, Wei; Wang, Dunyou

    2014-05-01

    Energy efficiency in surmounting the reaction energy barrier and vibrational enhancement on reactivity of the Cl + CHD3/CD4 → HCl/DCl + CD3 reactions have been studied using the reduced dimensional, time-dependent wavepacket method in six degrees of freedom. All the vibrational excitations of CHD3/CD4 enhance the reactivity and the C-H/C-D stretching motions have the biggest impact on the reactivity. Both reactions’ vibrational energies raise the reactivity more effectively than the translational energies except at very low collision energies. In other words, except at very low collision energies, the Polanyi rules hold for these two late-barrier polyatomic reactions.

  1. Vibrational autoionization of state-selective jet-cooled methanethiol (CH3SH) investigated with infrared vacuum-ultraviolet photoionization

    Energy Technology Data Exchange (ETDEWEB)

    Xie, Min; Sen, Zhitao; Pratt, S. T.; Lee, Yuan-Pern

    2017-11-21

    Vibrational autoionization of Rydberg states provides key information about nonadiabatic processes above an ionization threshold. We employed time-of-flight mass detection of CH3SH+ to record vibrational-state selective photo-ionization efficiency (PIE) spectra of jet-cooled methanethiol (CH3SH) on exciting CH3SH to a specific vibrationally excited state with an infrared (IR) laser, followed by excitation with a tunable laser in the vacuum-ultraviolet (VUV) region for ionization. Autoionizing Rydberg states assigned to the ns, np, nd and nf series are identified. When IR light at 2601 (ν3, SH stretching mode) and 2948 cm-12, CH3 symmetric stretching mode) was employed, the Rydberg series converged to the respective vibrationally excited (ν3 and ν2) states of CH3SH+. When IR light at 3014 cm-1 (overlapped ν19, CH3 antisymmetric stretching and CH2 antisymmetric stretching modes) was employed, two converging limits towards vibrationally excited states (ν1 and ν9) of CH3SH+ were observed. In contrast, when IR light at 2867 cm-1 (2ν10, overtone of CH3 deformation mode) and 2892 cm-1 (2ν4, overtone of CH2 scissoring mode) was employed, both Δν = -1 and Δν = -2 ionization transitions were observed; there is evidence for direct ionization from the initial state into the CH3SH+ (v4+ = 1) continuum. In all observed IR-VUV-PIE spectra, the ns and nd series show intensity greater than the other Rydberg series, which is consistent with the fact that the highest-occupied molecular orbital of CH3SH is a p-like lone pair orbital on the S atom. The quantum yields for autoionization of various vibrational excited states are discussed.

  2. Damage-free vibrational spectroscopy of biological materials in the electron microscope.

    Science.gov (United States)

    Rez, Peter; Aoki, Toshihiro; March, Katia; Gur, Dvir; Krivanek, Ondrej L; Dellby, Niklas; Lovejoy, Tracy C; Wolf, Sharon G; Cohen, Hagai

    2016-03-10

    Vibrational spectroscopy in the electron microscope would be transformative in the study of biological samples, provided that radiation damage could be prevented. However, electron beams typically create high-energy excitations that severely accelerate sample degradation. Here this major difficulty is overcome using an 'aloof' electron beam, positioned tens of nanometres away from the sample: high-energy excitations are suppressed, while vibrational modes of energies <1 eV can be 'safely' investigated. To demonstrate the potential of aloof spectroscopy, we record electron energy loss spectra from biogenic guanine crystals in their native state, resolving their characteristic C-H, N-H and C=O vibrational signatures with no observable radiation damage. The technique opens up the possibility of non-damaging compositional analyses of organic functional groups, including non-crystalline biological materials, at a spatial resolution of ∼10 nm, simultaneously combined with imaging in the electron microscope.

  3. Developing ligands for palladium(II)-catalyzed C-H functionalization: intimate dialogue between ligand and substrate.

    Science.gov (United States)

    Engle, Keary M; Yu, Jin-Quan

    2013-09-20

    Homogeneous transition-metal-catalyzed reactions are indispensable to all facets of modern chemical synthesis. It is thus difficult to imagine that for much of the early 20th century, the reactivity and selectivity of all known homogeneous metal catalysts paled in comparison to their heterogeneous and biological counterparts. In the intervening decades, advances in ligand design bridged this divide, such that today some of the most demanding bond-forming events are mediated by ligand-supported homogeneous metal species. While ligand design has propelled many areas of homogeneous catalysis, in the field of Pd(II)-catalyzed C-H functionalization, suitable ligand scaffolds are lacking, which has hampered the development of broadly practical transformations based on C-H functionalization logic. In this Perspective, we offer an account of our research employing three ligand scaffolds, mono-N-protected amino acids, 2,6-disubstituted pyridines, and 2,2'-bipyridines, to address challenges posed by several synthetically versatile substrate classes. Drawing on this work, we discuss principles of ligand design, such as the need to match a ligand to a particular substrate class, and how ligand traits such as tunability and modularity can be advantageous in reaction discovery.

  4. Hydrogen atom abstraction from C-H bonds of benzylamides by the aminoxyl radical BTNO: a kinetic study.

    Science.gov (United States)

    Coniglio, Alessandra; Galli, Carlo; Gentili, Patrizia; Vadalà, Raffaella

    2009-01-07

    The aminoxyl radical BTNO (benzotriazole-N-oxyl; >N-O*) is generated from HBT (1-hydroxybenzotriazole; >N-OH) by oxidation with a Ce(IV) salt. BTNO presents a broad absorption band with lambda(max) 474 nm that lends itself to investigate the kinetics of H-abstraction from H-donor substrates by spectrophotometry. Thus, rate constants (k(H)) of H-abstraction by BTNO from CH(2)-groups alpha to the nitrogen atom in X-substituted-(N-acetyl)benzylamines (X-C(6)H(4)CH(2)NHCOCH(3)) have been determined in MeCN solution at 25 degrees C. Correlation of the k(H)(X) data with the Hammett sigma(+) parameters gives a small value for rho (-0.65) that is compatible with a radical H-abstraction step. The sizeable value (k(H)/k(D)=8.8) of the kinetic isotope effect from a suitably deuteriated amide substrate further confirms H-abstraction as rate-determining. Evidence is acquired for the relevance of stereoelectronic effects that speed up the H-abstraction whenever the scissile C-H bond is co-linear with either the nitrogen lone-pair of the amide moiety or an adjacent aromatic group. An assessment of the dissociation energy value of the benzylic C-H bond in ArCH(2)NHCOMe is accordingly reported.

  5. Relationship between Plasma Parameters and Carbon Atom Coordination in a-C:H Films Prepared by RF Glow Discharge Decomposition

    Science.gov (United States)

    Yamamoto, Kenji; Ichikawa, Yosuke; Nakayama, Takehisa; Tawada, Yoshihisa

    1988-08-01

    Amorphous C:H films were prepared by rf glow discharge decomposition from CH4 using a permanent magnet system to apply a static magnetic field perpendicular to the rf electric field. The structure and properties of a-C:H films have been investigated systematically with respect to the hydrogen content, hardness and coordination of carbon atoms as a function of rf power (self-bias voltage). The coordination of carbon atoms has been determined by solid-state 13C magic angle spinning nuclear magnetic resonance measurements. It is found that the fraction of graphitic (sp2) versus tetrahedral (sp3) bonding increases with increasing rf power (negative self-bias voltage). Film hardness is understood in terms of the balance between the incorporated hydrogen and the fraction of graphitic (sp2) versus tetrahedral (sp3) bonding. The production of ionic and neutral species from a glow discharge has also been monitored by mass spectroscopy and optical emission spectroscopy to investigate the relation between plasma parameters and carbon atom coordination. Using these measurements and negative self-bias measurements, it is shown that the coordination of carbon atoms is determined not only by the energy of impinging ions on the substrate but also by the type of active species. In addition, the neutral and ionic C2H2 related species are thought to be some of the species which increase the fraction of graphitic (sp2) versus tetrahedral (sp3) bonding.

  6. The design, construction and testing of a microcombustion calorimeter suitable for organic compounds containing C, H and O

    Energy Technology Data Exchange (ETDEWEB)

    Davalos, Juan Z.; Roux, M. Victoria [CSIC, Lab. de Termoquimica, Madrid (Spain)

    2000-10-01

    To obtain reliable standard energies of combustion with small amounts of C, H, O compounds, a new microcombustion calorimetry system has been set up. The design, construction, calibration and measurement experiments are described. The system includes a commercial combustion bomb with an internal volume of 22 cm{sup 3}. Samples of around 80 mg are suitable if one wants to retain the same levels of accuracy and reproducibility as those in macrocombustion experiments. Calibration of the calorimeter was performed using benzoic acid. {delta} (Calorimeter) = 2083.74{+-}0.48JK{sup -1} was obtained. Combustion measurements using m-methoxybenzoic acid were made in order to verify the chemistry of the combustion process involved in the corresponding analysis of results and the accuracy of the measurement of combustion energy. The uncertainty of the results shows that the instrument described and the experimental procedure used for the determination of enthalpies of formation of compounds containing C, H and O provide a high reliability. (Author)

  7. VIBRATION ISOLATION SYSTEM PROBABILITY ANALYSIS

    Directory of Open Access Journals (Sweden)

    Smirnov Vladimir Alexandrovich

    2012-10-01

    Full Text Available The article deals with the probability analysis for a vibration isolation system of high-precision equipment, which is extremely sensitive to low-frequency oscillations even of submicron amplitude. The external sources of low-frequency vibrations may include the natural city background or internal low-frequency sources inside buildings (pedestrian activity, HVAC. Taking Gauss distribution into account, the author estimates the probability of the relative displacement of the isolated mass being still lower than the vibration criteria. This problem is being solved in the three dimensional space, evolved by the system parameters, including damping and natural frequency. According to this probability distribution, the chance of exceeding the vibration criteria for a vibration isolation system is evaluated. Optimal system parameters - damping and natural frequency - are being developed, thus the possibility of exceeding vibration criteria VC-E and VC-D is assumed to be less than 0.04.

  8. Random vibrations theory and practice

    CERN Document Server

    Wirsching, Paul H; Ortiz, Keith

    1995-01-01

    Random Vibrations: Theory and Practice covers the theory and analysis of mechanical and structural systems undergoing random oscillations due to any number of phenomena— from engine noise, turbulent flow, and acoustic noise to wind, ocean waves, earthquakes, and rough pavement. For systems operating in such environments, a random vibration analysis is essential to the safety and reliability of the system. By far the most comprehensive text available on random vibrations, Random Vibrations: Theory and Practice is designed for readers who are new to the subject as well as those who are familiar with the fundamentals and wish to study a particular topic or use the text as an authoritative reference. It is divided into three major sections: fundamental background, random vibration development and applications to design, and random signal analysis. Introductory chapters cover topics in probability, statistics, and random processes that prepare the reader for the development of the theory of random vibrations a...

  9. Renewable Formate from C-H Bond Formation with CO2: Using Iron Carbonyl Clusters as Electrocatalysts.

    Science.gov (United States)

    Loewen, Natalia D; Neelakantan, Taruna V; Berben, Louise A

    2017-09-19

    As a society, we are heavily dependent on nonrenewable petroleum-derived fuels and chemical feedstocks. Rapid depletion of these resources and the increasingly evident negative effects of excess atmospheric CO 2 drive our efforts to discover ways of converting excess CO 2 into energy dense chemical fuels through selective C-H bond formation and using renewable energy sources to supply electrons. In this way, a carbon-neutral fuel economy might be realized. To develop a molecular or heterogeneous catalyst for C-H bond formation with CO 2 requires a fundamental understanding of how to generate metal hydrides that selectively donate H - to CO 2 , rather than recombining with H + to liberate H 2 . Our work with a unique series of water-soluble and -stable, low-valent iron electrocatalysts offers mechanistic and thermochemical insights into formate production from CO 2 . Of particular interest are the nitride- and carbide-containing clusters: [Fe 4 N(CO) 12 ] - and its derivatives and [Fe 4 C(CO) 12 ] 2- . In both aqueous and mixed solvent conditions, [Fe 4 N(CO) 12 ] - forms a reduced hydride intermediate, [H-Fe 4 N(CO) 12 ] - , through stepwise electron and proton transfers. This hydride selectively reacts with CO 2 and generates formate with >95% efficiency. The mechanism for this transformation is supported by crystallographic, cyclic voltammetry, and spectroelectrochemical (SEC) evidence. Furthermore, installation of a proton shuttle onto [Fe 4 N(CO) 12 ] - facilitates proton transfer to the active site, successfully intercepting the hydride intermediate before it reacts with CO 2 ; only H 2 is observed in this case. In contrast, isoelectronic [Fe 4 C(CO) 12 ] 2- features a concerted proton-electron transfer mechanism to form [H-Fe 4 C(CO) 12 ] 2- , which is selective for H 2 production even in the presence of CO 2 , in both aqueous and mixed solvent systems. Higher nuclearity clusters were also studied, and all are proton reduction electrocatalysts, but none

  10. Thin films of hydrogenated amorphous carbon (a-C:H) obtained through chemical vapor deposition assisted by plasma; Peliculas delgadas de carbono amorfo hidrogenado (a-C:H) obtenidas mediante deposito quimico de vapores asistido por plasma

    Energy Technology Data Exchange (ETDEWEB)

    Mejia H, J.A.; Camps C, E.E.; Escobar A, L.; Romero H, S.; Chirino O, S. [ININ, 52045 Ocoyoacac, Estado de Mexico (Mexico); Muhl S, S. [IIM-UNAM, 04510 Mexico D.F. (Mexico)

    2004-07-01

    Films of hydrogenated amorphous carbon (a-C:H) were deposited using one source of microwave plasma with magnetic field (type ECR), using mixtures of H{sub 2}/CH{sub 4} in relationship of 80/20 and 95/05 as precursory gases, with work pressures of 4X10{sup -4} to 6x10{sup -4} Torr and an incident power of the discharge of microwaves with a constant value of 400 W. It was analyzed the influence among the properties of the films, as the deposit rate, the composition and the bonding types, and the deposit conditions, such as the flow rates of the precursory gases and the polarization voltage of the sample holders. (Author)

  11. Chaotic vortex induced vibrations

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, J.; Sheridan, J. [Fluids Laboratory for Aeronautical and Industrial Research (FLAIR), Department of Mechanical and Aerospace Engineering, Monash University, Melbourne, Victoria 3800 (Australia); Leontini, J. S. [Department of Mechanical and Product Design Engineering, Swinburne University of Technology, Hawthorn, Victoria 3122 (Australia); Lo Jacono, D. [Institut de Mécanique des Fluides de Toulouse (IMFT), CNRS, UPS and Université de Toulouse, 31400 Toulouse (France)

    2014-12-15

    This study investigates the nature of the dynamic response of an elastically mounted cylinder immersed in a free stream. A novel method is utilized, where the motion of the body during a free vibration experiment is accurately recorded, and then a second experiment is conducted where the cylinder is externally forced to follow this recorded trajectory. Generally, the flow response during both experiments is identical. However, particular regimes exist where the flow response is significantly different. This is taken as evidence of chaos in these regimes.

  12. Lattice Vibrations in Chlorobenzenes:

    DEFF Research Database (Denmark)

    Reynolds, P. A.; Kjems, Jørgen; White, J. W.

    1974-01-01

    Lattice vibrational dispersion curves for the ``intermolecular'' modes in the triclinic, one molecule per unit cell β phase of p‐C6D4Cl2 and p‐C6H4Cl2 have been obtained by inelastic neutron scattering. The deuterated sample was investigated at 295 and at 90°K and a linear extrapolation to 0°K...... was applied in order to correct for anharmonic effects. Calculations based on the atom‐atom model for van der Waals' interaction and on general potential parameters for the aromatic compounds agree reasonably well with the experimental observations. There is no substantial improvement in fit obtained either...

  13. Quantum dynamics of vibrational excitations and vibrational charge ...

    Indian Academy of Sciences (India)

    Quantum dynamics of vibrational excitations and vibrational charge transfer processes in H+ + O2 collisions at collision energy 23 eV ... The Fritz Haber Research Centre and The Department of Physical Chemisry, Hebrew University of Jerusalem, Jerusalem, Israel 91904; Department of Chemistry, Indian Institute of ...

  14. Sequential meta-C-H olefination of synthetically versatile benzyl silanes: effective synthesis of meta-olefinated toluene, benzaldehyde and benzyl alcohols.

    Science.gov (United States)

    Patra, Tuhin; Watile, Rahul; Agasti, Soumitra; Naveen, Togati; Maiti, Debabrata

    2016-02-04

    Tremendous progress has been made towards ortho-selective C-H functionalization in the last three decades. However, the activation of distal C-H bonds and their functionalization has remained fairly underdeveloped. Herein, we report sequential meta-C-H functionalization by performing selective mono-olefination and bis-olefination with late stage modification of the C-Si as well as Si-O bonds. Temporary silyl connection was found to be advantageous due to its easy installation, easy removal and wide synthetic diversification.

  15. Literature survey on anti-vibration gloves

    CSIR Research Space (South Africa)

    Sampson, E

    2003-08-01

    Full Text Available ............................................................................................................... 1 2. HAND ARM VIBRATION SYNDROME (HAVS).......................................................... 2 2.1 Hand-arm vibration................................................. Error! Bookmark not defined. 2.2 Human Response to vibration...

  16. Ligandless Palladium-Catalyzed Regioselective Direct C-H Arylation of Imidazo[1,2-a]imidazole Derivatives.

    Science.gov (United States)

    Grosse, Sandrine; Pillard, Christelle; Massip, Stéphane; Marchivie, Mathieu; Jarry, Christian; Bernard, Philippe; Guillaumet, Gérald

    2015-09-04

    Herein a novel access to functionalizable 6-substituted imidazo[1,2-a]imidazole scaffolds is described. The reactivity of this heterobicyclic unit toward direct C-H arylation was studied, and conditions allowing regioselective arylation at position 3 were successfully developed. The practicability of this method is manifested by the ligandless conditions and low catalyst loading. The strategy is functional group tolerant and provides rapid access to a large variety of 3,6-di(hetero)arylated imidazo[1,2-a]imidazole derivatives. A second arylation at position 2 was then carried out, and a library of diversified 2,3,6-tri(hetero)arylated imidazo[1,2-a]imidazoles was generated in good yields. A one-pot, two-step procedure was finally developed.

  17. Regioselective C-H hydroxylation of omeprazole sulfide by Bacillus megaterium CYP102A1 to produce a human metabolite.

    Science.gov (United States)

    Jang, Hyun-Hee; Ryu, Sang-Hoon; Le, Thien-Kim; Doan, Tiep Thi My; Nguyen, Thi Huong Ha; Park, Ki Deok; Yim, Da-Eun; Kim, Dong-Hyun; Kang, Choong-Kyung; Ahn, Taeho; Kang, Hyung-Sik; Yun, Chul-Ho

    2017-01-01

    To find a simple enzymatic strategy for the efficient synthesis of the expensive 5'-hydroxyomeprazole sulfide, a recently identified minor human metabolite, from omeprazole sulfide, which is an inexpensive substrate. The practical synthetic strategy for the 5'-OH omeprazole sulfide was accomplished with a set of highly active CYP102A1 mutants, which were obtained by blue colony screening from CYP102A1 libraries with a high conversion yield. The mutant and even the wild-type enzyme of CYP102A1 catalyzed the high regioselective (98 %) C-H hydroxylation of omeprazole sulfide to 5'-OH omeprazole sulfide with a high conversion yield (85-90 %). A highly efficient synthesis of 5'-OH omeprazole sulfide was developed using CYP102A1 from Bacillus megaterium as a biocatalyst.

  18. Mechanistic Insights of a Selective C-H Alkylation of Alkenes by a Ru-based Catalyst and Alcohols

    KAUST Repository

    Poater, Albert

    2016-09-11

    Density functional theory calculations have been used to investigate the reaction mechanism for [(C6H6)(PCy3)(CO) RuH](+) (1; Cy, cyclohexyl) mediated alkylation of indene substrate using ethanol as solvent. According to Yi et al. [ Science 2011, 333, 1613] the plausible reaction mechanism involves a cationic Rualkenyl species, which is initially formed from 1 with two equivalents of the olefin substrate via the vinylic C-H activation and an alkane elimination step. Once the active catalytic species is achieved the oxidative addition step is faced. The latter step together with the next C-C bond formation might display the upper barrier of the catalytic cycle. Having these experimental insights at hand, we investigated in detail the whole reaction pathway using several computational DFT approaches including alternative pathways, higher in energy.

  19. Microwave-assisted extraction and a new determination method for total steroid saponins from Dioscorea zingiberensis C.H. Wright.

    Science.gov (United States)

    Ren, Yao; Chen, Yu; Hu, Bohan; Wu, Hui; Lai, Furao; Li, Xiaofeng

    2015-12-01

    An efficient microwave-assisted extraction (MAE) technique was applied to isolate total steroid saponins from Dioscorea zingiberensis C.H. Wright (DZW). The optimal extracting conditions were established as 75% ethanol as solvent, ratio of solid/liquid 1:20 (g/ml), temperature 75 °C, irradiation power 600 W and three extraction cycles of 6 min each. Scanning electron microscopy (SEM) images of DZW processed by four different extractions provided visual evidence of the disruption effect on DZW. Diosgenin was quantified by HPLC and examined further by LC-ESI/MS after acid hydrolysis. Total steroid saponins were calculated using diosgenin from total steroid saponins. The MAE procedure was optimized, validated and compared with other conventional extraction processes. This report provides a convenient technology for the extraction and quantification of total saponins of DZW combining MAE with HPLC and LC-ESI/MS for the first time. Copyright © 2015 Elsevier Inc. All rights reserved.

  20. An unusual endo-selective C-H hydroarylationof norbornene by the Rh(I)-catalyzed reactionof benzamides.

    Science.gov (United States)

    Shibata, Kaname; Natsui, Satoko; Tobisu, Mamoru; Fukumoto, Yoshiya; Chatani, Naoto

    2017-11-13

    Hydroarylation is an environmentally attractive strategy which incorporates all of the atoms contained in the substrates into the desired products. Almost all the hydroarylations of norbornene reported to date involve an exo-selective reaction. Here we show the endo-selective hydroarylation of norbornene in the Rh(I)-catalyzed reaction of aromatic amides. The addition of sterically bulky carboxylic acids enhances the endo-selectivity of the reaction. The results of deuterium-labeling experiments show that both the ortho-carbon and the ortho-hydrogen atoms of aromatic amides were attached to the same carbon atom of the norbornane skeleton in the hydroarylation product. These results clearly suggest that hydrometalation or carbometalation, which are commonly accepted mechanisms for the catalytic hydroarylation of C-H bonds, are not involved as the key step in the present reaction, and suggest that the reaction involves a rhodium carbene complex generated from norbornene as the key intermediate.

  1. Understanding the differential performance of Rh2(esp)2 as a catalyst for C-H amination.

    Science.gov (United States)

    Zalatan, David N; Du Bois, J

    2009-06-10

    Catalytic amination of saturated C-H bonds is performed efficiently with the use of Rh(2)(esp)(2). Efforts to identify pathways for catalyst degradation and/or arrest have revealed a single-electron oxidation event that gives rise to a red-colored, mixed-valence dimer, [Rh(2)(esp)(2)](+). This species is fortuitously reduced by carboxylic acid, a byproduct generated in the reaction cycle with each turnover of the diacyloxyiodine oxidant. These findings have led to the conclusion that the high performance of Rh(2)(esp)(2) is due in part to the superior kinetic stability of its one-electron oxidized form relative to other dimeric Rh complexes.

  2. Use of chemical auxiliaries to control p450 enzymes for predictable oxidations at unactivated C-h bonds of substrates.

    Science.gov (United States)

    Auclair, Karine; Polic, Vanja

    2015-01-01

    Cytochrome P450 enzymes (P450s) have the ability to oxidize unactivated C-H bonds of substrates with remarkable regio- and stereoselectivity. Comparable selectivity for chemical oxidizing agents is typically difficult to achieve. Hence, there is an interest in exploiting P450s as potential biocatalysts. Despite their impressive attributes, the current use of P450s as biocatalysts is limited. While bacterial P450 enzymes typically show higher activity, they tend to be highly selective for one or a few substrates. On the other hand, mammalian P450s, especially the drug-metabolizing enzymes, display astonishing substrate promiscuity. However, product prediction continues to be challenging. This review discusses the use of small molecules for controlling P450 substrate specificity and product selectivity. The focus will be on two approaches in the area: (1) the use of decoy molecules, and (2) the application of substrate engineering to control oxidation by the enzyme.

  3. Oxygen activation and intramolecular C-H bond activation by an amidate-bridged diiron(II) complex.

    Science.gov (United States)

    Jones, Matthew B; Hardcastle, Kenneth I; Hagen, Karl S; MacBeth, Cora E

    2011-07-18

    A diiron(II) complex containing two μ-1,3-(κN:κO)-amidate linkages has been synthesized using the 2,2',2''-tris(isobutyrylamido)triphenylamine (H(3)L(iPr)) ligand. The resulting diiron complex, 1, reacts with dioxygen (or iodosylbenzene) to effect intramolecular C-H bond activation at the methine position of the ligand isopropyl group. The ligand-activated product, 2, has been isolated and characterized by a variety of methods including X-ray crystallography. Electrospray ionization mass spectroscopy of 2 prepared from(18)O(2) was used to confirm that the oxygen atom incorporated into the ligand framework is derived from molecular oxygen.

  4. Modeling the absorption behavior of solar thermal collector coatings utilizing graded alpha-C:H/TiC layers.

    Science.gov (United States)

    Gruber, D P; Engel, G; Sormann, H; Schüler, A; Papousek, W

    2009-03-10

    Wavelength selective coatings are of common use in order to enhance the efficiency of devices heated by radiation such as solar thermal collectors. The use of suitable materials and the optimization of coating layer thicknesses are advisable ways to maximize the absorption. Further improvement is achievable by embedding particles in certain layers in order to modify material properties. We focus on optimizing the absorption behavior of a solar collector setup using copper as substrate, a layer of amorphous hydrogenated carbon with embedded titanium carbide particles (a-C:H/TiC), and an antireflection coating of amorphous silicon dioxide (aSiO(2)). For the setup utilizing homogeneous particle distribution, a relative absorption of 90.98% was found, while inhomogeneous particle embedding yielded 98.29%. These results are particularly interesting since until now, absorption of more than 95% was found only by using embedded Cr but not by using the more biocompatible Ti.

  5. A Ni(iii) complex stabilized by silica nanoparticles as an efficient nanoheterogeneous catalyst for oxidative C-H fluoroalkylation.

    Science.gov (United States)

    Khrizanforov, Mikhail N; Fedorenko, Svetlana V; Strekalova, Sofia O; Kholin, Kirill V; Mustafina, Asiya R; Zhilkin, Mikhail Ye; Khrizanforova, Vera V; Osin, Yuri N; Salnikov, Vadim V; Gryaznova, Tatyana V; Budnikova, Yulia H

    2016-07-26

    We have developed Ni(III)-doped silica nanoparticles ([(bpy)xNi(III)]@SiO2) as a recyclable, low-leaching, and efficient oxidative functionalization nanocatalyst for aromatic C-H bonds. The catalyst is obtained by doping the complex [(bpy)3Ni(II)] on silica nanoparticles along with its subsequent electrooxidation to [(bpy)xNi(III)] without an additional oxidant. The coupling reaction of arenes with perfluoroheptanoic acid occurs with 100% conversion of reactants in a single step at room temperature under nanoheterogeneous conditions. The catalyst content is only 1% with respect to the substrates under electrochemical regeneration conditions. The catalyst can be easily separated from the reaction mixture and reused a minimum of five times. The results emphasize immobilization on the silica support and the electrochemical regeneration of Ni(III) complexes as a facile route for developing an efficient nanocatalyst for oxidative functionalization.

  6. Graphene Oxide Catalyzed C-H Bond Activation: The Importance of Oxygen Functional Groups for Biaryl Construction.

    Science.gov (United States)

    Gao, Yongjun; Tang, Pei; Zhou, Hu; Zhang, Wei; Yang, Hanjun; Yan, Ning; Hu, Gang; Mei, Donghai; Wang, Jianguo; Ma, Ding

    2016-02-24

    A heterogeneous, inexpensive, and environmentally friendly graphene oxide catalytic system for the C-H bond arylation of benzene enables the formation of biaryl compounds in the presence of aryl iodides. The oxygen functional groups in these graphene oxide sheets and the addition of KOtBu are essential for the observed catalytic activity. Reactions with various model compounds and DFT calculations confirmed that these negatively charged oxygen atoms promote the overall transformation by stabilizing and activating K(+) ions, which in turns facilitates the activation of the C-I bond. However, the graphene π system also greatly facilitates the overall reaction as the aromatic coupling partners are easily adsorbed. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Rh(III)-Catalyzed Diastereoselective C-H Bond Addition/Cyclization Cascade of Enone Tethered Aldehydes.

    Science.gov (United States)

    Boerth, Jeffrey A; Ellman, Jonathan A

    2016-02-01

    The Rh(III)-catalyzed cascade addition of a C-H bond across alkene and carbonyl π-bonds is reported. The reaction proceeds under mild reaction conditions with low catalyst loading. A range of directing groups were shown to be effective as was the functionalization of alkenyl in addition to aromatic C(sp2)-H bonds. When the enone and aldehyde electrophile were tethered together, cyclic β-hydroxy ketones with three contiguous stereocenters were obtained with high diastereoselectivity. The intermolecular three-component cascade reaction was demonstrated for both aldehyde and imine electrophiles. Moreover, the first x-ray structure of a cationic Cp*Rh(III) enolate with interatomic distances consistent with an η3-bound enolate is reported.

  8. Direct Synthesis of Protoberberine Alkaloids by Rh-Catalyzed C-H Bond Activation as the Key Step.

    Science.gov (United States)

    Jayakumar, Jayachandran; Cheng, Chien-Hong

    2016-01-26

    A one-pot reaction of substituted benzaldehydes with alkyne-amines by a Rh-catalyzed C-H activation and annulation to afford various natural and unnatural protoberberine alkaloids is reported. This reaction provides a convenient route for the generation of a compound library of protoberberine salts, which recently have attracted great attention because of their diverse biological activities. In addition, pyridinium salt derivatives can also be formed in good yields from α,β-unsaturated aldehydes and amino-alkynes. This reaction proceeds with excellent regioselectivity and good functional group compatibility under mild reaction conditions by using O2 as the oxidant. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. Photolytic C-H activation and dehydrogenation of alkanes at cyclopentadienyl iridium complexes in a perfluorinated solvent.

    Science.gov (United States)

    Rábay, Battist; Braun, Thomas; Falkenhagen, Jan P

    2013-06-14

    The fluorinated complex [(Cp(f))Ir(CO)2] (2) [Cp(f) = C5H4(CH2)2(CF2)5CF3] serves as a precursor for the photolytic activation of C-H bonds in alkanes to give [(Cp(f))Ir(CH3)(H)(CO)] (3), [(Cp(f))Ir(C5H9)(H)(CO)] (4), [(Cp(f))Ir(C6H11)(H)(CO)] (5) or [(Cp(f))Ir(C8H15)(H)(CO)] (6). In C7F14 as a solvent the latter react to yield the corresponding olefins as well as [(Cp(f))Ir(H)2(CO)] (7). Photocatalytic experiments revealed that [(Cp(f))Ir(CO)2] (2) and the non-fluorinated compound [(Cp)Ir(CO)2] (1) dehydrogenate cyclohexane in C7F14. In C6H12 as a solvent a decomposition of the catalysts was observed.

  10. Vibrational Sensing in Marine Invertebrates

    Science.gov (United States)

    1997-09-30

    VIBRATIONAL SENSING IN MARINE INVERTEBRATES Peter A. Jumars School of Oceanography University of Washington Box 357940 Seattle, WA 98195-7940 (206...DATES COVERED 00-00-1997 to 00-00-1997 4. TITLE AND SUBTITLE Vibrational Sensing in Marine Invertebrates 5a. CONTRACT NUMBER 5b. GRANT NUMBER

  11. Vibrations and Stability: Solved Problems

    DEFF Research Database (Denmark)

    Thomsen, Jon Juel

    Worked out solutions for exercise problems in J. J. Thomsen 'Vibrations and Stability: Advanced Theory, Analysis, and Tools', Springer, Berlin - Heidelberg, 2003.......Worked out solutions for exercise problems in J. J. Thomsen 'Vibrations and Stability: Advanced Theory, Analysis, and Tools', Springer, Berlin - Heidelberg, 2003....

  12. Tropine forming tropinone reductase gene from Withania somnifera (Ashwagandha: biochemical characteristics of the recombinant enzyme and novel physiological overtones of tissue-wide gene expression patterns.

    Directory of Open Access Journals (Sweden)

    Amit Kumar Kushwaha

    expression profiles are discussed with respect to their physiological overtones.

  13. Tropine Forming Tropinone Reductase Gene from Withania somnifera (Ashwagandha): Biochemical Characteristics of the Recombinant Enzyme and Novel Physiological Overtones of Tissue-Wide Gene Expression Patterns

    Science.gov (United States)

    Kushwaha, Amit Kumar; Sangwan, Neelam Singh; Trivedi, Prabodh Kumar; Negi, Arvind Singh; Misra, Laxminarain; Sangwan, Rajender Singh

    2013-01-01

    profiles are discussed with respect to their physiological overtones. PMID:24086372

  14. Tropine forming tropinone reductase gene from Withania somnifera (Ashwagandha): biochemical characteristics of the recombinant enzyme and novel physiological overtones of tissue-wide gene expression patterns.

    Science.gov (United States)

    Kushwaha, Amit Kumar; Sangwan, Neelam Singh; Trivedi, Prabodh Kumar; Negi, Arvind Singh; Misra, Laxminarain; Sangwan, Rajender Singh

    2013-01-01

    profiles are discussed with respect to their physiological overtones.

  15. IR and Raman spectra, ab initio and density functional computations of the vibrational spectra, molecular geometries and atomic charges of uracil and 5-aminouracil

    Science.gov (United States)

    Singh, J. S.

    2014-09-01

    Infrared (IR) and Raman spectra of uracil and 5-aminouracil have been recorded and analyzed between the region 200-4000 cm-1. The optimized molecular geometries, atomic polar tensor (APT) charges and vibrational characteristics have been studied theoretically using restricted Hartree-Fock (RHF) and density functional theory (DFT) methods. Using the Becke’s exchange in conjunction with Lee-Yang-Parr’s correlation functional and Becke’s three-parameter hybrid method (B3LYP), the ab initio and DFT calculations were carried out to study the optimized molecular fundamental vibrational frequencies for uracil and 5-aminouracil by employing Gaussian-03 program. The fundamental vibrational frequencies along with their corresponding intensities in IR and Raman activities and depolarization ratios of the Raman lines have also been calculated using the RHF and DFT methods employing different basis sets. In quantum chemical calculations, the most of B3LYP/6-311++G** vibrational frequencies are in the excellent agreement with available experimental assignments and helped in the reassignments of some fundamental vibrational modes. On the basis of calculated results, the assignments of some missing frequencies in the experimental study are proposed. Assuming under the Cs point group for both molecules, the distribution of normal mode of vibrations between the two species as planar (a‧) and non-planar (a″) are given by 25a‧ + 11a″, of which 30 modes (21a‧ + 9a″) correspond to the uracil moiety and 6 modes (4a‧ + 2a″) to the NH2 group. Kekule ring stretching mode is found to be comparatively higher frequency magnitude than the mode of uracil due to the involvement of hydrogen bonding of amino group. But, the ring breathing is found to be lower frequency magnitude compared to those for uracil which could be due to mass effect of the NH2 group in place of the hydrogen atom. All other bands have also been assigned different fundamentals/overtones/combinations.

  16. The origins of vibration theory

    Science.gov (United States)

    Dimarogonas, A. D.

    1990-07-01

    The Ionian School of natural philosophy introduced the scientific method of dealing with natural phenomena and the rigorous proofs for abstract propositions. Vibration theory was initiated by the Pythagoreans in the fifth century BC, in association with the theory of music and the theory of acoustics. They observed the natural frequency of vibrating systems and proved that it is a system property and that it does not depend on the excitation. Pythagoreans determined the fundamental natural frequencies of several simple systems, such as vibrating strings, pipes, vessels and circular plates. Aristoteles and the Peripatetic School founded mechanics and developed a fundamental understanding of statics and dynamics. In Alexandrian times there were substantial engineering developments in the field of vibration. The pendulum as a vibration, and probably time, measuring device was known in antiquity, and was further developed by the end of the first millennium AD.

  17. Additive- and Metal-Free, Predictably 1,2- and 1,3-Regioselective, Photoinduced Dual C-H/C-X Borylation of Haloarenes.

    Science.gov (United States)

    Mfuh, Adelphe M; Nguyen, Vu T; Chhetri, Bhuwan; Burch, Jessica E; Doyle, John D; Nesterov, Vladimir N; Arman, Hadi D; Larionov, Oleg V

    2016-07-13

    We report herein a simple, additive- and metal-free, photoinduced, dual C-H/C-X borylation of chloro-, bromo-, and iodoarenes. The reaction produces 1,2- and 1,3-diborylarenes on gram scales under batch and continuous flow conditions. The regioselectivity of the dual C-H/C-X borylation is determined by the solvent and the substituents in the parent haloarenes.

  18. Computation and interpretation of vibrational spectra on the structure of Losartan using ab initio and Density Functional methods

    Science.gov (United States)

    Latha, B.; Gunasekaran, S.; Srinivasan, S.; Ramkumaar, G. R.

    2014-11-01

    The solid phase FTIR and FT-Raman spectra of Losartan have been recorded in the region 400-4000 cm-1. The spectra were interpreted in terms of fundamental modes, combination and overtone bands. The structure of the molecule was optimized and the structural characteristics were determined by Quantum chemical methods. The vibrational frequencies yield good agreement between observed and calculated values. The infrared and Raman spectra were also predicted from the calculated intensities. (1)H and (13)C NMR spectra were recorded and resonance chemical shifts of the molecule were calculated. UV-Visible spectrum of the compound was recorded in the region 200-600 nm and the electronic properties HOMO and LUMO energies calculated by TD-HF approach. NBO atomic charges of the molecules and second order perturbation theory analysis of Fock matrix also calculated and interpreted. The geometrical parameters, energies, harmonic vibrational frequencies, IR intensities, Raman intensities, and absorption wavelengths were compared with experimental and theoretical data of the molecule.

  19. The Stereoselective Formation of Bicyclic Enamines with Bridgehead Unsaturation via Tandem C-H Bond Activation/Alkenylation/Electrocyclization

    Energy Technology Data Exchange (ETDEWEB)

    Ellman, Jonathan A.; Yotphan, Sirilata; Bergman, Robert

    2007-12-10

    Rhodium-catalyzed intermolecular C-H activation of {alpha}, {beta}-unsaturated imines in the presence of alkynes leads to a tandem process in which coupling to the alkyne occurs at the {beta}-C-H bond of the imine, followed by electrocyclization of the resulting azatriene intermediates to give dihydropyridines (eq 1). Consideration of the intramolecular version of this overall transformation (Scheme 1) raises interesting regiochemical issues. For example in a compound such as 1, where the nitrogen and alkyne are connected by a 4-carbon tether, the presumed first-formed hydrido(vinyl)rhodium function can add to the triple bond in a 1,2-fashion, producing complex 2 with a new endocyclic double bond. Alternatively, addition might occur in a 2,1-fashion, leading to product 4 with an exocyclic double bond. We now wish to report that this intramolecular cyclization occurs smoothly at 100 C, and the exocyclic double bond route is exclusively followed. Remarkably, products such as 4 do not resist further cyclization. Even though both the transition state for this process and the resulting product are presumably strained, the overall transformation leads to good yields of unusual bridgehead doubly-bonded enamines such as 5. The unique chemistry of conjugated enamine 5 is consistent with the increased strain of this molecule as well as with inhibited conjugation between the nitrogen lone pair and the adjacent double bond (vida infra). We began our investigation into the C-H activation/cyclization of alkyne-tethered imine 1 by extensive screening of transition metal catalysts for this process. Rhodium-based catalysts were found to be the most efficient (Table 1), leading exclusively to the bridgehead dienamine; none of the catalysts that were employed in the screening led to quinolizidine 3 or to the product of intramolecular Diels-Alder reaction. The optimized reaction conditions employ the electron-rich monophosphine ligand (p-NMe{sub 2})PhPEt{sub 2} in 1:1 ratio relative

  20. Vibration response of misaligned rotors

    Science.gov (United States)

    Patel, Tejas H.; Darpe, Ashish K.

    2009-08-01

    Misalignment is one of the common faults observed in rotors. Effect of misalignment on vibration response of coupled rotors is investigated in the present study. The coupled rotor system is modelled using Timoshenko beam elements with all six dof. An experimental approach is proposed for the first time for determination of magnitude and harmonic nature of the misalignment excitation. Misalignment effect at coupling location of rotor FE model is simulated using nodal force vector. The force vector is found using misalignment coupling stiffness matrix, derived from experimental data and applied misalignment between the two rotors. Steady-state vibration response is studied for sub-critical speeds. Effect of the types of misalignment (parallel and angular) on the vibration behaviour of the coupled rotor is examined. Along with lateral vibrations, axial and torsional vibrations are also investigated and nature of the vibration response is also examined. It has been found that the misalignment couples vibrations in bending, longitudinal and torsional modes. Some diagnostic features in the fast Fourier transform (FFT) of torsional and longitudinal response related to parallel and angular misalignment have been revealed. Full spectra and orbit plots are effectively used to reveal the unique nature of misalignment fault leading to reliable misalignment diagnostic information, not clearly brought out by earlier studies.

  1. Tissue vibration in prolonged running.

    Science.gov (United States)

    Friesenbichler, Bernd; Stirling, Lisa M; Federolf, Peter; Nigg, Benno M

    2011-01-04

    The impact force in heel-toe running initiates vibrations of soft-tissue compartments of the leg that are heavily dampened by muscle activity. This study investigated if the damping and frequency of these soft-tissue vibrations are affected by fatigue, which was categorized by the time into an exhaustive exercise. The hypotheses were tested that (H1) the vibration intensity of the triceps surae increases with increasing fatigue and (H2) the vibration frequency of the triceps surae decreases with increasing fatigue. Tissue vibrations of the triceps surae were measured with tri-axial accelerometers in 10 subjects during a run towards exhaustion. The frequency content was quantified with power spectra and wavelet analysis. Maxima of local vibration intensities were compared between the non-fatigued and fatigued states of all subjects. In axial (i.e. parallel to the tibia) and medio-lateral direction, most local maxima increased with fatigue (supporting the first hypothesis). In anterior-posterior direction no systematic changes were found. Vibration frequency was minimally affected by fatigue and frequency changes did not occur systematically, which requires the rejection of the second hypothesis. Relative to heel-strike, the maximum vibration intensity occurred significantly later in the fatigued condition in all three directions. With fatigue, the soft tissue of the triceps surae oscillated for an extended duration at increased vibration magnitudes, possibly due to the effects of fatigue on type II muscle fibers. Thus, the protective mechanism of muscle tuning seems to be reduced in a fatigued muscle and the risk of potential harm to the tissue may increase. Copyright © 2010 Elsevier Ltd. All rights reserved.

  2. Oxidative addition of an aromatic ortho C-H bond of tetraphosphine to asymmetric diiridium(i) centres.

    Science.gov (United States)

    Nakajima, Takayuki; Noda, Sayo; Sakamoto, Miyuki; Matsui, Aya; Nakamae, Kanako; Kure, Bunsho; Ura, Yasuyuki; Tanase, Tomoaki

    2016-03-21

    Reactions of a tetraphosphine, meso-bis{[(diphenylphosphinomethyl)phenyl]phosphino}propane (dpmppp), with [IrCl(cod)]2 and CO (1 atm) or isocyanide (RNC) in the presence of NH4PF6 at 80-100 °C in dichloromethane/acetonitrile/acetone and/or methanol mixed solvents afforded asymmetric diiridium(ii) complexes, [Ir2(H)(Cl)(μ-(dpmppp-H)-κP(4)C)(CO)3]PF6 (1) and [Ir2(H)(μ-(dpmppp-H)-κP(4)C)(RNC)4)]-(PF6)2 (R = 2,6-xylyl (2), 2,4,6-mesityl (3); dpmppp-H = {PPh(o-C6H4)CH2P(Ph)(CH2)3P(Ph)CH2PPh2}(-)). A similar reaction with (t)BuNC resulted in the formation of a mononuclear Ir(III) complex of [Ir(H)(dpmppp-κP(3))((t)BuNC)2](PF6)2 (4). Complexes 1-3 were characterized by ESI mass spectrometry, (1)H and (31)P NMR spectroscopy and X-ray diffraction analyses. They were found to consist of cis/trans-P,P asymmetric Ir(II)-Ir(II) bonded dinuclear structures derived from oxidative addition of an ortho C-H bond of dpmppp (Ir-Ir = 2.8044(2) Å (1), 2.8569(2) Å (2), and 2.8524(5) Å (3)), resulting in a [IrPCCIr] intermetallic cyclometal-bridge and a terminal hydride. DFT calculations indicated the presence of Ir-Ir, Ir-H, and Ir-Cortho covalent bonds. Initial stages of the reactions with CO and XylNC at room temperature were investigated by (31)P{(1)H} NMR spectroscopy and found to contain a symmetrical Ir(I) dinuclear unit with dpmppp that was readily transformed into 1 and 2 upon heating. The Ir intermediate with XylNC, [Ir2(XylNC)4(μ-dpmppp)](PF6)2 (6), was isolated and characterized by X-ray crystallography and DFT calculations as an electron-deficient 32e(-) Ir species involving a Ir(I)→Ir(I) dative bond (2.7989(5) Å). The reaction pathways from 6 to 2 were investigated by DFT calculations. The present study suggested that a novel oxidative addition of an ortho C-H bond proceeded on the cis/trans-P,P asymmetric diiridium(i) scaffold supported by the tetraphosphine, dpmppp, which was assumed to be facilitated by dimetal cooperation with switching Ir→Ir dative

  3. Molecular vibrations the theory of infrared and Raman vibrational spectra

    CERN Document Server

    Wilson, E Bright; Cross, Paul C

    1980-01-01

    Pedagogical classic and essential reference focuses on mathematics of detailed vibrational analyses of polyatomic molecules, advancing from application of wave mechanics to potential functions and methods of solving secular determinant.

  4. Avoid heat transfer equipment vibration

    Energy Technology Data Exchange (ETDEWEB)

    Ganapathy, V.

    1987-06-01

    Tube bundles in heat exchangers, boilers, superheaters and heaters are often subject to vibration and noise problems. Vibration can lead to tube thinning and wear, resulting in tube failures. Excessive noise can be a problem to plant operating personnel. Large gas pressure drop across the equipment is also a side effect, which results in large operating costs. With the design checks presented in this paper, one can predict during design if problems associated with noise and vibration are likely to occur in petroleum refineries.

  5. Five intermolecular vibrations of the CO2 dimer observed via infrared combination bands

    Science.gov (United States)

    Norooz Oliaee, J.; Dehghany, M.; Rezaei, Mojtaba; McKellar, A. R. W.; Moazzen-Ahmadi, N.

    2016-11-01

    The weakly bound van der Waals dimer (CO2)2 has long been of considerable theoretical and experimental interest. Here, we study its low frequency intermolecular vibrations by means of combination bands in the region of the CO2 monomer ν3 fundamental (≈2350 cm-1), which are observed using a tunable infrared laser to probe a pulsed supersonic slit jet expansion. With the help of a recent high level ab initio calculation by Wang, Carrington, and Dawes, four intermolecular frequencies are assigned: the in-plane disrotatory bend (22.26 cm-1); the out-of-plane torsion (23.24 cm-1); twice the disrotatory bend (31.51 cm-1); and the in-plane conrotatory bend (92.25 cm-1). The disrotatory bend and torsion, separated by only 0.98 cm-1, are strongly mixed by Coriolis interactions. The disrotatory bend overtone is well behaved, but the conrotatory bend is highly perturbed and could not be well fitted. The latter perturbations could be due to tunneling effects, which have not previously been observed experimentally for CO2 dimer. A fifth combination band, located 1.3 cm-1 below the conrotatory bend, remains unassigned.

  6. Pyrroloindolone synthesis via a Cp*Co(III)-catalyzed redox-neutral directed C-H alkenylation/annulation sequence.

    Science.gov (United States)

    Ikemoto, Hideya; Yoshino, Tatsuhiko; Sakata, Ken; Matsunaga, Shigeki; Kanai, Motomu

    2014-04-09

    A unique synthetic utility of a Cp*Co(III) catalyst in comparison with related Cp*Rh(III) catalysts is described. A C2-selective indole alkenylation/annulation sequence proceeded smoothly with catalytic amount of a [Cp*Co(III)(C6H6)](PF6)2 complex and KOAc. Intramolecular addition of an alkenyl-Cp*Co species to a carbamoyl moiety gave pyrroloindolones in 58-89% yield in one pot. Clear difference was observed between the catalytic activity of the Cp*Co(III) complex and those of Cp*Rh(III) complexes, highlighting the unique nucleophilic activity of the organocobalt species. The Cp*Co(III) catalysis was also suitable for simple alkenylation process of N-carbamoyl indoles, and broad range of alkynes, including terminal alkynes, were applicable to give C2-alkenylated indoles in 50-99% yield. Mechanistic studies on C-H activation step under Cp*Co(III) catalysis with the aid of an acetate unit as well as evaluation of the difference between organo-Co(III) species and organo-Rh(III) species are also described.

  7. Light-Induced C-H Arylation of (Hetero)arenes by In Situ Generated Diazo Anhydrides.

    Science.gov (United States)

    Cantillo, David; Mateos, Carlos; Rincon, Juan A; de Frutos, Oscar; Kappe, C Oliver

    2015-09-07

    Diazo anhydrides (Ar-N=N-O-N=N-Ar) have been known since 1896 but have rarely been used in synthesis. This communication describes the development of a photochemical catalyst-free C-H arylation methodology for the preparation of bi(hetero)aryls by the one-pot reaction of anilines with tert-butyl nitrite and (hetero)arenes under neutral conditions. The key step in this procedure is the in situ formation and subsequent photochemical (>300 nm) homolytic cleavage of a transient diazo anhydride intermediate. The generated aryl radical then efficiently reacts with a (hetero)arene to form the desired bi(hetero)aryls producing only nitrogen, water, and tert-butanol as byproducts. The scope of the reaction for several substituted anilines and (hetero)arenes was investigated. A continuous-flow protocol increasing selectivity and safety has been developed enabling the experimentally straightforward preparation of a variety of substituted bi(hetero)aryls within 45 min of reaction time. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Biomass Oxidation: Formyl C-H Bond Activation by the Surface Lattice Oxygen of Regenerative CuO Nanoleaves.

    Science.gov (United States)

    Amaniampong, Prince N; Trinh, Quang Thang; Wang, Bo; Borgna, Armando; Yang, Yanhui; Mushrif, Samir H

    2015-07-27

    An integrated experimental and computational investigation reveals that surface lattice oxygen of copper oxide (CuO) nanoleaves activates the formyl C-H bond in glucose and incorporates itself into the glucose molecule to oxidize it to gluconic acid. The reduced CuO catalyst regains its structure, morphology, and activity upon reoxidation. The activity of lattice oxygen is shown to be superior to that of the chemisorbed oxygen on the metal surface and the hydrogen abstraction ability of the catalyst is correlated with the adsorption energy. Based on the present investigation, it is suggested that surface lattice oxygen is critical for the oxidation of glucose to gluconic acid, without further breaking down the glucose molecule into smaller fragments, because of C-C cleavage. Using CuO nanoleaves as catalyst, an excellent yield of gluconic acid is also obtained for the direct oxidation of cellobiose and polymeric cellulose, as biomass substrates. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. C-H activation with elemental sulfur: synthesis of cyclic thioureas from formaldehyde aminals and S8.

    Science.gov (United States)

    Denk, M K; Gupta, S; Brownie, J; Tajammul, S; Lough, A J

    2001-10-15

    The C-H activation of cyclic formaldehyde aminals LCH2 (L = RN-CH2CH2CH2-NR and RNCH2CH2-NR, R = Me, Et, iPr, tBu, or Ph) with S8 proceeds at unusually low temperatures (Tflammable CS2. For R = tBu, the ionic carbenium thiocyanates [LCH]+ SCN- dominate the product spectrum and the respective thioureas are obtained in low yield. The reactivity of the analogous sulfur and oxygen ring systems towards S8 was investigated. 1,3-Dithiolane is cleanly converted into 1,3-dithiolane-2-thione (S8, 14 d, 190 degrees C) and resembles the cyclic formaldehyde aminals in this respect. 1,3-Dioxolane (L = OCH2CH2O) is completely inert towards sulfur even under forceful reaction conditions (190 degrees C, 14 d). The formation of thioureas from aminals was investigated at the CBS-4 and B3LYP/6-31G(d) levels of theory.

  10. Copper-mediated C-H activation/C-S cross-coupling of heterocycles with thiols

    KAUST Repository

    Ranjit, Sadananda

    2011-11-04

    We report the synthesis of a series of aryl- or alkyl-substituted 2-mercaptobenzothiazoles by direct thiolation of benzothiazoles with aryl or alkyl thiols via copper-mediated aerobic C-H bond activation in the presence of stoichiometric CuI, 2,2′-bipyridine and Na 2CO 3. We also show that the approach can be extended to thiazole, benzimidazole, and indole substrates. In addition, we present detailed mechanistic investigations on the Cu(I)-mediated direct thiolation reactions. Both computational studies and experimental results reveal that the copper-thiolate complex [(L)Cu(SR)] (L: nitrogen-based bidentate ligand such as 2,2′-bipyridine; R: aryl or alkyl group) is the first reactive intermediate responsible for the observed organic transformation. Furthermore, our computational studies suggest a stepwise reaction mechanism based on a hydrogen atom abstraction pathway, which is more energetically feasible than many other possible pathways including β-hydride elimination, single electron transfer, hydrogen atom transfer, oxidative addition/reductive elimination, and σ-bond metathesis. © 2011 American Chemical Society.

  11. Bulky α-diimine palladium complexes: highly efficient for direct C-H bond arylation of heteroarenes under aerobic conditions.

    Science.gov (United States)

    Ouyang, Jia-Sheng; Li, Yan-Fang; Shen, Dong-Sheng; Ke, Zhuofeng; Liu, Feng-Shou

    2016-10-14

    Through the strategy to enhance the bulkiness on both the backbone and the N-aryl moieties, we designed and synthesized a type of bulky α-diimine palladium complex (i.e., {[Ar-N[double bond, length as m-dash]C(R)-C(R)[double bond, length as m-dash]N-Ar]PdCl2, (Ar = 2-benzhydryl-4,6-dimethylphenyl)}, C1, R = H; C2, R = An; C3, R = Ph). The structures of these palladium complexes were well characterized, while C1 and C3 were further characterized by X-ray diffraction. The catalytic performances of the precatalysts were screened for direct C-H bond arylation of heteroarenes. The bidentate N,N-palladium complex C3 with both a backbone and N-aryl bulkiness was found to be a highly efficient precatalyst under aerobic conditions. With a low palladium loading of 0.5-0.1 mol%, a variety of heteroarenes with challenging bulky steric aryl bromides as well as heteroaryl bromides are all applicable for this cross-coupling reaction.

  12. Manganese-Substituted Myoglobin: Characterization and Reactivity of an Oxidizing Intermediate towards a Weak C-H Bond

    Directory of Open Access Journals (Sweden)

    Kari L. Stone

    2015-05-01

    Full Text Available Metal-substituted hemoproteins have been examined by biochemists for decades, but their potential for diverse functionalities has not been thoroughly investigated. By replacing hemoproteins with non-native metals, heme-containing proteins could be capable of performing a range of chemistries not allowed for in the native protein. The metal within the heme of the oxygen-carrying hemoprotein, myoglobin, can readily be replaced with other first row transition metals such as cobalt, chromium and manganese. Upon oxidation with two-electron oxidants (ex. meta-chloroperbenzoic acid, an oxidizing intermediate is produced in manganese-substituted myoglobin. Electron paramagnetic resonance analyses confirm the oxidation of Mn(III to Mn(IV. With the addition of weak C-H bonds of 1,4 cyclohexadiene, hydrogen atom abstraction is exhibited by the oxidizing intermediate that displays a second-order rate constant of 2.79 +/− 0.22 M−1 s−1 by the metal-oxo species. The replacement of the iron ion with a manganese ion at the active site of myoglobin displays oxidative capabilities that are not shown in native myoglobin.

  13. 14 CFR 33.63 - Vibration.

    Science.gov (United States)

    2010-01-01

    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Vibration. 33.63 Section 33.63 Aeronautics... STANDARDS: AIRCRAFT ENGINES Design and Construction; Turbine Aircraft Engines § 33.63 Vibration. Each engine... because of vibration and without imparting excessive vibration forces to the aircraft structure. ...

  14. 14 CFR 33.83 - Vibration test.

    Science.gov (United States)

    2010-01-01

    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Vibration test. 33.83 Section 33.83... STANDARDS: AIRCRAFT ENGINES Block Tests; Turbine Aircraft Engines § 33.83 Vibration test. (a) Each engine must undergo vibration surveys to establish that the vibration characteristics of those components that...

  15. 14 CFR 33.33 - Vibration.

    Science.gov (United States)

    2010-01-01

    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Vibration. 33.33 Section 33.33 Aeronautics... STANDARDS: AIRCRAFT ENGINES Design and Construction; Reciprocating Aircraft Engines § 33.33 Vibration. The... vibration and without imparting excessive vibration forces to the aircraft structure. ...

  16. 14 CFR 33.43 - Vibration test.

    Science.gov (United States)

    2010-01-01

    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Vibration test. 33.43 Section 33.43... STANDARDS: AIRCRAFT ENGINES Block Tests; Reciprocating Aircraft Engines § 33.43 Vibration test. (a) Each engine must undergo a vibration survey to establish the torsional and bending vibration characteristics...

  17. 49 CFR 178.819 - Vibration test.

    Science.gov (United States)

    2010-10-01

    ... 49 Transportation 2 2010-10-01 2010-10-01 false Vibration test. 178.819 Section 178.819... Testing of IBCs § 178.819 Vibration test. (a) General. The vibration test must be conducted for the... vibration test. (b) Test method. (1) A sample IBC, selected at random, must be filled and closed as for...

  18. Rectangular Parallelepiped Vibration in Plane Strain State

    OpenAIRE

    Hanckowiak, Jerzy

    2004-01-01

    In this paper we present a vibration spectrum of a homogenous parallelepiped (HP) under the action of volume and surface forces resulting from the exponent displacements entering the Fourier transforms. Vibration under the action of axial surface tractions and the free vibration are described separately. A relationship between the high frequency vibration and boundary conditions (BC) is also considered.

  19. Vibrational Damping of Composite Materials

    OpenAIRE

    Biggerstaff, Janet M.

    2006-01-01

    The purpose of this research was to develop new methods of vibrational damping in polymeric composite materials along with expanding the knowledge of currently used vibrational damping methods. A new barrier layer technique that dramatically increased damping in viscoelastic damping materials that interacted with the composite resin was created. A method for testing the shear strength of damping materials cocured in composites was developed. Directional damping materials, where the loss facto...

  20. Vibration Theory, Vol. 1B

    DEFF Research Database (Denmark)

    Asmussen, J. C.; Nielsen, Søren R. K.

    The present collection of MATLAB exercises has been published as a supplement to the textbook, Svingningsteori, Bind 1 and the collection of exercises in Vibration theory, Vol. 1A, Solved Problems. Throughout the exercise references are made to these books. The purpose of the MATLAB exercises...... is to give a better understanding of the physical problems in linear vibration theory and to surpress the mathematical analysis used to solve the problems. For this purpose the MATLAB environment is excellent....

  1. Harmonic vibrations of multispan beams

    DEFF Research Database (Denmark)

    Dyrbye, Claes

    1996-01-01

    Free and forced harmonic vibrations of multispan beams are determined by a method which implies 1 equation regardless of the configuration. The necessary formulas are given in the paper. For beams with simple supports and the same length of all (n) spans, there is a rather big difference between...... the n´th and the (n+1)´th eigenfrequency. The reason for this phenomenon is explained.Keywords: Vibrations, Eigenfrequencies, Beams....

  2. Smart accelerometer. [vibration damage detection

    Science.gov (United States)

    Bozeman, Richard J., Jr. (Inventor)

    1994-01-01

    The invention discloses methods and apparatus for detecting vibrations from machines which indicate an impending malfunction for the purpose of preventing additional damage and allowing for an orderly shutdown or a change in mode of operation. The method and apparatus is especially suited for reliable operation in providing thruster control data concerning unstable vibration in an electrical environment which is typically noisy and in which unrecognized ground loops may exist.

  3. Improved Predictions for Geotechnical Vibrations

    OpenAIRE

    Macijauskas, Darius

    2015-01-01

    In urban areas where the infrastructure is dense and construction of new structures is near existing and sensitive buildings, frequently vibrations, caused by human activities, occur. Generated waves in the soil may adversely affect surrounding buildings. These vibrations have to be predicted a priori by using currently available knowledge of the soil dynamics. Current research, conducted by Deltares research institute, showed that the reliability of methods for prediction of m...

  4. Stress analysis of vibrating pipelines

    Science.gov (United States)

    Zachwieja, Janusz

    2017-03-01

    The pipelines are subject to various constraints variable in time. Those vibrations, if not monitored for amplitude and frequency, may result in both the fatigue damage in the pipeline profile at high stress concentration and the damage to the pipeline supports. If the constraint forces are known, the system response may be determined with high accuracy using analytical or numerical methods. In most cases, it may be difficult to determine the constraint parameters, since the industrial pipeline vibrations occur due to the dynamic effects of the medium in the pipeline. In that case, a vibration analysis is a suitable alternative method to determine the stress strain state in the pipeline profile. Monitoring the pipeline vibration levels involves a comparison between the measured vibration parameters and the permissible values as depicted in the graphs for a specific pipeline type. Unfortunately, in most cases, the studies relate to the petrochemical industry and thus large diameter, long and straight pipelines. For a pipeline section supported on both ends, the response in any profile at the entire section length can be determined by measuring the vibration parameters at two different profiles between the pipeline supports. For a straight pipeline section, the bending moments, variable in time, at the ends of the analysed section are a source of the pipe excitation. If a straight pipe section supported on both ends is excited by the bending moments in the support profile, the starting point for the stress analysis are the strains, determined from the Euler-Bernoulli equation. In practice, it is easier to determine the displacement using the experimental methods, since the factors causing vibrations are unknown. The industrial system pipelines, unlike the transfer pipelines, are straight sections at some points only, which makes it more difficult to formulate the equation of motion. In those cases, numerical methods can be used to determine stresses using the

  5. Iron-Carbonyl-Catalyzed Redox-Neutral [4+2] Annulation of N-H Imines and Internal Alkynes by C-H Bond Activation.

    Science.gov (United States)

    Jia, Teng; Zhao, Chongyang; He, Ruoyu; Chen, Hui; Wang, Congyang

    2016-04-18

    Stoichiometric C-H bond activation of arenes mediated by iron carbonyls was reported by Pauson as early as in 1965, yet the catalytic C-H transformations have not been developed. Herein, an iron-catalyzed annulation of N-H imines and internal alkynes to furnish cis-3,4-dihydroisoquinolines is described, and represents the first iron-carbonyl-catalyzed C-H activation reaction of arenes. Remarkablely, this is also the first redox-neutral [4+2] annulation of imines and alkynes proceeding by C-H activation. The reaction also features only cis stereoselectivity and excellent atom economy as neither base, nor external ligand, nor additive is required. Experimental and theoretical studies reveal an oxidative addition mechanism for C-H bond activation to afford a dinuclear ferracycle and a synergetic diiron-promoted H-transfer to the alkyne as the turnover-determining step. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Vibrational modes of nanolines

    Science.gov (United States)

    Heyliger, Paul R.; Flannery, Colm M.; Johnson, Ward L.

    2008-04-01

    Brillouin-light-scattering spectra previously have been shown to provide information on acoustic modes of polymeric lines fabricated by nanoimprint lithography. Finite-element methods for modeling such modes are presented here. These methods provide a theoretical framework for determining elastic constants and dimensions of nanolines from measured spectra in the low gigahertz range. To make the calculations feasible for future incorporation in inversion algorithms, two approximations of the boundary conditions are employed in the calculations: the rigidity of the nanoline/substrate interface and sinusoidal variation of displacements along the nanoline length. The accuracy of these approximations is evaluated as a function of wavenumber and frequency. The great advantage of finite-element methods over other methods previously employed for nanolines is the ability to model any cross-sectional geometry. Dispersion curves and displacement patterns are calculated for modes of polymethyl methacrylate nanolines with cross-sectional dimensions of 65 nm × 140 nm and rectangular or semicircular tops. The vibrational displacements and dispersion curves are qualitatively similar for the two geometries and include a series of flexural, Rayleigh-like, and Sezawa-like modes. This paper is a contribution of the National Institute of Standards and Technology and is not subject to copyright in the United States.

  7. Vibrationally state selected ion molecule experimental and computational studies of both reactant charge states of [nitrogen dioxide + ethyne]+ and HOD+ with nitrogen dioxide

    Science.gov (United States)

    Boyle, Jason M.

    2011-12-01

    Ion molecule studies have not only determined reactivity of systems that would have otherwise been unavailable, but also provide a perspective that improves the understanding of the mechanisms that drive reaction. Presented here are studies of three ion molecule systems one of which is accompanied by an extensive set of direct dynamics trajectory calculations. In the first system presented, NO2+ in six different vibrational states was reacted with C2H2 over the center-of-mass energy range from 0.03 to 3.3 eV. The effects of the symmetric bend overtone (0200) excitation are particularly strong (factor of 4) while the delta overtone (0220) effects are much weaker. A large set of quasi-classical trajectories were calculated at the PBE1PBE/6-311G** level of theory, in an attempt to understand the mechanistic origins of this observation. The trajectories reproduce experiment where comparable. Analysis of these trajectories resolves the mechanistic origins of this vibrational effect. Similar experimental measurements were made for the first excited electronic state of this system where the charge is localized on the acetylene. The C 2H2+ reactant was prepared in four distinct modes. Because both reactants have one unpaired electron, collisions can occur with either singlet or triplet coupling of these unpaired electrons, and the contributions the three channels (charge, O-, and O transfer) are separated based on distinct recoil dynamics. The effects of C2H 2+ vibration are modest, but mode specific. Integral cross sections and product recoil velocity distributions were also measured for reaction of HOD+ with NO2, in which the HOD+ reactant was prepared in its ground state, and with mode-selective excitation in the 001 (OH stretch), 100 (OD stretch) and bend (010) modes. In addition, we measured the 300 K thermal kinetics in a selected ion flow tube reactor and report product branching ratios different from previous measurements. Reaction is found to occur on both the

  8. Discovery of Cellulose Surface Layer Conformation by Nonlinear Vibrational Spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Libing; Fu, Li; Wang, Hong-fei; Yang, Bin

    2017-03-14

    Significant questions remain with respect to the structure and polymorphs of cellulose. These include the cellulose surface layers and the bulk crystalline core as well as the conformational differences. The Total Internal Reflection Sum Frequency Generation Vibrational Spectroscopy (TIR-SFG-VS) combined with the conventional SFG-VS (non-TIR) can help to resolve these questions by selectively characterizing the molecular structures of surface layers and the crystalline core of cellulose. From the SFG spectra in the C-H and O-H regions, we found that the surface layers of Avicel are essentially amorphous; while the surface layers of Iβ cellulose are crystalline but with different structural and spectroscopic signatures than that of its crystalline core. This work demonstrates the capacity of TIR and Non-TIR SFG-VS tools in selectively studying the structures and polymorphs of cellulose. In addition, these results also suggest that the assignments of major vibrational peaks for cellulose need to be further determined.

  9. Interexaminer reliability in clinical measurement of L*C*h* values of anterior teeth using a spectrophotometer.

    Science.gov (United States)

    Hassel, Alexander J; Grossmann, Anne-christiane; Schmitter, Marc; Balke, Zibandeh; Buzello, Anja M

    2007-01-01

    The objective of this study was to investigate interexaminer reliability in the clinical measurement of the L*C*h* (lightness/value, chroma, hue) values of anterior teeth using a spectrophotometer (Vita Easyshade). The basic color of the maxillary right central incisors and canines of 23 subjects was spectrophotometrically determined by 4 clinicians and an experienced user (development manager) of the spectrophotometer. Also, to analyze the effect of different training with the instrument on interexaminer reliability, 2 of the clinicians were instructed in the use of the spectrophotometer by the experienced examiner, whereas the others instructed themselves by studying the operating manual. Agreement between all examiners was acceptable to excellent (intraclass coefficient > 0.4). The mean value of the measured differences for the central incisors of all subjects for L* values was 5 (for C* = 3.8, h* = 2.7 degrees) and for canines, the mean L* was 4.5 (C* = 3, h* = 1.6 degrees). Results from comparison of the 2 different training methods were inconsistent. Agreement with the experienced examiner ranged from not acceptable (C* values for incisors of self-instructed examiners) to excellent. The distribution of the measurements of 1 subject could lead to deviations in color, probably with clinical impact. For canines, the measurements were at least equally reproducible (in some cases significantly more reproducible) compared to central incisors. Because of the small number of examiners and the inconsistent results, it was not possible to reach a definite conclusion about the effect of different training methods on interexaminer reliability.

  10. Ny arkitektur for nordmenn i Iowa. Arkitekt C.H. Griese, Luther College og kirker i 1860-årene

    Directory of Open Access Journals (Sweden)

    Jens Christian Eldal

    2015-12-01

    Full Text Available The Norwegian Evangelical-Lutheran Church in America decided in 1861 to build their first college close to the western frontier of The Upper Midwest. The site chosen was a bluff above Upper Iowa River, highly visible from Decorah, a small town founded only 12 years earlier, few years after the first settlers arrived. The college building became a relatively vast structure erected between 1862 and 1865, completed to its originally planned symmetrical composition in 1874. The building style and its composition were common among American colleges and universities further east in the US. It is also demonstrated how the Luther College building façade in composition and detailing shows clear influences from a specific German building. This particular building has been designated as especially typical of the German Rundbogenstil (Style of the Rounded Arch with its great mix of various stylistic elements. The architect was known as C. H. Griese from Cleveland, Ohio. He is identified as Charles Henry Griese (1821–1909, who immigrated from Germany about 1850 and was known as a mason and contractor, from now on also as an architect. In 1869, Griese also designed the three Norwegian Lutheran churches of Washington Prairie, Stavanger and Glenwood in rural Decorah. They represented a Neo Gothic style which was new to the area, and had an evident architectural character contrasting the more ordinary vernacular churches in the area. They signify a change of style and, like the college building, they demonstrate architectural ambitions new to these Norwegians, giving insight also into the general architectural and vernacular development in the area.

  11. Development of deuterium labeling method based on the heterogeneous platinum group metal-catalyzed C-H activation.

    Science.gov (United States)

    Sajiki, Hironao

    2013-01-01

    Deuterium (D) labeled compounds are utilized in various scientific fields such as mechanistic elucidation of reactions, preparation of new functional materials, tracers for microanalysis, deuterium labeled heavy drugs and so on. Although the H-D exchange reaction is a straightforward method to produce deuterated organic compounds, many precedent methods require expensive deuterium gas and/or harsh reaction conditions. A part of our leading research agendas is intended to the development of novel and functional heterogeneous platinum-group catalysts and the reclamation of unknown functionalities of existing heterogeneous platinum-group catalysts. During the course of the study, benzylic positions of substrates were site-selectively deuterated under mild and palladium-on-carbon (Pd/C)-catalyzed hydrogenation conditions in heavy water (D2O). Heat conditions promoted the H-D exchange reactivity and facilitated the H-D exchange reaction at not only the benzylic sites but also inactive C-H bonds and heterocyclic nuclei. It is noteworthy that platinum-on-carbon (Pt/C) indicated a quite high affinity toward aromatic nuclei, and the H-D exchange reaction was strongly enhanced by the use of Pt/C as a catalyst under milder conditions. The mixed use of Pd/C and Pt/C was found to be more efficient in the H-D exchange reaction compared to the independent use of Pd/C or Pt/C. Furthermore, simple alkanes could also be efficiently deuterated under rhodium-on-carbon (Rh/C)-catalyzed conditions. The use of ruthenium-on-carbon (Ru/C) enabled the regiospecific and efficient deuterium incorporation at α-positions of alcohols and results were applied as a regio- and stereoselective multi-deuteration method of sugar derivatives.

  12. Visible Light-Induced Oxidative Chlorination of Alkyl sp3 C-H Bonds with NaCl/Oxone at Room Temperature.

    Science.gov (United States)

    Zhao, Mengdi; Lu, Wenjun

    2017-09-01

    A visible light-induced monochlorination of cyclohexane with sodium chloride (5:1) has been successfully accomplished to afford chlorocyclohexane in excellent yield by using Oxone as the oxidant in H2O/CF3CH2OH at room temperature. Other secondary and primary alkyl sp3 C-H bonds of cycloalkanes and functional branch/linear alkanes can also be chlorinated, respectively, under similar conditions. The selection of a suitable organic solvent is crucial in these efficient radical chlorinations of alkanes in two-phase solutions. It is studied further by the achievement of high chemoselectivity in the chlorination of the benzyl sp3 C-H bond or the aryl sp2 C-H bond of toluene.

  13. Double C-H bond activation of acetylene by atomic boron in forming aromatic cyclic-HBC2BH in solid neon.

    Science.gov (United States)

    Jian, Jiwen; Li, Wei; Wu, Xuan; Zhou, Mingfei

    2017-06-01

    The organo-boron species formed from the reactions of boron atoms with acetylene in solid neon are investigated using matrix isolation infrared spectroscopy with isotopic substitutions as well as quantum chemical calculations. Besides the previously reported single C-H bond activation species, a cyclic-HBC2BH diboron species is formed via double C-H bond activation of acetylene. It is characterized to have a closed-shell singlet ground state with planar D2h symmetry. Bonding analysis indicates that it is a doubly aromatic species involving two delocalized σ electrons and two delocalized π electrons. This finding reveals the very first example of double C-H bond activation of acetylene in forming new organo-boron compounds.

  14. Visible-light-driven oxidation of primary C-H bonds over CdS with dual co-catalysts graphene and TiO2.

    Science.gov (United States)

    Yang, Min-Quan; Zhang, Yanhui; Zhang, Nan; Tang, Zi-Rong; Xu, Yi-Jun

    2013-11-22

    Selective activation of primary C-H bonds for fine chemicals synthesis is of crucial importance for the sustainable exploitation of available feedstocks. Here, we report a viable strategy to synthesize ternary GR-CdS-TiO2 composites with an intimate spatial integration and sheet-like structure, which is afforded by assembling two co-catalysts, graphene and TiO2, into the semiconductor CdS matrix with specific morphology as a visible light harvester. The GR-CdS-TiO2 composites are able to serve as a highly selective visible-light-driven photocatalyst for oxidation of saturated primary C-H bonds using benign oxygen as oxidant under ambient conditions. This work demonstrates a wide, promising scope of adopting co-catalyst strategy to design more efficient semiconductor-based photocatalyst toward selective activation of C-H bonds using solar light and molecular oxygen.

  15. Catalytic functionalization of unactivated sp3 C-H bonds via exo-directing groups: synthesis of chemically differentiated 1,2-diols.

    Science.gov (United States)

    Ren, Zhi; Mo, Fanyang; Dong, Guangbin

    2012-10-17

    We describe a Pd-catalyzed site-selective functionalization of unactivated aliphatic C-H bonds, providing chemically differentiated 1,2-diols from monoalcohol derivatives. The oxime was employed as both a directing group (DG) and an alcohol surrogate for this transformation. As demonstrated in a range of substrates, the C-H bonds β to the oxime group are selectively oxidized. Besides activation of the methyl groups, methylene groups (CH(2)) in cyclic substrates and methine groups (CH) at bridge-head positions can also be functionalized. In addition, an intriguing oxidative skeleton rearrangement was observed using the menthol-derived substrate. The use of exo-directing groups in C-H activation, as illustrated in this work, would potentially open doors for the discovery of new transformations and new cleavable DGs.

  16. Transition Metal-Catalyzed Carbonylative C-H Bond Functionalization of Arenes and C(sp(3))-H Bond of Alkanes.

    Science.gov (United States)

    Gadge, Sandip T; Gautam, Prashant; Bhanage, Bhalchandra M

    2016-04-01

    In this article, we present the progress made in the area of carbonylative C-H functionalization, with special emphasis on arenes and alkanes. The importance of directing group assistance and C-H functionalization using CO surrogates is also included. The budding development in the area of transition metal-catalyzed C(sp(3))-H activation makes us feel it necessary to file a summary on the past, as well as current, contributions and a prospective outlook on the transition metal-catalyzed carbonylative transformation of C-H bonds, which is the focus of this review. © 2016 The Chemical Society of Japan & Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Inserção C-H de carbenóides de ródio em água e reutilização do catalisador Rhodium (II carbene C-H insertion in water and catalyst reuse

    Directory of Open Access Journals (Sweden)

    Nuno R. Candeias

    2007-01-01

    Full Text Available A five-session laboratory experiment is described for the synthesis of a beta-lactam via Rh(II catalysed intramolecular C-H insertion of a alpha-diazo-alpha-ethoxycarbonylacetamide. The metallo-carbene, responsible for the C-H bond activation, was generated from the diazo substrate and the catalyst Rh2(OAc4. The high stability and solubility of the catalyst and the exclusive C-H insertion of the Rh-carbene allows the synthesis of this important heterocycle in water and the catalyst reutilization.

  18. Evaluation of hand-arm vibration reducing effect of anti-vibration glove

    OpenAIRE

    樹野, 淳也; 前田, 節雄; 横田, 和樹; 平, 雄一郎

    2015-01-01

    Many kinds of the anti-vibration glove have been developed for reducing hand-arm vibration during the operation with vibration tools. International standard ISO 10819 evaluates the physical effect of gloves' vibration transmissibility but not evaluates the physiological effect of human hands. Thus, in this paper, we proposed the evaluation using the temporary threshold shift of vibrotactile perception threshold to evaluate the hand-arm vibration reducing effect of anti-vibration glove. We per...

  19. Rhenium-Catalyzed Synthesis of 1,3-Diiminoisoindolines via Insertion of Carbodiimides into a C-H Bond of Aromatic and Heteroaromatic Imidates.

    Science.gov (United States)

    Wang, Zijia; Sueki, Shunsuke; Kanai, Motomu; Kuninobu, Yoichiro

    2016-05-20

    The rhenium-catalyzed synthesis of 1,3-diiminoisoindolines and their related compounds from aromatic or heteroaromatic imidates and carbodiimides are reported via C-H bond activation. This reaction is the first example of a transition-metal-catalyzed insertion of carbodiimides into an aromatic or heteroaromatic C-H bond and a novel method for synthesizing 1,3-diiminoisoindolines and their related compounds. Unsymmetrical 1,3-diiminoisoindolines were easily obtained using this method. The reaction proceeded in good to excellent yield using a variety of substrates.

  20. A theoretical study into a trans-dioxo Mn(V) porphyrin complex that does not follow the oxygen rebound mechanism in C-H bond activation reactions.

    Science.gov (United States)

    Cho, Kyung-Bin; Nam, Wonwoo

    2016-01-18

    Previous experimental results revealed that the C-H bond activation reaction by a synthetic trans-dioxo Mn(V) porphyrin complex, [(TF4TMAP)OMn(V)O](3+), does not occur via the well-known oxygen rebound mechanism, which has been well demonstrated in Fe(IV)O porphyrin π-cation radical reactions. In the present study, theoretical calculations offer an explanation through the energetics involved in the C-H bond activation reaction, where a multi-spin state scenario cannot be excluded.

  1. C-H functionalization: thoroughly tuning ligands at a metal ion, a chemist can greatly enhance catalyst's activity and selectivity.

    Science.gov (United States)

    Shul'pin, Georgiy B

    2013-09-28

    This brief essay consists of a few "exciting stories" devoted to relations within a metal-complex catalyst between a metal ion and a coordinated ligand. When, as in the case of a human couple, the rapport of the partners is cordial and a love cements these relations, a chemist finds an ideal married couple, in other words he obtains a catalyst of choice which allows him to functionalize C-H bonds very efficiently and selectively. Examples of such lucky marriages in the catalytic world of ions and ligands are discussed here. Activity of the catalyst is characterized by turnover number (TON) or turnover frequency (TOF) as well as by yield of a target product. Introducing a chelating N,N- or N,O-ligand to the catalyst molecule (this can be an iron or manganese derivative) sharply enhances its activity. However, the activity of vanadium derivatives (with additionally added to the solution pyrazinecarboxylic acid, PCA) as well as of various osmium complexes does not dramatically depend on the nature of ligands surrounding metal ions. Complexes of these metals are very efficient catalysts in oxidations with H2O2. Osmium derivatives are record-holders exhibiting extremely high TONs whereas vanadium complexes are on the second position. Finally, elegant examples of alkane functionalization on the ions of non-transition metals (aluminium, gallium etc.) are described when one ligand within the metal complex (namely, hydroperoxyl ligand HOO(-)) helps other ligand of this complex (H2O2 molecule coordinated to the metal) to disintegrate into two species, generating very reactive hydroxyl radical. Hydrogen peroxide molecule, even ligated to the metal ion, is perfectly stable without the assistance of the neighboring HOO(-) ligand. This ligand can be easily oxidized donating an electron to its partner ligand (H2O2). In an analogous case, when the central ion in the catalyst is a transition metal, this ion changing its oxidation state can donate an electron to the coordinated H2O2

  2. Ruthenium-Catalyzed C-H Bond Activation Approach to Azolyl Aminals and Hemiaminal Ethers, Mechanistic Evaluations, and Isomer Interconversion.

    Science.gov (United States)

    Singh, Manish K; Akula, Hari K; Satishkumar, Sakilam; Stahl, Lothar; Lakshman, Mahesh K

    2016-03-04

    C(sp3)-N bond-forming reactions between benzotriazole and 5,6-dimethylbenzotriazole with N-methylpyrrolidinone, tetrahydrofuran, tetrahydropyran, diethyl ether, 1,4-dioxane, and isochroman have been conducted using RuCl3•3H2O/t-BuOOH in 1,2-dichloroethane. In all cases, N1 and N2 alkylation products were obtained, and these are readily separated by chromatography. One of these products, 1-(isochroman-1-yl)-5,6-dimethyl-1H-benzotriazole, was examined by X-ray crystallography. It is the first such compound to be analyzed by this method, and notably, the benzotriazolyl moiety is quasi-axially disposed, consistent with the anomeric effect. This has plausible consequences, not observed previously. In contrast to other hemiaminal ether-forming reactions, which proceed via radicals, this Ru-catalyzed process is not suppressed in the presence of a radical inhibitor. Therefore, an oxoruthenium-species-mediated rapid formation of an oxocarbenium intermediate is believed to occur. In the radical-trapping experiment, previously unknown products containing both the benzotriazole and the TEMPO unit have been identified. In these products, it is likely that the benzotriazole is introduced via a Ru-catalyzed C-N bond formation, whereas C-O bond-formation with TEMPO occurs via a radical reaction. We show that reactions of THF with TEMPO are influenced by ambient light. A competitive reaction of THF and THF-d8 with benzotriazole indicated that C-H bond cleavage occurs ca. 5 times faster than C-D cleavage. This is comparable to other metal-mediated radical reactions of THF, but lower than that observed for a reaction catalyzed by n-Bu4N+I-. Detailed mechanistic experiments and comparisons are described. The catalytic system was also evaluated for reactions of benzimidazole, imidazole, 1,2,4-triazole, and 1,2,3-triazole with THF, and successful reactions were achieved in each case. In the course of our studies, we discovered an unexpected but significant isomerization of some of the

  3. Ultrasonic metal welding with a vibration source using longitudinal and torsional vibration transducers

    Science.gov (United States)

    Asami, Takuya; Tamada, Yosuke; Higuchi, Yusuke; Miura, Hikaru

    2017-07-01

    Conventional ultrasonic metal welding for joining dissimilar metals uses a linear vibration locus, although this method suffers from problems such as low overall weld strength. Our previous studies have shown that ultrasonic welding with a planar vibration locus improves the weld strength. However, the vibration source in our previous studies had problems in longitudinal-torsional vibration controllability and small welding tip. Therefore, the study of the optimal shape of the vibration locus was difficult. Furthermore, improvement of weld strength cannot be expected. We have developed a new ultrasonic vibration source that can control the longitudinal-torsional vibration and can connect to a large welding tip. In this study, we clarified the longitudinal-torsional vibration controllability of the developed ultrasonic vibration source. Moreover, we clarified that using the planar locus of the developed vibration source produced a higher weld strength than our previous studies, and clarified the optimal shape of the vibration locus.

  4. C-H activation of imidazolium salts by Pt(0) at ambient temperature: synthesis of hydrido platinum bis(carbene) compounds.

    Science.gov (United States)

    Duin, Marcel A; Clement, Nicolas D; Cavell, Kingsley J; Elsevier, Cornelis J

    2003-02-07

    A zerovalent platinum(carbene) complex with two monoalkene ligands, which is able to activate C-H bonds of imidazolium salts at room temperature to yield isolable hydrido platinum(II) bis(carbene) compounds, has been synthesised for the first time.

  5. A potential role of substrate as a base for deprotonation pathway in Rh-catalysed C-H amination of heteroArenes: DFT insights

    KAUST Repository

    Ajitha, Manjaly John

    2016-03-29

    The possibility of direct introduction of a new functionality through C–H bond activation is an attractive strategy in covalent synthesis. Here, we investigated the mechanism of Rh-catalysed C-H amination of the hetero-aryl substrate (2-phenylpyridine) using phenyl azide as nitrogen source by density functional theory (DFT). For the deprotocyclometallation and protodecyclometallation processes of the title reaction, we propose a stepwise base-assisted mechanism (pathway I) instead of previously reported concerted mechanism (pathway II). In the new mechanism proposed here, 2-phenylpyridine acts as a base in the initial deprotonation step (C-H bond cleavage) and transports the proton towards the final protonation step. In fact, the N-H bond of the strong conjugate acid (formed during initial C-H bond cleavage) considered in pathway I (via TS4) is more acidic than the C-H bond of the neutral substrate considered in pathway II (via TS5). The higher activation barrier of TS5 mainly originates from the ring strain of the four membered cyclic transition state. The vital role of base, as disclosed here, can potentially have broader mechanistic implications for the development of reaction conditions of transition metal catalysed reactions.

  6. Optimization of the contact resistance in the interface structure of n-type Al/a-SiC:H by thermal annealing for optoelectronics applications

    Energy Technology Data Exchange (ETDEWEB)

    Ambrosio, Roberto; Mireles, Jose Jr. [Technology and Engineering Institute, Ciudad Juarez University UACJ, Av. Del Charro 450N, 32310, Chihuahua (Mexico); Torres, Alfonso; Zuniga, Carlos; Moreno, Mario [National Institute for Astrophysics Optics and Electronics INAOE, Luis E. Erro 1, PO Box 51 and 216, 7200, Puebla (Mexico)

    2010-07-15

    The presented work meets the requirements for integration of amorphous silicon carbon films with silicon technology in order to obtain a complete optoelectronic system such as light emitting diodes and its electronic readout circuits. The key enabler for this integration scheme is the low temperature of deposition of a-SiC:H films and an ohmic behavior in the interface metal/a-SiC:H. In this work, the optimization of the interface Al/a-SiC:H films are performed by means of thermal annealing timing. The a-SiC:H films were deposited by enhanced chemical vapor deposition from CH{sub 4}/SiH{sub 4} and C{sub 2}H{sub 2}/SiH{sub 4} mixtures. The structural and optical properties of the deposited films are presented. An implantation phosphorous dose was used for doping before fabrication of patterned aluminum contacts. The implanted films were electrically characterized by the transfer length method (TLM) measuring a sheet resistance value as low as 171 M{omega}/square. The Schottky behavior was improved to ohmic behavior after several hours in thermal annealing treatments at 350 C, which allows to obtain a reasonable contact resistance values in the range from 8.6 to 26.8 k{omega}. (Abstract Copyright [2010], Wiley Periodicals, Inc.)

  7. Propane σ-Complexes on PdO(101): Spectroscopic Evidence of the Selective Coordination and Activation of Primary C-H Bonds.

    Science.gov (United States)

    Zhang, Feng; Pan, Li; Choi, Juhee; Mehar, Vikram; Diulus, John T; Asthagiri, Aravind; Weaver, Jason F

    2015-11-16

    Achieving selective C-H bond cleavage is critical for developing catalytic processes that transform small alkanes to value-added products. The present study clarifies the molecular-level origin for an exceptionally strong preference for propane to dissociate on the crystalline PdO(101) surface via primary C-H bond cleavage. Using reflection absorption infrared spectroscopy (RAIRS) and density functional theory (DFT) calculations, we show that adsorbed propane σ-complexes preferentially adopt geometries on PdO(101) in which only primary C-H bonds datively interact with the surface Pd atoms at low propane coverages and are thus activated under typical catalytic reaction conditions. We show that a propane molecule achieves maximum stability on PdO(101) by adopting a bidentate geometry in which a H-Pd dative bond forms at each CH3 group. These results demonstrate that structural registry between the molecule and surface can strongly influence the selectivity of a metal oxide surface in activating alkane C-H bonds. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. High selectivity for primary C-H bond cleavage of propane σ-complexes on the PdO(101) surface.

    Science.gov (United States)

    Weaver, Jason F; Hakanoglu, Can; Antony, Abbin; Asthagiri, Aravind

    2011-10-12

    We investigated regioselectivity in the initial C-H bond activation of propane σ-complexes on the PdO(101) surface using temperature programmed reaction spectroscopy (TPRS) experiments. We observe a significant kinetic isotope effect (KIE) in the initial C-H(D) bond cleavage of propane on PdO(101) such that the dissociation yield of C(3)H(8) is 2.7 times higher than that of C(3)D(8) at temperatures between 150 and 200 K. Measurements of the reactivity of (CH(3))(2)CD(2) and (CD(3))(2)CH(2) show that deuteration of the methyl groups is primarily responsible for the lower reactivity of C(3)D(8) relative to C(3)H(8), and thus that 1° C-H bond cleavage is the preferred pathway for propane activation on PdO(101). By analyzing the rate data within the context of a kinetic model for precursor-mediated dissociation, we estimate that 90% of the propane σ-complexes which dissociate on PdO(101) during TPRS do so by 1° C-H bond cleavage.

  9. Competitive C-C and C-H bond scission in the ethanol oxidation reaction on Cu(100) and the effect of an alkaline environment.

    Science.gov (United States)

    Wu, Zhipeng; Zhang, Minhua; Jiang, Haoxi; Zhong, Chuan-Jian; Chen, Yifei; Wang, Lichang

    2017-06-14

    Direct ethanol fuel cell technology is impeded by inefficient, yet expensive anode catalysts. As such, research on effective and cheap anode catalysts towards complete ethanol oxidation reaction (EOR) is greatly needed. Herein, we report the investigations of the competitive C-C and C-H bond scissions in the EOR involving CH3CO, CH2CO, and CHCO species on Cu(100) using density functional theory and transition state theory calculations. The easiest C-C bond cleavage was found in CH2CO while the most difficult C-H bond cleavage was also found in CH2CO, both with an activation energy of 1.02 eV. The feasible C-C bond scission may take place in CH2CO with a rate constant ratio of the C-C to the C-H bond scission at 100 °C of 0.32. Furthermore, in an alkaline environment, the C-H bond scission activation barrier is considerably lowered but the C-C bond cleavage activation barrier is slightly increased for both CH3CO and CH2CO species. The reaction of CH3CO species on Cu(100) under alkaline conditions produces mainly acetic acid with a barrier of 0.49 eV and a rate constant of 4.93 × 105 s-1 at 100 °C.

  10. Rhodium-Catalyzed Oxidative Benzannulation of N-Pivaloylanilines with Internal Alkynes through Dual C-H Bond Activation: Synthesis of Highly Substituted Naphthalenes.

    Science.gov (United States)

    Zhang, Xuan; Yu, Xiaoqiang; Feng, Xiujuan; Yamamoto, Yoshinori; Almansour, Abdulrahman I; Arumugam, Natarajan; Kumar, Raju Suresh; Bao, Ming

    2016-11-22

    An efficient method was developed for the synthesis of highly substituted naphthalenes through rhodium-catalyzed oxidative benzannulation of N-pivaloylanilines with internal alkynes. The benzannulation reaction proceeded smoothly through dual C-H bond activation to produce the corresponding highly substituted naphthalene products in satisfactory to good yields. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. TEM characterization of a Cr/Ti/TiC graded interlayer for magnetron-sputtered TiC/a-C : H nanocomposite coatings

    NARCIS (Netherlands)

    Galvan, D.; Pei, Y.T.; Hosson, J.Th.M. De

    A TiC/a-C:H nanocomposite coating is deposited on top of a Cr/Ti/TiC graded interlayer. Cross-section transmission electron microscopy is employed to investigate the detailed structure of the interlayer and the coating. Five different phases are formed as a consequence of the compositional gradient

  12. Alkane Activation at Ambient Temperatures: Unusual Selectivities, C-C, C-H Bond Scission versus C-C Bond Coupling

    NARCIS (Netherlands)

    Trionfetti, C.; Agiral, A.; Gardeniers, Johannes G.E.; Lefferts, Leonardus; Seshan, Kulathuiyer

    2008-01-01

    Activating bonds: A cold plasma generated by dielectric barrier discharge in a microreactor converts alkanes (C1–C3) at atmospheric pressure. Large amounts of products with higher molecular weight than the starting hydrocarbons are observed showing that C-H activation at lower T favourably leads to

  13. Palladium-catalyzed C-H bond carboxylation of acetanilides: an efficient usage of N,N-dimethyloxamic acid as the carboxylate source.

    Science.gov (United States)

    Wu, Yinuo; Jiang, Cheng; Wu, Deyan; Gu, Qiong; Luo, Zhang-Yi; Luo, Hai-Bin

    2016-01-21

    N,N-Dimethyloxamic acid can be successfully employed as a carboxylate precursor in the palladium-catalyzed direct C-H carboxylation of acetanilides. The reaction proceeds smoothly under mild conditions over a broad range of substrates with high functional group tolerance, affording substituted N-acyl anthranilic acids in moderate to high yields.

  14. C8-Selective Acylation of Quinoline N-Oxides with α-Oxocarboxylic Acids via Palladium-Catalyzed Regioselective C-H Bond Activation.

    Science.gov (United States)

    Chen, Xiaopei; Cui, Xiuling; Wu, Yangjie

    2016-08-05

    A facile and efficient protocol for palladium-catalyzed C8-selective acylation of quinoline N-oxides with α-oxocarboxylic acids has been developed. In this approach, N-oxide was utilized as a stepping stone for the remote C-H functionalization. The reactions proceeded efficiently under mild reaction conditions with excellent regioselectivity and broad functional group tolerance.

  15. Catalytic C-H bond activation at nanoscale Lewis acidic aluminium fluorides: H/D exchange reactions at aromatic and aliphatic hydrocarbons.

    Science.gov (United States)

    Prechtl, Martin H G; Teltewskoi, Michael; Dimitrov, Anton; Kemnitz, Erhard; Braun, Thomas

    2011-12-16

    Nanoscopic amorphous Lewis acidic aluminium fluorides, such as aluminium chlorofluoride (ACF) and high-surface aluminium fluoride (HS-AlF(3)), are capable of activating C-H bonds of aliphatic hydrocarbons. H/D exchange reactions are catalysed under mild conditions (40 °C). Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Additional Value of CH4 Measurement in a Combined 13C/H2 Lactose Malabsorption Breath Test: A Retrospective Analysis

    Science.gov (United States)

    Houben, Els; De Preter, Vicky; Billen, Jaak; Van Ranst, Marc; Verbeke, Kristin

    2015-01-01

    The lactose hydrogen breath test is a commonly used, non-invasive method for the detection of lactose malabsorption and is based on an abnormal increase in breath hydrogen (H2) excretion after an oral dose of lactose. We use a combined 13C/H2 lactose breath test that measures breath 13CO2 as a measure of lactose digestion in addition to H2 and that has a better sensitivity and specificity than the standard test. The present retrospective study evaluated the results of 1051 13C/H2 lactose breath tests to assess the impact on the diagnostic accuracy of measuring breath CH4 in addition to H2 and 13CO2. Based on the 13C/H2 breath test, 314 patients were diagnosed with lactase deficiency, 138 with lactose malabsorption or small bowel bacterial overgrowth (SIBO), and 599 with normal lactose digestion. Additional measurement of CH4 further improved the accuracy of the test as 16% subjects with normal lactose digestion and no H2-excretion were found to excrete CH4. These subjects should have been classified as subjects with lactose malabsorption or SIBO. In conclusion, measuring CH4-concentrations has an added value to the 13C/H2 breath test to identify methanogenic subjects with lactose malabsorption or SIBO. PMID:26371034

  17. Mechanical Vibrations Modeling and Measurement

    CERN Document Server

    Schmitz, Tony L

    2012-01-01

    Mechanical Vibrations:Modeling and Measurement describes essential concepts in vibration analysis of mechanical systems. It incorporates the required mathematics, experimental techniques, fundamentals of modal analysis, and beam theory into a unified framework that is written to be accessible to undergraduate students,researchers, and practicing engineers. To unify the various concepts, a single experimental platform is used throughout the text to provide experimental data and evaluation. Engineering drawings for the platform are included in an appendix. Additionally, MATLAB programming solutions are integrated into the content throughout the text. This book also: Discusses model development using frequency response function measurements Presents a clear connection between continuous beam models and finite degree of freedom models Includes MATLAB code to support numerical examples that are integrated into the text narrative Uses mathematics to support vibrations theory and emphasizes the practical significanc...

  18. Nonplanar tertiary amides in rigid chiral tricyclic dilactams. Peptide group distortions and vibrational optical activity.

    Science.gov (United States)

    Pazderková, Markéta; Profant, Václav; Hodačová, Jana; Sebestík, Jaroslav; Pazderka, Tomáš; Novotná, Pavlína; Urbanová, Marie; Safařík, Martin; Buděšínský, Miloš; Tichý, Miloš; Bednárová, Lucie; Baumruk, Vladimír; Maloň, Petr

    2013-08-22

    We investigate amide nonplanarity in vibrational optical activity (VOA) spectra of tricyclic spirodilactams 5,8-diazatricyclo[6,3,0,0(1,5)]undecan-4,9-dione (I) and its 6,6',7,7'-tetradeuterio derivative (II). These rigid molecules constrain amide groups to nonplanar geometries with twisted pyramidal arrangements of bonds to amide nitrogen atoms. We have collected a full range vibrational circular dichroism (VCD) and Raman optical activity (ROA) spectra including signals of C-H and C-D stretching vibrations. We report normal-mode analysis and a comparison of calculated to experimental VCD and ROA. The data provide band-to-band assignment and offer a possibility to evaluate roles of constrained nonplanar tertiary amide groups and rigid chiral skeletons. Nonplanarity shows as single-signed VCD and ROA amide I signals, prevailing the couplets expected to arise from the amide-amide interaction. Amide-amide coupling dominates amide II (mainly C'-N stretching, modified in tertiary amides by the absence of a N-H bond) transitions (strong couplet in VCD, no significant ROA) probably due to the close proximity of amide nitrogen atoms. At lower wavenumbers, ROA spectra exhibit another likely manifestation of amide nonplanarity, showing signals of amide V (δ(oop)(N-C) at ~570 cm(-1)) and amide VI (δ(oop)(C'═O) at ~700 cm(-1) and ~650 cm(-1)) vibrations.

  19. DOWNHOLE VIBRATION MONITORING & CONTROL SYSTEM

    Energy Technology Data Exchange (ETDEWEB)

    Martin E. Cobern

    2004-08-31

    The deep hard rock drilling environment induces severe vibrations into the drillstring, which can cause reduced rates of penetration (ROP) and premature failure of the equipment. The only current means of controlling vibration under varying conditions is to change either the rotary speed or the weight-on-bit (WOB). These changes often reduce drilling efficiency. Conventional shock subs are useful in some situations, but often exacerbate the problems. The objective of this project is development of a unique system to monitor and control drilling vibrations in a ''smart'' drilling system. This system has two primary elements: (1) The first is an active vibration damper (AVD) to minimize harmful axial, lateral and torsional vibrations. The hardness of this damper will be continuously adjusted using a robust, fast-acting and reliable unique technology. (2) The second is a real-time system to monitor drillstring vibration, and related parameters. This monitor adjusts the damper according to local conditions. In some configurations, it may also send diagnostic information to the surface via real-time telemetry. The AVD is implemented in a configuration using magnetorheological (MR) fluid. By applying a current to the magnetic coils in the damper, the viscosity of the fluid can be changed rapidly, thereby altering the damping coefficient in response to the measured motion of the tool. Phase I of this program entailed modeling and design of the necessary subsystems and design, manufacture and test of a full laboratory prototype. Phase I of the project was completed by the revised end date of May 31, 2004. The objectives of this phase were met, and all prerequisites for Phase II have been completed.

  20. DOWNHOLE VIBRATION MONITORING & CONTROL SYSTEM

    Energy Technology Data Exchange (ETDEWEB)

    Martin E. Cobern

    2004-10-13

    The deep hard rock drilling environment induces severe vibrations into the drillstring, which can cause reduced rates of penetration (ROP) and premature failure of the equipment. The only current means of controlling vibration under varying conditions is to change either the rotary speed or the weight-on-bit (WOB). These changes often reduce drilling efficiency. Conventional shock subs are useful in some situations, but often exacerbate the problems. The objective of this project is development of a unique system to monitor and control drilling vibrations in a ''smart'' drilling system. This system has two primary elements: (1) The first is an active vibration damper (AVD) to minimize harmful axial, lateral and torsional vibrations. The hardness of this damper will be continuously adjusted using a robust, fast-acting and reliable unique technology. (2) The second is a real-time system to monitor drillstring vibration, and related parameters. This monitor adjusts the damper according to local conditions. In some configurations, it may also send diagnostic information to the surface via real-time telemetry. The AVD is implemented in a configuration using magnetorheological (MR) fluid. By applying a current to the magnetic coils in the damper, the viscosity of the fluid can be changed rapidly, thereby altering the damping coefficient in response to the measured motion of the tool. Phase I of this program entailed modeling and design of the necessary subsystems and design, manufacture and test of a full laboratory prototype. Phase I of the project was completed by the revised end date of May 31, 2004. The objectives of this phase were met, and all prerequisites for Phase II have been completed. The month of June, 2004 was primarily occupied with the writing of the Phase I Final Report, the sole deliverable of Phase I, which will be submitted in the next quarter. Redesign of the laboratory prototype and design of the downhole (Phase II) prototype was

  1. Stroboscopic shearography for vibration analysis

    Science.gov (United States)

    Steinchen, Wolfgang; Kupfer, Gerhard; Maeckel, Peter; Voessing, Frank

    1999-09-01

    Digital Shearography, a laser interferometric technique in conjunction with the digital image processing, has the potential for vibration analysis due to its simple optical system and insensitivity against small rigid body motions. This paper will focus on its recent developments for vibration analysis and for nondestructive testing (NDT) by dynamic (harmonical) excitation. With the introduction of real time observation using automatically refreshing reference frame, both small and large rigid body motions are greatly suppressed. The development of a smaller and more mobile measuring device in conjunction with a user guided comfortable program Shearwin enables the digital shearography to be applied easily as an industrial online testing tool.

  2. Vibrational Collapse of Hexapod Packings

    Science.gov (United States)

    Zhao, Yuchen; Ding, Jingqiu; Barés, Jonathan; Zheng, Hu; Dierichs, Karola; Menges, Achim; Behringer, Robert

    2017-06-01

    Columns made of convex noncohesive grains like sand collapse after being released from a confining container. However, structures built from non-convex grains can be stable without external support. In the current experiments, we investigate the effect of vibration on destroying such columns. The change of column height during vertical vibration, can be well characterized by stretched exponential relaxation when the column is short, which is in agreement with previous work, while a faster collapse happens when the column is tall. We investigate the collapse after the fast process including its dependence on column geometry, and on interparticle and basal friction.

  3. Innovative Techniques Simplify Vibration Analysis

    Science.gov (United States)

    2010-01-01

    In the early years of development, Marshall Space Flight Center engineers encountered challenges related to components in the space shuttle main engine. To assess the problems, they evaluated the effects of vibration and oscillation. To enhance the method of vibration signal analysis, Marshall awarded Small Business Innovation Research (SBIR) contracts to AI Signal Research, Inc. (ASRI), in Huntsville, Alabama. ASRI developed a software package called PC-SIGNAL that NASA now employs on a daily basis, and in 2009, the PKP-Module won Marshall s Software of the Year award. The technology is also used in many industries: aircraft and helicopter, rocket engine manufacturing, transportation, and nuclear power."

  4. FT-IR and Raman spectra, ab initio and density functional computations of the vibrational spectra, molecular geometries and atomic charges of uracil and 5-halogenated uracils (5-X-uracils; X = F, Cl, Br, I)

    Science.gov (United States)

    Singh, J. S.

    2014-01-01

    Raman (200-4000 cm-1) and FT-IR (400-4000 cm-1) spectra of uracil and 5-halogenated uracils (5-X-uracils; X = F, Cl, Br, I) have been recorded and analyzed in the range 200-4000 cm-1. The optimized molecular geometries, atomic polar tensor (APT) charges and vibrational characteristics have been studied theoretically using restricted Hartree-Fock (RHF) and density functional theory (DFT) methods. Ab initio and DFT calculations [using Becke's exchange in conjunction with Lee-Yang-Parr's correlation functional and Becke's three-parameter hybrid method (B3LYP)] were carried out to study the optimized molecular fundamental vibrational frequencies for uracil and 5-halogenated uracils by employing Gaussian-03 program. Gauss View software was used to make the vibrational analysis. Raman and IR spectra have been computed theoretically for the uracil and 5-halogenated molecules. The fundamental vibrational frequencies along with their corresponding intensities in IR and Raman activities and depolarization ratios of the Raman lines have also been calculated using the RHF and DFT methods employing different basis sets. Quantum chemical calculations helped in the reassignments of some fundamental vibrational modes. Most of the B3LYP/6-311++G∗∗ vibrational frequencies are in excellent agreement with available experimental assignments. The ring breathing and kekule stretching modes are found to lower magnitudes compared to those for uracil which could be due to mass effect of halogen atom in place of the hydrogen atom. The C-X (X = F, Cl, Br, I) stretching frequency is distinctly separated from the CH/NH ring stretching frequencies on the pyrimidine ring. All other bands have also been assigned different fundamentals/overtones/combinations.

  5. Energetics, structures, vibrational frequencies, vibrational absorption, vibrational circular dichroism and Raman intensities of Leu-enkephalin

    DEFF Research Database (Denmark)

    Jalkanen, Karl J.

    2003-01-01

    Here we present several low energy conformers of Leu-enkephalin (LeuE) calculated with the density functional theory using the Becke 3LYP hybrid functional and the 6-31G* basis set. The structures, conformational energies, vibrational frequencies, vibrational absorption (VA) intensities......, vibrational circular dichroism (VCD) intensities and Raman scattering intensities are reported for the conformers of LeuE which are expected to be populated at room temperature. The species of LeuE-present in non-polar solvents is the neutral non-ionic species with the NH2 and CO2H groups, in contrast...... to the zwitterionic neutral species with the NH3+ and CO2- groups which predominates in aqueous solution and in the crystal. All of our attempts to find the zwitterionic species in the isolated state failed, with the result that a hydrogen atom from the positively charged N-terminus ammonium group transferred either...

  6. Resonant vibration control of rotating beams

    DEFF Research Database (Denmark)

    Svendsen, Martin Nymann; Krenk, Steen; Høgsberg, Jan Becker

    2011-01-01

    Rotatingstructures,like e.g.wind turbine blades, may be prone to vibrations associated with particular modes of vibration. It is demonstrated, how this type of vibrations can be reduced by using a collocated sensor–actuator system, governed by a resonant controller. The theory is here demonstrated...... modal connectivity, only very limited modal spill-over is generated. The controller acts by resonance and therefore has only a moderate energy consumption, and successfully reduces modal vibrations at the resonance frequency....

  7. A Solid Phase Vibrational Circular Dichroism Study of Polypeptide-Surfactant Interaction.

    Science.gov (United States)

    Novotná, Pavlína; Urbanová, Marie

    2015-12-01

    We studied the interaction of poly-l-lysine (PLL) and poly-l-arginine (PLAG) with sodium dodecyl sulfate (SDS) surfactant and the interaction of poly-l-glutamic acid (PLGA) and poly-l-aspartic acid (PLAA) with tetradecyltrimethylammonium bromide (TTAB) surfactant using vibrational circular dichroism (VCD) spectroscopy in the region of C-H stretching vibration and in the Amide I region both in solution and in mulls. A chirality transfer from polypeptides to achiral surfactants was observed in the C-H stretching region, where measurements in solution were impossible. This observation was enabled by a special sample treatment technique using lyophilization and the preparation of mulls. This technique demonstrated itself as an interesting and beneficial tool for VCD measurements. In addition, we observed that SDS changed the secondary structure of PLL to the β-sheet and of PLAG to the α-helix. TTAB disrupted the PLGA and PLAA structure. These results were obtained in the mull but were confirmed by the VCD spectra measured in solution and by electronic circular dichroism. The chirality transfer from the polypeptides to SDS was caused by polypeptides ordered into a specific conformation during the interaction, while in the TTBA system it was induced primarily by the chirality of the amino acid residues. © 2015 Wiley Periodicals, Inc.

  8. Low-energy isovector quadrupole vibrations

    Energy Technology Data Exchange (ETDEWEB)

    Faessler, A.; Nojarov, R.

    1986-01-23

    The low-lying isovector quadrupole vibrations are described by an extension of the vibrational model allowing independent proton and neutron vibrations coupled by the symmetry energy. The recently detected low-lying isovector states in nearly spherical nuclei with N=84 are described well concerning their energies and E2/M1 mixing ratios. (orig.).

  9. Ground Vibration Measurements at LHC Point 4

    Energy Technology Data Exchange (ETDEWEB)

    Bertsche, Kirk; /SLAC; Gaddi, Andrea; /CERN

    2012-09-17

    Ground vibration was measured at Large Hadron Collider (LHC) Point 4 during the winter shutdown in February 2012. This report contains the results, including power and coherence spectra. We plan to collect and analyze vibration data from representative collider halls to inform specifications for future linear colliders, such as ILC and CLIC. We are especially interested in vibration correlations between final focus lens locations.

  10. Rotor Vibration Reduction via Active Hybrid Bearings

    DEFF Research Database (Denmark)

    Nicoletti, Rodrigo; Santos, Ilmar

    2002-01-01

    The use of fluid power to reduce and control rotor vibration in rotating machines is investigated. An active hybrid bearing is studied, whose main objective is to reduce wear and vibration between rotating and stationary machinery parts. By injecting pressurised oil into the oil film, through...... with experiment, and simulations show the feasibility of controlling shaft vibration through this active device....

  11. 33 CFR 159.103 - Vibration test.

    Science.gov (United States)

    2010-07-01

    ... 33 Navigation and Navigable Waters 2 2010-07-01 2010-07-01 false Vibration test. 159.103 Section...) POLLUTION MARINE SANITATION DEVICES Design, Construction, and Testing § 159.103 Vibration test. The device... subjected to a sinusoidal vibration for a period of 12 hours, 4 hours in each of the x, y, and z planes, at...

  12. 14 CFR 27.907 - Engine vibration.

    Science.gov (United States)

    2010-01-01

    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Engine vibration. 27.907 Section 27.907... STANDARDS: NORMAL CATEGORY ROTORCRAFT Powerplant General § 27.907 Engine vibration. (a) Each engine must be installed to prevent the harmful vibration of any part of the engine or rotorcraft. (b) The addition of the...

  13. 14 CFR 29.251 - Vibration.

    Science.gov (United States)

    2010-01-01

    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Vibration. 29.251 Section 29.251... STANDARDS: TRANSPORT CATEGORY ROTORCRAFT Flight Miscellaneous Flight Requirements § 29.251 Vibration. Each part of the rotorcraft must be free from excessive vibration under each appropriate speed and power...

  14. 14 CFR 29.907 - Engine vibration.

    Science.gov (United States)

    2010-01-01

    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Engine vibration. 29.907 Section 29.907... STANDARDS: TRANSPORT CATEGORY ROTORCRAFT Powerplant General § 29.907 Engine vibration. (a) Each engine must be installed to prevent the harmful vibration of any part of the engine or rotorcraft. (b) The...

  15. 14 CFR 27.251 - Vibration.

    Science.gov (United States)

    2010-01-01

    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Vibration. 27.251 Section 27.251... STANDARDS: NORMAL CATEGORY ROTORCRAFT Flight Miscellaneous Flight Requirements § 27.251 Vibration. Each part of the rotorcraft must be free from excessive vibration under each appropriate speed and power...

  16. 49 CFR 178.608 - Vibration standard.

    Science.gov (United States)

    2010-10-01

    ... 49 Transportation 2 2010-10-01 2010-10-01 false Vibration standard. 178.608 Section 178.608... Testing of Non-bulk Packagings and Packages § 178.608 Vibration standard. (a) Each packaging must be capable of withstanding, without rupture or leakage, the vibration test procedure outlined in this section...

  17. 49 CFR 178.985 - Vibration test.

    Science.gov (United States)

    2010-10-01

    ... 49 Transportation 2 2010-10-01 2010-10-01 false Vibration test. 178.985 Section 178.985... Testing of Large Packagings § 178.985 Vibration test. (a) General. All rigid Large Packaging and flexible Large Packaging design types must be capable of withstanding the vibration test. (b) Test method. (1) A...

  18. Vibration measurements on timber frame floors

    NARCIS (Netherlands)

    Kuilen, J.W.G. van de; Oosterhout, G.P.C. van; Donkervoort, R.

    1998-01-01

    In the design of lightweight floors vibrational aspects become more and more important. With the foreseen introduction of Eurocode 5 the vibration of timber floors becomes a part of the design for serviceability. Design rules for the vibrational behaviour are given in Eurocode 5. The first rule is

  19. Vibrations in a moving flexible robot arm

    Science.gov (United States)

    Wang, P. K. C.; Wei, Jin-Duo

    1987-01-01

    The vibration in a flexible robot arm modeled by a moving slender prismatic beam is considered. It is found that the extending and contracting motions have destabilizing and stabilizing effects on the vibratory motions, respectively. The vibration analysis is based on a Galerkin approximation with time-dependent basis functions. Typical numerical results are presented to illustrate the qualitative features of vibrations.

  20. Vibration Theory, Vol. 1A

    DEFF Research Database (Denmark)

    Nielsen, Søren R. K.

    The present collection of solved problems has been published as a supplement to the textbook Svingningsteori. Bind 1. Lineær svingningsteori,Aalborg tekniske Universitetsforlag, 1991, whicj is used in the introductory course on linear vibration theory that is being given on th e8th semester...

  1. Vibration Damping Circuit Card Assembly

    Science.gov (United States)

    Hunt, Ronald Allen (Inventor)

    2016-01-01

    A vibration damping circuit card assembly includes a populated circuit card having a mass M. A closed metal container is coupled to a surface of the populated circuit card at approximately a geometric center of the populated circuit card. Tungsten balls fill approximately 90% of the metal container with a collective mass of the tungsten balls being approximately (0.07) M.

  2. Wideband Piezomagnetoelastic Vibration Energy Harvesting

    DEFF Research Database (Denmark)

    Lei, Anders; Thomsen, Erik Vilain

    2014-01-01

    This work presents a small-scale wideband piezomagnetoelastic vibration energy harvester (VEH) aimed for operation at frequencies of a few hundred Hz. The VEH consists of a tape-casted PZT cantilever with thin sheets of iron foil attached on each side of the free tip. The wideband operation...

  3. Ultrafast vibrations of gold nanorings

    DEFF Research Database (Denmark)

    Kelf, T; Tanaka, Y; Matsuda, O

    2011-01-01

    We investigate the vibrational modes of gold nanorings on a silica substrate with an ultrafast optical technique. By comparison with numerical simulations, we identify several resonances in the gigahertz range associated with axially symmetric deformations of the nanoring and substrate. We...

  4. Effect of shelf aging on vibration transmissibility of anti-vibration gloves.

    Science.gov (United States)

    Shibata, Nobuyuki

    2017-10-05

    Anti-vibration gloves have been used in real workplaces to reduce vibration transmitted through hand-held power tools to the hand. Generally materials used for vibration attenuation in gloves are resilient materials composed of certain synthetic and/or composite polymers. The mechanical characteristics of the resilient materials used in anti-vibration gloves are prone to be influenced by environmental conditions such as temperature, humidity, and photo-irradiation, which cause material degradation and aging. This study focused on the influence of shelf aging on the vibration attenuation performance of air-packaged anti-vibration gloves following 2 years of shelf aging. Effects of shelf aging on the vibration attenuation performance of anti-vibration gloves were examined according to the Japan industrial standard JIS T8114 test protocol. The findings indicate that shelf aging induces the reduction of vibration attenuation performance in air-packaged anti-vibration gloves.

  5. N-H Stretching Excitations in Adenosine-Thymidine Base Pairs in Solution: Base Pair Geometries, Infrared Line Shapes and Ultrafast Vibrational Dynamics

    Science.gov (United States)

    Greve, Christian; Preketes, Nicholas K.; Fidder, Henk; Costard, Rene; Koeppe, Benjamin; Heisler, Ismael A.; Mukamel, Shaul; Temps, Friedrich; Nibbering, Erik T. J.; Elsaesser, Thomas

    2013-01-01

    We explore the N-H stretching vibrations of adenosine-thymidine base pairs in chloroform solution with linear and nonlinear infrared spectroscopy. Based on estimates from NMR measurements and ab initio calculations, we conclude that adenosine and thymidine form hydrogen bonded base pairs in Watson-Crick, reverse Watson-Crick, Hoogsteen and reverse Hoogsteen configurations with similar probability. Steady-state concentration- and temperature dependent linear FT-IR studies, including H/D exchange experiments, reveal that these hydrogen-bonded base pairs have complex N-H/N-D stretching spectra with a multitude of spectral components. Nonlinear 2D-IR spectroscopic results, together with IR-pump-IR-probe measurements, as also corroborated by ab initio calculations, reveal that the number of N-H stretching transitions is larger than the total number of N-H stretching modes. This is explained by couplings to other modes, such as an underdamped low-frequency hydrogen-bond mode, and a Fermi resonance with NH2 bending overtone levels of the adenosine amino-group. Our results demonstrate that modeling based on local N-H stretching vibrations only is not sufficient and call for further refinement of the description of the N-H stretching manifolds of nucleic acid base pairs of adenosine and thymidine, incorporating a multitude of couplings with fingerprint and low-frequency modes. PMID:23234439

  6. Quinoline-2-carboimine copper complex immobilized on amine functionalized silica coated magnetite nanoparticles: a novel and magnetically retrievable catalyst for the synthesis of carbamates via C-H activation of formamides.

    Science.gov (United States)

    Sharma, R K; Dutta, Sriparna; Sharma, Shivani

    2015-01-21

    In the present study, we report the synthesis of a highly efficient and magnetically retrievable catalytic system (Cu-2QC@Am-SiO2@Fe3O4) through the covalent immobilization of quinoline-2-carboxaldehyde (2QC) on an amine functionalized silica coated ferrite nanosupport followed by metallation with copper acetate. The structure of the organic-inorganic hybrid nanomaterial has been confirmed using various physicochemical techniques such as Powder X-Ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FT-IR), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Energy Dispersive X-Ray Spectroscopy (EDS), Energy Dispersive X-Ray Fluorescence Spectroscopy (ED-XRF), Atomic Absorption Spectroscopy (AAS), Inductively Coupled Plasma Spectroscopy (ICP) and Vibrating Sample Magnetometry (VSM). The resulting nanocatalyst exhibits a remarkable catalytic efficacy in the synthesis of industrially and pharmaceutically significant carbamates via the C-H activation of formamides under solvent free conditions. The most important attribute of the present methodology is that the catalyst can be recovered simply through an external magnetic force and reused several times without any significant deterioration in its activity. Furthermore, the heterogeneity test has been carried out in order to ensure the intrinsic stability of the nanostructured catalyst. The activity of the Cu-2QC@Am-SiO2@Fe3O4 nanocatalyst has been found to be far more superior in comparison with the literature precedents in terms of the product yield, cost and reusability of the catalyst. Besides, ambient reaction conditions, simple workup procedure, wide substrate scope and cost effectiveness are some of the other outstanding features of this protocol that make it economical and sustainable.

  7. Merging Visible Light Photoredox Catalysis with Metal Catalyzed C-H Activations: On the Role of Oxygen and Superoxide Ions as Oxidants.

    Science.gov (United States)

    Fabry, David C; Rueping, Magnus

    2016-09-20

    The development of efficient catalytic systems for direct aromatic C-H bond functionalization is a long-desired goal of chemists, because these protocols provide environmental friendly and waste-reducing alternatives to classical methodologies for C-C and C-heteroatom bond formation. A key challenge for these transformations is the reoxidation of the in situ generated metal hydride or low-valent metal complexes of the primary catalytic bond forming cycle. To complete the catalytic cycle and to regenerate the C-H activation catalyst, (super)stoichiometric amounts of Cu(II) or Ag(I) salts have often been applied. Recently, "greener" approaches have been developed by applying molecular oxygen in combination with Cu(II) salts, internal oxidants that are cleaved during the reaction, or solvents or additives enabling the metal hydride reoxidation. All these approaches improved the environmental friendliness but have not overcome the obstacles associated with the overall limited functional group and substrate tolerance. Hence, catalytic processes that do not feature the unfavorable aspects described above and provide products in a streamlined as well as economically and ecologically advantageous manner would be desirable. In this context, we decided to examine visible light photoredox catalysis as a new alternative to conventionally applied regeneration/oxidation procedures. This Account summarizes our recent advances in this expanding area and will highlight the new concept of merging distinct redox catalytic processes for C-H functionalizations through the application of visible light photoredox catalysis. Photoredox catalysis can be considered as catalytic electron-donating or -accepting processes, making use of visible-light absorbing homogeneous and heterogeneous metal-based catalysts, as well as organic dye sensitizers or polymers. As a consequence, photoredox catalysis is, in principle, an ideal tool for the recycling of any given metal catalyst via a coupled

  8. High-Valent Manganese-Oxo Valence Tautomers and the Influence of Lewis/Brönsted Acids on C-H Bond Cleavage.

    Science.gov (United States)

    Baglia, Regina A; Krest, Courtney M; Yang, Tzuhsiung; Leeladee, Pannee; Goldberg, David P

    2016-10-17

    The addition of Lewis or Brönsted acids (LA = Zn(OTf)2, B(C6F5)3, HBArF, TFA) to the high-valent manganese-oxo complex MnV(O)(TBP8Cz) results in the stabilization of a valence tautomer MnIV(O-LA)(TBP8Cz•+). The ZnII and B(C6F5)3 complexes were characterized by manganese K-edge X-ray absorption spectroscopy (XAS). The position of the edge energies and the intensities of the pre-edge (1s to 3d) peaks confirm that the Mn ion is in the +4 oxidation state. Fitting of the extended X-ray absorption fine structure (EXAFS) region reveals 4 N/O ligands at Mn-Nave = 1.89 Å and a fifth N/O ligand at 1.61 Å, corresponding to the terminal oxo ligand. This Mn-O bond length is elongated compared to the MnV(O) starting material (Mn-O = 1.55 Å). The reactivity of MnIV(O-LA)(TBP8Cz•+) toward C-H substrates was examined, and it was found that H• abstraction from C-H bonds occurs in a 1:1 stoichiometry, giving a MnIV complex and the dehydrogenated organic product. The rates of C-H cleavage are accelerated for the MnIV(O-LA)(TBP8Cz•+) valence tautomer as compared to the MnV(O) valence tautomer when LA = ZnII, B(C6F5)3, and HBArF, whereas for LA = TFA, the C-H cleavage rate is slightly slower than when compared to MnV(O). A large, nonclassical kinetic isotope effect of kH/kD = 25-27 was observed for LA = B(C6F5)3 and HBArF, indicating that H-atom transfer (HAT) is the rate-limiting step in the C-H cleavage reaction and implicating a potential tunneling mechanism for HAT. The reactivity of MnIV(O-LA)(TBP8Cz•+) toward C-H bonds depends on the strength of the Lewis acid. The HAT reactivity is compared with the analogous corrole complex MnIV(O-H)(tpfc•+) recently reported (J. Am. Chem. Soc. 2015, 137, 14481-14487).

  9. The effects of sound level and vibration magnitude on the relative discomfort of noise and vibration.

    Science.gov (United States)

    Huang, Yu; Griffin, Michael J

    2012-06-01

    The relative discomfort caused by noise and vibration, how this depends on the level of noise and the magnitude of vibration, and whether the noise and vibration are presented simultaneously or sequentially has been investigated in a laboratory study with 20 subjects. Noise and vertical vibration were reproduced with all 49 combinations of 7 levels of noise and 7 magnitudes of vibration to allow the discomfort caused by one of the stimuli to be judged relative to the other stimulus using magnitude estimation. In four sessions, subjects judged noise relative to vibration and vibration relative to noise, with both simultaneous and sequential presentations of the stimuli. The equivalence of noise and vibration was not greatly dependent on whether the stimuli were simultaneous or sequential, but highly dependent on whether noise was judged relative to vibration or vibration was judged relative to noise. When judging noise, higher magnitude vibrations appeared to mask the discomfort caused by low levels of noise. When judging vibration, higher level noises appeared to mask the discomfort caused by low magnitudes of vibration. The judgment of vibration discomfort was more influenced by noise than the judgment of noise discomfort was influenced by vibration.

  10. Transient vibration of wind turbine blades

    Science.gov (United States)

    Li, Yuanzhe; Li, Minghai; Jiang, Feng

    2017-09-01

    This article aims to the transient vibration of wind turbine blades. We firstly introduce transient vibration and previous studies in this area. The report then shows the fundamental equations and derivation of Euler Equation. A 3-D beam are created to compare the analytical and numerical result. In addition we operate the existing result and Patran result of a truncation wedge beam, especially the frequencies of free vibration and transient vibration. Transient vibration cannot be vanished but in some case it can be reduced.

  11. Characterization of the quasi-one-dimensional compounds δ-(EDT-TTF-CONMe{sub 2}){sub 2}X, X=AsF{sub 6} and Br by vibrational spectroscopy and density functional theory calculations

    Energy Technology Data Exchange (ETDEWEB)

    Peterseim, Tobias; Dressel, Martin [1. Physikalisches Institut, Universität Stuttgart, Pfaffenwaldring 57, 70550 Stuttgart (Germany); Antal, Ágnes [1. Physikalisches Institut, Universität Stuttgart, Pfaffenwaldring 57, 70550 Stuttgart (Germany); Institute of Condensed Matter Physics, École Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne (Switzerland); Batail, Patrick [Laboratoire MOLTECH, UMR 6200 CNRS-Université d' Angers, Bt. K, UFR Sciences, 2 Boulevard Lavoisier, F-49045 Angers (France); Drichko, Natalia [1. Physikalisches Institut, Universität Stuttgart, Pfaffenwaldring 57, 70550 Stuttgart (Germany); Department of Physics and Astronomy, Johns Hopkins University, Baltimore, Maryland 21218 (United States)

    2014-02-14

    We have investigated the infrared spectra of the quarter-filled charge-ordered insulators δ-(EDT-TTF-CONMe{sub 2}){sub 2}X (X= AsF{sub 6}, Br) along all three crystallographic directions in the temperature range from 300 to 10 K. DFT-assisted normal mode analysis of the neutral and ionic EDT-TTF-CONMe{sub 2} molecule allows us to assign the experimentally observed intramolecular modes and to obtain relevant information on the charge ordering and intramolecular interactions. From frequencies of charge-sensitive vibrations we deduce that the charge-ordered state is already present at room temperature and does not change on cooling, in agreement with previous NMR measurements. The spectra taken along the stacking direction clearly show features of vibrational overtones excited due to the anharmonic electronic molecule potential caused by the large charge disproportionation between the molecular sites. The shift of certain vibrational modes indicates the onset of the structural transition below 200 K.

  12. The superconducting gap structure of PrOs{sub 4}Sb{sub 12} and CeRu{sub 2} probed by C(H,{phi})

    Energy Technology Data Exchange (ETDEWEB)

    Custers, J. [Institute for Solid State Physics, University of Tokyo, Kashiwa, Chiba 277-8581 (Japan) and Institute of Solid State Physics, Vienna University of Technology, 1040 Vienna (Austria)]. E-mail: custers@issp.u-tokyo.ac.jp; Yamada, A. [Institute for Solid State Physics, University of Tokyo, Kashiwa, Chiba 277-8581 (Japan); Tayama, T. [Institute for Solid State Physics, University of Tokyo, Kashiwa, Chiba 277-8581 (Japan); Sakakibara, T. [Institute for Solid State Physics, University of Tokyo, Kashiwa, Chiba 277-8581 (Japan); Sugawara, H. [Faculty of Integrated Arts and Sciences, University of Tokushima, Tokushima 770-8502 (Japan); Aoki, Y. [Department of Physics, Tokyo Metropolitan University, Hachioji, Tokyo 192-0397 (Japan); Sato, H. [Department of Physics, Tokyo Metropolitan University, Hachioji, Tokyo 192-0397 (Japan); Onuki, Y. [Department of Physics, Osaka University, Toyonaka, Osaka 560-0043 (Japan); Machida, K. [Department of Physics, Okayama University, Okayama 700-8530 (Japan)

    2007-03-15

    We have performed measurements of the angle-resolved specific heat C(H,{phi}) on PrOs{sub 4}Sb{sub 12} and the well-known s-wave superconductor CeRu{sub 2} in order to gain information about their respective superconducting (SC) gap structure. PrOs{sub 4}Sb{sub 12} exhibits pronounced minima (maxima) in C(H,{phi}) along the [100] ([111]) directions. CeRu{sub 2} shows minima (maxima) along the [110] ([100]) directions. The field dependence of the oscillation amplitude of C({phi}), vertical bar A vertical bar, shows similar behavior for both suggesting finite minima in the SC gap, where C({phi}) is smallest. On the other hand, in comparison the temperature dependence of |A| shows aberrant behavior.

  13. Limits on top FCNC decay t$\\rightarrow$cH and t$\\rightarrow$c$\\gamma$ from CLIC at 380 GeV

    CERN Document Server

    Zarnecki, Aleksander

    2018-01-01

    FCNC top decays are very strongly suppressed in the Standard Model and the observation of any such decay would be a direct signature of physics beyond SM. Many "new physics" scenarios predict contributions to FCNC processes and the largest enhancement in many models is for t$\\rightarrow$cH decay. Enhancements for the decay channel t$\\rightarrow$c$\\gamma$ are more modest, but the decay still has a clearly identifiable kinematic signature. Prospects for measuring these decays at CLIC running at 380 GeV were studied with full detector simulation, taking the luminosity distribution, beam polarization and beam induced background into account. Top pair production events with t$\\rightarrow$cH decays can be identified based on the kinematic constraints and flavour tagging information. The analysis was divided into three steps: classification of top pair candidate events, event quality determination and kinematic reconstruction based on signal or background hypotheses, and final separation of signal from background. T...

  14. Application of Taguchi Method to the Optimization of a-C:H Coatings Deposited Using Ion Beam Assisted Physical Vapor Deposition

    Directory of Open Access Journals (Sweden)

    W. H. Kao

    2015-02-01

    Full Text Available The Taguchi design method is used to optimize the adhesion, hardness, and wear resistance properties of a-C:H coatings deposited on AISI M2 steel substrates using the ion beam assisted physical vapor deposition method. The adhesion strength of the coatings is evaluated by means of scratch tests, while the hardness is measured using a nanoindentation tester. Finally, the wear resistance is evaluated by performing cyclic ball-on-disc wear tests. The Taguchi experimental results show that the optimal deposition parameters are as follows: a substrate bias voltage of 90 V, an ion beam voltage of 1 kV, an acetylene flow rate of 21 sccm, and a working distance of 7 cm. Given these optimal processing conditions, the a-C:H coating has a critical load of 99.8 N, a hardness of 25.5 GPa, and a wear rate of 0.4 × 10−6 mm3/Nm.

  15. The Unexpected Reactivity of the Carbon Sites on the Nanostructured Carbon Catalysts towards the C-H Bond Activation from the Analysis of the Aromaticity.

    Science.gov (United States)

    Sun, XiaoYing; Li, Bo; Su, DangSheng

    2016-06-06

    It is believed that the oxygen groups on the carbon catalysts are responsible for the observed reactivity for C-H bond activations. On the other hand, the oxygen groups also reduce the aromaticity of the host. The loss of the aromaticity increases reactivities of the carbon atoms and they become the active sites for the C-H bond activation. The newly identified C-C site exhibits the comparable catalytic performance in the oxidative dehydrogenation (ODH) of propane compared with the conventional oxygen groups like quinone and ketone. A series of calculations indicate that the aromaticity might be a useful descriptor for the carbon catalysts. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Multiple Rabi Splittings under Ultrastrong Vibrational Coupling.

    Science.gov (United States)

    George, Jino; Chervy, Thibault; Shalabney, Atef; Devaux, Eloïse; Hiura, Hidefumi; Genet, Cyriaque; Ebbesen, Thomas W

    2016-10-07

    From the high vibrational dipolar strength offered by molecular liquids, we demonstrate that a molecular vibration can be ultrastrongly coupled to multiple IR cavity modes, with Rabi splittings reaching 24% of the vibration frequencies. As a proof of the ultrastrong coupling regime, our experimental data unambiguously reveal the contributions to the polaritonic dynamics coming from the antiresonant terms in the interaction energy and from the dipolar self-energy of the molecular vibrations themselves. In particular, we measure the opening of a genuine vibrational polaritonic band gap of ca. 60 meV. We also demonstrate that the multimode splitting effect defines a whole vibrational ladder of heavy polaritonic states perfectly resolved. These findings reveal the broad possibilities in the vibrational ultrastrong coupling regime which impact both the optical and the molecular properties of such coupled systems, in particular, in the context of mode-selective chemistry.

  17. Vibrations on board and health effects

    DEFF Research Database (Denmark)

    Jensen, Anker; Jepsen, Jørgen Riis

    2014-01-01

    for such relation among seafarers except for fishermen, who, however, are also exposed to additional recognised physical risk factors at work. The assessment and reduction of vibrations by naval architects relates to technical implications of this impact for the ships’ construction, but has limited value......There is only limited knowledge of the exposure to vibrations of ships’ crews and their risk of vibration-induced health effects. Exposure to hand-arm vibrations from the use of vibrating tools at sea does not differ from that in the land-based trades. However, in contrast to most other work places...... of the health consequences of whole body vibrations in land-transportation, such exposure at sea may affect ships’ passengers and crews. While the relation of back disorders to high levels of whole body vibration has been demonstrated among e.g. tractor drivers, there are no reported epidemiological evidence...

  18. Chelerythrine delayed tumor growth and increased survival duration of Dalton′s lymphoma bearing BALB/c H 2d mice by activation of NK cells in vivo

    Directory of Open Access Journals (Sweden)

    Sanjay Kumar

    2015-01-01

    Full Text Available Aim: The aims of the present investigation were to evaluate the antitumor effect of chelerythrine (CHE on in vivo growth and survival duration of BALB/c (H 2d mice bearing Dalton′s lymphoma (DL and enhanced function of tumor associated NK cells (TANK cells. Materials and Methods: BALB/c (H 2d mice at 8-10 weeks of age of either sex were used. Increasing concentration of CHE (1.25, 2.5, and 5.0 mg/kg, staurosporine (0.625, 1.0, 1.5, and 2.0 mg/kg and cyclophosphamide (25, 50, 100, and 200 mg/kg were administered intraperitoneally and tumor regression and survival duration of tumor bearing host were determined, and thereafter expression of NKG2D and NKG2A on TANK cells were detected. Results: Our results show that treatment with 2.5 mg/kg of CHE results in a significant reduction in mean tumor volume and increased survival duration of DL bearing BALB/c (H 2d mice when compared to control. Activating receptor NKG2D on TANK cells were observed upregulated in contrast to inhibitory receptor NKG2A. Conclusions: CHE reduced mean tumor volume and increased survival duration of DL bearing BALB/c (H 2d mice. Increased expression of activating receptor NKG2D on TANK cells results in recovery of immunosuppression during tumor progression. Therefore, CHE could be a potential anticancer therapeutic agent that may be used to replace chemo-radio-therapy in future.

  19. Room-temperature and transition-metal-free Mizoroki-Heck-type reaction. Synthesis of E-stilbenes by photoinduced C-H functionalization.

    Science.gov (United States)

    Guastavino, Javier F; Budén, María E; Rossi, Roberto A

    2014-10-03

    We report a conceptually different approach toward E-stilbene syntheses by photoinduced direct C-H arylation of alkenes at rt without the addition of transition metals, with a broad range of aryl halides, including ArI, ArBr, and even ArCl. This is the first time that this reaction has been produced without extra solvent but with 18-crown-6 ether and t-BuOK in only 15 min of reaction.

  20. Iodine-catalyzed [Formula: see text] C-H bond activation by selenium dioxide: synthesis of diindolylmethanes and di(3-indolyl)selanides.

    Science.gov (United States)

    Naidu, P Seetham; Majumder, Swarup; Bhuyan, Pulak J

    2015-11-01

    An efficient reaction protocol was developed for the synthesis of several diindolylmethane derivatives via the [Formula: see text] C-H bond activation of aryl methyl ketones by [Formula: see text] and indoles in the presence of catalytic amounts of [Formula: see text] at 80 [Formula: see text] using dioxane as solvent. Unexpectedly, an interesting class of di(3-indolyl)selenide compounds was isolated when the reaction was carried out at room temperature.

  1. GIAO C-H COSY Simulations Merged with Artificial Neural Networks Pattern Recognition Analysis. Pushing the Structural Validation a Step Forward.

    Science.gov (United States)

    Zanardi, María M; Sarotti, Ariel M

    2015-10-02

    The structural validation problem using quantum chemistry approaches (confirm or reject a candidate structure) has been tackled with artificial neural network (ANN) mediated multidimensional pattern recognition from experimental and calculated 2D C-H COSY. In order to identify subtle errors (such as regio- or stereochemical), more than 400 ANNs have been built and trained, and the most efficient in terms of classification ability were successfully validated in challenging real examples of natural product misassignments.

  2. Constitutive expression of the c-H-ras oncogene inhibits doxorubicin-induced apoptosis and promotes cell survival in a rhabdomyosarcoma cell line.

    Science.gov (United States)

    Nooter, K.; Boersma, A. W.; Oostrum, R. G.; Burger, H.; Jochemsen, A. G.; Stoter, G.

    1995-01-01

    Drugs used in anti-cancer chemotherapy are thought to exert their cytotoxic action by induction of apoptosis. Genes have been identified which can mediate or modulate this drug-induced apoptosis, among which are c-myc, p53 and bcl-2. Since expression of oncogenic ras genes is a frequent observation in human cancer, we investigated the effects of the c-H-ras oncogene on anti-cancer drug-induced apoptosis. Apoptosis induced by a 2 h doxorubicin exposure was measured by in situ nick translation and flow cytometry in a rat cell line (R2T24) stably transfected with the c-H-ras oncogene and in a control cell line (R2NEO) transfected only with the antibiotic resistance gene neo. Both cell lines (R2T24 and R2NEO) had nearly identical growth characteristics, including cell doubling time, distribution over the cell cycle phases and plating efficiency in soft agar. Doxorubicin exposure of the R2NEO cells led to massive induction of apoptosis. In contrast, R2T24 cells, expressing the c-H-ras oncogene, showed significantly less apoptosis after doxorubicin incubation. Doxorubicin induced approximately 3- to 5-fold less cytotoxicity in the R2T24 cells than in the R2NEO cells, as determined by clonogenic assay in soft agar. No difference was observed in intracellular doxorubicin accumulation between the two cell lines, indicating that the classical, P-glycoprotein-mediated multidrug resistance phenotype is not involved in the observed differences in drug sensitivity. In conclusion, our data show that constitutive expression of the c-H-ras oncogene suppresses doxorubicin-induced apoptosis and promotes cell survival, suggesting that human tumours with ras oncogene expression might be less susceptible to doxorubicin treatment. PMID:7880739

  3. Palladium(II)-Catalyzed C-H Bond Activation/C-C and C-O Bond Formation Reaction Cascade: Direct Synthesis of Coumestans.

    Science.gov (United States)

    Neog, Kashmiri; Borah, Ashwini; Gogoi, Pranjal

    2016-12-02

    A palladium catalyzed cascade reaction of 4-hydroxycoumarins and in situ generated arynes has been developed for the direct synthesis of coumestans. This cascade strategy proceeds via C-H bond activation/C-O and C-C bond formations in a single reaction vessel. This methodology affords moderate to good yields of coumestans and is tolerant of a variety of functional groups including halide. The methodology was applied to the synthesis of natural product flemichapparin C.

  4. Troponate/Aminotroponate Ruthenium-Arene Complexes: Synthesis, Structure, and Ligand-Tuned Mechanistic Pathway for Direct C-H Bond Arylation with Aryl Chlorides in Water.

    Science.gov (United States)

    Dwivedi, Ambikesh D; Binnani, Chinky; Tyagi, Deepika; Rawat, Kuber S; Li, Pei-Zhou; Zhao, Yanli; Mobin, Shaikh M; Pathak, Biswarup; Singh, Sanjay K

    2016-07-05

    A series of water-soluble troponate/aminotroponate ruthenium(II)-arene complexes were synthesized, where O,O and N,O chelating troponate/aminotroponate ligands stabilized the piano-stool mononuclear ruthenium-arene complexes. Structural identities for two of the representating complexes were also established by single-crystal X-ray diffraction studies. These newly synthesized troponate/aminotroponate ruthenium-arene complexes enable efficient C-H bond arylation of arylpyridine in water. The unique structure-activity relationship in these complexes is the key to achieve efficient direct C-H bond arylation of arylpyridine. Moreover, the steric bulkiness of the carboxylate additives systematically directs the selectivity toward mono- versus diarylation of arylpyridines. Detailed mechanistic studies were performed using mass-spectral studies including identification of several key cyclometalated intermediates. These studies provided strong support for an initial cycloruthenation driven by carbonate-assisted deprotonation of 2-phenylpyridine, where the relative strength of η(6)-arene and the troponate/aminotroponate ligand drives the formation of cyclometalated 2-phenylpyridine Ru-arene species, [(η(6)-arene)Ru(κ(2)-C,N-phenylpyridine) (OH2)](+) by elimination of troponate/aminotroponate ligands and retaining η(6)-arene, while cyclometalated 2-phenylpyridine Ru-troponate/aminotroponate species [(κ (2)-troponate/aminotroponate)Ru(κ(2)-C,N-phenylpyridine)(OH2)2] was generated by decoordination of η(6)-arene ring during initial C-H bond activation of 2-phenylpyridine. Along with the experimental mass-spectral evidence, density functional theory calculation also supports the formation of such species for these complexes. Subsequently, these cycloruthenated products activate aryl chloride by facile oxidative addition to generate C-H arylated products.

  5. Homo- and heteroleptic alkoxycarbene f-element complexes and their reactivity towards acidic N-H and C-H bonds.

    Science.gov (United States)

    Arnold, Polly L; Cadenbach, Thomas; Marr, Isobel H; Fyfe, Andrew A; Bell, Nicola L; Bellabarba, Ronan; Tooze, Robert P; Love, Jason B

    2014-10-14

    The reactivity of a series of organometallic rare earth and actinide complexes with hemilabile NHC-ligands towards substrates with acidic C-H and N-H bonds is described. The synthesis, characterisation and X-ray structures of the new heteroleptic mono- and bis(NHC) cyclopentadienyl complexes LnCp2(L) 1 (Ln = Sc, Y, Ce; L = alkoxy-tethered carbene [OCMe2CH2(1-C{NCHCHN(i)Pr})]), LnCp(L)2 (Ln = Y) , and the homoleptic tetrakis(NHC) complex Th(L)4 4 are described. The reactivity of these complexes, and of the homoleptic complexes Ln(L)3 (Ln = Sc 3, Ce), with E-H substrates is described, where EH = pyrrole C4H4NH, indole C8H6NH, diphenylacetone Ph2CC(O)Me, terminal alkynes RC≡CH (R = Me3Si, Ph), and cyclopentadiene C5H6. Complex 1-Y heterolytically cleaves and adds pyrrole and indole N-H across the metal carbene bond, whereas 1-Ce does not, although 3 and 4 form H-bonded adducts. Complexes 1-Y and 1-Sc form adducts with CpH without cleaving the acidic C-H bond, 1-Ce cleaves the Cp-H bond, but 2 reacts to form the very rare H(+)-[C5H5](-)-H(+) motif. Complex 1-Ce cleaves alkyne C-H bonds but the products rearrange upon formation, while complex 1-Y cleaves the C-H bond in diphenylacetone forming a product which rearranges to the Y-O bonded enolate product.

  6. Palladium-Catalyzed C-H Arylation of α,β-Unsaturated Imines: Catalyst-Controlled Synthesis of Enamine and Allylic Amine Derivatives.

    Science.gov (United States)

    Li, Minyan; González-Esguevillas, María; Berritt, Simon; Yang, Xiaodong; Bellomo, Ana; Walsh, Patrick J

    2016-02-18

    A unique chemo- and regioselective α- and γ-arylation of palladium azapentadienyl intermediates is presented. Two distinct catalysts and sets of conditions successfully controlled the regioselectivity of the arylation. These methods provide the first umpolung C-H functionalization of azapentadienyl palladium intermediates and enable the divergent synthesis of allylic amine and enamine derivatives, which are of significant interest in the pharmaceutical industry. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Access to the meta position of arenes through transition metal catalysed C-H bond functionalisation: a focus on metals other than palladium.

    Science.gov (United States)

    Mihai, Madalina T; Genov, Georgi R; Phipps, Robert J

    2018-01-02

    The elaboration of simple arenes in order to access more complex substitution patterns is a crucial endeavor for synthetic chemists, given the central role that aromatic rings play in all manner of important molecules. Classical methods are now routinely used alongside stoichiometric organometallic approaches and, most recently, transition metal catalysis in the range of methodologies that are available to elaborate arene C-H bonds. Regioselectivity is an important consideration when selecting a method and, of all those available, it is arguably those that target the meta position that are fewest in number. The rapid development of transition metal-catalysed C-H bond functionalisation over the last few decades has opened new possibilities for meta-selective C-H functionalisation through the diverse reactivity of transition metals and their compatibility with a wide range of directing groups. The pace of discovery of such processes has grown rapidly in the last five years in particular and it is the purpose of this review to examine these but in doing so to place the focus on metals other than palladium, the specific contributions of which have been very recently reviewed elsewhere. It is hoped this will serve to highlight to the reader the breadth of current strategies and mechanisms that have been used to tackle this challenge, which may inspire further progress in the field.

  8. Laser-induced transformation of supramolecular complexes: approach to controlled formation of hybrid multi-yolk-shell Au-Ag@a-C:H nanostructures

    Science.gov (United States)

    Manshina, A. A.; Grachova, E. V.; Povolotskiy, A. V.; Povolotckaia, A. V.; Petrov, Y. V.; Koshevoy, I. O.; Makarova, A. A.; Vyalikh, D. V.; Tunik, S. P.

    2015-07-01

    In the present work an efficient approach of the controlled formation of hybrid Au-Ag-C nanostructures based on laser-induced transformation of organometallic supramolecular cluster compound is suggested. Herein the one-step process of the laser-induced synthesis of hybrid multi-yolk-shell Au-Ag@a-C:H nanoparticles which are bimetallic gold-silver subnanoclusters dispersed in nanospheres of amorphous hydrogenated a-C:H carbon is reported in details. It has been demonstrated that variation of the experimental parameters such as type of the organometallic precursor, solvent, deposition geometry and duration of laser irradiation allows directed control of nanoparticles’ dimension and morphology. The mechanism of Au-Ag@a-C:H nanoparticles formation is suggested: the photo-excitation of the precursor molecule through metal-to-ligand charge transfer followed by rupture of metallophilic bonds, transformation of the cluster core including red-ox intramolecular reaction and aggregation of heterometallic species that results in the hybrid metal/carbon nanoparticles with multi-yolk-shell architecture formation. It has been found that the nanoparticles obtained can be efficiently used for the Surface-Enhanced Raman Spectroscopy label-free detection of human serum albumin in low concentration solution.

  9. Microcystin-LR degradation by solar photo-Fenton, UV-A/photo-Fenton and UV-C/H2O2: a comparative study.

    Science.gov (United States)

    de Freitas, Adriane M; Sirtori, Carla; Lenz, Cesar A; Peralta Zamora, Patricio G

    2013-04-01

    This work assessed the effectiveness of several methods on degradation of microcystin-LR (MC-LR) by different Advanced Oxidation Processes, like solar photo-Fenton, UV-A/photo-Fenton and UV-C/H2O2. UV-C/H2O2 and UV-A/photo-Fenton processes were carried out in a bench scale photochemical apparatus and the solar photo-Fenton treatment was performed in a CPC photoreactor. MC-LR degradation was monitored by LC-ESI-MS/MS and kinetic parameters were calculated for all systems evaluated. The results demonstrated that UV-C/H2O2 was the most efficient method, showing a reduction of over 90% of initial MC-LR after 5 min of reaction. Solar and photo-Fenton/UVA had a rate decrease of 88 and 76% after the same time, respectively. The kinetic study indicated that the solar photo-Fenton and artificial radiation (UV-A) processes were very similar in their efficiency. The use of sunlight instead of artificial UV radiation significantly reduced the cost of photocatalytic treatment systems; it is also an environmentally friendly method, since it utilizes renewable energy.

  10. Simultaneous structure-activity studies and arming of natural products by C-H amination reveal cellular targets of eupalmerin acetate

    Science.gov (United States)

    Li, Jing; Cisar, Justin S.; Zhou, Cong-Ying; Vera, Brunilda; Williams, Howard; Rodríguez, Abimael D.; Cravatt, Benjamin F.; Romo, Daniel

    2013-06-01

    Natural products have a venerable history of, and enduring potential for the discovery of useful biological activity. To fully exploit this, the development of chemical methodology that can functionalize unique sites within these complex structures is highly desirable. Here, we describe the use of rhodium(II)-catalysed C-H amination reactions developed by Du Bois to carry out simultaneous structure-activity relationship studies and arming (alkynylation) of natural products at ‘unfunctionalized’ positions. Allylic and benzylic C-H bonds in the natural products undergo amination while olefins undergo aziridination, and tertiary amine-containing natural products are converted to amidines by a C-H amination-oxidation sequence or to hydrazine sulfamate zwitterions by an unusual N-amination. The alkynylated derivatives are ready for conversion into cellular probes that can be used for mechanism-of-action studies. Chemo- and site-selectivity was studied with a diverse library of natural products. For one of these—the marine-derived anticancer diterpene, eupalmerin acetate—quantitative proteome profiling led to the identification of several protein targets in HL-60 cells, suggesting a polypharmacological mode of action.

  11. The bending vibrational levels of the acetylene cation: a case study of the Renner-Teller effect in a molecule with two degenerate bending vibrations.

    Science.gov (United States)

    Tang, Sheunn-Jiun; Chou, Yung-Ching; Lin, Jim Jr-Min; Hsu, Yen-Chu

    2006-10-07

    Forty three vibronic levels of C2H2+, X 2Pi u, with upsilon4 = 0-6, upsilon5 = 0-3, and K = 0-4, lying at energies of 0-3520 cm(-1) above the zero-point level, have been recorded at rotational resolution. These levels were observed by double resonance, using 1+1' two-color pulsed-field ionization zero-kinetic-energy photoelectron spectroscopy. The intermediate states were single rovibrational levels chosen from the A1Au, 4nu3 (K = 1-2), 5nu3 (K = 1), nu2+4nu3 (K = 0), and 47,206 cm(-1) (K = 1) levels of C2H2. Seven of the trans-bending levels of C2H2+ (upsilon4 = 0-3, K = 0-2) had been reported previously by Pratt et al. [J. Chem. Phys. 99, 6233 (1993)]; our results for these levels agree well with theirs. A full analysis has been carried out, including the Renner-Teller effect and the vibrational anharmonicity for both the trans- and cis-bending vibrations. The rotational structure of the lowest 16 vibronic levels (consisting of the complete set of levels with upsilon4 + upsilon5 < or = 2, except for the unobserved upper (2Pi u component of the 2nu4 overtone) could be fitted by least squares using 16 parameters to give an rms deviation of 0.21 cm(-1). The vibronic coupling parameter epsilon5 (about whose magnitude there has been controversy) was determined to be -0.0273(7). For the higher vibronic levels, an additional parameter, r45, was needed to allow for the Darling-Dennison resonance between the two bending manifolds. Almost all the observed levels of the upsilon4 + upsilon5 = 3 and 4 polyads (about half of the predicted number) could then be assigned. In a final fit to 39 vibronic levels with upsilon4 + upsilon5 < or = 5, an rms deviation of 0.34 cm(-1) was obtained using 20 parameters. An interesting finding is that Hund's spin-coupling cases (a) and (b) both occur in the Sigmau components of the nu4 + 2nu5 combination level. The ionization potential of C2H2 (from the lowest rotational level of the ground state to the lowest rotational level of the cation

  12. Vibration characteristics of casing string under the exciting force of an electric vibrator

    Directory of Open Access Journals (Sweden)

    Yiyong Yin

    2017-11-01

    Full Text Available Vibration cementing is a new technique that can significantly improve the bond strength of cementing interface. To popularize this technique, it is necessary to solve the key problem of how to make cementing string generate downhole radial vibration in the WOC stage. For this purpose, an electric vibrator was developed. With this vibrator, electric energy is converted into mechanical energy by means of a high-temperature motor vibration unit. The motor vibration unit rotates the eccentric block through an output shaft to generate an exciting source, which produces an axial-rotating exciting force at the bottom of the casing string. Then, the vibration characteristics of vertical well casing string under the exciting force were analyzed by using the principal coordinate analysis method, and the response model of casing string to an electric vibrator was developed. Finally, the effects of casing string length, exciting force and vibration frequency on the vibration amplitude at the lowermost of the casing string were analyzed based on a certain casing program. It is indicated that the casing string length and the square of vibration frequency are inversely proportional to the vibration amplitude at the lowermost of the casing string, and the exciting force is proportional to the vibration amplitude at the lowermost of the casing string. These research results provide a theoretical support for the application of vibration cementing technology to the cementing sites with different requirements on well depth and amplitude.

  13. Iodine-Promoted Oxidative Cross-Coupling of Unprotected Anilines with Methyl Ketones: A Site-Selective Direct C-H Bond Functionalization to C4-Dicarbonylation of Anilines.

    Science.gov (United States)

    Wu, Xia; Gao, Qinghe; Geng, Xiao; Zhang, Jingjing; Wu, Yan-Dong; Wu, An-Xin

    2016-05-20

    An unprecedented direct dual C-H bond functionalization of unprotected anilines and methyl ketones has been demonstrated. It is the first example of iodine-promoted highly chemo- and site-selective oxidative C-H/C-H cross-coupling of anilines and methyl ketones to furnish the C4-dicarbonylation of anilines in moderate to good yields. Moreover, coproduct HI acted as a catalyst in the reaction. The salient feature of this approach is unprecedented C-H functionalization rather than N-H functionalization of unprotected anilines.

  14. Vibrational damping of composite materials

    Science.gov (United States)

    Biggerstaff, Janet M.

    The purpose of this research was to develop new methods of vibrational damping in polymeric composite materials along with expanding the knowledge of currently used vibrational damping methods. A new barrier layer technique that dramatically increased damping in viscoelastic damping materials that interacted with the composite resin was created. A method for testing the shear strength of damping materials cocured in composites was developed. Directional damping materials, where the loss factor and modulus could be tailored by changing the angle, were produced and investigated. The addition of particles between composite prepreg layers to increase damping was studied. Electroviscoelastic materials that drastically changed properties such as loss factor and modulus with an applied voltage were manufactured and tested.

  15. Vibration of imperfect rotating disk

    Directory of Open Access Journals (Sweden)

    Půst L.

    2011-12-01

    Full Text Available This study is concerned with the theoretical and numerical calculations of the flexural vibrations of a bladed disk. The main focus of this study is to elaborate the basic background for diagnostic and identification methods for ascertaining the main properties of the real structure or an experimental model of turbine disks. The reduction of undesirable vibrations of blades is proposed by using damping heads, which on the experimental model of turbine disk are applied only on a limited number of blades. This partial setting of damping heads introduces imperfection in mass, stiffness and damping distribution on the periphery and leads to more complicated dynamic properties than those of a perfect disk. Calculation of FEM model and analytic—numerical solution of disk behaviour in the limited (two modes frequency range shows the splitting of resonance with an increasing speed of disk rotation. The spectrum of resonance is twice denser than that of a perfect disk.

  16. Dynamical response of vibrating ferromagnets

    CERN Document Server

    Gaganidze, E; Ziese, M

    2000-01-01

    The resonance frequency of vibrating ferromagnetic reeds in a homogeneous magnetic field can be substantially modified by intrinsic and extrinsic field-related contributions. Searching for the physical reasons of the field-induced resonance frequency change and to study the influence of the spin glass state on it, we have measured the low-temperature magnetoelastic behavior and the dynamical response of vibrating amorphous and polycrystalline ferromagnetic ribbons. We show that the magnetoelastic properties depend strongly on the direction of the applied magnetic field. The influence of the re-entrant spin glass transition on these properties is discussed. We present clear experimental evidence that for applied fields perpendicular to the main area of the samples the behavior of ferromagnetic reeds is rather independent of the material composition and magnetic state, exhibiting a large decrease of the resonance frequency. This effect can be very well explained with a model based on the dynamical response of t...

  17. Vibrational coupling in plasmonic molecules.

    Science.gov (United States)

    Yi, Chongyue; Dongare, Pratiksha D; Su, Man-Nung; Wang, Wenxiao; Chakraborty, Debadi; Wen, Fangfang; Chang, Wei-Shun; Sader, John E; Nordlander, Peter; Halas, Naomi J; Link, Stephan

    2017-10-31

    Plasmon hybridization theory, inspired by molecular orbital theory, has been extremely successful in describing the near-field coupling in clusters of plasmonic nanoparticles, also known as plasmonic molecules. However, the vibrational modes of plasmonic molecules have been virtually unexplored. By designing precisely configured plasmonic molecules of varying complexity and probing them at the individual plasmonic molecule level, intramolecular coupling of acoustic modes, mediated by the underlying substrate, is observed. The strength of this coupling can be manipulated through the configuration of the plasmonic molecules. Surprisingly, classical continuum elastic theory fails to account for the experimental trends, which are well described by a simple coupled oscillator picture that assumes the vibrational coupling is mediated by coherent phonons with low energies. These findings provide a route to the systematic optical control of the gigahertz response of metallic nanostructures, opening the door to new optomechanical device strategies. Published under the PNAS license.

  18. A night with good vibrations

    CERN Multimedia

    2002-01-01

    Next week-end, the Geneva Science History Museum invites you to a Science Night under the banner of waves and vibrations. Scientists, artists and storytellers from more than forty institutes and local or regional associations will show that waves and vibrations form an integral part of our environment. You will be able to get in contact with the nature of waves through interactive exhibitions on sound and light and through hands-on demonstrations arranged in the Park of the Perle du Lac. On the CERN stand, you will be able to measure the speed of light with a bar of chocolate, and understand the scattering of waves with plastic ducks. Amazing, no? In addition to the stands, the Night will offer many other activities: reconstructions of experiments, a play, a concert of crystal glasses, an illuminated fountain, a house of spirits. More information Science Night, 6 and 7 July, Park of the Perle du Lac, Geneva

  19. Vibration Control in Periodic Structures

    DEFF Research Database (Denmark)

    Høgsberg, Jan Becker

    2017-01-01

    Within the framework of periodic structures, the calibration of RL shunted piezoelectric inclusions is investigated with respect to maximum damping of a particular wave form. A finite element setting is assumed, with local shunted inclusions inside the unit cell. The effect of the shunts is repre....... The presentation contains dispersion diagrams and vibration amplitude curves for the optimally calibrated RL shunt system in a 1-D periodic structure with local piezoelectric inclusions....

  20. 2-Chloro- and 2-bromo-3-pyridinecarboxaldehydes: structures, rotamers, fermi resonance and vibration modes.

    Science.gov (United States)

    Yenagi, Jayashree; Shettar, Anita; Tonannavar, J

    2011-09-01

    FT-Infrared (4000-400 cm(-1)) and NIR-FT-Raman (4000-50 cm(-1)) spectral measurements have been made for 2-chloro- and 2-bromo-3-pyridinecarboxaldehydes. A DFT vibration analysis at B3LYP/6-311++G (d,p) level, valence force-fields and vibrational mode calculations have been performed. Aided by very good agreement between observed and computed vibration spectra, a complete assignment of fundamental vibration modes to the observed absorptions and Raman bands has been proposed. Orientations of the aldehydic group have produced two oblate asymmetric rotamers for each molecule, ON-trans and ON-cis: the ON-trans rotamer being more stable than cis by 3.42 kcal mol(-1) for 2-chloro-3-pyridinecarboxaldehyde and 3.68 kcal mol(-1) for 2-bromo-3-pyridinecarboxaldehyde. High potential energy barrier ca 14 kcal/mol, induced by steric hindrance, restricts rotamers' population to ON-trans only. It is observed that, in the presence of bromine, C-H stretching modes are pronounced; a missing characteristic ring mode in chlorine's presence shows at 1557 cm(-1); the characteristic ring mode at 1051 cm(-1) is diminished; a mixed mode near 707 cm(-1) is enhanced. Further, an observed doublet near 1696-1666 cm(-1) in both IR and Raman spectra is explained on the basis of Fermi resonance between aldehydic carbonyl stretching at 1696 cm(-1) and a combination mode of ring stretch near 1059 cm(-1) and deformation vibration, 625 cm(-1). A strong Raman aldehydic torsional mode at 62 cm(-1) is interpreted to correspond to the dominant ON-trans over cis rotamers population. Copyright © 2011 Elsevier B.V. All rights reserved.

  1. Package security recorder of vibration

    Science.gov (United States)

    Wang, Xiao-na; Hu, Jin-liang; Song, Shi-de

    2013-08-01

    This paper introduces a new kind of electronic product — Package Security Recorder of Vibration. It utilizes STC89C54RD+ LQFP-44 MCU as its main controller. At the same time, it also utilizes Freescale MMA845A 3-Axis 8-bit/12-bit Digital Accelerometer and Maxim DS1302 Trickle Charge Timekeeping Chip. It utilizes the MCU to read the value of the accelerometer and the value of the timekeeping chip, and records the data into the inner E2PROM of MCU. The whole device achieves measuring, reading and recording the time of the vibration and the intensity of the vibration. When we need the data, we can read them out. The data can be used in analyzing the condition of the cargo when it transported. The device can be applied to monitor the security of package. It solves the problem of responsibility affirming, when the valuable cargo are damaged while it transported. It offers powerful safeguard for the package. It's very value for application.

  2. RESEARCH OF THE HIGH HARMONICS INDIVIDUAL BLADE CONTROL EFFECT ON VIBRATIONS CAUSED BY THE HELICOPTER MAIN ROTOR THRUST

    Directory of Open Access Journals (Sweden)

    2016-01-01

    Full Text Available The paper presents numerical results analysis of main rotor vibration due to helicopter main rotor thrust pulsation.The calculation method, the object of research and numerical research results with the aim to reduce the amplitude of the vibrations transmitted to the hub from the helicopters main rotor by the individual blade control in azimuth by the installation angle of blades cyclic changes are set out in the article. The individual blades control law for a five-blade main rotor based on the blade frequencies is made. It allows reducing the vibration from thrust. Research takes into account the main rotor including and excluding the blade flapping motion. The minimal vibrations regime is identified.Numerical study of variable loads caused by unsteady flow around the main rotor blades at high relative speeds of flight, which transmitted to the rotor hub, is made. The scheme of a thin lifting surface and the rotor vortex theory are used for simulation of the aerodynamic loads on blades. Non - uniform loads caused by the thrust, decomposed on the blade harmonic and its overtones. The largest values of deviation from the mean amplitude thrust are received. The analysis of variable loads with a traditional control system is made. Algorithms of higher harmonics individual blade control capable of reducing the thrust pulsation under the average value of thrust are developed.Numerical research shows that individual blade control of high harmonics reduces variable loads. The necessary change in the blade installation is about ± 0,2 degree that corresponds to the maximum displacement of the additional con- trol stick is about 1 mm.To receive the overall picture is necessary to consider all six components of forces and moments. Control law with own constants will obtained for each of them. It is supposed, that each of six individual blade control laws have an impact on other components. Thus, the problem reduces to the optimization issue. The

  3. Actively controlled vibration welding system and method

    Science.gov (United States)

    Cai, Wayne W.; Kang, Bongsu; Tan, Chin-An

    2013-04-02

    A vibration welding system includes a controller, welding horn, an active material element, and anvil assembly. The assembly may include an anvil body connected to a back plate and support member. The element, e.g., a piezoelectric stack or shape memory alloy, is positioned with respect to the assembly. The horn vibrates in a desirable first direction to form a weld on a work piece. The element controls any vibrations in a second direction by applying calibrated response to the anvil body in the second direction. A method for controlling undesirable vibrations in the system includes positioning the element with respect to the anvil assembly, connecting the anvil body to the support member through the back plate, vibrating the horn in a desirable first direction, and transmitting an input signal to the element to control vibration in an undesirable second direction.

  4. Coupled rotor/airframe vibration analysis

    Science.gov (United States)

    Sopher, R.; Studwell, R. E.; Cassarino, S.; Kottapalli, S. B. R.

    1982-01-01

    A coupled rotor/airframe vibration analysis developed as a design tool for predicting helicopter vibrations and a research tool to quantify the effects of structural properties, aerodynamic interactions, and vibration reduction devices on vehicle vibration levels is described. The analysis consists of a base program utilizing an impedance matching technique to represent the coupled rotor/airframe dynamics of the system supported by inputs from several external programs supplying sophisticated rotor and airframe aerodynamic and structural dynamic representation. The theoretical background, computer program capabilities and limited correlation results are presented in this report. Correlation results using scale model wind tunnel results show that the analysis can adequately predict trends of vibration variations with airspeed and higher harmonic control effects. Predictions of absolute values of vibration levels were found to be very sensitive to modal characteristics and results were not representative of measured values.

  5. High force vibration testing with wide frequency range

    Science.gov (United States)

    Romero, Edward F.; Jepsen, Richard A.; Gregory, Danny Lynn

    2013-04-02

    A shaker assembly for vibration testing includes first and second shakers, where the first shaker includes a piezo-electric material for generating vibration. A support structure permits a test object to be supported for vibration of the test object by both shakers. An input permits an external vibration controller to control vibration of the shakers.

  6. Estimation of lower flammability limits of C-H compounds in air at atmospheric pressure, evaluation of temperature dependence and diluent effect.

    Science.gov (United States)

    Mendiburu, Andrés Z; de Carvalho, João A; Coronado, Christian R

    2015-03-21

    Estimation of the lower flammability limits of C-H compounds at 25 °C and 1 atm; at moderate temperatures and in presence of diluent was the objective of this study. A set of 120 C-H compounds was divided into a correlation set and a prediction set of 60 compounds each. The absolute average relative error for the total set was 7.89%; for the correlation set, it was 6.09%; and for the prediction set it was 9.68%. However, it was shown that by considering different sources of experimental data the values were reduced to 6.5% for the prediction set and to 6.29% for the total set. The method showed consistency with Le Chatelier's law for binary mixtures of C-H compounds. When tested for a temperature range from 5 °C to 100 °C, the absolute average relative errors were 2.41% for methane; 4.78% for propane; 0.29% for iso-butane and 3.86% for propylene. When nitrogen was added, the absolute average relative errors were 2.48% for methane; 5.13% for propane; 0.11% for iso-butane and 0.15% for propylene. When carbon dioxide was added, the absolute relative errors were 1.80% for methane; 5.38% for propane; 0.86% for iso-butane and 1.06% for propylene. Copyright © 2014 Elsevier B.V. All rights reserved.

  7. Experimental Research on Vibration Fatigue of CFRP and Its Influence Factors Based on Vibration Testing

    OpenAIRE

    Fan, Zhengwei; Jiang, Yu; Zhang, Shufeng; Chen, Xun

    2017-01-01

    A new research method based on vibration testing for the vibration fatigue of FRP was proposed in this paper. Through the testing on a closed-loop controlled vibration fatigue test system, the vibration fatigue phenomenon of typical carbon-fiber-reinforced plastic (CFRP) cantilevered laminate specimens was carefully studied. Moreover, a method based on the frequency response function was proposed to monitor the fatigue damage accumulation of specimens. On the basis of that, the influence fact...

  8. Vibrational dynamics of crystalline L-alanine

    Energy Technology Data Exchange (ETDEWEB)

    Bordallo, H.N.; Eckert, J. [Los Alamos National Lab., NM (United States); Barthes, M. [Univ. Montpellier II (France)

    1997-11-01

    The authors report a new, complete vibrational analysis of L-alanine and L-alanine-d{sub 4} which utilizes IINS intensities in addition to frequency information. The use of both isotopomers resulted in a self-consistent force field for and assignment of the molecular vibrations in L-alanine. Some details of the calculation as well as a comparison of calculated and observed IINS spectra are presented. The study clarifies a number of important issues on the vibrational dynamics of this molecule and presents a self-consistent force field for the molecular vibrations in crystalline L-alanine.

  9. Analysis of potential helicopter vibration reduction concepts

    Science.gov (United States)

    Landgrebe, A. J.; Davis, M. W.

    1985-01-01

    Results of analytical investigations to develop, understand, and evaluate potential helicopter vibration reduction concepts are presented in the following areas: identification of the fundamental sources of vibratory loads, blade design for low vibration, application of design optimization techniques, active higher harmonic control, blade appended aeromechanical devices, and the prediction of vibratory airloads. Primary sources of vibration are identified for a selected four-bladed articulated rotor operating in high speed level flight. The application of analytical design procedures and optimization techniques are shown to have the potential for establishing reduced vibration blade designs through variations in blade mass and stiffness distributions, and chordwise center-of-gravity location.

  10. Ruthenium(II)-catalyzed synthesis of pyrrole- and indole-fused isocoumarins by C-H bond activation in DMF and water

    Digital Repository Service at National Institute of Oceanography (India)

    Singh, K.S.; Sawant, S.G.; Dixneuf, P.H.

    stream_size 26907 stream_content_type text/plain stream_name ChemCatChem_8_1046a.pdf.txt stream_source_info ChemCatChem_8_1046a.pdf.txt Content-Encoding UTF-8 Content-Type text/plain; charset=UTF-8 Author version...: ChemCatChem, vol.8(6); 2016; 1046-1050 Ruthenium(II) catalysed synthesis of pyrrole and indole fused isocoumarins via C-H bond activation in DMF and water† Keisham S. Singh*,a Sneha G. Sawanta, Pierre H. Dixneuf*,b Abstract: Pyrrole and indole...

  11. Determination of Fatty Acid, C, H, N and Trace Element Composition in Grape Seed by GC/MS, FTIR, Elemental Analyzer and ICP/OES

    OpenAIRE

    Seçilmiş Canbay, Hale; Bardakçı, Belgin

    2011-01-01

    Abstract: Four different methods were used for the investigation of fatty acid, C, H, N and trace element composition of grape seed oil and pulp. The fatty acid profile of the grape seed oil was measured by GC/MS. Moreover, structural analysis of the oil was carried out by FT/IR spectrometry with a Zn Se ATR accessory. The quantification of selected metals Na, K, Mg, Ca, Mn, Fe, Zn and Cu in grape seed oil and pulp was carried out using microwave assisted digestion followed by ICP/OES. Grape ...

  12. Interplay of Electronic Cooperativity and Exchange Coupling in Regulating the Reactivity of Diiron(IV)-oxo Complexes towards C-H and O-H Bond Activation.

    Science.gov (United States)

    Ansari, Azaj; Ansari, Mursaleem; Singha, Asmita; Rajaraman, Gopalan

    2017-07-26

    Activation of inert C-H bonds such as those of methane are extremely challenging for chemists but in nature, the soluble methane monooxygenase (sMMO) enzyme readily oxidizes methane to methanol by using a diiron(IV) species. This has prompted chemists to look for similar model systems. Recently, a (μ-oxo)bis(μ-carboxamido)diiron(IV) ([Fe(IV)2 O(L)2 ](2+) L=N,N-bis-(3',5'-dimethyl-4'-methoxypyridyl-2'-methyl)-N'-acetyl-1,2-diaminoethane) complex has been generated by bulk electrolysis and this species activates inert C-H bonds almost 1000 times faster than mononuclear Fe(IV) =O species and at the same time selectively activates O-H bonds of alcohols. The very high reactivity and selectivity of this species is puzzling and herein we use extensive DFT calculations to shed light on this aspect. We have studied the electronic and spectral features of diiron {Fe(III) -μ(O)-Fe(III) }(+2) (complex I), {Fe(III) -μ(O)-Fe(IV) }(+3) (II), and {Fe(IV) -μ(O)-Fe(IV) }(+4) (III) complexes. Strong antiferromagnetic coupling between the Fe centers leads to spin-coupled S=0, S=3/2, and S=0 ground state for species I-III respectively. The mechanistic study of the C-H and O-H bond activation reveals a multistate reactivity scenario where C-H bond activation is found to occur through the S=4 spin-coupled state corresponding to the high-spin state of individual Fe(IV) centers. The O-H bond activation on the other hand, occurs through the S=2 spin-coupled state corresponding to an intermediate state of individual Fe(IV) centers. Molecular orbital analysis reveals σ-π/π-π channels for the reactivity. The nature of the magnetic exchange interaction is found to be switched during the course of the reaction and this offers lower energy pathways. Significant electronic cooperativity between two metal centers during the course of the reaction has been witnessed and this uncovers the reason behind the efficiency and selectivity observed. The catalyst is found to prudently choose the

  13. Polycyclization Enabled by Relay Catalysis: One-Pot Manganese-Catalyzed C-H Allylation and Silver-Catalyzed Povarov Reaction.

    Science.gov (United States)

    Chen, Shi-Yong; Li, Qingjiang; Liu, Xu-Ge; Wu, Jia-Qiang; Zhang, Shang-Shi; Wang, Honggen

    2017-06-09

    In this study, a Mn I /Ag I -based relay catalysis process is described for the one-pot synthesis of polycyclic products by a formal [3+2] and [4+2] cycloaddition reaction cascade. A manganese(I) complex catalyzed the first example of directed C-H allylation with allenes, setting the stage for an in situ Povarov cyclization catalyzed by silver(I). The reaction proceeds with high bond-forming efficiency (three C-C bonds), broad substrate scope, high regio- and stereoselectivity, and 100 % atom economy. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Copper-catalyzed direct C-H arylation of pyridine N-oxides with arylboronic esters: one-pot synthesis of 2-arylpyridines.

    Science.gov (United States)

    Shen, Yan; Chen, Jiuxi; Liu, Miaochang; Ding, Jinchang; Gao, Wenxia; Huang, Xiaobo; Wu, Huayue

    2014-04-28

    The first example of the copper-catalyzed direct C-H arylation of pyridine N-oxides with arylboronic esters has been developed, leading to a wide range of 2-arylpyridines in a one-pot synthesis with moderate to good yields without an additional reductant. This transformation allows for rapid access to a variety of 2-arylpyridines using an inexpensive catalytic system that would be more difficult to access with traditional methods. Thus, this method represents a simple and practical procedure to access 2-arylpyridines.

  15. Palladium-Catalyzed Direct C-H Arylations of Dioxythiophenes Bearing Reactive Functional Groups: A Step-Economical Approach for Functional π-Conjugated Oligoarenes

    KAUST Repository

    Liu, Ching-Yuan

    2015-06-25

    A Pd-catalyzed and single-step C-H arylation of dioxythiophene derivates bearing unprotected reactive functional groups (-OH, -COOH, -N3) in a phosphine-free manner has been developed. Various dioxythiopene-based oligoarenes with extended π-conjugation are obtained with good yields (up to 90%). These oligoarenes display suitable optical properties (absorption and emission maxima, quantum yields) and contain reactive functional groups suitable for further conjugations with bioactive molecules. This new methodology is step economical (fewer synthetic steps), environmental friendly (no toxic metal-containing side-poducts) and the oligoarenes synthesized are potentially applicable for bio-labeling, bioimaging, and biosensing.

  16. Why metal-oxos react with dihydroanthracene and cyclohexadiene at comparable rates, despite having different C-H bond strengths. A computational study.

    Science.gov (United States)

    Klein, Johannes E M N; Dereli, Büsra; Que, Lawrence; Cramer, Christopher J

    2016-08-18

    1,4-Cyclohexadiene (CHD) and 9,10-dihydroanthracene (DHA) are two substrates used to probe the steric requirements of metal-oxo oxidants in H-atom-transfer (HAT) reactions, based on the assumption that they have comparable C-H bond dissociation enthalpies (BDEs). We use computations to demonstrate that the BDE of DHA is ∼3.5 kcal mol(-1) larger than that of CHD and that their often comparable reactivity is based on a competing interplay of bond strengths and favorable van der Waals interactions.

  17. Annulation of Alkynyl Aryl Ethers with Allyl Pivalates To Give 2,3-Bismethylenechromanes through Double C-H Bond Cleavage.

    Science.gov (United States)

    Minami, Yasunori; Sakai, Megumi; Anami, Tomohiro; Hiyama, Tamejiro

    2016-07-18

    The treatment of silylethynyloxyarenes with allylic pivalates in the presence of a palladium catalyst led to efficient C-H bond cleavage in both substrates and a novel annulation reaction to give 2,3-bismethylenechromanes. When ortho-allylated silylethynyloxybenzenes were used as the substrates, the same products were obtained. This result shows that site-selective intramolecular hydrovinylation is involved in the annulation reaction. The synthetic utility of the products was demonstrated by the construction of condensed polycycles. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Heteroarene-Directed Oxidative sp(2) C-H Bond Allylation with Aliphatic Alkenes Catalyzed by an (Electron-Deficient η(5)-Cyclopentadienyl)rhodium(III) Complex.

    Science.gov (United States)

    Takahama, Yuji; Shibata, Yu; Tanaka, Ken

    2016-06-17

    It has been established that the oxidative sp(2) C-H bond allylation with aliphatic alkenes proceeds under mild conditions by using heteroarenes as directing groups and an (electron-deficient η(5)-cyclopentadienyl)rhodium(III) complex, [Cp(E)RhCl2]2, as a precatalyst. In sharp contrast, the use of [Cp*RhCl2]2 instead of [Cp(E)RhCl2]2 led to a complex mixture of products under the same reaction conditions.

  19. Mechanochemical Iridium(III)-Catalyzed C-H Bond Amidation of Benzamides with Sulfonyl Azides under Solvent-Free Conditions in a Ball Mill.

    Science.gov (United States)

    Hermann, Gary N; Becker, Peter; Bolm, Carsten

    2016-03-07

    Mechanochemical conditions have been applied to an iridium(III)-catalyzed C-H bond amidation process for the first time. In the absence of solvent, the mechanochemical activation enables the formation of an iridium species that catalyzes the ortho-selective amidation of benzamides with sulfonyl azides as the nitrogen source. As the reaction proceeds in the absence of organic solvents without external heating and yields the desired products in excellent yields within short reaction times, this method constitutes a powerful, fast, and environmentally benign alternative to the common solvent-based standard approaches. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Vibration fatigue using modal decomposition

    Science.gov (United States)

    Mršnik, Matjaž; Slavič, Janko; Boltežar, Miha

    2018-01-01

    Vibration-fatigue analysis deals with the material fatigue of flexible structures operating close to natural frequencies. Based on the uniaxial stress response, calculated in the frequency domain, the high-cycle fatigue model using the S-N curve material data and the Palmgren-Miner hypothesis of damage accumulation is applied. The multiaxial criterion is used to obtain the equivalent uniaxial stress response followed by the spectral moment approach to the cycle-amplitude probability density estimation. The vibration-fatigue analysis relates the fatigue analysis in the frequency domain to the structural dynamics. However, once the stress response within a node is obtained, the physical model of the structure dictating that response is discarded and does not propagate through the fatigue-analysis procedure. The structural model can be used to evaluate how specific dynamic properties (e.g., damping, modal shapes) affect the damage intensity. A new approach based on modal decomposition is presented in this research that directly links the fatigue-damage intensity with the dynamic properties of the system. It thus offers a valuable insight into how different modes of vibration contribute to the total damage to the material. A numerical study was performed showing good agreement between results obtained using the newly presented approach with those obtained using the classical method, especially with regards to the distribution of damage intensity and critical point location. The presented approach also offers orders of magnitude faster calculation in comparison with the conventional procedure. Furthermore, it can be applied in a straightforward way to strain experimental modal analysis results, taking advantage of experimentally measured strains.