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Sample records for catalytic c-h bond

  1. Catalytic C-H bond functionalisation chemistry: the case for quasi-heterogeneous catalysis.

    Science.gov (United States)

    Reay, Alan J; Fairlamb, Ian J S

    2015-11-25

    This feature article examines the potential of heterogeneous Pd species to mediate catalytic C-H bond functionalisation processes employing suitable substrates (e.g. aromatic/heteroaromatic compounds). A focus is placed on the reactivity of supported and non-supported Pd nanoparticle (PdNPs) catalysts, in addition to the re-appropriation of well-established heterogeneous Pd catalysts such as Pd/C. Where possible, reasonable comparisons are made between PdNPs and traditional 'homogeneous' Pd precatalyst sources (which form PdNPs). The involvement of higher order Pd species in traditional cross-coupling processes, such as Mizoroki-Heck, Sonogashira and Suzuki-Miyaura reactions, allows the exemplification of potential future topics for study in the area of catalytic C-H bond functionalisation processes. PMID:26439875

  2. Catalytic C-H bond stannylation: a new regioselective pathway to C-Sn bonds via C-H bond functionalization.

    Science.gov (United States)

    Doster, Meghan E; Hatnean, Jillian A; Jeftic, Tamara; Modi, Sunjay; Johnson, Samuel A

    2010-09-01

    The ubiquitous Stille coupling reaction utilizes Sn-C bonds and is of great utility to organic chemists. Unlike the B-C bonds used in the Miyaura-Suzuki coupling reaction, which are readily obtained via direct borylation of C-H bonds, routes to organotin compounds via direct C-H bond functionalization are lacking. Here we report that the nickel-catalyzed reaction of fluorinated arenes and pyridines with vinyl stannanes does not provide the expected vinyl compounds via C-F activation but rather provides new Sn-C bonds via C-H functionalization with the loss of ethylene. This mechanism provides a new unanticipated methodology for the direct conversion of C-H bonds to carbon-heteroatom bonds. PMID:20690675

  3. Catalytic C-H bond addition of pyridines to allenes by a rare-Earth catalyst.

    Science.gov (United States)

    Song, Guoyong; Wang, Baoli; Nishiura, Masayoshi; Hou, Zhaomin

    2015-06-01

    The catalytic C-H addition of pyridines to allenes has been achieved for the first time by using a half-sandwich scandium catalyst, thus constituting a straightforward and atom-economical route for the synthesis of alkenylated pyridine derivatives. The reaction proceeded regio- and stereoselectively, affording a new family of alkenylated pyridine compounds which are otherwise difficult to synthesize. A cationic Sc-η(2) -pyridyl species was isolated and confirmed to be a key catalyst species in this transformation. PMID:25899713

  4. C-H bond activation by f-block complexes.

    Science.gov (United States)

    Arnold, Polly L; McMullon, Max W; Rieb, Julia; Kühn, Fritz E

    2015-01-01

    Most homogeneous catalysis relies on the design of metal complexes to trap and convert substrates or small molecules to value-added products. Organometallic lanthanide compounds first gave a tantalizing glimpse of their potential for catalytic C-H bond transformations with the selective cleavage of one C-H bond in methane by bis(permethylcyclopentadienyl)lanthanide methyl [(η(5) -C5 Me5 )2 Ln(CH3 )] complexes some 25 years ago. Since then, numerous metal complexes from across the periodic table have been shown to selectively activate hydrocarbon C-H bonds, but the challenges of closing catalytic cycles still remain; many f-block complexes show great potential in this important area of chemistry. PMID:25384554

  5. Bipodal surface organometallic complexes with surface N-donor ligands and application to the catalytic cleavage of C-H and C-C bonds in n -Butane

    KAUST Repository

    Bendjeriou-Sedjerari, Anissa

    2013-11-27

    We present a new generation of "true vicinal" functions well-distributed on the inner surface of SBA15: [(Sî - Si-NH 2)(≡Si-OH)] (1) and [(≡Si-NH2)2] (2). From these amine-modified SBA15s, two new well-defined surface organometallic species [(≡Si-NH-)(≡Si-O-)]Zr(CH2tBu) 2 (3) and [(≡Si-NH-)2]Zr(CH2tBu) 2 (4) have been obtained by reaction with Zr(CH2tBu) 4. The surfaces were characterized with 2D multiple-quantum 1H-1H NMR and infrared spectroscopies. Energy-filtered transmission electron microscopy (EFTEM), mass balance, and elemental analysis unambiguously proved that Zr(CH2tBu)4 reacts with these vicinal amine-modified surfaces to give mainly bipodal bis(neopentyl)zirconium complexes (3) and (4), uniformly distributed in the channels of SBA15. (3) and (4) react with hydrogen to give the homologous hydrides (5) and (6). Hydrogenolysis of n-butane catalyzed by these hydrides was carried out at low temperature (100 C) and low pressure (1 atm). While (6) exhibits a bis(silylamido)zirconium bishydride, [(≡Si-NH-)2]Zr(H) 2 (6a) (60%), and a bis(silylamido)silyloxozirconium monohydride, [(≡Si-NH-)2(≡Si-O-)]ZrH (6b) (40%), (5) displays a new surface organometallic complex characterized by an 1H NMR signal at 14.46 ppm. The latter is assigned to a (silylimido)(silyloxo)zirconium monohydride, [(≡Si-Nî)(≡Si-O-)]ZrH (5b) (30%), coexistent with a (silylamido)(silyloxo)zirconium bishydride, [(≡Si-NH-)(≡Si-O-)] Zr(H)2 (5a) (45%), and a silylamidobis(silyloxo)zirconium monohydride, [(≡Si-NH-)(≡Si-O-)2]ZrH (5c) (25%). Surprisingly, nitrogen surface ligands possess catalytic properties already encountered with silicon oxide surfaces, but interestingly, catalyst (5) with chelating [N,O] shows better activity than (6) with chelating [N,N]. © 2013 American Chemical Society.

  6. 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. PMID:26959863

  7. Evidence for 5-Center 4-Electron Bonding in (C...H...C...H...C) Array

    Czech Academy of Sciences Publication Activity Database

    Ponec, Robert; Juzakov, Gleb

    2003-01-01

    Roč. 68, č. 21 (2003), s. 8284-8286. ISSN 0022-3263 R&D Projects: GA AV ČR IAA4072006 Institutional research plan: CEZ:AV0Z4072921 Keywords : multicenter bonding * generalized population analysis * multicenter bond indices Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 3.297, year: 2003

  8. 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.

  9. Trifluoromethylallylation of Heterocyclic C-H Bonds with Allylic Carbonates under Rhodium Catalysis.

    Science.gov (United States)

    Choi, Miji; Park, Jihye; Sharma, Satyasheel; Jo, Hyeim; Han, Sangil; Jeon, Mijin; Mishra, Neeraj Kumar; Han, Sang Hoon; Lee, Jong Suk; Kim, In Su

    2016-06-01

    The rhodium(III)-catalyzed γ-trifluoromethylallylation of various heterocyclic C-H bonds with CF3-substituted allylic carbonates is described. These reactions provide direct access to linear CF3-containing allyl frameworks with complete trans-selectivity via C-H bond activation followed by a formal SN-type reaction pathway. PMID:27187625

  10. 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

    2016-03-01

    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. PMID:26853936

  11. C-H bond halogenation catalyzed or mediated by copper: an overview.

    Science.gov (United States)

    Hao, Wenyan; Liu, Yunyun

    2015-01-01

    Carbon-halogen (C-X) bonds are amongst the most fundamental groups in organic synthesis, they are frequently and widely employed in the synthesis of numerous organic products. The generation of a C-X bond, therefore, constitutes an issue of universal interest. Herein, the research advances on the copper-catalyzed and mediated C-X (X = F, Cl, Br, I) bond formation via direct C-H bond transformation is reviewed. PMID:26664634

  12. Non-specificity of C-H bond rupture by γ radiolysis of 3-methylpentane glass

    International Nuclear Information System (INIS)

    Some authors using esr data claimed that there is a high selectivity for the rupture of a particular C-H bond after the radiolysis of solid branched alkanes. Using the identification of dimer isomers and very low total dose, we have established the identity of the trapped radical produced at 77 K by the radiolysis of 3-methylpentane, all the parent radicals are formed. If there is a different probability of breaking a particular C-H bond, the bond rupture is not much less selective in liquid than in the glassy state

  13. 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. PMID:27002210

  14. 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

  15. 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

  16. 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}.

  17. 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. PMID:27088815

  18. 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.

  19. Site-selective and stereoselective functionalization of unactivated C-H bonds.

    Science.gov (United States)

    Liao, Kuangbiao; Negretti, Solymar; Musaev, Djamaladdin G; Bacsa, John; Davies, Huw M L

    2016-05-12

    The laboratory synthesis of complex organic molecules relies heavily on the introduction and manipulation of functional groups, such as carbon-oxygen or carbon-halogen bonds; carbon-hydrogen bonds are far less reactive and harder to functionalize selectively. The idea of C-H functionalization, in which C-H bonds are modified at will instead of the functional groups, represents a paradigm shift in the standard logic of organic synthesis. For this approach to be generally useful, effective strategies for site-selective C-H functionalization need to be developed. The most practical solutions to the site-selectivity problem rely on either intramolecular reactions or the use of directing groups within the substrate. A challenging, but potentially more flexible approach, would be to use catalyst control to determine which site in a particular substrate would be functionalized. Here we describe the use of dirhodium catalysts to achieve highly site-selective, diastereoselective and enantioselective C-H functionalization of n-alkanes and terminally substituted n-alkyl compounds. The reactions proceed in high yield, and functional groups such as halides, silanes and esters are compatible with this chemistry. These studies demonstrate that high site selectivity is possible in C-H functionalization reactions without the need for a directing or anchoring group present in the molecule. PMID:27172046

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

    Energy Technology Data Exchange (ETDEWEB)

    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 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.

  1. 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

    2016-03-01

    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. PMID:26686276

  2. 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

  3. 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.

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

    Science.gov (United States)

    Jašíková, Lucie; Hanikýřová, Eva; Schröder, Detlef; Roithová, Jana

    2012-04-01

    Metal-oxide cations are models of catalyst mediating the C-H bond activation of organic substrates. One of the most powerful reagents suggested in the gas phase is based on CuO(+) . Here, we describe the activation of the aromatic C-H bonds of phenanthroline in its complex with CuO(+) . The reaction sequence starts with a hydrogen atom abstraction by the oxygen atom from the 2-position of the phenanthroline ring, followed by OH migration to the ring. Using infrared multiphoton spectroscopy, it is shown that the reaction can be energetically facilitated by additional coordination of a water ligand to the copper ion. As the reaction is intramolecular, a spectroscopic characterization of the product is mandatory in order to unambiguously address the reaction mechanism. PMID:22689621

  5. Activation of C-H and B-H bonds through agostic bonding: an ELF/QTAIM insight.

    Science.gov (United States)

    Zins, Emilie-Laure; Silvi, Bernard; Alikhani, M Esmaïl

    2015-04-14

    Agostic bonding is of paramount importance in C-H bond activation processes. The reactivity of the σ C-H bond thus activated will depend on the nature of the metallic center, the nature of the ligand involved in the interaction and co-ligands, as well as on geometric parameters. Because of their importance in organometallic chemistry, a qualitative classification of agostic bonding could be very much helpful. Herein we propose descriptors of the agostic character of bonding based on the electron localization function (ELF) and Quantum Theory of Atoms in Molecules (QTAIM) topological analysis. A set of 31 metallic complexes taken, or derived, from the literature was chosen to illustrate our methodology. First, some criteria should prove that an interaction between a metallic center and a σ X-H bond can indeed be described as "agostic" bonding. Then, the contribution of the metallic center in the protonated agostic basin, in the ELF topological description, may be used to evaluate the agostic character of bonding. A σ X-H bond is in agostic interaction with a metal center when the protonated X-H basin is a trisynaptic basin with a metal contribution strictly larger than the numerical uncertainty, i.e. 0.01 e. In addition, it was shown that the weakening of the electron density at the X-Hagostic bond critical point with respect to that of X-Hfree well correlates with the lengthening of the agostic X-H bond distance as well as with the shift of the vibrational frequency associated with the νX-H stretching mode. Furthermore, the use of a normalized parameter that takes into account the total population of the protonated basin, allows the comparison of the agostic character of bonding involved in different complexes. PMID:25760795

  6. Recent advances in copper-catalyzed C-H bond amidation.

    Science.gov (United States)

    Wan, Jie-Ping; Jing, Yanfeng

    2015-01-01

    Copper catalysis has been known as a powerful tool for its ubiquitous application in organic synthesis. One of the fundamental utilities of copper catalysis is in the C-N bond formation by using carbon sources and nitrogen functional groups such as amides. In this review, the recent progress in the amidation reactions employing copper-catalyzed C-H amidation is summarized. PMID:26664644

  7. Titanium-Thiolate-Aluminum-Carbide Complexes by Multiple C-H Bond Activation.

    Science.gov (United States)

    Guérin; Stephan

    1999-12-16

    All three C-H bonds of a methyl group are activated in the reaction of [Cp(iPr(3)PN)Ti(SR)(2)] with AlMe(3) [Eq. (1)]. The Ti-Al-carbide clusters formed contain a severely distorted tetrahedral carbide carbon atom with a relatively short bond to Ti, which is attributed to a relative increase in the Lewis acidity of the Ti center as a result of the interaction of the S and N donors with Al. PMID:10649329

  8. Direct Oxidation of Aliphatic C-H Bonds in Amino-Containing Molecules under Transition-Metal-Free Conditions.

    Science.gov (United States)

    Li, Xin; Che, Xing; Chen, Gui-Hua; Zhang, Jun; Yan, Jia-Lei; Zhang, Yun-Fei; Zhang, Li-Sheng; Hsu, Chao-Ping; Gao, Yi Qin; Shi, Zhang-Jie

    2016-03-18

    By employing a simple, inexpensive, and transition-metal-free oxidation system, secondary C-H bonds in a series of phthaloyl protected primary amines and amino acid derivatives were oxidized to carbonyls with good regioselectivities. This method could also be applied to oxidize tertiary C-H bonds and modify synthetic dipeptides. PMID:26949833

  9. A Metallacycle Fragmentation Strategy for Vinyl Transfer from Enol Carboxylates to Secondary Alcohol C-H Bonds via Osmium- or Ruthenium-Catalyzed Transfer Hydrogenation.

    Science.gov (United States)

    Park, Boyoung Y; Luong, Tom; Sato, Hiroki; Krische, Michael J

    2015-06-24

    A strategy for catalytic vinyl transfer from enol carboxylates to activated secondary alcohol C-H bonds is described. Using XPhos-modified ruthenium(0) or osmium(0) complexes, enol carboxylate-carbonyl oxidative coupling forms transient β-acyloxy-oxametallacycles, which eliminate carboxylate to deliver allylic ruthenium(II) or osmium(II) alkoxides. Reduction of the metal(II) salt via hydrogen transfer from the secondary alcohol reactant releases the product of carbinol C-H vinylation and regenerates ketone and zero-valent catalyst. PMID:26066660

  10. A direct experimental evidence for an aromatic C-H⋯O hydrogen bond by fluorescence-detected infrared spectroscopy

    Science.gov (United States)

    Venkatesan, V.; Fujii, A.; Ebata, T.; Mikami, N.

    2004-08-01

    Formation of a weak aromatic C-H⋯O hydrogen bond has been discerned both experimentally and computationally in the 1,2,4,5-tetrafluorobenzene (TFB)-water system. The intermolecular structure of the isolated TFB-water cluster in a supersonic jet was characterized using fluorescence-detected infrared spectroscopy. The formation of a weak hydrogen bond in the cluster was directly evidenced by a low-frequency shift and intensity enhancement of the hydrogen-bonded aromatic C-H stretch in the TFB moiety. This is the first direct observation of an aromatic C-H⋯O hydrogen bond in isolated gas phase clusters.

  11. 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.

  12. 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).

  13. Inserting CO2 into Aryl C-H Bonds of Metal-Organic Frameworks: CO2 Utilization for Direct Heterogeneous C-H Activation.

    Science.gov (United States)

    Gao, Wen-Yang; Wu, Haifan; Leng, Kunyue; Sun, Yinyong; Ma, Shengqian

    2016-04-25

    Described for the first time is that carbon dioxide (CO2 ) can be successfully inserted into aryl C-H bonds of the backbone of a metal-organic framework (MOF) to generate free carboxylate groups, which serve as Brønsted acid sites for efficiently catalyzing the methanolysis of epoxides. The work delineates the very first example of utilizing CO2 for heterogeneous C-H activation and carboxylation reactions on MOFs, and opens a new avenue for CO2 chemical transformations under mild reaction conditions. PMID:27080057

  14. 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.

  15. 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.

  16. Insertion of singlet chlorocarbenes across C-H bonds in alkanes: Evidence for two phase mechanism

    Indian Academy of Sciences (India)

    M Ramalingam; K Ramasami; P Venuvanalingam

    2007-09-01

    Transition states for the insertion reactions of singlet mono and dichlorocarbenes (1CHCl and 1CCl2) into C-H bonds of alkanes (methane, ethane, propane and -butane) have been investigated at MP2 and DFT levels with 6-31g ( , ) basis set. The of 1CHCl and 1CCl2 may interact with alkane’s filled fragment orbital of either or symmetry. So chlorocarbenes insertion reactions have been investigated for both (/) approaches. The approach has been adjudicated to be the minimum energy path over the approach both at the MP2 and DFT levels. Mulliken, NPA and ESP derived charge analyses have been carried out along the minimal energy reaction path using the IRC method for 1CHCl and 1CCl2 insertions into the primary and secondary C-H bonds of propane. The occurrence of TSs either in the electrophilic or nucleophilic phase has been identified through NBO charge analyses in addition to the net charge flow from alkane to the carbene moiety.

  17. 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

    2015-11-01

    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) 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. PMID

  18. Enzymatic hydroxylation of an unactivated methylene C-H bond guided by molecular dynamics simulations

    Science.gov (United States)

    Narayan, Alison R. H.; Jiménez-Osés, Gonzalo; Liu, Peng; Negretti, Solymar; Zhao, Wanxiang; Gilbert, Michael M.; Ramabhadran, Raghunath O.; Yang, Yun-Fang; Furan, Lawrence R.; Li, Zhe; Podust, Larissa M.; Montgomery, John; Houk, K. N.; Sherman, David H.

    2015-08-01

    The hallmark of enzymes from secondary metabolic pathways is the pairing of powerful reactivity with exquisite site selectivity. The application of these biocatalytic tools in organic synthesis, however, remains under-utilized due to limitations in substrate scope and scalability. Here, we report how the reactivity of a monooxygenase (PikC) from the pikromycin pathway is modified through computationally guided protein and substrate engineering, and applied to the oxidation of unactivated methylene C-H bonds. Molecular dynamics and quantum mechanical calculations were used to develop a predictive model for substrate scope, site selectivity and stereoselectivity of PikC-mediated C-H oxidation. A suite of menthol derivatives was screened computationally and evaluated through in vitro reactions, where each substrate adhered to the predicted models for selectivity and conversion to product. This platform was also expanded beyond menthol-based substrates to the selective hydroxylation of a variety of substrate cores ranging from cyclic to fused bicyclic and bridged bicyclic compounds.

  19. Synthesis of Indole-2-carboxylate Derivatives via Palladium-Catalyzed Aerobic Amination of Aryl C-H Bonds.

    Science.gov (United States)

    Clagg, Kyle; Hou, Haiyun; Weinstein, Adam B; Russell, David; Stahl, Shannon S; Koenig, Stefan G

    2016-08-01

    A direct oxidative C-H amination affording 1-acetyl indolecarboxylates starting from 2-acetamido-3-arylacrylates has been achieved. Indole-2-carboxylates can be targeted with a straightforward deacetylation of the initial reaction products. The C-H amination reaction is carried out using a catalytic Pd(II) source with oxygen as the terminal oxidant. The scope and application of this chemistry is demonstrated with good to high yields for numerous electron-rich and electron-poor substrates. Further reaction of selected products via Suzuki arylation and deacetylation provides access to highly functionalized indole structures. PMID:27404018

  20. Photocatalytic benzylic C-H bond oxidation with a flavin scandium complex.

    Science.gov (United States)

    Mühldorf, Bernd; Wolf, Robert

    2015-05-18

    The enhanced reduction potential of riboflavin tetraacetate coordinating to scandium triflate enables the challenging photocatalytic C-H oxidation of electron-deficient alkylbenzenes and benzyl alcohols. PMID:25647055

  1. Intramolecular C-H Bond Activation through a Flexible Ester Linkage

    Czech Academy of Sciences Publication Activity Database

    Shaffer, Christopher; Schröder, Detlef; Gutz, Ch.; Lutzen, A.

    2012-01-01

    Roč. 51, č. 32 (2012), s. 8097-8100. ISSN 1433-7851 Grant ostatní: European Research Council(XE) AdG HORIZOMS Institutional support: RVO:61388963 Keywords : C-H activation * copper * gas phase * ion mobility * oxidation Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 13.734, year: 2012

  2. 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 ostatní: 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

  3. Lactamization of sp(2) C-H Bonds with CO2 : Transition-Metal-Free and Redox-Neutral.

    Science.gov (United States)

    Zhang, Zhen; Liao, Li-Li; Yan, Si-Shun; Wang, Lei; He, Yun-Qi; Ye, Jian-Heng; Li, Jing; Zhi, Yong-Gang; Yu, Da-Gang

    2016-06-13

    The first direct use of carbon dioxide in the lactamization of alkenyl and heteroaryl C-H bonds to synthesize important 2-quinolinones and polyheterocycles in moderate to excellent yields is reported. Carbon dioxide, a nontoxic, inexpensive, and readily available greenhouse gas, acts as an ideal carbonyl source. Importantly, this transition-metal-free and redox-neutral process is eco-friendly and desirable for the pharmaceutical industry. Moreover, these reactions feature a broad substrate scope, good functional group tolerance, facile scalability, and easy product derivatization. PMID:27095584

  4. Enantioselective Intramolecular Hydroarylation of Alkenes via Directed C-H Bond Activation

    Energy Technology Data Exchange (ETDEWEB)

    Harada, Hitoshi; Thalji, Reema; Bergman, Robert; Ellman, Jonathan

    2008-05-22

    Highly enantioselective catalytic intramolecular ortho-alkylation of aromatic imines containing alkenyl groups tethered at the meta position relative to the imine directing group has been achieved using [RhCl(coe){sub 2}]{sub 2} and chiral phosphoramidite ligands. Cyclization of substrates containing 1,1- and 1,2-disubstituted as well as trisubstituted alkenes were achieved with enantioselectivities >90% ee for each substrate class. Cyclization of substrates with Z-alkene isomers proceeded much more efficiently than substrates with E-alkene isomers. This further enabled the highly stereoselective intramolecular alkylation of certain substrates containing Z/E-alkene mixtures via a Rh-catalyzed alkene isomerization with preferential cyclization of the Z-isomer.

  5. Palladium Catalyzed Allylic C-H Alkylation

    DEFF Research Database (Denmark)

    Engelin, Casper Junker; Fristrup, Peter

    2011-01-01

    The atom-efficiency of one of the most widely used catalytic reactions for forging C-C bonds, the Tsuji-Trost reaction, is limited by the need of preoxidized reagents. This limitation can be overcome by utilization of the recently discovered palladium-catalyzed C-H activation, the allylic C...

  6. 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. PMID:26119659

  7. Short hydrogen bonds in the catalytic mechanism of serine proteases

    Directory of Open Access Journals (Sweden)

    VLADIMIR LESKOVAC

    2008-04-01

    Full Text Available The survey of crystallographic data from the Protein Data Bank for 37 structures of trypsin and other serine proteases at a resolution of 0.78–1.28 Å revealed the presence of hydrogen bonds in the active site of the enzymes, which are formed between the catalytic histidine and aspartate residues and are on average 2.7 Å long. This is the typical bond length for normal hydrogen bonds. The geometric properties of the hydrogen bonds in the active site indicate that the H atom is not centered between the heteroatoms of the catalytic histidine and aspartate residues in the active site. Taken together, these findings exclude the possibility that short “low-barrier” hydrogen bonds are formed in the ground state structure of the active sites examined in this work. Some time ago, it was suggested by Cleland that the “low-barrier hydrogen bond” hypothesis is operative in the catalytic mechanism of serine proteases, and requires the presence of short hydrogen bonds around 2.4 Å long in the active site, with the H atom centered between the catalytic heteroatoms. The conclusions drawn from this work do not exclude the validity of the “low-barrier hydrogen bond” hypothesis at all, but they merely do not support it in this particular case, with this particular class of enzymes.

  8. Identification of the Chemical Bonding Prompting Adhesion of a-C:H Thin Films on Ferrous Alloy Intermediated by a SiCx:H Buffer Layer.

    Science.gov (United States)

    Cemin, F; Bim, L T; Leidens, L M; Morales, M; Baumvol, I J R; Alvarez, F; Figueroa, C A

    2015-07-29

    Amorphous carbon (a-C) and several related materials (DLCs) may have ultralow friction coefficients that can be used for saving-energy applications. However, poor chemical bonding of a-C/DLC films on metallic alloys is expected, due to the stability of carbon-carbon bonds. Silicon-based intermediate layers are employed to enhance the adherence of a-C:H films on ferrous alloys, although the role of such buffer layers is not yet fully understood in chemical terms. The chemical bonding of a-C:H thin films on ferrous alloy intermediated by a nanometric SiCx:H buffer layer was analyzed by X-ray photoelectron spectroscopy (XPS). The chemical profile was inspected by glow discharge optical emission spectroscopy (GDOES), and the chemical structure was evaluated by Raman and Fourier transform infrared spectroscopy techniques. The nature of adhesion is discussed by analyzing the chemical bonding at the interfaces of the a-C:H/SiCx:H/ferrous alloy sandwich structure. The adhesion phenomenon is ascribed to specifically chemical bonding character at the buffer layer. Whereas carbon-carbon (C-C) and carbon-silicon (C-Si) bonds are formed at the outermost interface, the innermost interface is constituted mainly by silicon-iron (Si-Fe) bonds. The oxygen presence degrades the adhesion up to totally delaminate the a-C:H thin films. The SiCx:H deposition temperature determines the type of chemical bonding and the amount of oxygen contained in the buffer layer. PMID:26135943

  9. Rhodium(III)-Catalyzed Directed ortho-C-H Bond Functionalization of Aromatic Ketazines via C-S and C-C Coupling.

    Science.gov (United States)

    Wen, Jing; Wu, An; Wang, Mingyang; Zhu, Jin

    2015-11-01

    Described herein is a convenient and efficient method for sulfuration and olefination of aromatic ketazines via rhodium-catalyzed oxidative C-H bond activation. A range of substituted substrates are supported, and a possible mechanism is proposed according to experimental results of kinetic isotopic effect, reversibility studies, and catalysis of rhodacycle intermediate c1. PMID:26417874

  10. Nickel-Catalyzed Aromatic C-H Functionalization.

    Science.gov (United States)

    Yamaguchi, Junichiro; Muto, Kei; Itami, Kenichiro

    2016-08-01

    Catalytic C-H functionalization using transition metals has received significant interest from organic chemists because it provides a new strategy to construct carbon-carbon bonds and carbon-heteroatom bonds in highly functionalized, complex molecules without pre-functionalization. Recently, inexpensive catalysts based on transition metals such as copper, iron, cobalt, and nickel have seen more use in the laboratory. This review describes recent progress in nickel-catalyzed aromatic C-H functionalization reactions classified by reaction types and reaction partners. Furthermore, some reaction mechanisms are described and cutting-edge syntheses of natural products and pharmaceuticals using nickel-catalyzed aromatic C-H functionalization are presented. PMID:27573407

  11. Rhodium-Catalyzed Intramolecular C-H Silylation by Silacyclobutanes.

    Science.gov (United States)

    Zhang, Qing-Wei; An, Kun; Liu, Li-Chuan; Guo, Shuangxi; Jiang, Chenran; Guo, Huifang; He, Wei

    2016-05-17

    Silacyclobutane was discovered to be an efficient C-H bond silylation reagent. Under the catalysis of Rh(I) /TMS-segphos, silacyclobutane undergoes sequential C-Si/C-H bond activations, affording a series of π-conjugated siloles in high yields and regioselectivities. The catalytic cycle was proposed to involve a rarely documented endocyclic β-hydride elimination of five-membered metallacycles, which after reductive elimination gave rise to a Si-Rh(I) species that is capable of C-H activation. PMID:27073004

  12. Intramolecular C-H bond activation and redox isomerization across two-electron mixed valence diiridium cores.

    Energy Technology Data Exchange (ETDEWEB)

    Esswein, A. J.; Veige, A. S.; Piccoli, P. M. B.; Schultz, A. J.; Nocera, D. G.; MIT

    2008-03-24

    Metal-metal cooperativity enables the reaction of carbon-based substrates at diiridium two-electron mixed valence centers. Arylation of Ir{sub 2}{sup 0,II}(tfepma){sub 3}Cl{sub 2} (1) (tfepma = bis[(bistrifluoroethoxy)phosphino]methylamine) with RMgBr (R = C{sub 6}H{sub 5} and C{sub 6}D{sub 5}) is followed by C-H bond activation to furnish the bridging benzyne complex Ir{sub 2}II,II(tfepma){sub 3}({mu}-C{sub 6}H4)(C{sub 6}H{sub 5})H (2), as the kinetic product. At ambient temperature, 2 isomerizes to Ir{sub 2}{sup I,III}(tfepma){sub 3}({mu}-C{sub 6}H4)(C{sub 6}H{sub 5})H (3) (k{sub obs} = 9.57 {+-} 0.10 x 10{sup -5} s{sup -1} at 31.8 C, {Delta}H{sup {+-}} = 21.7 {+-} 0.3 kcal/mol, {Delta}S{sup {+-}} = -7.4 {+-} 0.9 eu), in which the benzyne moiety is conserved and the Ir{sup III} center is ligated by terminal hydride and phenyl groups. The same reaction course is observed for arylation of 1 with C{sub 6}D{sub 5}MgBr to produce 2-d{sub 10} and 3-d{sub 10} accompanied by an inverse isotope effect, k{sub h}/k{sub d} = 0.44 (k{sub obs} = 2.17 {+-} 0.10 x 10{sup -4} s{sup -1} in C{sub 6}D{sub 6} solution at 31.8 C, {Delta}H{sup {+-}} = 24.9 {+-} 0.7 kcal/mol, {Delta}S{sup {+-}} = -6.4 {+-} 2.4 eu). 2 reacts swiftly with hydrogen to provide Ir{sub 2}{sup II,II}(tfepma){sub 3}H{sub 4} as both the syn and anti isomers (4-syn and 4-anti, respectively). The hydrides of 4-syn were directly located by neutron diffraction analysis. X-ray crystallographic examination of 2, 2-d{sub 10}, 3, and 4-syn indicates that cooperative reactivity at the bimetallic diiridium core is facilitated by the ability of the two-electron mixed valence framework to accommodate the oxidation state changes and ligand rearrangements attendant to the reaction of the substrate.

  13. Promotional effects of chemisorbed oxygen and hydroxide in the activation of C-H and O-H bonds over transition metal surfaces

    Science.gov (United States)

    Hibbitts, David; Neurock, Matthew

    2016-08-01

    Electronegative coadsorbates such as atomic oxygen (O*) and hydroxide (OH*) can act as Brønsted bases when bound to Group 11 as well as particular Group 8-10 metal surfaces and aid in the activation of X-H bonds. First-principle density functional theory calculations were carried out to systematically explore the reactivity of the C-H bonds of methane and surface methyl intermediates as well as the O-H bond of methanol directly and with the assistance of coadsorbed O* and OH* intermediates over Group 11 (Cu, Ag, and Au) and Group 8-10 transition metal (Ru, Rh, Pd, Os, Ir, and Pt) surfaces. C-H as well as O-H bond activation over the metal proceeds via a classic oxidative addition type mechanism involving the insertion of the metal center into the C-H or O-H bond. O* and OH* assist C-H and O-H activation over particular Group 11 and Group 8-10 metal surfaces via a σ-bond metathesis type mechanism involving the oxidative addition of the C-H or O-H bond to the metal along with a reductive deprotonation of the acidic C-H and O-H bond over the M-O* or M-OH* site pair. The O*- and OH*-assisted C-H activation paths are energetically preferred over the direct metal catalyzed C-H scission for all Group 11 metals (Cu, Ag, and Au) with barriers that are 0.4-1.5 eV lower than those for the unassisted routes. The barriers for O*- and OH*-assisted C-H activation of CH4 on the Group 8-10 transition metals, however, are higher than those over the bare transition metal surfaces by as much as 1.4 eV. The C-H activation of adsorbed methyl species show very similar trends to those for CH4 despite the differences in structure between the weakly bound methane and the covalently adsorbed methyl intermediates. The activation of the O-H bond of methanol is significantly promoted by O* as well as OH* intermediates over both the Group 11 metals (Cu, Ag, and Au) as well as on all Group 8-10 metals studied (Ru, Rh, Pd, Os, Ir, and Pt). The O*- and OH*-assisted CH3O-H barriers are 0.6 to 2

  14. Unified view of oxidative C-H bond cleavage and sulfoxidation by a nonheme iron(IV)-oxo complex via Lewis acid-promoted electron transfer.

    Science.gov (United States)

    Park, Jiyun; Morimoto, Yuma; Lee, Yong-Min; Nam, Wonwoo; Fukuzumi, Shunichi

    2014-04-01

    Oxidative C-H bond cleavage of toluene derivatives and sulfoxidation of thioanisole derivatives by a nonheme iron(IV)-oxo complex, [(N4Py)Fe(IV)(O)](2+) (N4Py = N,N-bis(2-pyridylmethyl)-N-bis(2-pyridyl)methylamine), were remarkably enhanced by the presence of triflic acid (HOTf) and Sc(OTf)3 in acetonitrile at 298 K. All the logarithms of the observed second-order rate constants of both the oxidative C-H bond cleavage and sulfoxidation reactions exhibit remarkably unified correlations with the driving forces of proton-coupled electron transfer (PCET) and metal ion-coupled electron transfer (MCET) in light of the Marcus theory of electron transfer when the differences in the formation constants of precursor complexes between PCET and MCET were taken into account, respectively. Thus, the mechanisms of both the oxidative C-H bond cleavage of toluene derivatives and sulfoxidation of thioanisole derivatives by [(N4Py)Fe(IV)(O)](2+) in the presence of HOTf and Sc(OTf)3 have been unified as the rate-determining electron transfer, which is coupled with binding of [(N4Py)Fe(IV)(O)](2+) by proton (PCET) and Sc(OTf)3 (MCET). There was no deuterium kinetic isotope effect (KIE) on the oxidative C-H bond cleavage of toluene via the PCET pathway, whereas a large KIE value was observed with Sc(OTf)3, which exhibited no acceleration of the oxidative C-H bond cleavage of toluene. When HOTf was replaced by DOTf, an inverse KIE (0.4) was observed for PCET from both toluene and [Ru(II)(bpy)3](2+) (bpy =2,2'-bipyridine) to [(N4Py)Fe(IV)(O)](2+). The PCET and MCET reactivities of [(N4Py)Fe(IV)(O)](2+) with Brønsted acids and various metal triflates have also been unified as a single correlation with a quantitative measure of the Lewis acidity. PMID:24605985

  15. 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. PMID:26689172

  16. Iridium(iii)-catalyzed regioselective direct arylation of sp(2) C-H bonds with diaryliodonium salts.

    Science.gov (United States)

    Gao, Pan; Liu, Li; Shi, Zhuangzhi; Yuan, Yu

    2016-08-01

    A regioselective direct arylation of arenes and olefins at the ortho position is reported. The key to the high selectivity is the appropriate choice of diaryliodonium salts as the arylating reagent in the presence of a cationic iridium(iii) catalyst. The coordination of the metal with an oxygen atom or a nitrogen atom and subsequent C-H activation allows for direct arylation with coupling partners. This reaction proceeds under mild reaction conditions and with a high tolerance of various functional groups including many halide functional groups. PMID:27381238

  17. Iron(IV)hydroxide pKa and the Role of Thiolate Ligation in C-H Bond Activation by Cytochrome P450

    OpenAIRE

    Yosca, Timothy H.; Rittle, Jonathan; Krest, Courtney M.; Onderko, Elizabeth L.; Silakov, Alexey; Calixto, Julio C.; Behan, Rachel K.; Green, Michael T.

    2013-01-01

    Cytochrome P450 enzymes activate oxygen at heme iron centers to oxidize relatively inert substrate carbon-hydrogen bonds. Cysteine thiolate coordination to iron is posited to increase the pKa of compound II, an iron(IV)hydroxide complex, correspondingly lowering the one-electron reduction potential of compound I, the active catalytic intermediate, and decreasing the driving force for deleterious autooxidation of tyrosine and tryptophan residues in the enzyme’s framework. Here we report the pr...

  18. The structure and orientation of the C-H...OC hydrogen bonding in PHB studied by polarized infrared spectroscopy

    Czech Academy of Sciences Publication Activity Database

    Murakami, R.; Sato, H.; Dybal, Jiří; Iwata, T.; Zhang, J.; Tashiro, K.; Noda, I.; Ozaki, Y.

    Nishinomiya : Kwansei Gakuin University, 2005. s. 59. [International Symposium of Research Center for Environment Friendly Polymers /1./. 24.10.2005-25.10.2005, Nishinomiya] Institutional research plan: CEZ:AV0Z40500505 Keywords : poly(3-hydroxybutyrate) * polarized infrared spectra * hydrogen bonding Subject RIV: CD - Macromolecular Chemistry

  19. Hard three-dimensional sp2 carbon-bonded phase formed by ion beam irradiation of fullerene, a-C and polymeric a-C:H films

    International Nuclear Information System (INIS)

    The formation of new carbon amorphous phase through the ion irradiation of fullerene, a-C and polymeric a-C:H films is presented. The carbon films were subjected to N irradiation at 400 keV in the fluence range from 1013 to 3 x 1016 N cm-2. Modifications in the carbon structure, as function of the irradiation fluence, were investigated using the Rutherford backscattering spectrometry, nuclear reaction analysis, Fourier transform infrared, Raman spectroscopy, UV-VIS-NearIR spectrophotometry and nanoindentation techniques. After high fluence, the three carbon samples were transformed into very similar hard (∼14 GPa) and non-hydrogenated amorphous carbon layers with very low optical gaps (∼0.2 eV) and an unusual sp2 rich-bonded atomic network. The mechanical properties of the irradiated films correlated with the bonding topologies of this new sp2 carbon phase are analyzed in terms of the constraint-counting model. The results show that the unusual rigidity was achieved by the distortion of the sp2 carbon bond angles, giving origin to a constrained three-dimensional sp2 carbon bonded network

  20. Synthesis and orthogonal functionalization of oxazolo[5',4':4,5]pyrano[2,3-b]pyridine by intra- and intermolecular Pd-catalyzed direct C-H bond heteroarylation.

    Science.gov (United States)

    Théveau, Laure; Schneider, Cédric; Querolle, Olivier; Meerpoel, Lieven; Levacher, Vincent; Hoarau, Christophe

    2016-04-01

    The construction and subsequent orthogonal functionalization of a hitherto unknown oxazolo[5',4':4,5]pyrano[2,3-b]pyridine are reported. A palladium-catalyzed direct C-H bond functionalization methodology was used to build the tricyclic scaffold as well as to achieve the subsequent C-H bond functionalization at the C-2 position of the oxazole unit with various (hetero)aryl iodides. Remarkably, selective C-H construction and functionalization procedures preserve the chorine atom on the pyridine moiety offering a late-stage substitution site to progress drug design. PMID:26967763

  1. Driving Forces for Covalent Assembly of Porphyrins by Selective C-H Bond Activation and Intermolecular Coupling on a Copper Surface.

    Science.gov (United States)

    Floris, Andrea; Haq, Sam; In't Veld, Mendel; Amabilino, David B; Raval, Rasmita; Kantorovich, Lev

    2016-05-11

    Recent synthesis of covalent organic assemblies at surfaces has opened the promise of producing robust nanostructures for functional interfaces. To uncover how this new chemistry works at surfaces and understand the underlying mechanisms that control bond-breaking and bond-making processes at specific positions of the participating molecules, we study here the coupling reaction of tetra(mesityl)porphyrin molecules, which creates covalently connected networks on the Cu(110) surface by utilizing the 4-methyl groups as unique connection points. Using scanning tunneling microscopy (STM), state-of-the-art density functional theory (DFT), and Nudged Elastic Band (NEB) calculations, we show that the unique directionality of the covalent bonding is found to stem from a chain of highly selective C-H activation and dehydrogenation processes, followed by specific intermolecular C-C coupling reactions that are facilitated by the surface, by steric constraints, and by anisotropic molecular diffusion. These insights provide the first steps toward developing synthetic rules for complex two-dimensional covalent organic chemistry that can be enacted directly at a surface to deliver specific macromolecular structures designed for specific functions. PMID:27097295

  2. Exceptional sensitivity of metal-aryl bond energies to ortho-fluorine substituents: influence of the metal, the coordination sphere, and the spectator ligands on M-C/H-C bond energy correlations.

    Science.gov (United States)

    Clot, Eric; Mégret, Claire; Eisenstein, Odile; Perutz, Robin N

    2009-06-10

    DFT calculations are reported of the energetics of C-H oxidative addition of benzene and fluorinated benzenes, Ar(F)H (Ar(F) = C(6)F(n)H(5-n), n = 0-5) at ZrCp(2) (Cp = eta(5)-C(5)H(5)), TaCp(2)H, TaCp(2)Cl, WCp(2), ReCp(CO)(2), ReCp(CO)(PH(3)), ReCp(PH(3))(2), RhCp(PH(3)), RhCp(CO), IrCp(PH(3)), IrCp(CO), Ni(H(2)PCH(2)CH(2)PH(2)), Pt(H(2)PCH(2)CH(2)PH(2)). The change in M-C bond energy of the products fits a linear function of the number of fluorine substituents, with different coefficients corresponding to ortho-, meta-, and para-fluorine. The values of the ortho-coefficient range from 20 to 32 kJ mol(-1), greatly exceeding the values for the meta- and para-coefficients (2.0-4.5 kJ mol(-1)). Similarly, the H-C bond energies of Ar(F)H yield ortho- and para-coefficients of 10.4 and 3.4 kJ mol(-1), respectively, and a negligible meta-coefficient. These results indicate a large increase in the M-C bond energy with ortho-fluorine substitution on the aryl ring. Plots of D(M-C) vs D(H-C) yield slopes R(M-C/H-C) that vary from 1.93 to 3.05 with metal fragment, all in excess of values of 1.1-1.3 reported with other hydrocarbyl groups. Replacement of PH(3) by CO decreases R(M-C/H-C) significantly. For a given ligand set and metals in the same group of the periodic table, the value of R(M-C/H-C) does not increase with the strength of the M-C bond. Calculations of the charge on the aryl ring show that variations in ionicity of the M-C bonds correlate with variations in M-C bond energy. This strengthening of metal-aryl bonds accounts for numerous experimental results that indicate a preference for ortho-fluorine substituents. PMID:19453181

  3. The Molybdenum Active Site of Formate Dehydrogenase Is Capable of Catalyzing C-H Bond Cleavage and Oxygen Atom Transfer Reactions.

    Science.gov (United States)

    Hartmann, Tobias; Schrapers, Peer; Utesch, Tillmann; Nimtz, Manfred; Rippers, Yvonne; Dau, Holger; Mroginski, Maria Andrea; Haumann, Michael; Leimkühler, Silke

    2016-04-26

    Formate dehydrogenases (FDHs) are capable of performing the reversible oxidation of formate and are enzymes of great interest for fuel cell applications and for the production of reduced carbon compounds as energy sources from CO2. Metal-containing FDHs in general contain a highly conserved active site, comprising a molybdenum (or tungsten) center coordinated by two molybdopterin guanine dinucleotide molecules, a sulfido and a (seleno-)cysteine ligand, in addition to a histidine and arginine residue in the second coordination sphere. So far, the role of these amino acids in catalysis has not been studied in detail, because of the lack of suitable expression systems and the lability or oxygen sensitivity of the enzymes. Here, the roles of these active site residues is revealed using the Mo-containing FDH from Rhodobacter capsulatus. Our results show that the cysteine ligand at the Mo ion is displaced by the formate substrate during the reaction, the arginine has a direct role in substrate binding and stabilization, and the histidine elevates the pKa of the active site cysteine. We further found that in addition to reversible formate oxidation, the enzyme is further capable of reducing nitrate to nitrite. We propose a mechanistic scheme that combines both functionalities and provides important insights into the distinct mechanisms of C-H bond cleavage and oxygen atom transfer catalyzed by formate dehydrogenase. PMID:27054466

  4. Synthesis and characterization of ethylbis(2-pyridylethyl)amineruthenium complexes and two different types of C-H bond cleavage at an ethylene arm.

    Science.gov (United States)

    Fukui, Sohei; Kajihara, Akari; Hirano, Toshiyuki; Sato, Fumitoshi; Suzuki, Noriyuki; Nagao, Hirotaka

    2011-06-01

    Ruthenium complexes bearing ethylbis(2-pyridylethyl)amine (ebpea), which has flexible -C(2)H(4)- arms between the amine and the pyridyl groups and coordinates to a metal center in facial and meridional modes, have been synthesized and characterized. Three trichloro complexes, fac-[Ru(III)Cl(3)(ebpea)] (fac-[1]), mer-[Ru(III)Cl(3)(ebpea)] (mer-[1]), and mer-[Ru(II)Cl(3){η(2)-N(C(2)H(5))(C(2)H(4)py)═CH-CH(2)py}] (mer-[2]), were synthesized using the Ru blue solution. Formation of mer-[2] proceeded via a C-H activation of the CH(2) group next to the amine nitrogen atom of the ethylene arm. Reduction reactions of fac- and mer-[1] afforded a triacetonitrile complex mer-[Ru(II)(CH(3)CN)(3)(ebpea)](PF(6))(2) (mer-[3](PF(6))(2)). Five nitrosyl complexes fac-[RuX(2)(NO)(ebpea)]PF(6) (X = Cl for fac-[4]PF(6); X = ONO(2) for fac-[5]PF(6)) and mer-[RuXY(NO)(ebpea)]PF(6) (X = Cl, Y = Cl for mer-[4]PF(6); X = Cl, Y = CH(3)O for mer-[6]PF(6); X = Cl, Y = OH for mer-[7]PF(6)) were synthesized and characterized by X-ray crystallography. A reaction of mer-[2] in H(2)O-C(2)H(5)OH at room temperature afforded mer-[1]. Oxidation of C(2)H(5)OH in H(2)O-C(2)H(5)OH and i-C(3)H(7)OH in H(2)O-i-C(3)H(7)OH to acetaldehyde and acetone by mer-[2] under stirring at room temperature occurred with formation of mer-[1]. Alternative C-H activation of the CH(2) group occurred next to the pyridyl group, and formation of a C-N bond between the CH moiety and the nitrosyl ligand afforded a nitroso complex [Ru(II)(N(3))(2){N(O)CH(py)CH(2)N(C(2)H(5))C(2)H(4)py}] ([8]) in reactions of nitrosyl complexes with sodium azide in methanol, and reaction of [8] with hydrochloric acid afforded a corresponding chloronitroso complex [Ru(II)Cl(2){N(O)CH(py)CH(2)N(C(2)H(5))C(2)H(4)py}] ([9]). PMID:21517051

  5. Air/Water-Stable Tridentate NHC-PdII Complex; Catalytic C-H Activation of Hydrocarbons via H/D Exchange Process in D2O

    OpenAIRE

    Lee, Joo Ho; Yoo, Kyung Soo; Park, Chan Pil; Olsen, Janet M.; Sakaguchi, Satoshi; Surya Prakash, G. K.; Mathew, Thomas; Jung, Kyung Woon

    2009-01-01

    While developing novel catalysts for carbon-carbon or carbon-heteroatom coupling (N, O, or F), we were able to introduce tridentate NHC-amidate-alkoxide palladium(II) complexes. In aqueous solution, these NHC-Pd(II) complexes showed high ability for C-H activation of various hydrocarbons (cyclohexane, cyclopentane, dimethyl ether, THF, acetone, and toluene) under mild conditions.

  6. 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.

  7. A study on aromatic C-H⋯X (X = N, O) hydrogen bonds in 1,2,4,5-tetrafluorobenzene clusters using infrared spectroscopy and ab initio calculations

    Science.gov (United States)

    Venkatesan, V.; Fujii, A.; Mikami, N.

    2005-06-01

    The (1:1) clusters of 1,2,4,5-tetrafluorobenzene (TFB) with CH 3CN, CH 3OCH 3, and NH 3 were studied both experimentally and computationally. Using fluorescence-detected infrared (FDIR) spectroscopy, the aromatic C-H⋯X (X = N, O) hydrogen bond formation in the clusters was directly evidenced by a low-frequency shift and intensity enhancement of the aromatic C-H stretching vibration in the TFB moiety. The molecular structures, stabilization energies, and vibrational frequencies of the clusters were computed at the MP2/6-31+G* level. The observed low-frequency shifts of the aromatic C-H stretch in the clusters correlate with the proton affinities of the acceptor molecules.

  8. Activation of the C-H bond: catalytic hydroxylation of hydrocarbons by new cobaltic alkylperoxydic complexes; selective and catalytic cycloalkane dehydrogenation in presence of uranium for hydrogen transfer

    International Nuclear Information System (INIS)

    The aim of the thesis is to improve efficiency and selectivity of chemical reactions for alkane transformations. In the first part decomposition of hydroperoxides and hydrocarbon hydroxylation by cobalt complexes is studied. In the second part cycloalkanes are dehydrogenated into aromatics with a Pt catalyst, trapping hydrogen by uranium. Uranium hydride UH3 can yield very pure hydrogen at reasonable temperature

  9. Intermolecular insertion of an N,N-heterocyclic carbene into a nonacidic C-H bond: Kinetics, mechanism and catalysis by (K-HMDS)2 (HMDS = Hexamethyldisilazide).

    Science.gov (United States)

    Lloyd-Jones, Guy C; Alder, Roger W; Owen-Smith, Gareth J J

    2006-07-01

    The reaction of 2-[13C]-1-ethyl-3-isopropyl-3,4,5,6-tetrahydropyrimidin-1-ium hexafluorophosphate ([13C1]-1-PF6) with a slight excess (1.03 equiv) of dimeric potassium hexamethyldisilazide ("(K-HMDS)2") in toluene generates 2-[13C]-3-ethyl-1-isopropyl-3,4,5,6-tetrahydropyrimid-2-ylidene ([13C1]-2). The hindered meta-stable N,N-heterocyclic carbene [13C1]-2 thus generated undergoes a slow but quantitative reaction with toluene (the solvent) to generate the aminal 2-[13C]-2-benzyl-3-ethyl-1-isopropylhexahydropyrimidine ([13C1]-14) through formal C-H insertion of C2 (the "carbene carbon") at the toluene methyl group. Despite a significant pKa mismatch (Delta pKa 1+ and toluene estimated to be ca. 16 in DMSO) the reaction shows all the characteristics of a deprotonation mechanism, the reaction rate being strongly dependent on the toluene para substituent (rho = 4.8(+/-0.3)), and displaying substantial and rate-limiting primary (k(H)/k(D) = 4.2(+/-0.6)) and secondary (k(H)/k(D) = 1.18(+/-0.08)) kinetic isotope effects on the deuteration of the toluene methyl group. The reaction is catalysed by K-HMDS, but proceeds without cross over between toluene methyl protons and does not involve an HMDS anion acting as base to generate a benzyl anion. Detailed analysis of the reaction kinetics/kinetic isotope effects demonstrates that a pseudo-first-order decay in 2 arises from a first-order dependence on 2, a first-order dependence on toluene (in large excess) and, in the catalytic manifold, a complex noninteger dependence on the K-HMDS dimer. The rate is not satisfactorily predicted by equations based on the Brønsted salt-effect catalysis law. However, the rate can be satisfactorily predicted by a mole-fraction-weighted net rate constant: -d[2]/dt = ({x2 k(uncat)} + {(1-x2) k(cat)})[2]1[toluene]1, in which x2 is determined by a standard bimolecular complexation equilibrium term. The association constant (Ka) for rapid equilibrium-complexation of 2 with (K-HMDS)2 to form [2(K

  10. 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

    2016-08-01

    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. PMID:27441527

  11. 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.

    isocoumarin derivatives. These catalytic reactions can be performed in DMF and competively in water. COMMUNICATION Keisham S. Singh*,Sneha G. Sawant, Pierre H. Dixneuf * Page No. – Page No. Ruthenium(II) catalysed synthesis of pyrrole...

  12. Conserved water-mediated H-bonding dynamics of catalytic Asn 175 in plant thiol protease

    Indian Academy of Sciences (India)

    Tapas K Nandi; Hridoy R Bairagya; Bishnu P Mukhopadhyay; K Sekar; Dipankar Sukul; Asim K Bera

    2009-03-01

    The role of invariant water molecules in the activity of plant cysteine protease is ubiquitous in nature. On analysing the 11 different Protein DataBank (PDB) structures of plant thiol proteases, the two invariant water molecules W1 and W2 (W220 and W222 in the template 1PPN structure) were observed to form H-bonds with the Ob atom of Asn 175. Extensive energy minimization and molecular dynamics simulation studies up to 2 ns on all the PDB and solvated structures clearly revealed the involvement of the H-bonding association of the two water molecules in fixing the orientation of the asparagine residue of the catalytic triad. From this study, it is suggested that H-bonding of the water molecule at the W1 invariant site better stabilizes the Asn residue at the active site of the catalytic triad.

  13. Metal-Free sp(2)-C-H Borylation as a Common Reactivity Pattern of Frustrated 2-Aminophenylboranes.

    Science.gov (United States)

    Chernichenko, Konstantin; Lindqvist, Markus; Kótai, Bianka; Nieger, Martin; Sorochkina, Kristina; Pápai, Imre; Repo, Timo

    2016-04-13

    C-H borylation is a powerful and atom-efficient method for converting affordable and abundant chemicals into versatile organic reagents used in the production of fine chemicals and functional materials. Herein we report a facile C-H borylation of aromatic and olefinic C-H bonds with 2-aminophenylboranes. Computational and experimental studies reveal that the metal-free C-H insertion proceeds via a frustrated Lewis pair mechanism involving heterolytic splitting of the C-H bond by cooperative action of the amine and boryl groups. The adapted geometry of the reactive B and N centers results in an unprecedentently low kinetic barrier for both insertion into the sp(2)-C-H bond and intramolecular protonation of the sp(2)-C-B bond in 2-ammoniophenyl(aryl)- or -(alkenyl)borates. This common reactivity pattern serves as a platform for various catalytic reactions such as C-H borylation and hydrogenation of alkynes. In particular, we demonstrate that simple 2-aminopyridinium salts efficiently catalyze the C-H borylation of hetarenes with catecholborane. This reaction is presumably mediated by a borenium species isoelectronic to 2-aminophenylboranes. PMID:27003334

  14. Imidazolium-Based Dicationic Cyclophanes. Solid-State Aggregates with unconventional (C?H)+???Cl? Hydrogen Bonding Revealed by X-Ray Diffraction

    OpenAIRE

    Alcalde, Ermitas

    2007-01-01

    Abstract The first single-crystal X-ray crystallographic diffraction analysis of a dicationic heterophane showed a non-classic (CH)+???Cl hydrogen bond between the imidazolium rings and halide anions and the formation of unconventional charged assisted hydrogen bonds, which were the non-covalent forces driving the anion interactions shown by the dications 4?2X. Here we report the halide-templated controlled synthesis and chemical response in basic media of 4?2X. The...

  15. Mild Catalytic methods for Alkyl-Alkyl Bond Formation

    Energy Technology Data Exchange (ETDEWEB)

    Vicic, David A

    2009-08-10

    complexes of varying geometries; 6) we have determined that the geometry of aforementioned bridging hydride complexes is largely determined by external forces such as hydrogen bonding interactions and crystal packing forces; 7) we have found that the rate of reductive elimination of alkane from a (pyridyl-2-pyrrolide)AuMe2 complex is severely inhibited due to the rigid geometry of the pyridyl-2-pyrrolide ligand; 8) we have prepared, structurally characterized, and explored the reactivity of 1-adamantylzinc reagents as model nucleophiles for sterically challenging alkyl-alkyl cross-coupling reactions. The continued success of this work will lead to alkyl-alkyl cross-coupling catalysts with broad scope and selectivities. The work has potential to significantly impact science and technologies of interest to the DOE as the chemistry is focused on developing useful reactions using reagents that can be directly prepared from petroleum and natural gas feedstocks. Moreover, the developing synthetic chemistry can profoundly affect the way materials, fine chemicals, and drugs are made. Since the methodology we are developing can shorten existing synthetic protocols, proceed at room temperature, and operate under environmentally benign conditions, it can greatly reduce energy expenditures, especially considering the contribution of the chemical manufacturing field to the gross domestic product.

  16. Predicting the activation energy of catalytic dissociation of the heteroatomic AB bond

    International Nuclear Information System (INIS)

    Two analytical formalisms, adiabatic and diabatic ones, were developed for the description of catalytic dissociation of heteroatomic bond AB interacting with a metal surface in the adsorption processes. In the adiabatic formalism, the transition state was localized on a four-dimensional potential energy surface in classical approximation. This approach generalizes the previous three-dimensional model for dissociative adsorption of homonuclear molecules X2 on metals surfaces, and it was used for studying the effect of non-parallel orientation to a surface of O2 molecules in the adsorption precursor state. The second formalism takes into account a possible quantum character of vibrations along the chemical bond AB. The calculation of the activation energy in this approach is performed by the density matrix method. This approach is applied for studying catalytic dissociation of CO molecule on a Ni(1 1 1) surface. The calculated apparent activation energy for this reaction is compared with published data for this system

  17. Moving to Sustainable Metals. Multifunctional Ligands in Catalytic, Outer Sphere C-H, N-H and O-H Activation

    Energy Technology Data Exchange (ETDEWEB)

    Crabtree, Robert [Yale Univ., New Haven, CT (United States)

    2015-03-03

    Much of our work during this grant period has emphasized green chemistry and sustainability. For example, we were able to convert glycerine, a waste byproduct of biodiesel production, into lactic acid, a compound with numerous applications, notably in the food and cosmetics industry, as well as being a source material for a biodegradable plastic. This work required a catalyst, that ceases to work after a certain lapse of time. We were able to identify the way in which this deactivation occurs by identifying some of the metal catalyst deactivation products. These proved to be multimetallic clusters containing up to six metals and up to 14 hydrogen atoms. Both the catalytic reaction itself and the deactivation structures are novel and unexpected. We have previously proposed that nitrogen heterocycles could be good energy carriers in a low CO2 future world. In another part of our study, we found catalysts for introduction of hydrogen, an energy carrier that is hard to store, into nitrogen heterocycles. The mechanism of this process proved to be unusual in that the catalyst transfers the H2 to the heterocycle in the form of H+ and H-, first transferring the H+ and only then the H-. In a third area of study, some of our compounds, originally prepared for DOE catalysis purposes, also proved useful in hydrocarbon oxidation and in water oxidation. The latter is important in solar-to-fuel work, because, by analogy with natural photosynthesis, the goal of the Yale Solar Group of four PIs is to convert sunlight to hydrogen and oxygen, which requires water splitting catalysts. The catalysts that proved useful mediate the latter reaction: water oxidation to oxygen. In a more technical study, we developed methods for distinguishing the case where catalysis is mediated by a soluble catalyst from cases where catalysis arises from a deposit of finely divided solid. One particular application involved electrocatalysis

  18. Polymerization of ethylene by silica-supported dinuclear Cr(III) sites through an initiation step involving C-H bond activation.

    Science.gov (United States)

    Conley, Matthew P; Delley, Murielle F; Siddiqi, Georges; Lapadula, Giuseppe; Norsic, Sébastien; Monteil, Vincent; Safonova, Olga V; Copéret, Christophe

    2014-02-10

    The insertion of an olefin into a preformed metal-carbon bond is a common mechanism for transition-metal-catalyzed olefin polymerization. However, in one important industrial catalyst, the Phillips catalyst, a metal-carbon bond is not present in the precatalyst. The Phillips catalyst, CrO3 dispersed on silica, polymerizes ethylene without an activator. Despite 60 years of intensive research, the active sites and the way the first CrC bond is formed remain unknown. We synthesized well-defined dinuclear Cr(II) and Cr(III) sites on silica. Whereas the Cr(II) material was a poor polymerization catalyst, the Cr(III) material was active. Poisoning studies showed that about 65 % of the Cr(III) sites were active, a far higher proportion than typically observed for the Phillips catalyst. Examination of the spent catalyst and isotope labeling experiments showed the formation of a Si-(μ-OH)-Cr(III) species, consistent with an initiation mechanism involving the heterolytic activation of ethylene at Cr(III) O bonds. PMID:24505006

  19. A meta-selective C-H borylation directed by a secondary interaction between ligand and substrate

    Science.gov (United States)

    Kuninobu, Yoichiro; Ida, Haruka; Nishi, Mitsumi; Kanai, Motomu

    2015-09-01

    Regioselective C-H bond transformations are potentially the most efficient method for the synthesis of organic molecules. However, the presence of many C-H bonds in organic molecules and the high activation barrier for these reactions make these transformations difficult. Directing groups in the reaction substrate are often used to control regioselectivity, which has been especially successful for the ortho-selective functionalization of aromatic substrates. Here, we describe an iridium-catalysed meta-selective C-H borylation of aromatic compounds using a newly designed catalytic system. The bipyridine-derived ligand that binds iridium contains a pendant urea moiety. A secondary interaction between this urea and a hydrogen-bond acceptor in the substrate places the iridium in close proximity to the meta-C-H bond and thus controls the regioselectivity. 1H NMR studies and control experiments support the participation of hydrogen bonds in inducing regioselectivity. Reversible direction of the catalyst through hydrogen bonds is a versatile concept for regioselective C-H transformations.

  20. Water as a green solvent for efficient synthesis of isocoumarins through microwave-accelerated and Rh/Cu-catalyzed C-H/O-H bond functionalization

    Energy Technology Data Exchange (ETDEWEB)

    Li, Qiu; Yan, Yunnan; Wang, Xiaowei; Gong, Binwei; Tang, Xiaobo; Shi, JingJing; Xu, H. Eric; Yi, Wei [Shenyang; (Gannan); (Van Andel); (UST - China); (Chinese Aca. Sci.)

    2014-08-14

    Green chemistry that uses water as a solvent has recently received great attention in organic synthesis. Here we report an efficient synthesis of biologically important isocoumarins through direct cleavage of C–H/O–H bonds by microwave-accelerated and Rh/Cu-catalyzed oxidative annulation of various substituted benzoic acids, where water is used as the only solvent in the reactions. The remarkable features of this “green” methodology include high product yields, wide tolerance of various functional groups as substrates, and excellent region-/site-specificities, thus rendering this methodology a highly versatile and eco-friendly alternative to the existing methods for synthesizing isocoumarins and other biologically important derivatives such as isoquinolones.

  1. Importance of the oxygen bond strength for catalytic activity in soot oxidation

    DEFF Research Database (Denmark)

    Christensen, Jakob M.; Grunwaldt, Jan-Dierk; Jensen, Anker D.

    2016-01-01

    (loose contact) the rate constants for a number of catalytic materials outline a volcano curve when plotted against their heats of oxygen chemisorption. However, the optima of the volcanoes correspond to different heats of chemisorption for the two contact situations. In both cases the activation...... oxidation. The optimum of the volcano curve in loose contact is estimated to occur between the bond strengths of α-Fe2O3 and α-Cr2O3. Guided by an interpolation principle FeaCrbOx binary oxides were tested, and the activity of these oxides was observed to pass through an optimum for an FeCr2Ox binary oxide...

  2. Characterization of two alkyl hydroperoxide reductase C homologs alkyl hydroperoxide reductase C_H1 and alkyl hydroperoxide reductase C_H2 in Bacillus subtilis

    Institute of Scientific and Technical Information of China (English)

    Mee-Kyung; Cha; Yoo-Jeen; Bae; Kyu-Jeong; Kim; Byung-Joon; Park; Il-Han; Kim

    2015-01-01

    AIM: To identify alkyl hydroperoxide reductase subunit C(AhpC) homologs in Bacillus subtilis(B. subtilis) and to characterize their structural and biochemical properties. AhpC is responsible for the detoxification of reactive oxygen species in bacteria.METHODS: Two AhpC homologs(AhpC_H1 and AhpC_H2) were identified by searching the B. subtilis database; these were then cloned and expressed in Escherichia coli. AhpC mutants carrying substitutions of catalytically important Cys residues(C37S, C47 S, C166 S, C37/47 S, C37/166 S, C47/166 S, and C37/47/166 S for AhpC_H1; C52 S, C169 S, and C52/169 S for AhpC_H2) were obtained by site-directed mutagenesis and purified, and their structure-function relationship was analyzed. The B. subtilis ahp C genes were disrupted by the short flanking homology method, and the phenotypes of the resulting AhpC-deficient bacteria were examined.RESULTS: Comparative characterization of AhpC homologs indicates that AhpC_H1 contains an extra C37, which forms a disulfide bond with the peroxidatic C47, and behaves like an atypical 2-Cys AhpC, while AhpC_H2 functions like a typical 2-Cys AhpC. Tryptic digestion analysis demonstrated the presence of intramolecular Cys37-Cys47 linkage, which could be reduced by thioredoxin, resulting in the association of the dimer into higher-molecular-mass complexes. Peroxidase activity analysis of Cys→Ser mutants indicated that three Cys residues were involved in the catalysis. AhpC_H1 was resistant to inactivation by peroxide substrates, but had lower activity at physiological H2O2 concentrations compared to AhpC_H2, suggesting that in B. subtilis, the enzymes may be physiologically functional at different substrate concentrations. The exposure to organic peroxides induced AhpC_H1 expression, while AhpC_H1-deficient mutants exhibited growth retardation in the stationary phase, suggesting the role of AhpC_H1 as an antioxidant scavenger of lipid hydroperoxides and a stress-response factor in B. subtilis

  3. Ethenolysis: A Green Catalytic Tool to Cleave Carbon-Carbon Double Bonds.

    Science.gov (United States)

    Bidange, Johan; Fischmeister, Cédric; Bruneau, Christian

    2016-08-22

    Remarkable innovations have been made in the field of olefin metathesis due to the design and preparation of new catalysts. Ethenolysis, which is cross-metathesis with ethylene, represents one catalytic transformation that has been used with the purpose of cleaving internal carbon-carbon double bonds. The objectives were either the ring opening of cyclic olefins to produce dienes or the shortening of unsaturated hydrocarbon chains to degrade polymers or generate valuable shorter terminal olefins in a controlled manner. This Review summarizes several aspects of this reaction: the catalysts, their degradation in the presence of ethylene, some parameters driving their productivity, the side reactions, and the applications of ethenolysis in organic synthesis and in potential industrial applications. PMID:27359344

  4. Aromatic Cyanoalkylation through Double C-H Activation Mediated by Ni(III).

    Science.gov (United States)

    Zhou, Wen; Zheng, Shuai; Schultz, Jason W; Rath, Nigam P; Mirica, Liviu M

    2016-05-11

    Herein we report an atom- and step-economic aromatic cyanoalkylation reaction that employs nitriles as building blocks and proceeds through Csp(2)-H and Csp(3)-H bond activation steps mediated by Ni(III). In addition to cyanomethylation with MeCN, regioselective α-cyanoalkylation was observed with various nitrile substrates to generate secondary and tertiary nitriles. Importantly, to the best of our knowledge these are the first examples of C-H bond activation reactions occurring at a Ni(III) center, which may exhibit different reactivity and selectivity profiles than those corresponding to analogous Ni(II) centers. These studies provide guiding principles to design catalytic C-H activation and functionalization reactions involving high-valent Ni species. PMID:27120207

  5. Seven organic salts assembled from hydrogen-bonds of N-H⋯O, O-H⋯O, and C-H⋯O between acidic compounds and bis(benzimidazole)

    Science.gov (United States)

    Jin, Shouwen; Liu, Hui; Gao, Xin Jun; Lin, Zhanghui; Chen, Guqing; Wang, Daqi

    2014-10-01

    Seven crystalline organic acid-base adducts derived from 1,4-bis(benzimidazol-2-yl)butane/1,2-bis(2-benzimidazolyl)-1,2-ethanediol and acidic components (picric acid, 2-hydroxy-5-(phenyldiazenyl)benzoic acid, 5-sulfosalicylic acid, oxalic acid, and 1,5-naphthalenedisulfonic acid) were prepared and characterized by the single crystal X-ray diffraction analysis, IR, mp, and elemental analysis. All of the seven compounds are organic salts involving proton transfer from the acidic components to the bis(benzimidazole). For the salt 3, although a competing carboxyl group is present, it has been observed that only the proton at the -SO3H group is deprotonized rather than the H at the COOH. While in the salt 7, both COOH and SO3H were ionized to exhibit a valence number of -2. For 4, the oxalic acid existed as unionized molecule, monoanion, and dianion simultaneously in one compound. All supramolecular architectures of the organic salts 1-7 involve extensive intermolecular N-H⋯O, O-H⋯O, and C-H⋯O hydrogen bonds as well as other noncovalent interactions. Since the potentially hydrogen bonding phenol group is present in the ortho position to the carboxyl group in 2, 3, and 7, it forms the more facile intramolecular O-H⋯O hydrogen bonding. The role of weak and strong noncovalent interactions in the crystal packing is ascertained. These weak interactions combined, all the complexes displayed 3D framework structure.

  6. Disulfide bonds in the catalytic subunit of skeletal muscle protein phosphatase

    International Nuclear Information System (INIS)

    The protein phosphatase in skeletal muscle that inactivates phosphorylase and phosphorylase kinase and activates glycogen synthase is both inhibited and reversibly activated/inactivated by a heat-stable protein called inhibitor-2 (I2). This enzyme, called type-1 or MgATP-dependent protein phosphatase, has a catalytic subunit (C) of M/sub r/ = 38,000. Conversion of the inactive to the active conformer of C occurs by reaction with Mn2+ or Co2+, or by dephosphorylation of I2 bound to the C. The C active conformer is cleaved by trypsin to give a stable catalytic fragment of M/sub r/ = 33,000 which resists denaturation by 80% ethanol. This fragment of C was purified by polylysine and Sephadex chromatography to over 20,000 U/mg. After boiling the catalytic fragment of C in 0.1% dodecyl sulfate containing dithiothreitol (DTT), reaction with [14C]-iodoacetate labeled about 1 residue/molecule. However, the authors found the same extent of labeling without DTT in 6M guanidine at pH 9 and in parallel reactions that contained DTT, labeling was increased over 10-fold. The fully labeled protein migrated at M/sub r/ = 33,000 during gel electrophoresis. Chymotryptic digestion in dodecyl sulfate yielded eight major 14C peptides that were resolved by reversed-phase HPLC. The results are interpreted as evidence that C contains one free Cys residue and as many as 5 disulfide bonds. Multiple disulfides would account for the unusual stability of C and intramolecular disulfide interchange is proposed as the mechanism for conversion of the conformers

  7. Formation and High Reactivity of the anti-Dioxo Form of High-Spin μ-Oxodioxodiiron(IV) as the Active Species That Cleaves Strong C-H Bonds.

    Science.gov (United States)

    Kodera, Masahito; Ishiga, Shin; Tsuji, Tomokazu; Sakurai, Katsutoshi; Hitomi, Yutaka; Shiota, Yoshihito; Sajith, P K; Yoshizawa, Kazunari; Mieda, Kaoru; Ogura, Takashi

    2016-04-18

    Recently, it was shown that μ-oxo-μ-peroxodiiron(III) is converted to high-spin μ-oxodioxodiiron(IV) through O-O bond scission. Herein, the formation and high reactivity of the anti-dioxo form of high-spin μ-oxodioxodiiron(IV) as the active oxidant are demonstrated on the basis of resonance Raman and electronic-absorption spectral changes, detailed kinetic studies, DFT calculations, activation parameters, kinetic isotope effects (KIE), and catalytic oxidation of alkanes. Decay of μ-oxodioxodiiron(IV) was greatly accelerated on addition of substrate. The reactivity order of substrates is toluenebond cleavage of ethylbenzene than the most reactive diiron system reported so far. The KIE for the reaction with toluene/[D8 ]toluene is 95 at -30 °C, which the largest in diiron systems reported so far. The present diiron complex efficiently catalyzes the oxidation of various alkanes with H2 O2 . PMID:26970337

  8. A Germanium Isocyanide Complex Featuring (n → π*) Back-Bonding and Its Conversion to a Hydride/Cyanide Product via C-H Bond Activation under Mild Conditions

    OpenAIRE

    Brown, Zachary; Vasko, Petra; Fettinger, James; Tuononen, Heikki; Power, Philip

    2012-01-01

    Reaction of the diarylgermylene Ge(ArMe6)2 [ArMe6 = C6H3-2,6-(C6H2-2,4,6-(CH3)3)2] with tert-butyl isocyanide gave the Lewis adduct species (ArMe6)2GeCNBut, in which the isocyanide ligand displays a decreased C–N stretching frequency consistent with an n → π* back-bonding interaction. Density functional theory confirmed that the HOMO is a Ge–C bonding combination between the lone pair of electrons on the germanium atom and the C–N π* orbital of the isocyanide ligand. The complex undergoes fac...

  9. Gas-phase chemistry of Sc(CH{sub 3}){sub 2}{sup +} with alkenes: Activation of allylic C-H bonds by a d{sup 0} system and the migratory insertion of C=C bonds into Sc{sup +}-CH{sub 3} bonds

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Yongqing; Hill, Y.D.; Freiser, B.S. [Purdue Univ., West Lafayette, IN (United States)] [and others

    1992-11-04

    The gas-phase chemistry of Sc(CH{sub 3}){sub 2}{sup +} with alkenes was studied by Fourier transform mass spectrometry. The metal center on Sc(CH{sub 3}){sub 2}{sup +} is d{sup 0}, providing an opportunity to study alternative mechanisms of C-C or C-H activation other than the most common one involving oxidative addition. The elimination of H{sub 2} is observed in the reaction of Sc(CH{sub 3}){sub 2}{sup +} with ethylene, and the product ScC{sub 4}H{sub 8}{sup +} and ScC{sub 6}H{sub 10}{sup +} ions have a metal(methyl)(allyl) and metal-bisallyl structure, respectively, consistent with a proposed reaction mechanism involving the consecutive migratory insertion of ethylenes into the scandium-methyl bonds. In addition, theoretical calculations indicate that the metal(methyl)(allyl) structure is between 10 and 20 kcal/mol more stable than the metal(1-butene) isomer. Sc(CH{sub 3}){sub 2}{sup +} reacts with propene to form predominantly ScC{sub 4}H{sub 8}{sup +} by loss of CH{sub 4}, with minor amounts of ScC{sub 3}H{sub 4}{sup +} and ScC{sub 4}H{sub 6}{sup +} also observed. ScC{sub 4}H{sub 6}{sup +} is formed as either the exclusive or the predominant product ion in the reactions of Sc(CH{sub 3}){sub 2}{sup +} with butenes. Sc(CH{sub 3}){sub 2} reacts with cyclopentene to form predominantly ScC{sub 6}H{sub 8}{sup +} by losing CH{sub 4} and H{sub 2}. Isotope labeling studies with Sc(CD{sub 3}){sub 2}{sup +} and other structure studies indicate that all of the alkenes studied, with the exception of ethylene, react with Sc(CH{sub 3}){sub 2}{sup +} via a multicentered {sigma}-bond metathesis mechanism to activate allylic C-H bonds. Finally, the dehydrogenation reactions of Sc{sup +} with n-butane and neopentane were revisited, and a new mechanism is proposed for such chemistry in light of the new results from this study. 34 refs., 5 figs., 2 tabs.

  10. Iron-Catalyzed C-H Functionalization Processes.

    Science.gov (United States)

    Cera, Gianpiero; Ackermann, Lutz

    2016-10-01

    Iron-catalyzed C-H activation has recently emerged as an increasingly powerful tool for the step-economical transformation of unreactive C-H bonds. Particularly, the recent development of low-valent iron catalysis has set the stage for novel C-H activation strategies via chelation assistance. The low-cost, natural abundance, and low toxicity of iron prompted its very recent application in organometallic C-H activation catalysis. An overview of the use of iron catalysis in C-H activation processes is summarized herein up to May 2016. PMID:27573499

  11. Phosphinocyclodextrins as confining units for catalytic metal centres. Applications to carbon–carbon bond forming reactions

    Directory of Open Access Journals (Sweden)

    Matthieu Jouffroy

    2014-10-01

    Full Text Available The capacity of two cavity-shaped ligands, HUGPHOS-1 and HUGPHOS-2, to generate exclusively singly phosphorus-ligated complexes, in which the cyclodextrin cavity tightly wraps around the metal centre, was explored with a number of late transition metal cations. Both cyclodextrin-derived ligands were assessed in palladium-catalysed Mizoroki–Heck coupling reactions between aryl bromides and styrene on one hand, and the rhodium-catalysed asymmetric hydroformylation of styrene on the other hand. The inability of both chiral ligands to form standard bis(phosphine complexes under catalytic conditions was established by high-pressure NMR studies and shown to have a deep impact on the two carbon–carbon bond forming reactions both in terms of activity and selectivity. For example, when used as ligands in the rhodium-catalysed hydroformylation of styrene, they lead to both high isoselectivity and high enantioselectivity. In the study dealing with the Mizoroki–Heck reactions, comparative tests were carried out with WIDEPHOS, a diphosphine analogue of HUGPHOS-2.

  12. p-tert-Butylcalix[4]arene complexes of molybdenum and tungsten: reactivity of the calixarene methylene C-H bond and the facile migration of the metal around the phenolic rim of the calixarene.

    Science.gov (United States)

    Buccella, Daniela; Parkin, Gerard

    2006-12-20

    p-tert-Butylcalix[4]arene, [CalixBut(OH)4], reacts with Mo(PMe3)6 and W(PMe3)4(eta2-CH2PMe2)H to yield compounds of composition {[CalixBut(OH)2(O)2]M(PMe3)3H2} which exhibit unprecedented use of a C-H bond of a calixarene methylene group as a binding functionality in the form of agostic and alkyl hydride derivatives. Thus, X-ray diffraction studies demonstrate that, in the solid state, the molybdenum complex [CalixBut(OH)2(O)2]Mo(PMe3)3H2 exists as an agostic derivative with a Mo...H-C interaction, whereas the tungsten complex exists as a metallated trihydride [Calix-HBut(OH)2(O)2]W(PMe3)3H3. Solution 1H NMR spectroscopic studies, however, provide evidence that [Calix-HBut(OH)2(O)2]W(PMe3)3H3 is in equilibrium with its agostic isomer [CalixBut(OH)2(O)2]W(PMe3)3H2. Dynamic NMR spectroscopy also indicates that the [M(PMe3)3H2] fragments of both the molybdenum and tungsten complexes [CalixBut(OH)2(O)2]M(PMe3)3H2 migrate rapidly around the phenolic rim of the calixarene on the NMR time scale, an observation that is in accord with incorporation of deuterium into the methylene endo positions upon treatment of the isomeric mixture of [CalixBut(OH)2(O)2]W(PMe3)3H2 and [Calix-HBut(OH)2(O)2]W(PMe3)3H3 with D2. Treatment of {[CalixBut(OH)2(O)2]W(PMe3)3H2} with Ph2C2 gives the alkylidene complex [CalixBut(O)4]W=C(Ph)Ar [Ar = PhCC(Ph)CH2Ph]. PMID:17165791

  13. Reliability Tests of Aluminium Wedge Wire Bonding on Auto-catalytic Silver Immersion Gold (ASIG) PCB Metallization

    CERN Document Server

    Drozd, A; Kaufmann, S; Manolescu, F; McGill, I

    2011-01-01

    The Auto-catalytic Silver Immersion Gold (ASIG) PCB metallization is a new process that has clear advantages for PCB assembly especially with regard to lead-free soldering. As it may become a popular process in the future for electronics used in physics experiments, the quality of this metallization for aluminium wire bonding has been studied. Aluminium wedge wire bonding continues to be the interconnection method of choice for many physics detector sensors, for high density signal routing and for unpackaged die. Although advertised as having good quality for aluminium wire bonding, this study was performed to verify this claim as well as to test the longer term reliability of the wire bonds taking into consideration the environmental conditions and life-expectancy of devices, in particular for high energy physics detector applications. The tests were performed on PCBs made with the ASIG and ENIG (Electro-less Nickel Immersion Gold) processes at the same time in order to make a comparison with the current ind...

  14. Manganese Catalyzed C-H Halogenation.

    Science.gov (United States)

    Liu, Wei; Groves, John T

    2015-06-16

    The remarkable aliphatic C-H hydroxylations catalyzed by the heme-containing enzyme, cytochrome P450, have attracted sustained attention for more than four decades. The effectiveness of P450 enzymes as highly selective biocatalysts for a wide range of oxygenation reactions of complex substrates has driven chemists to develop synthetic metalloporphyrin model compounds that mimic P450 reactivity. Among various known metalloporphyrins, manganese derivatives have received considerable attention since they have been shown to be versatile and powerful mediators for alkane hydroxylation and olefin epoxidation. Mechanistic studies have shown that the key intermediates of the manganese porphyrin-catalyzed oxygenation reactions include oxo- and dioxomanganese(V) species that transfer an oxygen atom to the substrate through a hydrogen abstraction/oxygen recombination pathway known as the oxygen rebound mechanism. Application of manganese porphyrins has been largely restricted to catalysis of oxygenation reactions until recently, however, due to ultrafast oxygen transfer rates. In this Account, we discuss recently developed carbon-halogen bond formation, including fluorination reactions catalyzed by manganese porphyrins and related salen species. We found that biphasic sodium hypochlorite/manganese porphyrin systems can efficiently and selectively convert even unactivated aliphatic C-H bonds to C-Cl bonds. An understanding of this novel reactivity derived from results obtained for the oxidation of the mechanistically diagnostic substrate and radical clock, norcarane. Significantly, the oxygen rebound rate in Mn-mediated hydroxylation is highly correlated with the nature of the trans-axial ligands bound to the manganese center (L-Mn(V)═O). Based on the ability of fluoride ion to decelerate the oxygen rebound step, we envisaged that a relatively long-lived substrate radical could be trapped by a Mn-F fluorine source, effecting carbon-fluorine bond formation. Indeed, this idea

  15. Mapping the Hydrogen Bond Networks in the Catalytic Subunit of Protein Kinase A Using H/D Fractionation Factors.

    Science.gov (United States)

    Li, Geoffrey C; Srivastava, Atul K; Kim, Jonggul; Taylor, Susan S; Veglia, Gianluigi

    2015-07-01

    Protein kinase A is a prototypical phosphoryl transferase, sharing its catalytic core (PKA-C) with the entire kinase family. PKA-C substrate recognition, active site organization, and product release depend on the enzyme's conformational transitions from the open to the closed state, which regulate its allosteric cooperativity. Here, we used equilibrium nuclear magnetic resonance hydrogen/deuterium (H/D) fractionation factors (φ) to probe the changes in the strength of hydrogen bonds within the kinase upon binding the nucleotide and a pseudosubstrate peptide (PKI5-24). We found that the φ values decrease upon binding both ligands, suggesting that the overall hydrogen bond networks in both the small and large lobes of PKA-C become stronger. However, we observed several important exceptions, with residues displaying higher φ values upon ligand binding. Notably, the changes in φ values are not localized near the ligand binding pockets; rather, they are radiated throughout the entire enzyme. We conclude that, upon ligand and pseudosubstrate binding, the hydrogen bond networks undergo extensive reorganization, revealing that the open-to-closed transitions require global rearrangements of the internal forces that stabilize the enzyme's fold. PMID:26030372

  16. Identification and H(D)-bond energies of C-H(D)Cl interactions in chloride-haloalkane clusters: a combined X-ray crystallographic, spectroscopic, and theoretical study.

    Science.gov (United States)

    Serebryanskaya, Tatiyana V; Novikov, Alexander S; Gushchin, Pavel V; Haukka, Matti; Asfin, Ruslan E; Tolstoy, Peter M; Kukushkin, Vadim Yu

    2016-05-18

    The cationic (1,3,5-triazapentadiene)Pt(II) complex [Pt{NH[double bond, length as m-dash]C(N(CH2)5)N(Ph)C(NH2)[double bond, length as m-dash]NPh}2]Cl2 ([]Cl2) was crystallized from four haloalkane solvents giving [][Cl2(CDCl3)4], [][Cl2(CHBr3)4], [][Cl2(CH2Cl2)2], and [][Cl2(C2H4Cl2)2] solvates that were studied by X-ray diffraction. In the crystal structures of [][Cl2(CDCl3)4] and [][Cl2(CHBr3)4], the Cl(-) ion interacts with two haloform molecules via C-DCl(-) and C-HCl(-) contacts, thus forming the negatively charged isostructural clusters [Cl(CDCl3)2](-) and [Cl(CHBr3)2](-). In the structures of [][Cl2(CH2Cl2)2] and [][Cl2(C2H4Cl2)2], cations [](2+) are linked to a 3D-network by a system of H-bondings including one formed by each Cl(-) ion with CH2Cl2 or C2H4Cl2 molecules. The lengths and energies of these H-bonds in the chloride-haloalkane clusters were analyzed by DFT calculations (M06 functional) including AIM analysis. The crystal packing noticeably affected the geometry of the clusters, and energy of C-HCl(-) hydrogen bonds ranged from 1 to 6 kcal mol(-1). An exponential correlation (R(2) > 0.98) between the calculated Cl(-)H distances and the energies of the corresponding contacts was found and used to calculate hydrogen bond energies from the experimental Cl(-)H distances. Predicted energy values (3.3-3.9 kcal mol(-1) for the [Cl(CHCl3)2](-) cluster) are in a reasonable agreement with the energy of the Cl3C-HCl(-) bond estimated using ATRFTIR spectroscopy (2.7 kcal mol(-1)). PMID:27157359

  17. Advances and perspectives in catalytic oxidation of hydrocarbons in liquid phase

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    This review article summarizes recent advances in catalytic oxidation of hydrocarbons, especially presents two strategies for activation of C-H bonds or molecular oxygen. Based on our own research results, the applications of the two methods in the oxidation of cyclohexane, toluene and ethyl benzene, etc. are introduced, and the perspectives of the two methods are also discussed.

  18. Structure, bonding, and catalytic activity of monodisperse, transition-metal-substituted CeO2 nanoparticles.

    Science.gov (United States)

    Elias, Joseph S; Risch, Marcel; Giordano, Livia; Mansour, Azzam N; Shao-Horn, Yang

    2014-12-10

    We present a simple and generalizable synthetic route toward phase-pure, monodisperse transition-metal-substituted ceria nanoparticles (M0.1Ce0.9O2-x, M = Mn, Fe, Co, Ni, Cu). The solution-based pyrolysis of a series of heterobimetallic Schiff base complexes ensures a rigorous control of the size, morphology and composition of 3 nm M0.1Ce0.9O2-x crystallites for CO oxidation catalysis and other applications. X-ray absorption spectroscopy confirms the dispersion of aliovalent (M(3+) and M(2+)) transition metal ions into the ceria matrix without the formation of any bulk transition metal oxide phases, while steady-state CO oxidation catalysis reveals an order of magnitude increase in catalytic activity with copper substitution. Density functional calculations of model slabs of these compounds confirm the stabilization of M(3+) and M(2+) in the lattice of CeO2. These results highlight the role of the host CeO2 lattice in stabilizing high oxidation states of aliovalent transition metal dopants that ordinarily would be intractable, such as Cu(3+), as well as demonstrating a rational approach to catalyst design. The current work demonstrates, for the first time, a generalizable approach for the preparation of transition-metal-substituted CeO2 for a broad range of transition metals with unparalleled synthetic control and illustrates that Cu(3+) is implicated in the mechanism for CO oxidation on CuO-CeO2 catalysts. PMID:25406101

  19. Understanding of chemical bonding towards the enhancement of catalytic of Co(III)-doped ZrO2 catalyst material using x-ray photoelectron spectroscopy

    International Nuclear Information System (INIS)

    The x-ray photoelectron spectroscopy (XPS) analysis has demonstrated the formation metal ions in different oxidation states or similar oxidation state with different bonding character in the ZrO2 based catalyst material. Interaction of cobalt oxide with ZrO2 matrixes shows the formation of surface species of Zr-O-Co with Co in the +2 oxidation state and Co3O4-CoO in a mixture of +2 and +3 oxidation states. The formation of Zr-O-Co species in sample calcined at 400 degree C results in the more ionic character of Co-O bond and more covalent character of Zr-0 bond compared to their ordinary oxides. These behaviour cause the shifting of Co(2p) XPS peaks position towards higher binding energy and the Zr(3d) XPS peaks position towards lower binding energy. Meanwhile, the formation Of Co304-CoO in sample calcined at temperature of 600 degree C exhibits Co(2p) XPS peaks in the region correspond to the Co in the +2 and +3 oxidation states, which is more covalent in bonding character. The catalytic activity measurement of the catalyst material calcined at 600 oC showed that the existence of Co-O species with more covalent in bonding character gave the best catalytic performance towards 100 % conversion of carbon monoxide and propane. (Author)

  20. Scalable and sustainable electrochemical allylic C-H oxidation.

    Science.gov (United States)

    Horn, Evan J; Rosen, Brandon R; Chen, Yong; Tang, Jiaze; Chen, Ke; Eastgate, Martin D; Baran, Phil S

    2016-05-01

    New methods and strategies for the direct functionalization of C-H bonds are beginning to reshape the field of retrosynthetic analysis, affecting the synthesis of natural products, medicines and materials. The oxidation of allylic systems has played a prominent role in this context as possibly the most widely applied C-H functionalization, owing to the utility of enones and allylic alcohols as versatile intermediates, and their prevalence in natural and unnatural materials. Allylic oxidations have featured in hundreds of syntheses, including some natural product syntheses regarded as "classics". Despite many attempts to improve the efficiency and practicality of this transformation, the majority of conditions still use highly toxic reagents (based around toxic elements such as chromium or selenium) or expensive catalysts (such as palladium or rhodium). These requirements are problematic in industrial settings; currently, no scalable and sustainable solution to allylic oxidation exists. This oxidation strategy is therefore rarely used for large-scale synthetic applications, limiting the adoption of this retrosynthetic strategy by industrial scientists. Here we describe an electrochemical C-H oxidation strategy that exhibits broad substrate scope, operational simplicity and high chemoselectivity. It uses inexpensive and readily available materials, and represents a scalable allylic C-H oxidation (demonstrated on 100 grams), enabling the adoption of this C-H oxidation strategy in large-scale industrial settings without substantial environmental impact. PMID:27096371

  1. Réactions de cycloisomérisation d'ènynes en présence de complexes d'or, de platine et d'ions halogéniums - Approche combinatoire en présence de complexes de platine. Réactions d'acyloxylation par activation C-H d'aromatiques en présence de complexes d'or.

    OpenAIRE

    Pradal, Alexandre

    2012-01-01

    This manuscript concerns the development of electrophilic systems, involving gold and platinum π-Lewis acids or halogenium ions and their involvement in C-C triple bond (stereoselective enyne cycloisomerization reactions in the presence or in the absence of an external nucleophile and halocarbocyclization reactions) and C-H bond (acyloxylation reactions of hindered arenes) activation processes. The use of a catalytic system which consists in a binuclear gold (I) complex possessing the diphosp...

  2. Tetra-substituted olefin synthesis using palladium-catalysed C-H activation

    OpenAIRE

    Lopez Suarez, Laura; Suarez, Laura Lopez

    2012-01-01

    In an effort to obtain more efficient and greener chemical transformations, a substantial amount of research interest has been directed towards the use of arene C-H bonds as functional groups. Hydroarylation of alkynes through direct functionalisation of C-H bonds has been studied in recent years leading to the development of high-yielding metal-mediated processes. The main aim of the current work is the addition of a third component in the hydroarylation of alkynes trough C-H activation, in ...

  3. Rhodium-catalyzed C-C coupling reactions via double C-H activation.

    Science.gov (United States)

    Li, Shuai-Shuai; Qin, Liu; Dong, Lin

    2016-05-18

    Various rhodium-catalyzed double C-H activations are reviewed. These powerful strategies have been developed to construct C-C bonds, which might be widely embedded in complex aza-fused heterocycles, polycyclic skeletons and heterocyclic scaffolds. In particular, rhodium(iii) catalysis shows good selectivity and reactivity to functionalize the C-H bond, generating reactive organometallic intermediates in most of the coupling reactions. Generally, intermolecular, intramolecular and multi-component coupling reactions via double C-H activations with or without heteroatom-assisted chelation are discussed in this review. PMID:27099126

  4. Iridium-mediated Bond Activation and Water Oxidation as an Exemplary Case of CARISMA, A European Network for the Development of Catalytic Routines for Small Molecule Activation.

    Science.gov (United States)

    Licini, Giulia; Albrecht, Martin

    2015-01-01

    CARISMA is a currently running COST Action that pools leading European experts in computational and experimental chemistry to foster synergies for developing new catalytic processes for the transformation of abundant small molecules such as water, carbon dioxide, or ammonia into high-value chemicals and energy-relevant products. CARISMA promotes new collaborations, exchange of knowledge and skills, frontier training to young as well as established researchers, and a platform for the advancement of theoretical and experimental research in an iterative process, comprised of expertise in various connate domains including synthesis, catalysis, spectroscopy, kinetics, and computational chemistry. These interactions stimulate the discovery of new and efficient catalytic processes, illustrated in the second part of this contribution with the collaborative development of powerful iridium-based complexes for bond activation and water oxidation catalysis. PMID:26507475

  5. Catalytic diastereoselective tandem conjugate addition-elimination reaction of Morita-Baylis-Hillman C adducts by C-C bond cleavage

    KAUST Repository

    Yang, Wenguo

    2012-02-08

    Through the cleavage of the C-C bond, the first catalytic tandem conjugate addition-elimination reaction of Morita-Baylis-Hillman C adducts has been presented. Various S N2′-like C-, S-, and P-allylic compounds could be obtained with exclusive E configuration in good to excellent yields. The Michael product could also be easily prepared by tuning the β-C-substituent group of the α-methylene ester under the same reaction conditions. Calculated relative energies of various transition states by DFT methods strongly support the observed chemoselectivity and diastereoselectivity. © 2012 Wiley-VCH Verlag GmbH&Co. KGaA, Weinheim.

  6. Silver(I) NHC mediated C-C bond activation of alkyl nitriles and catalytic efficiency in oxazoline synthesis.

    Science.gov (United States)

    Heath, Rachael; Müller-Bunz, Helge; Albrecht, Martin

    2015-05-21

    Preparation of silver triazolylidene (trz) species from triazolium salts and Ag2O in refluxing MeCN leads to a selective C-C bond cleavage and the formation of complexes of general formula [(trz)Ag(CN)] from Calkyl-CN bond activation. Moreover, these silver carbene complexes are precursors of highly active catalysts for oxazoline formation via aldol condensation. PMID:25913007

  7. Synthetic Transformations through Alkynoxy-Palladium Interactions and C-H Activation.

    Science.gov (United States)

    Minami, Yasunori; Hiyama, Tamejiro

    2016-01-19

    Organic synthesis based on straightforward transformations is essential for environmentally benign manufacturing for the invention of novel pharmaceuticals, agrochemicals, and organoelectronic materials in order to ultimately realize a sustainable society. Metal-catalyzed C-H bond-cleaving functionalization has become a promising method for achieving the above goal. For site-selective C-H bond cleavage, so-called directing groups, i.e., ligands attached to substrates, are employed. Commonly utilized directing groups are carbonyls, imines, carboxyls, amides, and pyridyls, which σ-donate electron pairs to metals. On the other hand, unsaturated substrates such as alkenes and alkynes, which participate largely as reactants in organic synthesis, are prepared readily by a wide variety of synthetic transformations and are also employed as reactants in organometallic chemistry. Moreover, such unsaturated groups form complexes with some metals by ligation of their p orbitals via donation and back-donation. However, the use of unsaturated bonds as directing groups has not been studied extensively. We have been involved in the development of methods for the cleavage of C-H bonds by means of transition-metal catalysts to achieve new carbon-carbon bond-forming reactions and incidentally came to focus on the alkynoxy group (-OC≡C-), which shows a ketene-like resonance structure. We expected the alkynoxy group to interact electrophilically with a low-valent transition-metal complex in order to cleave adjacent C-H bonds. In this Account, we summarize our recent achievements on C-H activation based on interactions of palladium with the alkynoxy group in alkynyl aryl ethers. The alkynoxy group plays two roles in the transformation: as a directing group for adjacent C-H bond activation and as an acceptor for the carbon and hydrogen fragments. A typical example is palladium-catalyzed ortho-C-H bond activation in alkynoxyarenes followed by sequential insertion/annulation with

  8. Constructing a Catalytic Cycle for C-F to C-X (X = O, S, N) Bond Transformation Based on Gold-Mediated Ligand Nucleophilic Attack.

    Science.gov (United States)

    Hu, Ji-Yun; Zhang, Jing; Wang, Gao-Xiang; Sun, Hao-Ling; Zhang, Jun-Long

    2016-03-01

    A tricoordinated gold(I) chloride complex, tBuXantphosAuCl, supported by a sterically bulky 9,9-dimethyl-4,5-bis(di-tert-butylphosphino)xanthene ligand (tBuXantphos) was synthesized. This complex features a remarkably longer Au-Cl bond length [2.632(1) Å] than bicoordinated linear gold complexes (2.27-2.30 Å) and tricoordinated XantphosAuCl [2.462(1) Å]. Single-crystal X-ray diffraction analysis of a cocrystal of tBuXantphosAuCl and pentafluoronitrobenzene (PFNB) and UV-vis spectroscopic titration experiments revealed the existence of an anion-π interaction between the Cl anion ligand and PFNB. Stoichiometric reaction between PFNB and tBuXantphosAuOtBu, after replacement of Cl by a more nucleophilic tBuO anion ligand, showed higher reactivity and para selectivity in the transformation of C-F to C-OtBu bond, distinctively different from that when only KOtBu was used (ortho selectivity) under the identical condition. Mechanistic studies including density functional theory calculations suggested a gold-mediated nucleophilic ligand attack of the C-F bond pathway via an SNAr process. On the basis of these results, using trimethylsilyl derivatives TMS-X (X = OMe, SEt, NEt2) as the nucleophilic ligand source and the fluorine acceptor, catalytic transformation of the C-F bond of aromatic substrates to the C-X (X = O, S, N) bond was achieved with tBuXantphosAuCl as the catalyst (up to 20 turnover numbers). PMID:26872251

  9. Allylic and benzylic sp3 C-H oxidation in water.

    Science.gov (United States)

    Ang, Wei Jie; Lam, Yulin

    2015-01-28

    A copper-catalyzed method for the oxidation of allylic and benzylic sp(3) C-H by aqueous tert-butyl hydroperoxide (T-Hydro) in water using a recyclable fluorous ligand has been developed. The reaction procedure is tolerant to additional functional groups and the fluorous ligand could be reused with little loss of catalytic activity. PMID:25412371

  10. Effects of lithium-implantation on the hydrogen retention in both a-C:H and a-Si C:H materials submitted to deuterium bombardment

    Energy Technology Data Exchange (ETDEWEB)

    Barbier, G.; Chevarier, N.; Chevarier, A. [Lyon-1 Univ., 69 -Villeurbanne (France). Inst. de Physique Nucleaire; Ross, G.G.; El Khakani, M.A. [INRS-Energie et Materiaux, Varennes, PQ (Canada)

    1996-09-01

    The hydrogen release in plasma facing materials is a challenging problem for the hydrogen recycling. The hydrogen desorption from a-C:H and a-SiC:H materials induced by deuterium bombardment has been investigated. Prior to the deuterium bombardment, both materials were implanted with different fluences of lithium ions. Before and after each irradiation, depth profiles of H, Li and deuterium were determined by nuclear microanalysis. After deuterium bombardment, il is shown that the retention of the initial hydrogen in both materials was enhanced by increasing the total dose of the implanted Li. For the a-C:H samples, the hydrogen desorption under deuterium bombardment was strongly reduced by lithium implantation. This effect was also evidenced in a-SiC:H samples, even though it is less spectacular that in a-C:H. Also, nuclear analyses showed that the retained dose of deuterium decreases when the lithium concentration increases. This could be a result of the formation of Li-H bonds which occurs to the detriment of deuterium retention in both a-C:H and a-SiC:H materials. Preliminary results of both materials exposed to TdeV tokamak discharges confirms the role of Li in hydrogen retention, already observed in deuterium bombardment exposure. (author).

  11. Effects of hydrogen bonds in association with flavin and substrate in flavoenzyme d-amino acid oxidase. The catalytic and structural roles of Gly313 and Thr317.

    Science.gov (United States)

    Setoyama, Chiaki; Nishina, Yasuzo; Tamaoki, Haruhiko; Mizutani, Hisashi; Miyahara, Ikuko; Hirotsu, Ken; Shiga, Kiyoshi; Miura, Retsu

    2002-01-01

    According to the three-dimensional structure of a porcine kidney D-amino acid oxidase-substrate (D-leucine) complex model, the G313 backbone carbonyl recognizes the substrate amino group by hydrogen bonding and the side-chain hydroxyl of T317 forms a hydrogen bond with C(2)=O of the flavin moiety of FAD [Miura et al. (1997) J. Biochem. 122, 825-833]. We have designed and expressed the G313A and T317A mutants and compared their enzymatic and spectroscopic properties with those of the wild type. The G313A mutant shows decreased activities to various D-amino acids, but the pattern of substrate specificity is different from that of the wild type. The results imply that the hydrogen bond between the G313 backbone carbonyl and the substrate amino group plays important roles in substrate recognition and in defining the substrate specificity of D-amino acid oxidase. The T317A mutant shows a decreased affinity for FAD. The steady-state kinetic measurements indicate diminished activities of T317A to substrate D-amino acids. The transient kinetic parameters measured by stopped-flow spectroscopy revealed that T317 plays key roles in stabilizing the purple intermediate, a requisite intermediate in the oxidative half-reaction, and in enhancing the release of the product from the active site, thereby optimizing the overall catalytic process of D-amino acid oxidase. PMID:11754736

  12. Design and Synthesis of Chiral Zn2+ Complexes Mimicking Natural Aldolases for Catalytic C–C Bond Forming Reactions in Aqueous Solution

    Directory of Open Access Journals (Sweden)

    Susumu Itoh

    2014-01-01

    Full Text Available Extending carbon frameworks via a series of C–C bond forming reactions is essential for the synthesis of natural products, pharmaceutically active compounds, active agrochemical ingredients, and a variety of functional materials. The application of stereoselective C–C bond forming reactions to the one-pot synthesis of biorelevant compounds is now emerging as a challenging and powerful strategy for improving the efficiency of a chemical reaction, in which some of the reactants are subjected to successive chemical reactions in just one reactor. However, organic reactions are generally conducted in organic solvents, as many organic molecules, reagents, and intermediates are not stable or soluble in water. In contrast, enzymatic reactions in living systems proceed in aqueous solvents, as most of enzymes generally function only within a narrow range of temperature and pH and are not so stable in less polar organic environments, which makes it difficult to conduct chemoenzymatic reactions in organic solvents. In this review, we describe the design and synthesis of chiral metal complexes with Zn2+ ions as a catalytic factor that mimic aldolases in stereoselective C–C bond forming reactions, especially for enantioselective aldol reactions. Their application to chemoenzymatic reactions in aqueous solution is also presented.

  13. Decorative a-C:H coatings

    Czech Academy of Sciences Publication Activity Database

    Černý, F.; Jech, V.; Štěpánek, I.; Macková, Anna; Konvičková, S.

    roč. 256, 3 s. 1 (2009), s77-s81. ISSN 0169-4332 Institutional research plan: CEZ:AV0Z10480505 Keywords : a-C:H films * decorative coatings * adhesion Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.616, year: 2009

  14. Rhodium (II) carbene C-H insertion in water and catalyst reuse

    International Nuclear Information System (INIS)

    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 Rh2(OAc)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)

  15. Overcoming the "oxidant problem": strategies to use O2 as the oxidant in organometallic C-H oxidation reactions catalyzed by Pd (and Cu).

    Science.gov (United States)

    Campbell, Alison N; Stahl, Shannon S

    2012-06-19

    Oxidation reactions are key transformations in organic chemistry because they can increase chemical complexity and incorporate heteroatom substituents into carbon-based molecules. This principle is manifested in the conversion of petrochemical feedstocks into commodity chemicals and in the synthesis of fine chemicals, pharmaceuticals, and other complex organic molecules. The utility and function of these molecules correlate directly with the presence and specific placement of oxygen and nitrogen heteroatoms and other functional groups within the molecules. Methods for selective oxidation of C-H bonds have expanded significantly over the past decade, and their role in the synthesis of organic chemicals will continue to increase. Our group's contributions to this field are linked to our broader interest in the development and mechanistic understanding of aerobic oxidation reactions. Molecular oxygen (O(2)) is the ideal oxidant. Its low cost and lack of toxic byproducts make it a highly appealing reagent that can address key "green chemistry" priorities in industry. With strong economic and environmental incentives to use O(2), the commmodity chemicals industry often uses aerobic oxidation reactions. In contrast, O(2) is seldom used to prepare more-complex smaller-volume chemicals, a limitation that reflects, in part, the limited synthetic scope and utility of existing aerobic reactions. Pd-catalyzed reactions represent some of the most versatile methods for selective C-H oxidation, but they often require stoichiometric transition-metal or organic oxidants, such as Cu(II), Ag(I), or benzoquinone. This Account describes recent strategies that we have identified to use O(2) as the oxidant in these reactions. In Pd-catalyzed C-H oxidation reactions that form carbon-heteroatom bonds, the stoichiometric oxidant is often needed to promote difficult reductive elimination steps in the catalytic mechanism. To address this challenge, we have identified new ancillary ligands for

  16. N-Methylphthalimide-substituted benzimidazolium salts and PEPPSI Pd–NHC complexes: synthesis, characterization and catalytic activity in carbon–carbon bond-forming reactions

    Science.gov (United States)

    Gök, Yetkin; İlhan, İlhan Özer

    2016-01-01

    Summary A series of novel benzimidazolium salts (1–4) and their pyridine enhanced precatalyst preparation stabilization and initiation (PEPPSI) themed palladium N-heterocyclic carbene complexes [PdCl2(NHC)(Py)] (5–8), where NHC = 1-(N-methylphthalimide)-3-alkylbenzimidazolin-2-ylidene and Py = 3-chloropyridine, were synthesized and characterized by means of 1H and 13C{1H} NMR, UV–vis (for 5–8), ESI-FTICR-MS (for 2, 4, 6–8) and FTIR spectroscopic methods and elemental analysis. The synthesized compounds were tested in Suzuki–Miyaura cross-coupling (for 1–8) and arylation (for 5–8) reactions. As catalysts, they demonstrated a highly efficient route for the formation of asymmetric biaryl compounds even though they were used in very low loading. For example, all compounds displayed good catalytic activity for the C–C bond formation of 4-tert-butylphenylboronic acid with 4-chlorotoluene. PMID:26877810

  17. Theoretical studies of the proton transfer behaviors in molecular complexes analogous to catalytic triad of serine protease: Toward understanding the existence and significance of the low-barrier hydrogen-bond in enzymatic catalysis

    Institute of Scientific and Technical Information of China (English)

    LI Ping; WANG WeiHua; BI SiWei; SONG Rui; BU YuXiang

    2009-01-01

    A representative acetate-(5-methylimidazole)-methanol system has been employed as a model of cata-lytic triad in serine protease to validate the formation processes of low-barrier H-bonds (LBHB) at the B3LYP/6-311++G** level of theory, and variable H-bonding characters from conventional ones to LBHBs have been represented along with the proceedings of proton transfer. Solvent effect is an important factor in modulation of the existence of an LBHB, where an LBHB (or a conventional H-bond) in the gas phase can be changed into a non-LBHB (an LBHB) upon solvation. The origin of the additional stabili-zation energy arising from the LBHB may be attributed to the H-bonding energy difference before and after proton transfer because the shared proton can freely move between the proton donor and proton acceptor. Most importantly, the order of magnitude of the stabilization energy depends on the studied systems. Furthermore, the nonexistence of LBHBs in the catalytic triad of serine proteases has been verified in a more sophisticated model treated using the ONIOM method. As a result, only the single proton transfer mechanism in the catalytic triad has been confirmed and the origin of the powerful catalytic efficiency of serine proteases should be attributed to other factors rather than the LBHB.

  18. Theoretical studies of the proton transfer behaviors in molecular complexes analogous to catalytic triad of serine protease:Toward understanding the existence and significance of the low-barrier hydrogen-bond in enzymatic catalysis

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    A representative acetate-(5-methylimidazole)-methanol system has been employed as a model of catalytic triad in serine protease to validate the formation processes of lowbarrier H-bonds(LBHB) at the B3LYP/6-311++G level of theory,and variable H-bonding characters from conventional ones to LBHBs have been represented along with the proceedings of proton transfer.Solvent effect is an important factor in modulation of the existence of an LBHB,where an LBHB(or a conventional H-bond) in the gas phase can be changed into a non-LBHB(an LBHB) upon solvation.The origin of the additional stabili-zation energy arising from the LBHB may be attributed to the H-bonding energy difference before and after proton transfer because the shared proton can freely move between the proton donor and proton acceptor.Most importantly,the order of magnitude of the stabilization energy depends on the studied systems.Furthermore,the nonexistence of LBHBs in the catalytic triad of serine proteases has been verified in a more sophisticated model treated using the ONIOM method.As a result,only the single proton transfer mechanism in the catalytic triad has been confirmed and the origin of the powerful catalytic efficiency of serine proteases should be attributed to other factors rather than the LBHB.

  19. Palladium-catalysed transannular C-H functionalization of alicyclic amines

    Science.gov (United States)

    Topczewski, Joseph J.; Cabrera, Pablo J.; Saper, Noam I.; Sanford, Melanie S.

    2016-03-01

    Discovering pharmaceutical candidates is a resource-intensive enterprise that frequently requires the parallel synthesis of hundreds or even thousands of molecules. C-H bonds are present in almost all pharmaceutical agents. Consequently, the development of selective, rapid and efficient methods for converting these bonds into new chemical entities has the potential to streamline pharmaceutical development. Saturated nitrogen-containing heterocycles (alicyclic amines) feature prominently in pharmaceuticals, such as treatments for depression (paroxetine, amitifadine), diabetes (gliclazide), leukaemia (alvocidib), schizophrenia (risperidone, belaperidone), malaria (mefloquine) and nicotine addiction (cytisine, varenicline). However, existing methods for the C-H functionalization of saturated nitrogen heterocycles, particularly at sites remote to nitrogen, remain extremely limited. Here we report a transannular approach to selectively manipulate the C-H bonds of alicyclic amines at sites remote to nitrogen. Our reaction uses the boat conformation of the substrates to achieve palladium-catalysed amine-directed conversion of C-H bonds to C-C bonds on various alicyclic amine scaffolds. We demonstrate this approach by synthesizing new derivatives of several bioactive molecules, including varenicline.

  20. Direct C-H alkylation and indole formation of anilines with diazo compounds under rhodium catalysis.

    Science.gov (United States)

    Mishra, Neeraj Kumar; Choi, Miji; Jo, Hyeim; Oh, Yongguk; Sharma, Satyasheel; Han, Sang Hoon; Jeong, Taejoo; Han, Sangil; Lee, Seok-Yong; Kim, In Su

    2015-12-18

    The rhodium(III)-catalyzed direct functionalization of aniline C-H bonds with α-diazo compounds is described. These transformations provide a facile construction of ortho-alkylated anilines with diazo malonates or highly substituted indoles with diazo acetoacetates. PMID:26458276

  1. Deposition and characterisation of multilayer hard coatings. Ti/TiNδ/TiCxNy/(TiC) a-C:H/(Ti) a-C:H

    International Nuclear Information System (INIS)

    Multilayer hard coatings containing Ti, TiNδ, TiCxNy, (TiCm) a-C:H, (TiCn) a-C:H, and (Ti) a-C:H were deposited on commercially pure titanium substrates by using an asymmetric bipolar pulsed-dc reactive magnetron sputtering of a titanium target, with Ar, Ar+N2, Ar+N2+CH4, and Ar+CH4 gas mixtures. The microstructures, elemental compositions and bonding states of the interlayers and the coating surfaces were studied by using cross-sectional transmission electron microscopy (XTEM), electron energy loss spectroscopy (EELS), X-ray diffraction (XRD), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). The microstructure development of the multilayer coating was strongly influenced by target poisoning. As a result of the complete poisoning of the titanium target during the deposition of TiNδ and TiCxNy interlayers, the a-C:H interlayers containing graded titanium and nitrogen contents were found to develop successively to the TiCxNy interlayer without the formation of near-stoichiometric TiC. The (TiCm) a-C:H interlayer consisted of nano-particles of distorted fcc crystal structure embedded in the a-C:H matrix. The (TiCn) a-C:H and (Ti) a-C:H top layers were found to be a-C:H matrix without nano-particles. In the (Ti) a-C:H top layer there was no measurable amount of Ti observed, regardless of the variation of CH4 concentration between 37.5 and 60 % flow rate in Ar+-CH4 gas mixture. The top layer (Ti) a-C:H was found to contain approximately 10 atomic % nitrogen, due to N2 contamination during deposition caused by low conductance of N2 through the nominally closed valve of the mass flow controller. The change of the CH4 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 CH4 concentration of less than 50 % flow rate in Ar. The hardness and adhesion of the multilayer

  2. Synthesis of Antiviral Tetrahydrocarbazole Derivatives by Photochemical and Acid-catalyzed C-H Functionalization via Intermediate Peroxides (CHIPS)

    Science.gov (United States)

    Gulzar, Naeem; Klussmann, Martin

    2014-01-01

    The direct functionalization of C-H bonds is an important and long standing goal in organic chemistry. Such transformations can be very powerful in order to streamline synthesis by saving steps, time and material compared to conventional methods that require the introduction and removal of activating or directing groups. Therefore, the functionalization of C-H bonds is also attractive for green chemistry. Under oxidative conditions, two C-H bonds or one C-H and one heteroatom-H bond can be transformed to C-C and C-heteroatom bonds, respectively. Often these oxidative coupling reactions require synthetic oxidants, expensive catalysts or high temperatures. Here, we describe a two-step procedure to functionalize indole derivatives, more specifically tetrahydrocarbazoles, by C-H amination using only elemental oxygen as oxidant. The reaction uses the principle of C-H functionalization via Intermediate PeroxideS (CHIPS). In the first step, a hydroperoxide is generated oxidatively using visible light, a photosensitizer and elemental oxygen. In the second step, the N-nucleophile, an aniline, is introduced by Brønsted-acid catalyzed activation of the hydroperoxide leaving group. The products of the first and second step often precipitate and can be conveniently filtered off. The synthesis of a biologically active compound is shown. PMID:24998636

  3. Molybdenum(VI) network polymers based on anion-π interaction and hydrogen bonding: Synthesis, crystal structures and oxidation catalytic application

    Science.gov (United States)

    Li, Jia; Wang, Ge; Shi, Zhan; Yang, Mu; Luck, Rudy L.

    2009-11-01

    A crystallographic investigation of anion-π interactions and hydrogen bonds on the preferred structural motifs of molybdenum(VI) complexes has been carried out. Two molybdenum(VI) network polymers MoO 2F 4·(Hinca) 2 ( 1) and MoO 2F 3(H 2O)·(Hinpa) ( 2), where inca = isonicotinamide and inpa = isonipecotamide, have been synthesized, crystallographically characterized and successfully applied to alcohol oxidation reaction. Complex 1 crystallizes in the monoclinic space C2/ c: a = 16.832(3) Å, b = 8.8189(15) Å, c = 12.568(2) Å, β = 118.929(3)°, V = 1560.1(5) Å 3, Z = 4. Complex 2 crystallizes in the triclinic space P-1: a = 5.459(2) Å, b = 9.189(4) Å, c = 12.204(5) Å, α = 71.341(6)°, β = 81.712(7)°, γ = 77.705(7)°, V = 564.8(4) Å 3, Z = 2. Complex 1 consists of hydrogen bonding and anion-π interactions, both of which are considered as important factors for controlling the geometric features and packing characteristics of the crystal structure. The geometry of the sandwich complex of [MoO 2F 4] 2- with two pyridine rings indicates that the anion-π interaction is an additive and provides a base for the design and synthesis of new complexes. For complex 2, the anions and the protonated inpa ligands form a 2D supramolecular network by four different types of hydrogen contacts (N-H⋯F, N-H⋯O, O-H⋯F and O-H⋯O). The catalytic ability of complexes 1 and 2 has also been evaluated by applying them to the oxidation of benzyl alcohol with TBHP as oxidant.

  4. Mild and Selective Catalytic Hydrogenation of the C=C Bond in α,β-Unsaturated Carbonyl Compounds Using Supported Palladium Nanoparticles.

    Science.gov (United States)

    Nagendiran, Anuja; Pascanu, Vlad; Bermejo Gómez, Antonio; González Miera, Greco; Tai, Cheuk-Wai; Verho, Oscar; Martín-Matute, Belén; Bäckvall, Jan-E

    2016-05-17

    Chemoselective reduction of the C=C bond in a variety of α,β-unsaturated carbonyl compounds using supported palladium nanoparticles is reported. Three different heterogeneous catalysts were compared using 1 atm of H2 : 1) nano-Pd on a metal-organic framework (MOF: Pd(0) -MIL-101-NH2 (Cr)), 2) nano-Pd on a siliceous mesocellular foam (MCF: Pd(0) -AmP-MCF), and 3) commercially available palladium on carbon (Pd/C). Initial studies showed that the Pd@MOF and Pd@MCF nanocatalysts were superior in activity and selectivity compared to commercial Pd/C. Both Pd(0) -MIL-101-NH2 (Cr) and Pd(0) -AmP-MCF were capable of delivering the desired products in very short reaction times (10-90 min) with low loadings of Pd (0.5-1 mol %). Additionally, the two catalytic systems exhibited high recyclability and very low levels of metal leaching. PMID:27111403

  5. Mild metal-catalyzed C-H activation: examples and concepts.

    Science.gov (United States)

    Gensch, T; Hopkinson, M N; Glorius, F; Wencel-Delord, J

    2016-05-21

    Organic reactions that involve the direct functionalization of non-activated C-H bonds represent an attractive class of transformations which maximize atom- and step-economy, and simplify chemical synthesis. Due to the high stability of C-H bonds, these processes, however, have most often required harsh reaction conditions, which has drastically limited their use as tools for the synthesis of complex organic molecules. Following the increased understanding of mechanistic aspects of C-H activation gained over recent years, great strides have been taken to design and develop new protocols that proceed efficiently under mild conditions and duly benefit from improved functional group tolerance and selectivity. In this review, we present the current state of the art in this field and detail C-H activation transformations reported since 2011 that proceed either at or below ambient temperature, in the absence of strongly acidic or basic additives or without strong oxidants. Furthermore, by identifying and discussing the major strategies that have led to these improvements, we hope that this review will serve as a useful conceptual overview and inspire the next generation of mild C-H transformations. PMID:27072661

  6. Tandem Rh(III)-Catalyzed C-H Amination/Annulation Reactions: Synthesis of Indoloquinoline Derivatives in Water.

    Science.gov (United States)

    Shi, Liangliang; Wang, Baiquan

    2016-06-17

    An efficient Rh(III)-catalyzed synthetic method for indoloquinoline derivatives from readily available indoles and isoxazoles was developed. This annulation procedure undergoes tandem C-H activation, cyclization, and condensation steps. In this domino cyclization reaction, water is an efficient solvent. A catalytically competent five-membered rhodacycle has been isolated and characterized, thus revealing a key intermediate in the catalytic cycle. PMID:27266834

  7. Alcohols as alkylating agents in heteroarene C-H functionalization

    Science.gov (United States)

    Jin, Jian; MacMillan, David W. C.

    2015-09-01

    Redox processes and radical intermediates are found in many biochemical processes, including deoxyribonucleotide synthesis and oxidative DNA damage. One of the core principles underlying DNA biosynthesis is the radical-mediated elimination of H2O to deoxygenate ribonucleotides, an example of `spin-centre shift', during which an alcohol C-O bond is cleaved, resulting in a carbon-centred radical intermediate. Although spin-centre shift is a well-understood biochemical process, it is underused by the synthetic organic chemistry community. We wondered whether it would be possible to take advantage of this naturally occurring process to accomplish mild, non-traditional alkylation reactions using alcohols as radical precursors. Because conventional radical-based alkylation methods require the use of stoichiometric oxidants, increased temperatures or peroxides, a mild protocol using simple and abundant alkylating agents would have considerable use in the synthesis of diversely functionalized pharmacophores. Here we describe the development of a dual catalytic alkylation of heteroarenes, using alcohols as mild alkylating reagents. This method represents the first, to our knowledge, broadly applicable use of unactivated alcohols as latent alkylating reagents, achieved via the successful merger of photoredox and hydrogen atom transfer catalysis. The value of this multi-catalytic protocol has been demonstrated through the late-stage functionalization of the medicinal agents, fasudil and milrinone.

  8. Highly Chemical and Regio-selective Catalytic Oxidation with a Novel Manganese Catalyst

    Institute of Scientific and Technical Information of China (English)

    刘斌; 陈怡; 余成志; 沈征武

    2003-01-01

    The chemical selectivity of a novel active manganese compound [Mn2IVμ-O)3(TMTACN)2] (PF6)2 (1) in catalytic oxidation reactions depended on the structure of substrates and 1 was able to catalyze the oxidation of toluene into benzaldehyde and/or benzoic acid under very mild conditions. The following results were obtained: (1) The selectivity of the oxidation depended on the electronic density of double bonds. Reactivity was absent when strong electron-witherawing groups were conjugated with double bonds. (2) Allylic oxidation reactions mostly take place when double bond is present inside a ring system, whilst epoxiclarion reactions occur when the alkene moiety is part of linear chain. (3) In ring systems, the methylene group was more likely to be oxidized than the methyl group on ailylic position. As expected, the C--H bonds at the bridgeheads were unreactive.The secondary hydroxyl groups are more easily to be oxidized than the primary hydroxyl groups.

  9. 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.

  10. Polymeric thermal analysis of C + H and C + H + Ar ion implanted UHMWPE samples

    International Nuclear Information System (INIS)

    Chemical surface characterization of C + H hybrid ion implanted UHMWPE samples were carried out using DSC (differential scanning calorimeter) and TGA (thermal gravimetric analysis) techniques. Samples were implanted with a fluence of 1017 ion/cm2 and an extraction voltage of 30 kV. The study of TGA and DSC curves showed that: (1) Polymeric decomposition temperature increased (2) T m, ΔC p and ΔH m values changed while ΔC p and ΔH m increased. T g value could not be measured, because of some experimental limitations. However, the increase in ΔH m values showed that T g values increased (3) the branch density which indicated the increase in number of cross-link (M c) decreased in ion implanted samples and (4) increase in ΔH m values indicated increase in crystallinity of implanted surface of UHMWPE samples

  11. Polyketide Construction via Hydrohydroxyalkylation and Related Alcohol C-H Functionalizations: Reinventing the Chemistry of Carbonyl Addition

    OpenAIRE

    Dechert-Schmitt, Anne-Marie R.; Schmitt, Daniel C.; Xin GAO; Itoh, Takahiko; Krische, Michael J.

    2014-01-01

    Despite the longstanding importance of polyketide natural products in human medicine, nearly all commercial polyketide-based drugs are prepared through fermentation or semi-synthesis. The paucity of manufacturing routes involving de novo chemical synthesis reflects the inability of current methods to concisely address the preparation of these complex structures. Direct alcohol C-H bond functionalization via “C-C bond forming transfer hydrogenation” provides a powerful, new means of constructi...

  12. Amidines for Versatile Cobalt(III)-Catalyzed Synthesis of Isoquinolines through C-H Functionalization with Diazo Compounds.

    Science.gov (United States)

    Li, Jie; Tang, Mengyao; Zang, Lei; Zhang, Xiaolei; Zhang, Zhao; Ackermann, Lutz

    2016-06-01

    A cobalt(III)-catalyzed C-H/N-H bond functionalization for the synthesis of 1-aminoisoquinolines from aryl amidines and diazo compounds has been developed. The reaction proceeds under mild reaction conditions, obviates the need for oxidants, produces only N2 and H2O as the byproducts, and features a broad substrate scope. PMID:27219713

  13. Selective Synthesis of Isoquinolines by Rhodium(III)-Catalyzed C-H/N-H Functionalization with α-Substituted Ketones.

    Science.gov (United States)

    Li, Jie; Zhang, Zhao; Tang, Mengyao; Zhang, Xiaolei; Jin, Jian

    2016-08-01

    A rhodium(III)-catalyzed C-H/N-H bond functionalization for the synthesis of 1-aminoisoquinolines from aryl amidines and α-MsO/TsO/Cl ketones was achieved under mild reaction conditions. Thus, this approach provides a practical method for the site-selective synthesis of various synthetically valuable isoquinolines with wide functional group tolerance. PMID:27441726

  14. Computational Exploration of Rh(III)/Rh(V) and Rh(III)/Rh(I) Catalysis in Rhodium(III)-Catalyzed C-H Activation Reactions of N-Phenoxyacetamides with Alkynes.

    Science.gov (United States)

    Yang, Yun-Fang; Houk, K N; Wu, Yun-Dong

    2016-06-01

    The selective rhodium-catalyzed functionalization of arenes is greatly facilitated by oxidizing directing groups that act both as directing groups and internal oxidants. We report density functional theory (B3LYP and M06) investigations on the mechanism of rhodium(III)-catalyzed redox coupling reaction of N-phenoxyacetamides with alkynes. The results elucidated the role of the internal oxidizing directing group, and the role of Rh(III)/Rh(I) and Rh(III)/Rh(V) catalysis of C-H functionalizations. A novel Rh(III)-Rh(V)-Rh(III) cycle successfully rationalizes recent experimental observations by Liu and Lu et al. ( Liu , G. Angew. Chem. Int. Ed. 2013 , 52 , 6033 ) on the reactions of N-phenoxyacetamides with alkynes in different solvents. Natural Bond Orbital (NBO) analysis confirms the identity of Rh(V) intermediate in the catalytic cycle. PMID:27177448

  15. Measurement of the C/H ratio by neutrons

    International Nuclear Information System (INIS)

    A probe consisting of a Ra (α, n) Be neutron source and a boron-trifluoride-filled proportional counter were used for measuring the C/H ratio in hydrocarbons. The intensity of the thermal-neutron flux near the counter increases in proportion to the increase of the hydrogen concentration in the hydrocarbon surrounding the probe. The C/H ratio is found by measuring the density. The C/H ratio can be estimated as accurately by this method as by β-particle transmission. The errors resulting from the chemical nature of the hydrocarbon can be reduced to a minimum. The advantage of this method is that it renders possible an external measurement of the C/H ratio of hydrocarbons contained in steel vessels or thick steel piping by means of a portable apparatus. (author)

  16. Cobalt-Mediated Vinylic C-H Functionalization of Alkenes

    OpenAIRE

    Boyd, Warren Christopher

    2012-01-01

    The reaction of cobalt dinitrosyl complexes with alkenes to form cobalt dinitrosoalkane complexes is used to effect the C-H functionalization of alkenes. Deprotonation of cobalt dinitrosoalkane complexes, followed by reaction with neutral electrophiles, yields functionalized cobalt complexes. Thermolysis of such complexes with the parent alkene allows a migration of the cobalt dinitrosyl moiety to the parent alkene, releasing the organic product of C-H functionalization. Progress is presented...

  17. RIR MAPLE procedure for deposition of carbon rich Si/C/H films

    International Nuclear Information System (INIS)

    We applied the resonant infrared matrix assisted pulsed laser evaporation (RIR MAPLE) technique to demonstrate a new approach to a controlled deposition of carbon rich amorphous Si/C/H film. In absence of radicals and accelerated species commonly generated in PECVD and sputtering setups, the RIR MAPLE method does not decompose precursor molecules. Moreover, unlike the standard MAPLE procedure, in which solvent molecules absorb laser energy from excimer or near infrared lasers, we applied the pulsed TEA CO2 laser to excite the dendrimer precursor molecules in a frozen target. In this manner we achieved just cross-linking of the starting precursor on substrates and the deposition of carbon rich Si/C/H film. The film was analyzed by Fourier Transformed Infrared (FTIR), UV/VIS, Raman and X-ray Photoelectron (XPS) spectroscopy and Atomic Force Microscopy (AFM) technique. According to analyses the film retained the precursor elemental composition free of graphitic (sp2) clusters. In course of reaction only the peripheral allyl groups containing C=C bonds were opened to achieve cross-linking. Whereas annealing to 300 °C was necessary for the elimination of =C–H1, 2 bonds in the films prepared at 200 °C, those bonds vanished completely for the films prepared at substrate temperature 255 °C. The film posseses a smooth surface with root mean square (RMS) parameter up to 10 nm within scanned distance 2.5 μm.

  18. The dimers of glyoxal and acrolein with H 2O and HF: Negative intramolecular coupling and blue-shifted C-H stretch

    Science.gov (United States)

    Karpfen, Alfred; Kryachko, Eugene S.

    2010-04-01

    The structures and the vibrational spectra of the hydrogen-bonded complexes: glyoxal-H 2O, glyoxal-HF, acrolein-H 2O, and acrolein-HF, are investigated within the MP2/aug-cc-pVTZ computational approach. It is demonstrated that the calculated blue shifts of the C-H stretching frequencies in the glyoxal-H 2O complexes are only indirectly pertinent to hydrogen bonding to the C-H group. The comparison with the glyoxal-HF and the acrolein-HF complexes reveals that these blue shifts are a direct consequence of a negative intramolecular coupling between vicinal C dbnd O and C-H bonds in the aldehyde groups of isolated glyoxal and acrolein molecules. To support this interpretation, the halogen-bonded complexes glyoxal-BrF and acrolein-BrF are discussed.

  19. Local network structure of a-SiC:H and its correlation with dielectric function

    Science.gov (United States)

    Kageyama, Shota; Matsuki, Nobuyuki; Fujiwara, Hiroyuki

    2013-12-01

    The microscopic disordered structures of hydrogenated amorphous silicon carbide (a-Si1-xCx:H) layers with different carbon contents have been determined based on the correlations between the dielectric function in the ultraviolet/visible region and the local bonding states studied by high-sensitivity infrared attenuated total reflection spectroscopy. We find that the microscopic structure of the a-Si1-xCx:H layers fabricated by plasma-enhanced chemical vapor deposition shows a sharp structural transition at a boundary of x = 6.3 at. %. In the regime of x ≤ 6.3 at. %, (i) the amplitude of the a-SiC:H dielectric function reduces and (ii) the SiH2 content increases drastically with x, even though most of the C atoms are introduced into the tetrahedral sites without bonding with H. In the regime of x > 6.3 at. %, on the other hand, (i) the amplitude of the dielectric function reduces further and (ii) the concentration of the sp3 CHn (n = 2,3) groups increases. Moreover, we obtained the direct evidence that the sp2 C bonding state in the a-SiC matrix exists in the configuration of C = CH2 and the generation of the graphite-like C = CH2 unit suppresses the band gap widening significantly. At high C contents of x > 6.3 at. %, the a-SiC:H layers show quite porous structures due to the formation of microvoids terminated with the SiH2/CHn groups. By taking the SiH2/CHn microvoid generation in the network and the high-energy shift of the dielectric function by the local bonding states into account, the a-SiC:H dielectric function model has been established. From the analysis using this model, we have confirmed that the a-SiC:H optical properties in the ultraviolet/visible region are determined almost completely by the local network structures.

  20. Conformational preferences of heterochiral peptides. Crystal structures of heterochiral peptides Boc-(D) Val-(D) Ala-Leu-Ala-OMe and Boc-Val-Ala-Leu-(D) Ala-OMe--enhanced stability of beta-sheet through C-H...O hydrogen bonds.

    Science.gov (United States)

    Fabiola, G F; Bobde, V; Damodharan, L; Pattabhi, V; Durani, S

    2001-02-01

    The crystal structures of Boc-(D) Val-(D) Ala-Leu-Ala-OMe (vaLA) and Boc-Val-Ala-Leu-(D) Ala-OMe (VALa) have been determined. vaLA crystallises in space group P2(1),2(1),2(1), with a = 9.401 (4), b = 17.253 (5), c = 36.276 (9)A. V = 5,884 (3) A3, Z = 8, R = 0.086. VALa crystallises in space group P2(1) with a = 9.683 (9), b = 17.355 (7), c = 18.187 (9) A, beta = 95.84 (8) degrees , V = 3,040(4) A3, Z = 4, R = 0.125. There are two molecules in the asymmetric unit in antiparallel beta-sheet arrangement in both the structures. Several of the Calpha hydrogens are in hydrogen bonding contact with the carbonyl oxygen in the adjacent strand. An analysis of the observed conformational feature of D-chiral amino acid residues in oligopeptides, using coordinates of 123 crystal structures selected from the 1998 release of CSD has been carried out. This shows that all the residues except D-isoleucine prefer both extended and alphaL conformation though the frequence of occurence may not be equal. In addition to this, D-leucine, valine, proline and phenylalanine have assumed alphaR conformations in solid state. D-leucine has a strong preference for helical conformation in linear peptides whereas they prefer an extended conformation in cyclic peptides. PMID:11245253

  1. 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.

  2. Exploration of earth-abundant transition metals (Fe, Co, and Ni) as catalysts in unreactive chemical bond activations.

    Science.gov (United States)

    Su, Bo; Cao, Zhi-Chao; Shi, Zhang-Jie

    2015-03-17

    Activation of inert chemical bonds, such as C-H, C-O, C-C, and so on, is a very important area, to which has been drawn much attention by chemists for a long time and which is viewed as one of the most ideal ways to produce valuable chemicals. Under modern chemical bond activation logic, many conventionally viewed "inert" chemical bonds that were intact under traditional conditions can be reconsidered as novel functionalities, which not only avoids the tedious synthetic procedures for prefunctionalizations and the emission of undesirable wastes but also inspires chemists to create novel synthetic strategies in completely different manners. Although activation of "inert" chemical bonds using stoichiometric amounts of transition metals has been reported in the past, much more attractive and challenging catalytic transformations began to blossom decades ago. Compared with the broad application of late and noble transition metals in this field, the earth-abundant first-row transition-metals, such as Fe, Co, and Ni, have become much more attractive, due to their obvious advantages, including high abundance on earth, low price, low or no toxicity, and unique catalytic characteristics. In this Account, we summarize our recent efforts toward Fe, Co, and Ni catalyzed "inert" chemical bond activation. Our research first unveiled the unique catalytic ability of iron catalysts in C-O bond activation of both carboxylates and benzyl alcohols in the presence of Grignard reagents. The benzylic C-H functionalization was also developed via Fe catalysis with different nucleophiles, including both electron-rich arenes and 1-aryl-vinyl acetates. Cobalt catalysts also showed their uniqueness in both aromatic C-H activation and C-O activation in the presence of Grignard reagents. We reported the first cobalt-catalyzed sp(2) C-H activation/arylation and alkylation of benzo[h]quinoline and phenylpyridine, in which a new catalytic pathway via an oxidative addition process was demonstrated

  3. Synthesis of isoquinolines via Rh-catalyzed C-H activation/C-N cyclization with diazodiesters or diazoketoesters as a C2 source.

    Science.gov (United States)

    Wang, Jie; Zha, Shanke; Chen, Kehao; Zhang, Feifei; Zhu, Jin

    2016-06-01

    Synthesis of isoquinolines based on efficient C-C and C-N bond formation through Rh(iii)-catalyzed C-H activation and subsequent intramolecular cyclization is reported. Diazodiesters serving as a C2 source in the newly formed heterocycles are first demonstrated. Additionally, the Rh(iii)-catalyzed direct C-H activation/cyclization of benzimidates with diazoketoesters is also described. PMID:27146107

  4. 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...

  5. THERMODYNAMIC STUDIES OF HIGH TEMPERATURE EQUILIBRIA OF THE Si - N, Si - C - H AND Si - O - C - H SYSTEMS

    OpenAIRE

    Kostij, Ž.; Pavlovij, P.; Stefanovij, P.

    1990-01-01

    A model of system thermodynamic equilibrium and the obtained results in the temperature interval of 1000 [K] to 6000 [K] at p = const = 1 [bar] are presented for: 1) the Si-N system for Si3N4 synthesis from Si - powder in a nitrogen thermal arc plasma. 2) the Si-C-H system for SiC synthesis from Si-powder in a propane-butane thermal arc plasma (with added hydrogen) and 3) the Si-O-C-H system for SiC synthesis from SiO2-powder in a propane-butane thermal arc plasma (with added C-powder). The d...

  6. 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.

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

    International Nuclear Information System (INIS)

    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 (CO2) 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 CO2 in the working gas mixture (up to 0.2 for 24 sccm of CO2 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

  8. High growth rate of a-SiC:H films using ethane carbon source by HW-CVD method

    Indian Academy of Sciences (India)

    Mahesh M Kamble; Vaishali S Waman; Sanjay S Ghosh; Azam Mayabadi; Vasant G Sathe; T Shripathi; Habib M Pathan; Sandesh R Jadkar

    2013-12-01

    Hydrogenated amorphous silicon carbide (a-SiC:H) thin films were prepared using pure silane (SiH4) and ethane (C2H6), a novel carbon source, without hydrogen dilution using hot wire chemical vapour deposition (HW-CVD) method at low substrate temperature (200 °C) and at reasonably higher deposition rate (19.5 Å/s < d < 35.2 Å/s). Formation of a-SiC:H films has been confirmed from FTIR, Raman and XPS analysis. Influence of deposition pressure on compositional, structural, optical and electrical properties has been investigated. FTIR spectroscopy analysis revealed that there is decrease in C–H and Si–H bond densities while, Si–C bond density increases with increase in deposition pressure. Total hydrogen content drops from 22.6 to 14.4 at.% when deposition pressure is increased. Raman spectra show increase in structural disorder with increase in deposition pressure. It also confirms the formation of nearly stoichiometric a-SiC:H films. Bandgap calculated using both Tauc’s formulation and absorption at 104 cm-1 shows decreasing trend with increase in deposition pressure. Decrease in refractive index and increase in Urbach energy suggests increase in structural disorder and microvoid density in the films. Finally, it has been concluded that C2H6 can be used as an effective carbon source in HW-CVD method to prepare stoichiometric a-SiC:H films.

  9. Hydrogen Bonding to Alkanes: Computational Evidence

    DEFF Research Database (Denmark)

    Hammerum, Steen; Olesen, Solveig Gaarn

    2009-01-01

    The structural, vibrational, and energetic properties of adducts of alkanes and strong cationic proton donors were studied with composite ab initio calculations. Hydrogen bonding in [D-H+ H-alkyl] adducts contributes to a significant degree to the interactions between the two components, which is...... substantiated by NBO and AIM results. The hydrogen bonds manifest themselves in the same manner as conventional hydrogen bonds, D-H bond elongation, D-H vibrational stretching frequency red shift and intensity increase, and adduct stabilization. The alkane adducts also exhibit elongation of the C-H bonds...... involved and a concurrent red shift, which is rationalized in terms of charge-transfer interactions that cause simultaneous weakening of both the O-H and C-H bonds. Like other dihydrogen-bonded adducts, the adducts possess a bent structure and asymmetric bifurcated hydrogen bonds. The hydrogen bonds are...

  10. Thermodynamic assessement of the Fe-C-H-O system

    Energy Technology Data Exchange (ETDEWEB)

    Conejo, A.N.; Estrada, R.S.; Rodriguez, R.A. [Instituto Tecnologico Morelia (Mexico)

    2003-04-01

    The computation of phase stability diagrams to represent the formation of iron oxides, iron carbides and metallic iron involving the simultaneous effect of pressure (101.3 mbar to 101.3 bar), temperature (477 - 727 C) and reactant gas composition (C-H-O-based gas mixtures), has been carried out. It is proposed to employ ternary diagrams to include all process variables to represent the Fe-C-H-O system. The results can be used in a practical way to define operational conditions to reduce iron oxides into metallic iron as well as to carbidise the solid reactant to produce iron carbide, however, in this case, it has been found that the phase field for iron carbide is located in a region supersaturated with respect to carbon in the gas phase, consequently, if equilibrium prevails, the final solid products will include both iron carbide and free carbon. (orig.)

  11. Amorphous SiC:H- layers from precursors

    Energy Technology Data Exchange (ETDEWEB)

    Mueller, E.; Hilbig, A. [Institute of Ceramic Materials, Freiberg University of Mining and Technology, Gustav-Zeuner Strasse 3, D-09596 Freiberg (Germany); Wenzel, R.; Trommer, K.; Roewer, G. [Institute of Inorganic Chemistry, Freiberg University of Mining and Technology, Leipziger Strasse 29, D-09596 Freiberg (Germany); Sciurova, O.; Niklas, J.R. [Institute of Experimental Physics, Freiberg University of Mining and Technology, Silbermann Strasse 1, D-09596 Freiberg (Germany)

    2002-11-01

    Low-viscous polymers were synthesized in order to produce high purity amorphous SiC layers stabilised by hydrogen, whose optoelectronic properties were then studied in dependence on the pyrolysis conditions. The SiC:H thin layers were deposited by the conversion of an oligomer (chlorovinylsilane) into amorphous silicon carbide. The influence of Si:C ratio and the polymer structure on the composition and ceramic yield of the pyrolysis products is discussed. (Abstract Copyright [2002], Wiley Periodicals, Inc.)

  12. Ruthenium-catalyzed C-H/N-O bond functionalization: green isoquinolone syntheses in water.

    OpenAIRE

    Ackermann, Lutz; Fenner, Sabine

    2011-01-01

    Ruthenium-catalyzed isoquinolone syntheses with ample scope were accomplished through carboxylate assistance in environmentally benign water as a reaction medium. The high chemoselectivity of the ruthenium(II) carboxylate complex also set the stage for the direct use of free hydroxamic acids for annulations of alkynes.

  13. Isomerization of Internal Alkynes to Iridium(III Allene Complexes via C–H Bond Activation: Expanded Substrate Scope, and Progress towards a Catalytic Methodology

    Directory of Open Access Journals (Sweden)

    Neha Phadke

    2015-11-01

    Full Text Available The synthesis of a series of allene complexes (POCOPIr(η2-RC=.=CR’ 1b–4b (POCOP = 2,6-bis(di-tert-butylphosphonitobenzene via isomerization of internal alkynes is reported. We have demonstrated that the application of this methodology is viable for the isomerization of a wide variety of alkyne substrates. Deuterium labeling experiments support our proposed mechanism. The structures of the allene complexes 1b–4b were determined using spectroscopic data analysis. Additionally, the solid-state molecular structure of complex 2b was determined using single crystal X-ray diffraction studies and it confirmed the assignment of an iridium-bound allene isomerization product. The rates of isomerization were measured using NMR techniques over a range of temperatures to allow determination of thermodynamic parameters. Finally, we report a preliminary step towards developing a catalytic methodology; the allene may be liberated from the metal center by exposure of the complex to an atmosphere of carbon monoxide.

  14. Iridium-bipyridine periodic mesoporous organosilica catalyzed direct C-H borylation using a pinacolborane.

    Science.gov (United States)

    Maegawa, Yoshifumi; Inagaki, Shinji

    2015-08-01

    Heterogeneous catalysis for direct C-H borylation of arenes and heteroarenes in the combination of iridium (Ir) complex fixed on periodic mesoporous organosilica containing bipyridine ligands within the framework (Ir-BPy-PMO) and pinacolborane (HBpin) is reported. Ir-BPy-PMO showed higher catalytic activity toward the borylation of benzene with inexpensive HBpin compared to expensive bis(pinacolato)diboron (B2pin2). The precatalyst could be handled without the use of a glove box. The catalyst was easily recovered from reaction mixtures by simple filtration under air. The recovered catalyst still showed good catalytic activity for at least three more times for the borylation of benzene. A variety of arenes and heteroarenes were successfully borylated with high boron efficiency by Ir-BPy-PMO using HBpin, whereas almost no activity was observed for borylation of some heteroarenes with B2pin2. The system using Ir-BPy-PMO and HBpin was also utilized in syntheses of multi-boronated thiophene-based building blocks containing ladder-, acenefused-, and fused-thiophene skeletons. The combination of a stable and reusable solid catalyst and inexpensive HBpin is expected to be superior to conventional approaches for the development of industrial applications. PMID:25748945

  15. 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.

  16. Crystal Structures of Two Bacterial 3-Hydroxy-3-methylglutaryl-CoA Lyases Suggest a Common Catalytic Mechanism among a Family of TIM Barrel Metalloenzymes Cleaving Carbon-Carbon Bonds

    Energy Technology Data Exchange (ETDEWEB)

    Forouhar,F.; Hussain, M.; Farid, R.; Benach, J.; Abashidze, M.; Edstrom, W.; Vorobiev, S.; Montelione, G.; Hunt, J.; et al.

    2006-01-01

    The enzyme 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) lyase catalyzes the terminal steps in ketone body generation and leucine degradation. Mutations in this enzyme cause a human autosomal recessive disorder called primary metabolic aciduria, which typically kills victims because of an inability to tolerate hypoglycemia. Here we present crystal structures of the HMG-CoA lyases from Bacillus subtilis and Brucella melitensis at 2.7 and 2.3 {angstrom} resolution, respectively. These enzymes share greater than 45% sequence identity with the human orthologue. Although the enzyme has the anticipated triose-phosphate isomerase (TIM) barrel fold, the catalytic center contains a divalent cation-binding site formed by a cluster of invariant residues that cap the core of the barrel, contrary to the predictions of homology models. Surprisingly, the residues forming this cation-binding site and most of their interaction partners are shared with three other TIM barrel enzymes that catalyze diverse carbon-carbon bond cleavage reactions believed to proceed through enolate intermediates (4-hydroxy-2-ketovalerate aldolase, 2-isopropylmalate synthase, and transcarboxylase 5S). We propose the name 'DRE-TIM metallolyases' for this newly identified enzyme family likely to employ a common catalytic reaction mechanism involving an invariant Asp-Arg-Glu (DRE) triplet. The Asp ligates the divalent cation, while the Arg probably stabilizes charge accumulation in the enolate intermediate, and the Glu maintains the precise structural alignment of the Asp and Arg. We propose a detailed model for the catalytic reaction mechanism of HMG-CoA lyase based on the examination of previously reported product complexes of other DRE-TIM metallolyases and induced fit substrate docking studies conducted using the crystal structure of human HMG-CoA lyase (reported in the accompanying paper by Fu, et al. (2006) J. Biol. Chem. 281, 7526-7532). Our model is consistent with extensive mutagenesis

  17. Investigation of the structure and properties of a-C:H coatings with metal and silicon containing interlayers

    Science.gov (United States)

    Nöthe, M.; Breuer, U.; Koch, F.; Penkalla, H. J.; Rehbach, W. P.; Bolt, H.

    2001-07-01

    The structure of the interface of a-C:H coatings deposited with metal and Si-containing interlayers has been studied. Carbide forming metals (Al, Ti, Cr) can improve the chemical bonding compared with a substrate material which does not form carbides extensively by itself. In addition, a graded transition zone enlarges the interface between the carbon layer and the interlayer metal. In the present work the metal atoms were evaporated and ionized into a dense Ar plasma and deposited onto Si (100) substrates. A graded interface between the metal interlayer and the a-C:H coating was produced by introducing C 2H 2 with increasing amount into the Ar/He plasma during the PAPVD metal deposition process. The PACVD a-C:H deposition process was continued after the termination of metal evaporation to produce the pure a-C:H top layer. Further to Al-, Cr-, Ti- and Cu-interlayers, Si-containing interlayers were investigated. The Si-containing interlayers were deposited by a PACVD process using tetraethoxysilane Si(OC 2H 5) 4 (TEOS) and tetramethylsilane Si(CH 3) 4 (TMS). The characterization of the deposited layer systems was performed by SIMS, SNMS and XPS analyses as well as SEM and analytical TEM methods.

  18. Transition Metal Catalyzed Hydroarylation of Multiple Bonds: Exploration of Second Generation Ruthenium Catalysts and Extension to Copper Systems

    Energy Technology Data Exchange (ETDEWEB)

    T. Brent Gunnoe

    2011-02-17

    Catalysts provide foundational technology for the development of new materials and can enhance the efficiency of routes to known materials. New catalyst technologies offer the possibility of reducing energy and raw material consumption as well as enabling chemical processes with a lower environmental impact. The rising demand and expense of fossil resources has strained national and global economies and has increased the importance of accessing more efficient catalytic processes for the conversion of hydrocarbons to useful products. The goals of the research are to develop and understand single-site homogeneous catalysts for the conversion of readily available hydrocarbons into useful materials. A detailed understanding of these catalytic reactions could lead to the development of catalysts with improved activity, longevity and selectivity. Such transformations could reduce the environmental impact of hydrocarbon functionalization, conserve energy and valuable fossil resources and provide new technologies for the production of liquid fuels. This project is a collaborative effort that incorporates both experimental and computational studies to understand the details of transition metal catalyzed C-H activation and C-C bond forming reactions with olefins. Accomplishments of the current funding period include: (1) We have completed and published studies of C-H activation and catalytic olefin hydroarylation by TpRu{l_brace}P(pyr){sub 3}{r_brace}(NCMe)R (pyr = N-pyrrolyl) complexes. While these systems efficiently initiate stoichiometric benzene C-H activation, catalytic olefin hydroarylation is hindered by inhibition of olefin coordination, which is a result of the steric bulk of the P(pyr){sub 3} ligand. (2) We have extended our studies of catalytic olefin hydroarylation by TpRu(L)(NCMe)Ph systems to L = P(OCH{sub 2}){sub 3}CEt. Thus, we have now completed detailed mechanistic studies of four systems with L = CO, PMe{sub 3}, P(pyr){sub 3} and P(OCH{sub 2}){sub 3}CEt

  19. Trigonometric Basis Set Functions: Their Application to the C-H Stretching and Deformation Motions of Benzene and to Orbital Symmetry

    Science.gov (United States)

    Bor, G.; Kettle, Sidney F. A.

    1999-12-01

    The unifying power of the use of trigonometric basis functions in group character tables is demonstrated. Additionally, these functions provide a simple way of generating pictures of symmetry coordinates. This is illustrated for the in-plane stretch and out-of-plane deformation motions of the C-H bonds in benzene. Their application to orbital symmetry applications is also indicated.

  20. C-H activation reactions by yttrium and lutetium hydride complexes : H/D exchange vs metalation of hydrocarbons. Importance of the hybridization state at the α carbon

    NARCIS (Netherlands)

    Deelman, Berth-Jan; Teuben, Jan H.; Macgregor, Stuart A.; Eisenstein, Odile

    1995-01-01

    Extended Hückel (EHT) calculations have been used to discuss the two alternative σ-bond C-H metathesis reactions which occur with organo-lanthanide (Ln = Y, Lu) compounds. The two reactions lead either to H/H (H/D) exchange or to metalation and have been modelled by studying the interaction of a Cp2

  1. Multiple Bonds Between Metal Atoms

    CERN Document Server

    Cotton, F Albert; Walton, Richard A

    2006-01-01

    Provides a discussion of preparations, reactions, bonding, and physical properties for two of the d-block transition metals in groups 5-10. This title includes catalytic and chemotherapeutic applications, and discusses metal-metal bonds of orders 0.5 to 4 discussed in than 4000 compounds, with citations to approximately 2500 references.

  2. Ortho-Functionalized Aryltetrazines by Direct Palladium-Catalyzed C-H Halogenation: Application to Fast Electrophilic Fluorination Reactions.

    Science.gov (United States)

    Testa, Christelle; Gigot, Élodie; Genc, Semra; Decréau, Richard; Roger, Julien; Hierso, Jean-Cyrille

    2016-04-25

    A general catalyzed direct C-H functionalization of s-tetrazines is reported. Under mild reaction conditions, N-directed ortho-C-H activation of tetrazines allows the introduction of various functional groups, thus forming carbon-heteroatom bonds: C-X (X=I, Br, Cl) and C-O. Based on this methodology, we developed electrophilic mono- and poly-ortho-fluorination of tetrazines. Microwave irradiation was optimized to afford fluorinated s-aryltetrazines, with satisfactory selectivity, within only ten minutes. This work provides an efficient and practical entry for further accessing highly substituted tetrazine derivatives (iodo, bromo, chloro, fluoro, and acetate precursors). It gives access to ortho-functionalized aryltetrazines which are difficult to obtain by classical Pinner-like syntheses. PMID:27010438

  3. Preconversion catalytic deoxygenation of phenolic functional groups. Quarterly technical progress report, October 1--December 31, 1995

    Energy Technology Data Exchange (ETDEWEB)

    Kubiak, C.P.

    1996-07-01

    Recent research in the author`s laboratory has established the viability of the catalytic deoxygenation of phenols by Co monoxide. The deoxygenation of phenols is a problem of both fundamental and practical importance. The deoxygenation of phenols to arenes is a conceptually simple, yet a very difficult chemical transformation to achieve. The phenolic C-O bond energy of 103 kcal/mol is as strong as a benzene C-H bond and over 10 kcal/mol stronger than the C-O bonds of methanol or ethanol. Catalytic hydrodeoxygenation (HDO) of phenols over sulfided Mo/{gamma}-Al{sub 2}O{sub 3}, Ni-Mo/{gamma}-Al{sub 2}O{sub 3}, Co-Mo/{gamma}-Al{sub 2}O{sub 3} or other supported metal oxide catalysts can be achieved, at exceedingly high hydrogen pressures and temperature. Arene ring hydrogenation generally competes effectively with hydrodeoxygenation, and was found to occur an order of magnitude faster than HDO. As a consequence, most of the hydrogen is consumed in hydrogenation of the aromatic rings. HDO catalysts are easily poisoned. The inefficiency of catalysts for phenol deoxygenation in the presence of hydrogen can be attributed to the absence of a low energy mechanistic pathway for the hydrogenolysis of the strong phenol C-O bond. The authors are currently studying new transition metal catalysts for the efficient and selective deoxygenation of phenols using the Co/Co{sub 2} couple to remove phenolic oxygen atoms. The paper describes recent results on the mechanism of Co insertion into metal-oxygen bonds of phenoxides.

  4. Catalytic hydrocarbon reactions over supported metal oxides. Final report, August 1, 1986--July 31, 1995

    Energy Technology Data Exchange (ETDEWEB)

    Ekerdt, J.G.

    1995-10-20

    Oxide catalysis plays a central role in hydrocarbon processing and improvements in catalytic activity or selectivity are of great technological importance because these improvements will translate directly into more efficient utilization of hydrocarbon supplies and lower energy consumption in separation processes. An understanding of the relationships between surface structure and catalytic properties is needed to describe and improve oxide catalysts. The approach has been to prepare supported oxides that have a specific structure and oxidation state and then employ these structures in reaction studies. The current research program is focused on studying the fundamental relationships between structure and reactivity for two important reactions that are present in many oxide-catalyzed processes, partial oxidation and carbon-carbon bond formation. During the course of these studies the author has: (1) developed methods to form and stabilize various Mo and W oxide structures on silica; (2) studied C-H abstraction reactions over the fully oxidized cations; (3) studied C-C bond coupling by metathesis and reductive coupling of aldehydes and ketones over reduced cation structures; and (4) initiated a study of hydrogenation and hydrogenolysis over reduced cation structures.

  5. Rapid Construction of a Benzo-Fused Indoxamycin Core Enabled by Site-Selective C-H Functionalizations.

    Science.gov (United States)

    Bedell, T Aaron; Hone, Graham A B; Valette, Damien; Yu, Jin-Quan; Davies, Huw M L; Sorensen, Erik J

    2016-07-11

    Methods for functionalizing carbon-hydrogen bonds are featured in a new synthesis of the tricyclic core architecture that characterizes the indoxamycin family of secondary metabolites. A unique collaboration between three laboratories has engendered a design for synthesis featuring two sequential C-H functionalization reactions, namely a diastereoselective dirhodium carbene insertion followed by an ester-directed oxidative Heck cyclization, to rapidly assemble the congested tricyclic core of the indoxamycins. This project exemplifies how multi-laboratory collaborations can foster conceptually novel approaches to challenging problems in chemical synthesis. PMID:27206223

  6. Significant Cooperativity Between Ruthenium and Silicon in Catalytic Transformations of an Isocyanide.

    Science.gov (United States)

    Lipke, Mark C; Liberman-Martin, Allegra L; Tilley, T Don

    2016-08-01

    Complexes [PhBP3]RuH(η(3)-H2SiRR') (RR' = Me,Ph, 1a; RR' = Ph2, 1b; RR' = Et2, 1c) react with XylNC to form carbene complexes [PhBP3]Ru(H)═[C(H)(N(Xyl)(η(2)-H-SiRR'))] (2a-c; previously reported for 2a,b). Reactions of 1a-c with XylNC were further investigated to assess how metal complexes with multiple M-H-Si bonds can mediate transformations of unsaturated substrates. Complex 2a eliminates an N-methylsilacycloindoline product (3a) that results from hydrosilylation, hydrogenation, and benzylic C-H activation of XylNC. Turnover was achieved in a pseudocatalytic manner by careful control of the reaction conditions. Complex 1c mediates a catalytic isocyanide reductive coupling to furnish an alkene product (4) in a transformation that has precedent only in stoichiometric processes. The formations of 3a and 4 were investigated with deuterium labeling experiments, KIE and other kinetic studies, and by examining the reactivity of XylNC with an η(3)-H2SiMeMes complex (1d) to form a C-H activated complex (6). Complex 6 serves as a model for an intermediate in the formation of 3a, and NMR investigations at -30 °C reveal that 6 forms via a carbene complex (1d) that isomerizes to aminomethyl complex 7d. These investigations reveal that the formations of 3a and 4 involve multiple 4-, 5-, and 6-coordinate silicon species with 0, 1, 2, or 3 Ru-H-Si bonds. These mechanisms demonstrate exceptionally intricate roles for silicon in transition-metal-catalyzed reactions with a silane reagent. PMID:27384746

  7. Structure and spectroscopic properties of neutral and cationic tetratomic [C,H,N,Zn] isomers: A theoretical study

    International Nuclear Information System (INIS)

    The structure and spectroscopic parameters of the most relevant [C,H,N,Zn] isomers have been studied employing high-level quantum chemical methods. For each isomer, we provide predictions for their molecular structure, thermodynamic stabilities as well as vibrational and rotational spectroscopic parameters which could eventually help in their experimental detection. In addition, we have carried out a detailed study of the bonding situations by means of a topological analysis of the electron density in the framework of the Bader’s quantum theory of atoms in molecules. The analysis of the relative stabilities and spectroscopic parameters suggests two linear isomers of the neutral [C,H,N,Zn] composition, namely, cyanidehydridezinc HZnCN (1Σ) and hydrideisocyanidezinc HZnNC (1Σ), as possible candidates for experimental detections. For the cationic [C,H,N,Zn]+ composition, the most stable isomers are the ion-molecule complexes arising from the direct interaction of the zinc cation with either the nitrogen or carbon atom of either hydrogen cyanide or hydrogen isocyanide, namely, HCNZn+ (2Σ) and HCNZn+ (2Σ)

  8. Unexpected red shift of C-H vibrational band of Methyl benzoate

    CERN Document Server

    Maiti, Kiran Sankar; Scheurer, Christoph

    2016-01-01

    The C-H vibrational bands become more and more important in the structural determination of biological molecules with the development of CARS microscopy and 2DIR spectroscopy. Due to the congested pattern, near degeneracy, and strong anharmonicity of the C-H stretch vibrations, assignment of the C-H vibrational bands are often misleading. Anharmonic vibrational spectra calculation with multidimensional potential energy surface interprets the C-H vibrational spectra more accurately. In this article we have presented the importance of multidimensional potential energy surface in anharmonic vibrational spectra calculation and discuss the unexpected red shift of C-H vibrational band of Methyl benzoate.

  9. Proposal of an Amide-Directed Carbocupration Mechanism for Copper-Catalyzed meta-Selective C-H Arylation of Acetanilides by Diaryliodonium Salts

    Institute of Scientific and Technical Information of China (English)

    Song-lin Zhang; Yu-qiang Ding

    2011-01-01

    We examined the puzzling mechanism for Cu-catalyzed meta-C-H arylation reaction of anilides by diaryliodonium salts through systematic theoretical analysis.The previously proposed anti-oxy-cupration mechanism featuring anti- 1,2- or anti- 1,4-addition of cuprate and oxygen to the phenyl ring generating a meta-cuprated intermediate was excluded due to the large activation barriers.Alternatively,a new amide-directed carbocupration mechanism was proposed which involves a critical rate- and regio-determining step of amide-directed addition of the Cu(III)-aryl bond across the phenyl C2=C3 double bond to form an orthocuprated,meta-arylated intermediate.This mechanism is kinetically the most favored among several possible mechanisms such as ortho- or para-cupration/migration mechanism,direct meta C-H bond cleavage mediated by Cu(III) or Cu(I),and Cu(III)-catalyzed ortho-directed C-H bond activation mechanism.Furthermore,the predicted regioselectivity based on this mechanism has been shown to favor the meta-arylation that is consistent with the experimental observations.

  10. Study of the hydrogen behavior in amorphous hydrogenated materials of type a - C:H and a - SiC:H facing fusion reactor plasma

    International Nuclear Information System (INIS)

    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)

  11. Hydrogen behaviour study in plasma facing a-C:H and a-SiC:H hydrogenated amorphous materials for fusion reactors

    International Nuclear Information System (INIS)

    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. Firstly, 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 this 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 benefit 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 modeling of hydrogen diffusion under irradiation has been also proposed. (author)

  12. Intramolecular cyclopropanation and C-H insertion reactions with metal carbenoids generated from cyclopropenes.

    Science.gov (United States)

    Archambeau, Alexis; Miege, Frédéric; Meyer, Christophe; Cossy, Janine

    2015-04-21

    Activation of unsaturated carbon-carbon bonds by means of transition metal catalysts is an exceptionally active research field in organic synthesis. In this context, due to their high ring strain, cyclopropenes constitute an interesting class of substrates that displays a versatile reactivity in the presence of transition metal catalysts. Metal complexes of vinyl carbenes are involved as key intermediates in a wide variety of transition metal-catalyzed ring-opening reactions of cyclopropenes. Most of the reported transformations rely on intermolecular or intramolecular addition of nucleophiles to these latter reactive species. This Account focuses specifically on the reactivity of carbenoids resulting from the ring-opening of cyclopropenes in cyclopropanation and C-H insertion reactions, which are arguably two of the most representative transformations of metal complexes of carbenes. Compared with the more conventional α-diazo carbonyl compounds, the use of cyclopropenes as precursors of metal carbenoids in intramolecular cyclopropanation or C-H insertion reactions has been largely underexploited. One of the challenges is to devise appropriately substituted and readily available cyclopropenes that would not only undergo regioselective ring-opening under mild conditions but also trigger the subsequent desired transformations with a high level of chemoselectivity and stereoselectivity. These goals were met by considering several substrates derived from the readily available 3,3-dimethylcyclopropenylcarbinols or 3,3-dimethylcyclopropenylcarbinyl amines. In the case of 1,6-cyclopropene-enes, highly efficient and diastereoselective gold(I)-catalyzed ring-opening/intramolecular cyclopropanations were developed as a route to diversely substituted heterocycles and carbocycles possessing a bicyclo[4.1.0]heptane framework. The use of rhodium(II) catalysts enabled us to widen the scope of this transformation for the synthesis of medium-sized heterocyclic scaffolds

  13. CH Bond Activation of Hydrocarbons Mediated by Rare-Earth Metals and Actinides: Beyond σ-Bond Metathesis and 1,2-Addition

    OpenAIRE

    W. HUANG; Diaconescu, PL

    2015-01-01

    © 2015 Elsevier Inc. This review discusses C. H bond activation of hydrocarbons mediated by rare-earth metal complexes with an emphasis on type of mechanisms. The review is organized as follows: in the first part, C. H bond activations mediated by rare-earth metals and actinides following traditional reaction pathways, such as σ-bond metathesis and 1,2-addition, are summarized; in the second part, nontraditional C. H bond activation examples are discussed in detail in order to understand the ...

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

    Science.gov (United States)

    Jiang, Jinlong; Wang, Yubao; Du, Jinfang; Yang, Hua; Hao, Junying

    2016-08-01

    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 sp3 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 × 10-7 mm3/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.

  15. Impacts of hydrogen dilution on growth and optical properties of a-SiC:H films

    Institute of Scientific and Technical Information of China (English)

    HU; Zhihua; LIAO; Xianbo; DIAO; Hongwei; KONG; Guanglin; Z

    2004-01-01

    Hydrogenated amorphous silicon-carbon (a-SiC:H) films were deposited by plasma enhanced chemical vapor deposition (PECVD) with a fixed methane to silane ratio ([CH4]/[SiH4]) of 1.2 and a wide range of hydrogen dilution (RH=[H2]/[SiH4 + CH4]) values of 12, 22, 33, 102 and 135. The impacts of RH on the structural and optical properties of the films were investigated by using UV-VIS transmission, Fourier transform infrared (FTIR) absorption, Raman scattering and photoluminescence (PL) measur- ements. The effects of high temperature annealing on the films were also probed. It is found that with increasing hydrogen dilution, the optical band gap increases, and the PL peak blueshifts from ~1.43 to 1.62 Ev. In annealed state, the room temperature PL peak for the low RH samples disappears, while the PL peak for the high RH samples appears at ~2.08 Ev, which is attributed to nanocrystalline Si particles confined by Si-C and Si-O bonds.

  16. Disulfide bonds of acetylcholinesterase

    International Nuclear Information System (INIS)

    The positions of the inter- and intrasubunit disulfide bridges were established for the 11S form of acetylcholinesterase (AChE) isolated from Torpedo californica. A major form of AChE localized within the basal lamina of the synapse is a dimensionally asymmetric molecule which contains either two (13S) or three (17S) sets of catalytic subunits linked to collagenous and non-collagenous structural subunits. Limited proteolysis yields a tetramer of catalytic subunits which sediments at 11S. Each catalytic subunit contains 8 cysteine residues. Initially, these Cys residues were identified following trypsin digestion of the reduced protein alkylated with [14C]-iodoacetate. Peptides were resolved by gel filtration followed by reverse phase HPLC. To determine the disulfide bonding profile, native non-reduced 11S AChE was treated with a fluorescent, sulfhydryl-specific reagent, monobromobimane, prior to proteolytic digestion. One fluorescent Cys peptide was identified indicating that a single sulfhydryl residue was present in its reduced form. Three pairs of disulfide bonded peptides were identified, sequenced, and localized in the polypeptide chain. The Cys residue that is located in the C-terminal tryptic peptide was disulfide bonded to an identical peptide and thus forms the intersubunit crosslink. Finally, the cysteine positions have been compared with the sequence of the homologous protein, thyroglobulin. Both likely share a common pattern of folding

  17. Reaction Pathways and Energetics of Etheric C–O Bond Cleavage Catalyzed by Lanthanide Triflates

    Energy Technology Data Exchange (ETDEWEB)

    Assary, Rajeev S.; Atesin, Abdurrahman C.; Li, Zhi; Curtiss, Larry A.; Marks, Tobin J.

    2013-09-06

    Efficient and selective cleavage of etheric C-O bonds is crucial for converting biomass into platform chemicals and liquid transportation fuels. In this contribution, computational methods at the DFT B3LYP level of theory are employed to understand the efficacy of lanthanide triflate catalysts (Ln(OTf)3, Ln = La, Ce, Sm, Gd, Yb, and Lu) in cleaving etheric C-O bonds. In agreement with experiment, the calculations indicate that the reaction pathway for C-O cleavage occurs via a C-H → O-H proton transfer in concert with weakening of the C-O bond of the coordinated ether substrate to ultimately yield a coordinated alkenol. The activation energy for this process falls as the lanthanide ionic radius decreases, reflecting enhanced metal ion electrophilicity. Details of the reaction mechanism for Yb(OTf)3-catalyzed ring opening are explored in depth, and for 1-methyl-d3-butyl phenyl ether, the computed primary kinetic isotope effect of 2.4 is in excellent agreement with experiment (2.7), confirming that etheric ring-opening pathway involves proton transfer from the methyl group alpha to the etheric oxygen atom, which is activated by the electrophilic lanthanide ion. Calculations of the catalytic pathway using eight different ether substrates indicate that the more rapid cleavage of acyclic versus cyclic ethers is largely due to entropic effects, with the former C-O bond scission processes increasing the degrees of freedom/particles as the transition state is approached.

  18. The Stabilized Cation Pool Method: Metal- and Oxidant-Free Benzylic C-H/Aromatic C-H Cross-Coupling.

    Science.gov (United States)

    Hayashi, Ryutaro; Shimizu, Akihiro; Yoshida, Jun-Ichi

    2016-07-13

    Electrochemical oxidation of toluene derivatives in the presence of a sulfilimine gave benzylaminosulfonium ions as stabilized benzyl cation pools, which reacted with subsequently added aromatic nucleophiles to give the corresponding cross-coupling products. The transformation serves as a powerful metal- and chemical-oxidant-free method for benzylic C-H/aromatic C-H cross-coupling. The method has been successfully applied to synthesis of TP27, an inhibitor of PTPase. PMID:27341676

  19. Effect of deposition temperature and thermal annealing on the dry etch rate of a-C: H films for the dry etch hard process of semiconductor devices

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Seung Moo [Department of Materials Science and Engineering, Korea University, Anam-Dong, Sungbook-Ku, Seoul, 136-701 (Korea, Republic of); TC Technology Team, Samsung Electronics Co. Ltd., Nongseo-Dong, Kiheung-Ku, Yongin-Si, Gyeounggi-Do, 446-711 (Korea, Republic of); Won, Jaihyung [TC Technology Team, Samsung Electronics Co. Ltd., Nongseo-Dong, Kiheung-Ku, Yongin-Si, Gyeounggi-Do, 446-711 (Korea, Republic of); Yim, Soyoung [Department of Materials Science and Engineering, Korea University, Anam-Dong, Sungbook-Ku, Seoul, 136-701 (Korea, Republic of); Park, Se Jun; Choi, Jongsik; Kim, Jeongtae; Lee, Hyeondeok [TC Technology Team, Samsung Electronics Co. Ltd., Nongseo-Dong, Kiheung-Ku, Yongin-Si, Gyeounggi-Do, 446-711 (Korea, Republic of); Byun, Dongjin, E-mail: dbyun@korea.ac.kr [Department of Materials Science and Engineering, Korea University, Anam-Dong, Sungbook-Ku, Seoul, 136-701 (Korea, Republic of)

    2012-06-01

    The effect of deposition and thermal annealing temperatures on the dry etch rate of a-C:H films was investigated to increase our fundamental understanding of the relationship between thermal annealing and dry etch rate and to obtain a low dry etch rate hard mask. The hydrocarbon contents and hydrogen concentration were decreased with increasing deposition and annealing temperatures. The I(D)/I(G) intensity ratio and extinction coefficient of the a-C:H films were increased with increasing deposition and annealing temperatures because of the increase of sp{sup 2} bonds in the a-C:H films. There was no relationship between the density of the unpaired electrons and the deposition temperature, or between the density of the unpaired electrons and the annealing temperature. However, the thermally annealed a-C:H films had fewer unpaired electrons compared with the as-deposited ones. Transmission electron microscopy analysis showed the absence of any crystallographic change after thermal annealing. The density of the as-deposited films was increased with increasing deposition temperature. The density of the 600 Degree-Sign C annealed a-C:H films deposited under 450 Degree-Sign C was decreased but at 550 Degree-Sign C was increased, and the density of all 800 Degree-Sign C annealed films was increased. The dry etch rate of the as-deposited a-C:H films was negatively correlated with the deposition temperature. The dry etch rate of the 600 Degree-Sign C annealed a-C:H films deposited at 350 Degree-Sign C and 450 Degree-Sign C was faster than that of the as-deposited film and that of the 800 Degree-Sign C annealed a-C:H films deposited at 350 Degree-Sign C and 450 Degree-Sign C was 17% faster than that of the as-deposited film. However, the dry etch rate of the 550 Degree-Sign C deposited a-C:H film was decreased after annealing at 600 Degree-Sign C and 800 Degree-Sign C. The dry etch rate of the as-deposited films was decreased with increasing density but that of the annealed

  20. Catalytic hydrocarbon reactions over supported metal oxides. Progress report, April 1, 1994--January 31, 1995

    Energy Technology Data Exchange (ETDEWEB)

    Ekerdt, J.G.

    1995-01-31

    Oxide catalysis plays a central role in hydrocarbon processing and improvements in catalytic activity or selectivity are of great technological importance because these improvements will translate directly into more efficient utilization of hydrocarbon supplies and lower energy consumption in separation processes. An understanding of the relationships between surface structure and catalytic properties is needed to describe and improve oxide catalysts. Our approach has been to prepare supported oxides that have a specific structure and oxidation state and then employ these structures in reaction studies. Our current research program is focused on studying the fundamental relationships between structure and reactivity for two important reactions that are present in many oxide-catalyzed processes, partial oxidation and carbon-carbon bond formation. Oxide catalysis can be a complex process with both metal cation and oxygen anions participating in the chemical reactions. From an energy perspective carbon-carbon bond formation is particularly relevant to CO hydrogenation in isosynthesis. Hydrogenolysis and hydrogenation form the basis for heteroatom removal in fuels processing. Understanding the catalysis of these processes (and others) requires isolating reaction steps in the overall cycle and determining how structure and composition influence the individual reaction steps. Specially designed oxides, such as we use, permit one to study some of the steps in oxidation, carbon-carbon coupling and heteroatom removal catalysis. During the course of our studies we have: (1) developed methods to form and stabilize various Mo and W oxide structures on silica; (2) studied C-H abstraction reactions over the fully oxidized cations; (3) studied C-C bond coupling by methathesis and reductive coupling of aldehydes and ketones over reduced cation structures; and (4) initiated a study of hydrogenation and hydrogenolysis over reduced cation structures.

  1. Bifunctional catalytic electrode

    Science.gov (United States)

    Cisar, Alan (Inventor); Murphy, Oliver J. (Inventor); Clarke, Eric (Inventor)

    2005-01-01

    The present invention relates to an oxygen electrode for a unitized regenerative hydrogen-oxygen fuel cell and the unitized regenerative fuel cell having the oxygen electrode. The oxygen electrode contains components electrocatalytically active for the evolution of oxygen from water and the reduction of oxygen to water, and has a structure that supports the flow of both water and gases between the catalytically active surface and a flow field or electrode chamber for bulk flow of the fluids. The electrode has an electrocatalyst layer and a diffusion backing layer interspersed with hydrophilic and hydrophobic regions. The diffusion backing layer consists of a metal core having gas diffusion structures bonded to the metal core.

  2. Self-lubrication and wear behavior of TiC/a-C : H nanocomposite coatings

    NARCIS (Netherlands)

    Pei, Y. T.; Huizenga, P.; Galvan, D.; De Hosson, J. Th. M.; Chandra, T; Tsuzaki, K; Militzer, M; Ravindran, C

    2007-01-01

    Advanced TiC/a-C:H nanocomposite coatings have been produced via reactive deposition in a closed-field unbalanced magnetron sputtering system. In this paper, we report on the tribological behavior of TiC/a-C:H nanocomposite coatings in which ultra-low friction is tailored with superior wear resistan

  3. 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)

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

    Science.gov (United States)

    Bachmann, Svenja; Schulze, Marcus; Morasch, Jan; Hesse, Sabine; Hussein, Laith; Krell, Lisa; Schnagl, Johann; Stark, Robert W.; Narayan, Suman

    2016-05-01

    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 (O2) and hydrogen (H2) 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 H2 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 influenced by the environmental conditions.

  5. Thin films of hydrogenated amorphous carbon (a-C:H) obtained through chemical vapor deposition assisted by plasma

    International Nuclear Information System (INIS)

    Films of hydrogenated amorphous carbon (a-C:H) were deposited using one source of microwave plasma with magnetic field (type ECR), using mixtures of H2/CH4 in relationship of 80/20 and 95/05 as precursory gases, with work pressures of 4X10-4 to 6x10-4 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)

  6. On the catalytic gas phase oxidation of butadiene to furan

    Energy Technology Data Exchange (ETDEWEB)

    Kubias, B.; Rodemerck, U. [Institut fuer Angewandte Chemie Berlin-Adlershof e.V., Berlin (Germany); Ritschl, F.; Meisel, M. [Humboldt-Universitaet, Berlin (Germany). Inst. fuer Chemie

    1998-12-31

    Applying the thermochemical selectivity criterion of Hadnett et al. It is shown that the selectivity of the furan formation is not limited by a too low strength of the C-H bonds in furan when compared with the C-H bond dissociation energy in the educt molecule butadiene. In the oxidation of butadiene on a CsH{sub 2}PMo{sub 12}O{sub 40} catalyst a maximum yield of 22 mol% furan has been obtained. To improve this comparatively low furan yield oxidation activity of the catalyst must be lowered to prevent the consecutive reaction to maleic anhydride. (orig.)

  7. 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.

  8. Identification of nanoscale structure and morphology reconstruction in oxidized a-SiC:H thin films

    Energy Technology Data Exchange (ETDEWEB)

    Vasin, A.V.; Rusavsky, A.V.; Nazarov, A.N.; Lysenko, V.S.; Lytvyn, P.M.; Strelchuk, V.V. [Lashkaryov Institute of Semiconductor Physics, 41 Nauki Pr., Kiev 03028 (Ukraine); Kholostov, K.I.; Bondarenko, V.P. [Belarusian State University of Informatics and Radioelectronics, 6P. Brovki Str., Minsk 220013 (Belarus); Starik, S.P. [Bakul Institute of Superhard Materials, 2 Avtzavodskaya Str., Kiev 04074 (Ukraine)

    2012-11-01

    Highlights: Black-Right-Pointing-Pointer Increase of magnetron discharge power results in densification of a-SiC:H thin films. Black-Right-Pointing-Pointer The denser a-SiC:H material the better resistance to oxidation by oxygen. Black-Right-Pointing-Pointer Oxidation of soft a-SiC:H films can result in increase of electric conductivity. Black-Right-Pointing-Pointer Formation of graphitic clusters was found in a-SiC:H after annealing in oxygen. - Abstract: Oxidation behavior of a-SiC:H layers deposited by radio-frequency magnetron sputtering technique was examined by Kelvin probe force microscopy (KPFM) in combination with scanning electron microscopy, Fourier-transform infra-red spectroscopy and submicron selected area Raman scattering spectroscopy. Partially oxidized a-SiC:H samples (oxidation at 600 Degree-Sign C in oxygen) were examined to clarify mechanism of the oxidation process. Nanoscale and microscale morphological defects (pits) with dimension of about 50 nm and several microns respectively have appeared after thermal treatment. KPFM measurements exhibited the surface potential of the material in micro pits is significantly smaller in comparison with surrounding material. Submicron RS measurements indicates formation of graphite-like nano-inclusions in the pit defects. We conclude that initial stage of oxidation process in a-SiC:H films takes place not homogeneously throughout the layer but it is initiated in local nanoscale regions followed by spreading over all layer.

  9. C-H ACTIVATION REACTIONS BY YTTRIUM AND LUTETIUM HYDRIDE COMPLEXES - H/D EXCHANGE VS METALATION OF HYDROCARBONS - IMPORTANCE OF THE HYBRIDIZATION STATE AT THE ALPHA-CARBON

    NARCIS (Netherlands)

    DEELMAN, BJ; TEUBEN, JH; MACGREGOR, SA; EISENSTEN, O

    1995-01-01

    Extended Huckel (EHT) calculations have been used to discuss the two alternative sigma-bond C-H metathesis reactions which occur with organo-lanthanide (Ln = Y, Lu) compounds. The two reactions lead either to H/H (H/D) exchange or to metalation and have been modelled by studying the interaction of a

  10. Red-Shifting versus Blue-Shifting Hydrogen Bonds: Perspective from Ab Initio Valence Bond Theory.

    Science.gov (United States)

    Chang, Xin; Zhang, Yang; Weng, Xinzhen; Su, Peifeng; Wu, Wei; Mo, Yirong

    2016-05-01

    Both proper, red-shifting and improper, blue-shifting hydrogen bonds have been well-recognized with enormous experimental and computational studies. The current consensus is that there is no difference in nature between these two kinds of hydrogen bonds, where the electrostatic interaction dominates. Since most if not all the computational studies are based on molecular orbital theory, it would be interesting to gain insight into the hydrogen bonds with modern valence bond (VB) theory. In this work, we performed ab initio VBSCF computations on a series of hydrogen-bonding systems, where the sole hydrogen bond donor CF3H interacts with ten hydrogen bond acceptors Y (═NH2CH3, NH3, NH2Cl, OH(-), H2O, CH3OH, (CH3)2O, F(-), HF, or CH3F). This series includes four red-shifting and six blue-shifting hydrogen bonds. Consistent with existing findings in literature, VB-based energy decomposition analyses show that electrostatic interaction plays the dominating role and polarization plays the secondary role in all these hydrogen-bonding systems, and the charge transfer interaction, which denotes the hyperconjugation effect, contributes only slightly to the total interaction energy. As VB theory describes any real chemical bond in terms of pure covalent and ionic structures, our fragment interaction analysis reveals that with the approaching of a hydrogen bond acceptor Y, the covalent state of the F3C-H bond tends to blue-shift, due to the strong repulsion between the hydrogen atom and Y. In contrast, the ionic state F3C(-) H(+) leads to the red-shifting of the C-H vibrational frequency, owing to the attraction between the proton and Y. Thus, the relative weights of the covalent and ionic structures essentially determine the direction of frequency change. Indeed, we find the correlation between the structural weights and vibrational frequency changes. PMID:27074500

  11. 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.

  12. J.C.H. de Meijere (1866-1947), een voorzichtig geneticus en evolutiebioloog

    OpenAIRE

    Schoor, W.J. van der

    1991-01-01

    J.C.H. de Meijere (1866-1947), a cautious geneticist and evolutionary biologist

    After the success of Hugo de Vries' 'mutationism' during the socalled 'Eclipse of Darwinism' (see Bowler, 1983), Dutch biologists in the 20's and 30's had little interest in evolutionary theory. A remarkable exception was the entomologist J.C.H. de Meijere, who thought technical zoology and (1921-1936) genetics at Amsterdam...

  13. Copper-Catalyzed Oxidative C-H Amination of Tetrahydrofuran with Indole/Carbazole Derivatives.

    Science.gov (United States)

    Yang, Qingjing; Choy, Pui Ying; Fu, Wai Chung; Fan, Baomin; Kwong, Fuk Yee

    2015-11-01

    A simple α-C-H amination of cyclic ether with indole/carbazole derivatives has been accomplished by employing copper(II) chloride/bipy as the catalyst system. In the presence of the di-tert-butyl peroxide oxidant, cyclic ethers such as tetrahydrofuran, 1,4-dioxane, and tetrahydropyran successfully undergo C-H/N-H cross dehydrogenative coupling (CDC) with various carbazole or indole derivatives in good-to-excellent yields. PMID:26485515

  14. Initial Stages in the Rhodium(III)-Catalyzed C-H Bond Activation of Primary Alcohols in Aqueous Solution

    DEFF Research Database (Denmark)

    Eriksen, J.; Monsted, L.; Monsted, O.;

    2010-01-01

    ,4,8,11-tetraazacyclotetradecane) cation. The hydride complex is stable for extended periods of time in acidic solution in the absence of oxidants. In basic solutions a series of base-catalyzed reactions take place to yield ultimately the same mixture of [Rh(cycb)(OH)(2)](+) isomers as produced by base hydrolysis of the trans...

  15. Short Synthesis of Sulfur Analogues of Polyaromatic Hydrocarbons through Three Palladium-Catalyzed C-H Bond Arylations.

    Science.gov (United States)

    Hagui, Wided; Besbes, Néji; Srasra, Ezzeddine; Roisnel, Thierry; Soulé, Jean-François; Doucet, Henri

    2016-09-01

    An expeditious synthesis of a wide range of phenanthro[9,10-b]thiophene derivatives, which are a class of polyaromatic hydrocarbon (PAH) containing a sulfur atom, is reported. The synthetic scheme involves only two operations from commercially available thiophenes, 2-bromobenzenesulfonyl chlorides and aryl bromides. In the first step, palladium-catalyzed desulfitative arylation using 2-bromobenzenesulfonyl chlorides allows the synthesis of thiophene derivatives, which are substituted at the C4 position by an aryl group containing an ortho-bromo substituent. Then, a palladium-catalyzed one-pot cascade intermolecular C5-arylation of thiophene using aryl bromides followed by intramolecular arylation led to the corresponding phenanthro[9,10-b]thiophenes in a single operation. In addition, PAHs containing two or three sulfur atoms, as well as both sulfur and nitrogen atoms, were also designed by this strategy. PMID:27550151

  16. 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.

  17. 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.

  18. Synthesis, characterization and catalytic oxidation properties of multi-wall carbon nanotubes with a covalently attached copper(II) salen complex

    International Nuclear Information System (INIS)

    Hydroxyl functionalized copper(II) Schiff-base, N,N'-bis(4-hydroxysalicylidene)-ethylene-1,2-diaminecopper(II), [Cu((OH)2-salen)], has been covalently anchored on modified MWCNTs. The new modified MWCNTs ([Cu((OH)2-salen)]-MWCNTs) have been characterized by TEM, thermal analysis, XRD, XPS, UV-vis, DRS, FT-IR spectroscopy and elemental analysis. The modified copper(II) MWCNTs solid was used to affect the catalytic oxidation of ethylbenzene with tert-butylhydroperoxide as the oxidant at 333 K. The system is truly heterogeneous (no leaching observed) and reusable (no decrease in activity) in three consecutive runs. Acetophenone was the major product though small amounts of o- and p-hydroxyacetophenones were also formed revealing that C-H bond activation takes place both at benzylic and aromatic ring carbon atoms. Ring hydroxylation was more over the 'neat' complexes than over the encapsulated complexes.

  19. Synthesis, characterization and catalytic oxidation properties of multi-wall carbon nanotubes with a covalently attached copper(II) salen complex

    Energy Technology Data Exchange (ETDEWEB)

    Salavati-Niasari, Masoud, E-mail: salavati@kashanu.ac.ir [Institute of Nano Science and Nano Technology, University of Kashan, Kashan, P.O. Box 87317-51167 (Iran, Islamic Republic of); Department of Chemistry, University of Kashan, Kashan, P.O. Box 87317-51167 (Iran, Islamic Republic of); Bazarganipour, Mehdi [Department of Chemistry, University of Kashan, Kashan, P.O. Box 87317-51167 (Iran, Islamic Republic of)

    2009-06-15

    Hydroxyl functionalized copper(II) Schiff-base, N,N'-bis(4-hydroxysalicylidene)-ethylene-1,2-diaminecopper(II), [Cu((OH){sub 2}-salen)], has been covalently anchored on modified MWCNTs. The new modified MWCNTs ([Cu((OH){sub 2}-salen)]-MWCNTs) have been characterized by TEM, thermal analysis, XRD, XPS, UV-vis, DRS, FT-IR spectroscopy and elemental analysis. The modified copper(II) MWCNTs solid was used to affect the catalytic oxidation of ethylbenzene with tert-butylhydroperoxide as the oxidant at 333 K. The system is truly heterogeneous (no leaching observed) and reusable (no decrease in activity) in three consecutive runs. Acetophenone was the major product though small amounts of o- and p-hydroxyacetophenones were also formed revealing that C-H bond activation takes place both at benzylic and aromatic ring carbon atoms. Ring hydroxylation was more over the 'neat' complexes than over the encapsulated complexes.

  20. Thermal Modification of a-SiC:H Films Deposited by Plasma Enhanced Chemical Vapour Deposition from CH4+SiH4 Mixtures

    Institute of Scientific and Technical Information of China (English)

    刘玉学; 王宁会; 刘益春; 申德振; 范希武; 李灵燮

    2001-01-01

    The effects of thermal annealing on photoluminescence (PL) and structural properties of a-Si1-xCx :H films deposited by plasma enhanced chemical vapour deposition from CH4+SiH4 mixtures are studied by using infrared, PL and transmittance-reflectance spectra. In a-SiC:H network, high-temperature annealing gives rise to the effusion of hydrogen from strongly bonded hydrogen in SiH, SiH2, (SiH2)n, SiCHn and CHn configurations and the break of weak C-C, Si-Si and C-Si bonds. A structural rearrangement will occur, which causes a significant correlation of the position and intensity of the PL signal with the annealing temperature. The redshift of the PL peak is related to the destruction of the confining power of barriers. However, the PL intensity does not have a significant correlation with the annealing temperature for a C-rich a-SiC:H network, which refers to the formation of π-bond cluster as increasing carbon content. It is indicated that the thermal stability of C-rich a-Si1-xCx:H films is better than that of Si-like a-Si1-xCx :H films.

  1. Catalytic, enantioselective, vinylogous aldol reactions.

    Science.gov (United States)

    Denmark, Scott E; Heemstra, John R; Beutner, Gregory L

    2005-07-25

    In 1935, R. C. Fuson formulated the principle of vinylogy to explain how the influence of a functional group may be felt at a distant point in the molecule when this position is connected by conjugated double-bond linkages to the group. In polar reactions, this concept allows the extension of the electrophilic or nucleophilic character of a functional group through the pi system of a carbon-carbon double bond. This vinylogous extension has been applied to the aldol reaction by employing "extended" dienol ethers derived from gamma-enolizable alpha,beta-unsaturated carbonyl compounds. Since 1994, several methods for the catalytic, enantioselective, vinylogous aldol reaction have appeared, with which varying degrees of regio- (site), enantio-, and diastereoselectivity can be attained. In this Review, the current scope and limitations of this transformation, as well as its application in natural product synthesis, are discussed. PMID:15940727

  2. Direct functionalization of M-C (M = Pt(II), Pd(II)) bonds using environmentally benign oxidants, O2 and H2O2.

    Science.gov (United States)

    Vedernikov, Andrei N

    2012-06-19

    organometallic substrates studied form isolable high-valent Pt(IV) or Pd(IV) intermediates as a result of an oxidant attack at the M(II) atom. The resulting high-valent M(IV) intermediates undergo C-O reductive elimination, leading to products in high yields. Guidelines for the synthesis of products containing other C-X bonds (X = OAc, Cl, Br) while using O(2) or H(2)O(2) as oxidants are also discussed. Although the M(II)-C bond functionalization reactions including high-valent intermediates are well understood, the mechanism for the aerobic functionalization of benzylic Pd(II) complexes will require a more detailed exploration. Importantly, further optimization of the systems suitable for stoichiometric M(II)-C bond functionalization led to the development of catalytic reactions, including selective acetoxylation of benzylic C-H bonds with O(2) as the oxidant and hydroxylation of aromatic C-H bonds with H(2)O(2) in acetic acid solutions. Both reactions proceed efficiently with substrates that contain a directing heteroatom. This Account also describes catalytic methods for ethylene dioxygenation with H(2)O(2) using M(II) complexes supported by facially chelating ligands. Mechanistic studies of these new oxidation reactions point to important ways to improve their substrate scope and to develop "green" CH functionalization chemistry. PMID:22087633

  3. Regioselective and Stepwise Syntheses of Functionalized BODIPY Dyes through Palladium-Catalyzed Cross-Coupling Reactions and Direct C-H Arylations.

    Science.gov (United States)

    Feng, Zeya; Jiao, Lijuan; Feng, Yuanmei; Yu, Changjiang; Chen, Na; Wei, Yun; Mu, Xiaolong; Hao, Erhong

    2016-08-01

    Regioselective and stepwise syntheses of a series of functionalized BODIPY dyes through palladium-catalyzed cross-coupling reactions and direct C-H arylations have been developed. In particular, this method allows the straightforward synthesis of 2,6-dibromo-3,5-diarylBODIPYs and 2-bromo-3-arylBODIPYs from polybrominated BODIPYs. The X-ray structure of intermediates 5a-c indicated that the palladium was first inserted into the C-Br bonds at 3,5-positions of brominated BODIPYs. The resulting 2,6-dibromo-substituted BODIPYs are potential long wavelength photosensitizers which are not easily accessible using previous methods. PMID:27362954

  4. Rhodium(III) Catalyzed Carboamination of Alkenes Triggered by C-H Activation of N-Phenoxyacetamides under Redox-Neutral Conditions.

    Science.gov (United States)

    Hu, Zhiyong; Tong, Xiaofeng; Liu, Guixia

    2016-04-01

    N-Alkoxyacrylamides are coupled with N-phenoxyacetamides by Rh(III) catalysis through C-H functionalization and amido group transfer under external oxidant-free conditions, which affords acyclic alkene carboamination products in an atom-economical way. Mechanistic insight into this transformation indicates the amide group in N-alkoxyacrylamide plays a critical role in this C-C/C-N bond formation reaction. This methodology provides a highly efficient way to construct o-tyrosine derivatives under mild conditions. PMID:27002932

  5. C-H activation reactions by yttrium and lutetium hydride complexes: H/D exchange vs metalation of hydrocarbons. Importance of the hybridization state at the α carbon

    OpenAIRE

    Deelman, Berth-Jan; Teuben, Jan H.; Macgregor, Stuart A.; Eisenstein, Odile

    1995-01-01

    Extended Hückel (EHT) calculations have been used to discuss the two alternative σ-bond C-H metathesis reactions which occur with organo-lanthanide (Ln = Y, Lu) compounds. The two reactions lead either to H/H (H/D) exchange or to metalation and have been modelled by studying the interaction of a Cp2Ln+ fragment with [H-R-H]- and [R-H-H]- respectively. It is shown that the metallic fragment interacts in a similar way with the two organic fragments and that the preference for one of the two pat...

  6. CHEMICAL ACTIVATION OF MOLECULES BY METALS: EXPERIMENTAL STUDIES OF ELECTRON DISTRIBUTIONS AND BONDING

    Energy Technology Data Exchange (ETDEWEB)

    LICHTENBERGER, DENNIS L.

    2002-03-26

    This research program is directed at obtaining detailed experimental information on the electronic interactions between metals and organic molecules. These interactions provide low energy pathways for many important chemical and catalytic processes. A major feature of the program is the continued development and application of our special high-resolution valence photoelectron spectroscopy (UPS), and high-precision X-ray core photoelectron spectroscopy (XPS) instrumentation for study of organometallic molecules in the gas phase. The study involves a systematic approach towards understanding the interactions and activation of bound carbonyls, C-H bonds, methylenes, vinylidenes, acetylides, alkenes, alkynes, carbenes, carbynes, alkylidenes, alkylidynes, and others with various monometal, dimetal, and cluster metal species. Supporting ligands include -aryls, alkoxides, oxides, and phosphines. We are expanding our studies of both early and late transition metal species and electron-rich and electron-poor environments in order to more completely understand the electronic factors that serve to stabilize particular organic fragments and intermediates on metals. Additional new directions for this program are being taken in ultra-high vacuum surface UPS, XPS, scanning tunneling microscopy (STM) and atomic force microscopy (AFM) experiments on both physisorbed and chemisorbed organometallic thin films. The combination of these methods provides additional electronic structure information on surface-molecule and molecule-molecule interactions. A very important general result emerging from this program is the identification of a close relationship between the ionization energies of the species and the thermodynamics of the chemical and catalytic reactions of these systems.

  7. CHEMICAL ACTIVATION OF MOLECULES BY METALS: EXPERIMENTAL STUDIES OF ELECTRON DISTRIBUTIONS AND BONDING; FINAL

    International Nuclear Information System (INIS)

    This research program is directed at obtaining detailed experimental information on the electronic interactions between metals and organic molecules. These interactions provide low energy pathways for many important chemical and catalytic processes. A major feature of the program is the continued development and application of our special high-resolution valence photoelectron spectroscopy (UPS), and high-precision X-ray core photoelectron spectroscopy (XPS) instrumentation for study of organometallic molecules in the gas phase. The study involves a systematic approach towards understanding the interactions and activation of bound carbonyls, C-H bonds, methylenes, vinylidenes, acetylides, alkenes, alkynes, carbenes, carbynes, alkylidenes, alkylidynes, and others with various monometal, dimetal, and cluster metal species. Supporting ligands include -aryls, alkoxides, oxides, and phosphines. We are expanding our studies of both early and late transition metal species and electron-rich and electron-poor environments in order to more completely understand the electronic factors that serve to stabilize particular organic fragments and intermediates on metals. Additional new directions for this program are being taken in ultra-high vacuum surface UPS, XPS, scanning tunneling microscopy (STM) and atomic force microscopy (AFM) experiments on both physisorbed and chemisorbed organometallic thin films. The combination of these methods provides additional electronic structure information on surface-molecule and molecule-molecule interactions. A very important general result emerging from this program is the identification of a close relationship between the ionization energies of the species and the thermodynamics of the chemical and catalytic reactions of these systems

  8. FINAL TECHNICAL REPORT for grant DE-FG02-93ER14353 "Carbon-Hydrogen Bond Functionalization Catalyzed by Transition Metal Systems"

    Energy Technology Data Exchange (ETDEWEB)

    Goldman, Alan S

    2012-05-21

    Alkanes are our most abundant organic resource but are highly resistant to selective chemical transformations. Alkenes (olefins) by contrast are the single most versatile class of molecules for selective transformations, and are intermediates in virtually every petrochemical process as well as a vast range of commodity and fine chemical processes. Over the course of this project we have developed the most efficient catalysts to date for the selective conversion of alkanes to give olefins, and have applied these catalysts to other dehydrogenation reactions. We have also developed some of the first efficient catalysts for carbonylation of alkanes and arenes to give aldehydes. The development of these catalysts has been accompanied by elucidation of the mechanism of their operation and the factors controlling the kinetics and thermodynamics of C-H bond activation and other individual steps of the catalytic cycles. This fundamental understanding will allow the further improvement of these catalysts, as well as the development of the next generation of catalysts for the functionalization of alkanes and other molecules containing C-H bonds.

  9. Catalyst performance and mechanism of catalytic combustion of dichloromethane (CH2Cl2) over Ce doped TiO2.

    Science.gov (United States)

    Cao, Shuang; Wang, Haiqiang; Yu, Feixiang; Shi, Mengpa; Chen, Shuang; Weng, Xiaole; Liu, Yue; Wu, Zhongbiao

    2016-02-01

    TiO2 and Ce/TiO2 were synthesized and subsequently used for the catalytic combustion of DCM. TiO2 had abundant Lewis acid sites and was responsible for the adsorption and the rupture of C-Cl bonds. However, TiO2 tended to be inactivated because of chloride poisoning due to the adsorption and accumulation of Cl species over the surface. While, Ce/TiO2 obtained total oxidation of CH2Cl2 at 335°C and exhibited stable DCM removal activity on 100h long-time stability tests at 330°C without any catalyst deactivation. The doped cerium generated Ce(3+) chemical states and surface active oxygen, and therefore played important roles from two aspects as follows. First of all, the poisoning of Cl for Ce/TiO2 was inhibited to some extent by CeO2 due to the rapid removal of Cl on the surface of CeO2, which has been verified by NH3-IR characterization. In the other hand, CeO2 enhanced the further deep oxidation of C-H from byproducts and retained the certain oxidation of CO to CO2. Based on the DRIFT characterization and the catalysts activity tests, a two-step reaction pathway for the catalytic combustion of DCM on Ce/TiO2 catalyst was proposed. PMID:26550781

  10. Thermal shock and thermal cycling behaviour of amorphous a-C:H films on molybdenum substrates

    International Nuclear Information System (INIS)

    The thermal behaviour of a-C:H films (a stands for amorphous) deposited by the TEXTOR carbonization technique on molybdenum substrates was investigated in high power electron beam testing device for single and multiple shot sequences. The stationary thermal behaviour was also measured. The results for single shot testing are presented in a threshold damage diagram and show that the stability of a-C:H films on molybdenum is superior to that on steel. At higher or repeated loadings the films are converted gradually to molybdenum carbide. AES and SIMS depth profiling was used to investigate the concentration profiles and interface compositions of the films after various heat treatments. Their 1-h thermal stability on molybdenum extends to approximately 7000C in a stationary test. Results show that a-C:H films on molybdenum should be effective in shielding the molybdenum substrate from the plasma in a fusion device as long as the stated loading limits are not exceeded. (orig.)

  11. Compositional, structural and mechanical characteristics of nc-TiC/a-C:H nanocomposite films

    International Nuclear Information System (INIS)

    Nanocomposite nc-TiC/a-C:H films, with an unusual combination of superhardness, high elastic modulus and high elastic recovery, are prepared by filtered cathodic vacuum arc technique using the C2H2 gas as the precursor. The effects of filter coil current on compositional, structural and mechanical properties of the nc-TiC/a-C:H films have been investigated by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), energy disperse spectroscopy (EDS), microindentation and tribotester measurements. XPS and Raman analyses show that composition and nanostructure of the nc-TiC/a-C:H films can be changed by varying the filter coil current. By selecting the proper value of filter coil current, 2.5 A, one can remarkably enhance the mechanical properties of films such as superhardness (43.6 GPa). The superhardness can be ascribed to the phase variation and the nanostructure.

  12. Nature of chemical bond through positron annihilation

    International Nuclear Information System (INIS)

    Positron annihilation is an important alternative to Compton scattering for determination of electron momentum distribution. The possibility of studying the nature of chemical bond by positron annihilation technique is reviewed in this paper. General concepts connected with momentum space and chemical bond have been outlined. Estimation of positron wavefunction at carbon and hydrogen sites and the calculation of electron momentum distribution of C-H and C-C bonds are discussed. The annihilation with sigma electrons broadens the angular correlation curve while the annihilation with π electrons narrows the curve. The most significant part of this paper is the investigation of participation of d-orbital of sulphur in chemical bonding. Whether or not ligand perturbation is necessary for d-orbital contraction and consequent participation in bonding is controversial till now. A study of angular correlation of positron annihilation radiation on organic sulphides and sulphones is a direct evidence to conclude that ligand perturbation is necessary. (author)

  13. Modeling study of oxygenated fuels on diesel combustion: Effects of oxygen concentration, cetane number and C/H ratio

    International Nuclear Information System (INIS)

    Highlights: • The effects of oxygenated fuels on diesel combustion are extensively investigated. • CO and soot emissions are reduced with the increase of oxygen concentration. • The C–O bond in the oxygenated fuels inhibits the formation of soot precursor C2H2. • Small intermediates such as C2H4 and C2H6 are significantly reduced. • Oxygen concentration seems to be the dominating factor affecting the emissions. - Abstract: The present modeling study aims to gain better insights on the effects of oxygenated fuels on the diesel oxidation and emission formation processes under realistic engine operating conditions. To do that, various blend fuels formulated from diesel, biodiesel, ethanol and DMC fuels were obtained with different oxygen concentrations, cetane numbers and C/H ratios. Simulations were conducted using the coupled KIVA–CHEMKIN code on a light duty diesel engine at a fixed engine speed of 2400 rpm under full load conditions. Constructed numerical simulation models integrated with detailed chemical kinetics were validated against the experimental results with reliable accuracies. Simulation results revealed that as the overall oxygen concentration of the blend fuel increased, significant beneficial effects were shown with reduced NOx, CO and soot emissions. Particularly, with the increase of oxygen concentration, the peak CO concentration and its final emission level were found to be remarkably reduced due to the fuel borne oxygen, reduced carbon influx as well as the possibility accelerated CO oxidation rate. More tangible reductions were shown on the soot emissions probably because the C–O bond in the oxygenated blend fuels had played an important role in inhibiting the carbon atoms from soot formation. Furthermore, as oxygenated fuels were added, the peak concentration of the soot precursor C2H2 species and small hydrocarbon intermediates such as C2H4 and C2H6 were also significantly reduced. In general, it was found that compared to the

  14. Development of a Direct Photocatalytic C-H Fluorination for the Preparative Synthesis of Odanacatib.

    Science.gov (United States)

    Halperin, Shira D; Kwon, Daniel; Holmes, Michael; Regalado, Erik L; Campeau, Louis-Charles; DiRocco, Daniel A; Britton, Robert

    2015-11-01

    Late-stage C-H fluorination is an appealing reaction for medicinal chemistry. However, the application of this strategy to process research appears less attractive due to the formation and necessary purification of mixtures of organofluorines. Here we demonstrate that γ-fluoroleucine methyl ester, an intermediate critical to the large-scale synthesis of odanacatib, can be accessed directly from leucine methyl ester using a combination of the decatungstate photocatalyst and N-fluorobenzenesulfonimide in flow. This efficient C-H fluorination reaction compares favorably with several generations of classical γ-fluoroleucine process syntheses. PMID:26484983

  15. A Versatile, Traceless C-H Activation-Based Approach for the Synthesis of Heterocycles.

    Science.gov (United States)

    Zhou, Shuguang; Wang, Jinhu; Zhang, Feifei; Song, Chao; Zhu, Jin

    2016-05-20

    A versatile, traceless C-H activation-based approach for the synthesis of diversified heterocycles is reported. Rh(III)-catalyzed, N-amino-directed C-H alkenylation generates either olefination products or indoles (in situ annulation) in an atom- and step-economic manner at room temperature. The remarkable reactivity endowed by this directing group enables scale-up of the reaction to a 10 g scale at a very low catalyst loading (0.01 mol %/0.1 mol %). Ex situ annulation of olefination product provides entry into an array of heterocycles. PMID:27135982

  16. Mechanistic Insights into C-H Oxidations by Ruthenium(III)-Pterin Complexes: Impact of Basicity of the Pterin Ligand and Electron Acceptability of the Metal Center on the Transition States.

    Science.gov (United States)

    Mitome, Hiroumi; Ishizuka, Tomoya; Kotani, Hiroaki; Shiota, Yoshihito; Yoshizawa, Kazunari; Kojima, Takahiko

    2016-08-01

    A ruthenium(II) complex, [Ru(dmdmp)Cl(MeBPA)] (2) (Hdmdmp = N,N-dimethyl-6,7-dimethylpterin, MeBPA = N-methyl-N,N-bis(pyridylmethyl)amine), having a pterin derivative as a proton-accepting ligand, was synthesized and characterized. Complex 2 shows higher basicity than that of a previously reported Ru(II)-pterin complex, [Ru(dmdmp) (TPA)](+) (1) (TPA = tris(2-pyridylmethyl)amine). On the other hand, 1e(-)-oxidized species of 1 (1OX) exhibits higher electron-acceptability than that of 1e(-)-oxidized 2 (2OX). Bond dissociation enthalpies (BDE) of the two Ru(II) complexes having Hdmdmp as a ligand in proton-coupled electron transfer (PCET) to generate 1OX and 2OX were calculated to be 85 kcal mol(-1) for 1OX and 78 kcal mol(-1) for 2OX. The BDE values are large enough to perform H atom transfer from C-H bonds of organic molecules to the 1e(-)-oxidized complexes through PCET. The second-order rate constants (k) of PCET oxidation reactions were determined for 1OX and 2OX. The logarithms of normalized k values were proportional to the BDE values of C-H bonds of the substrates with slopes of -0.27 for 1OX and -0.44 for 2OX. The difference between 1OX and 2OX in the slopes suggests that the transition states in PCET oxidations of substrates by the two complexes bear different polarization, as reflection of difference in the electron acceptability and basicity of 1OX and 2OX. The more basic 2OX attracts a proton from a C-H bond via a more polarized transition state than that of 1OX; on the contrary, the more electron-deficient 1OX forms less polarized transition states in PCET oxidation reactions of C-H bonds. PMID:27403587

  17. Bond Boom

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    The Ministry of Finance recently kick-started a pilot program allowing local governments of Shanghai and Shenzhen,and Zhejiang and Guangdong provinces to issue bonds for the first time.How will the new policy affect fiscal capacities of local governments and the broader economy? What else should the country do to build a healthy bond market? Economists and experts discussed these issues in an interview with the Shanghai Securities Journal.Edited excerpts follow.

  18. Bond Boom

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    The Ministry of Finance recently kick-started a pilot program allowing local governments of Shanghai and Shenzhen, and Zhejiang and Guangdong provinces to issue bonds for the first time. How will the new policy affect fiscal capacities of local governments and the broader economy? What else should the country do to build a healthy bond market? Economists and experts discussed these issues in an interview with the ShanghaiSecuritiesJournal. Edited excerpts follow:

  19. Electrochemically induced C-H functionalization using bromide ion/2,2,6,6-tetramethylpiperidinyl-N-oxyl dual redox catalysts in a two-phase electrolytic system

    International Nuclear Information System (INIS)

    Highlights: •Electrocatalytic C-H bond functionalization of tetrahydroisoquinolines is reported. •The transformation is mediated by a bromide ion/TEMPO dual redox catalyst system. •The transformation is conducted in a two-phase electrolytic medium. •The mechanism is proposed to proceed via a sequence of oxidation and addition reactions involving water as a nucleophile. •The procedure features wide substrate scope, the use of mild reaction conditions. -- Abstract: The electrochemical oxidative functionalization of benzylic C-H bonds, mediated by a dual bromide ion/2,2,6,6-tetramethylpiperidinyl-N-oxyl (TEMPO) redox catalyst system in a two-phase electrolytic medium, has been explored using cyclic voltammetry (CV) and preparative electrolysis techniques. The results show that electron transfer between TEMPO+ and a neutral substrate occurs with an efficiency that depends upon the presence of a base. The preparative scale electrolysis led to the formation of dihydro-isoquinolinones, isochromanone and xanthenone in moderate to excellent yields. On the basis of the CV analysis and preparative electrolysis results, a reaction mechanism is proposed

  20. Preparation and comparison of a-C:H coatings using reactive sputter techniques

    Energy Technology Data Exchange (ETDEWEB)

    Keunecke, M., E-mail: martin.keunecke@ist.fraunhofer.d [Fraunhofer Institute for Surface Engineering and Thin Films (IST), Braunschweig (Germany); Weigel, K.; Bewilogua, K. [Fraunhofer Institute for Surface Engineering and Thin Films (IST), Braunschweig (Germany); Cremer, R.; Fuss, H.-G. [CemeCon AG, Wuerselen (Germany)

    2009-12-31

    Amorphous hydrogenated carbon (a-C:H) coatings are widely used in several industrial applications. These coatings commonly will be prepared by plasma activated chemical vapor deposition (PACVD). The main method used to prepare a-C:H coating in industrial scale is based on a glow discharge in a hydrocarbon gas like acetylene or methane using a substrate electrode powered with medium frequency (m.f. - some 10 to 300 kHz). Some aims of further development are adhesion improvement, increase of hardness and high coating quality on complex geometries. A relatively new and promising technique to fulfil these requirements is the deposition of a-C:H coatings by a reactive d.c. magnetron sputter deposition from a graphite target with acetylene as reactive gas. An advancement of this technique is the deposition in a pulsed magnetron sputter process. Using these three mentioned techniques a-C:H coatings were prepared in the same deposition machine. For adhesion improvement different interlayer systems were applied. The effect of different substrate bias voltages (d.c. and d.c. pulse) was investigated. By applying the magnetron sputter technique in the d.c. pulse mode, plastic hardness values up to 40 GPa could be reached. Besides hardness other mechanical properties like resistance against abrasive wear were measured and compared. Cross sectional SEM images showed the growth structure of the coatings.

  1. C$^+$/H$_2$ Gas in Star-Forming Clouds and Galaxies

    CERN Document Server

    Nordon, Raanan

    2016-01-01

    We present analytic theory for the total column density of singly ionized carbon (C$^+$) in the optically thick photon dominated regions (PDRs) of far-UV irradiated (star-forming) molecular clouds. We derive a simple formula for the C$^+$ column as a function of the cloud (hydrogen) density, the far-UV field intensity, and metallicity, encompassing the wide range of galaxy conditions. We verify our analysis with detailed numerical PDR models. For optically thick gas, most of the C$^+$ column is mixed with hydrogen that is primarily molecular (H$_2$), and this "C$^+$/H$_2$" gas layer accounts for almost all of the `CO-dark' molecular gas in PDRs. The C$^+$/H$_2$ column density is limited by dust shielding and is inversely proportional to the metallicity down to $\\sim$0.1 solar. At lower metallicities, H$_2$ line blocking dominates and the C$^+$/H$_2$ column saturates. Applying our theory to CO surveys in low redshift spirals we estimate the fraction of C$^+$/H$_2$ gas out of the total molecular gas to be typic...

  2. 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

    The synthesis of all eight rare, but biologically important L-hexoses as the according thioglycosyl donors was achieved through a procedure involving the C-H activation of their corresponding 6-deoxy-L-hexoses. The key steps of the procedure were the silylation of the OH group at C4 followed by an...

  3. Mesoporous silica nanoparticles for biomedical and catalytical applications

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Xiaoxing [Iowa State Univ., Ames, IA (United States)

    2011-01-01

    Mesoporous silica materials, discovered in 1992 by the Mobile Oil Corporation, have received considerable attention in the chemical industry due to their superior textual properties such as high surface area, large pore volume, tunable pore diameter, and narrow pore size distribution. Among those materials, MCM-41, referred to Mobile Composition of Matter NO. 41, contains honeycomb liked porous structure that is the most common mesoporous molecular sieve studied. Applications of MCM-41 type mesoporous silica material in biomedical field as well as catalytical field have been developed and discussed in this thesis. The unique features of mesoporous silica nanoparticles were utilized for the design of delivery system for multiple biomolecules as described in chapter 2. We loaded luciferin into the hexagonal channels of MSN and capped the pore ends with gold nanoparticles to prevent premature release. Luciferase was adsorbed onto the outer surface of the MSN. Both the MSN and the gold nanoparticles were protected by poly-ethylene glycol to minimize nonspecific interaction of luciferase and keep it from denaturating. Controlled release of luciferin was triggered within the cells and the enzymatic reaction was detected by a luminometer. Further developments by varying enzyme/substrate pairs may provide opportunities to control cell behavior and manipulate intracellular reactions. MSN was also served as a noble metal catalyst support due to its large surface area and its stability with active metals. We prepared MSN with pore diameter of 10 nm (LP10-MSN) which can facilitate mass transfer. And we successfully synthesized an organo silane, 2,2'-Bipyridine-amide-triethoxylsilane (Bpy-amide-TES). Then we were able to functionalize LP10-MSN with bipyridinyl group by both post-grafting method and co-condensation method. Future research of this material would be platinum complexation. This Pt (II) complex catalyst has been reported for a C-H bond activation reaction as an

  4. Catalytic deallylation of allyl- and diallylmalonates.

    Science.gov (United States)

    Necas, David; Turský, Matyás; Kotora, Martin

    2004-08-25

    Substituted allylmalonates undergo the selective C-C bond cleavage in the presence of triethylaluminum and a catalytic amount of nickel and ruthenium phosphine complexes, resulting in the loss of the allyl moiety and formation of monosubstituted malonates. Comparison of reactivity of the nickel and ruthenium complexes showed that the use of the former is general with respect to the structure of the substituted allylmalonates, and the activity of the latter depended on the substitution pattern of the double bond of the allylic moiety. The smooth deallylation may encourage the use of the allyl group as a protective group for the acidic hydrogen in malonates. PMID:15315416

  5. Distinguishing Bonds.

    Science.gov (United States)

    Rahm, Martin; Hoffmann, Roald

    2016-03-23

    The energy change per electron in a chemical or physical transformation, ΔE/n, may be expressed as Δχ̅ + Δ(VNN + ω)/n, where Δχ̅ is the average electron binding energy, a generalized electronegativity, ΔVNN is the change in nuclear repulsions, and Δω is the change in multielectron interactions in the process considered. The last term can be obtained by the difference from experimental or theoretical estimates of the first terms. Previously obtained consequences of this energy partitioning are extended here to a different analysis of bonding in a great variety of diatomics, including more or less polar ones. Arguments are presented for associating the average change in electron binding energy with covalence, and the change in multielectron interactions with electron transfer, either to, out, or within a molecule. A new descriptor Q, essentially the scaled difference between the Δχ̅ and Δ(VNN + ω)/n terms, when plotted versus the bond energy, separates nicely a wide variety of bonding types, covalent, covalent but more correlated, polar and increasingly ionic, metallogenic, electrostatic, charge-shift bonds, and dispersion interactions. Also, Q itself shows a set of interesting relations with the correlation energy of a bond. PMID:26910496

  6. Deposition of a-C:H films on a nanotrench pattern by bipolar PBII&D

    Science.gov (United States)

    Hirata, Yuki; Nakahara, Yuya; Nagato, Keisuke; Choi, Junho

    2016-06-01

    In this study, hydrogenated amorphous carbon (a-C:H) films were deposited on a nanotrench pattern (300 nm pitch, aspect ratio: 2.0) by bipolar-type plasma based ion implantation and deposition technique (bipolar PBII&D), and the effects of bipolar pulse on the film properties were investigated. Moreover, the behaviour of ions and radicals surrounding the nanotrench was analyzed to clarify the coating mechanism and properties of the a-C:H films on the nanotrench. Further, thermal nanoimprint lithography was carried out using the nanotrench pattern coated with a-C:H films as the mold, and the mold release properties were evaluated. All nanotrench surfaces were successfully coated with the a-C:H films, but the film thickness on the top, sidewall, and bottom surfaces of the trench were not uniform. The surface roughness of the a-C:H films was found to decrease at a higher positive voltage; this happens due to the higher electron temperature around the nanotrench because of the surface migration of plasma particles arrived on the trench. The effects of the negative voltage on the behaviour of ions and radicals near the sidewall of the nanotrench are quite similar to those near the microtrench reported previously (Park et al 2014 J. Phys. D: Appl. Phys. 47 335306). However, the positive pulse voltage was also found to affect the behaviour of ions and radicals near the sidewall surface. The incident angles of ions on the sidewall surface increased with the positive pulse voltage because the energy of incoming ions on the trench decreases with increasing positive voltage. Moreover, the incident ion flux on the sidewall is affected by the positive voltage history. Further, the radical flux decreases with increasing positive voltage. It can be concluded that a higher positive voltage at a lower negative voltage condition is good to obtain better film properties and higher film thickness on the sidewall surface. Pattern transfer properties for the nanoimprint formed by

  7. Can laccases catalyze bond cleavage in lignin?

    DEFF Research Database (Denmark)

    Munk, Line; Sitarz, Anna Katarzyna; Kalyani, Dayanand;

    2015-01-01

    these enzymes may help degrading lignin, using oxygen as the oxidant. Laccases can catalyze polymerization of lignin, but the question is whether and how laccases can directly catalyze modification of lignin via catalytic bond cleavage. Via a thorough review of the available literature and detailed...

  8. Anisotropic surface properties of micro/nanostructured a-C:H:F thin films with self-assembly applications

    OpenAIRE

    Freire Soler, Víctor Manuel; Corbella Roca, Carles; Bertrán Serra, Enric; Portal-Marco, S.; Rubio-Roy, M.; Andújar Bella, José Luis

    2012-01-01

    The singular properties of hydrogenated amorphous carbon (a-C:H) thin filmsdeposited by pulsed DC plasma enhanced chemical vapor deposition (PECVD), such as hardness and wear resistance, make it suitable as protective coating with low surface energy for self-assembly applications. In this paper, we designed fluorine-containing a-C:H (a-C:H:F) nanostructured surfaces and we characterized them for self-assembly applications. Sub-micron patterns were generated on silicon through laser lithograph...

  9. Platinum containing amorphous hydrogenated carbon (a-C:H/Pt) thin films as selective solar absorbers

    International Nuclear Information System (INIS)

    We have investigated a double-cermet structured thin film in which an a-C:H thin film was used as an anti-reflective (AR) layer and two platinum-containing amorphous hydrogenated carbon (a-C:H/Pt) thin films were used as the double cermet layers. A reactive co-sputter deposition method was used to prepare both the anti-reflective and cermet layers. Effects of the target power and heat treatment were studied. The obtained films were characterized using X-ray diffraction, scanning electron microscopy, high-resolution transmission electron microscopy. The optical absorptance and emittance of the as deposited and annealed films were determined using UV–vis-NIR spectroscopy. We show that the optical absorptance of the resulting double-cermet structured thin film is as high as 96% and remains to be 91% after heat treatment at 400 °C, indicating the thermal stability of the film

  10. Top Quark Flavor Changing Decay t → cH0 in Little Higgs Model

    Institute of Scientific and Technical Information of China (English)

    Farshid Tabbakh; LIU Jing-Jing; MA Wen-Gan; ZHANG Ren-You; HOU Hong-Sheng

    2005-01-01

    We study theoretically the quantum effects of the littlest Higgs model (LH) mediated by flavor changing one-loop Feynman diagrams on the rare decay process t → cH0. The comparison of the decay width in the LH model with that in the standard model (SM) is made. We find that the decay branch ratio of t → cH0 in the LH model is at most of the order ~ 10-12, which is two order larger than in the SM. The numerical results show that the difference between the branch ratios in the LH model and the SM is generally sensitive to the LH model parameters, such as symmetry breaking scale f, Higgs boson mass mH0, and x = v'4f /v2 in our chosen parameter space, but relatively insensitive to the value choice of the cosine of the mixing angle c and the ratio λ1/λ2.

  11. Platinum containing amorphous hydrogenated carbon (a-C:H/Pt) thin films as selective solar absorbers

    Energy Technology Data Exchange (ETDEWEB)

    Lan, Yung-Hsiang; Brahma, Sanjaya [Department of Materials Science and Engineering, National Cheng Kung University, Tainan 701, Taiwan (China); Tzeng, Y.H. [Department of Electrical Engineering, National Cheng Kung University, Tainan 701, Taiwan (China); Ting, Jyh-Ming, E-mail: jting@mail.ncku.edu.tw [Department of Materials Science and Engineering, National Cheng Kung University, Tainan 701, Taiwan (China); Research Center for Energy Technology and Strategy, National Cheng Kung University, Tainan 701, Taiwan (China)

    2014-10-15

    We have investigated a double-cermet structured thin film in which an a-C:H thin film was used as an anti-reflective (AR) layer and two platinum-containing amorphous hydrogenated carbon (a-C:H/Pt) thin films were used as the double cermet layers. A reactive co-sputter deposition method was used to prepare both the anti-reflective and cermet layers. Effects of the target power and heat treatment were studied. The obtained films were characterized using X-ray diffraction, scanning electron microscopy, high-resolution transmission electron microscopy. The optical absorptance and emittance of the as deposited and annealed films were determined using UV–vis-NIR spectroscopy. We show that the optical absorptance of the resulting double-cermet structured thin film is as high as 96% and remains to be 91% after heat treatment at 400 °C, indicating the thermal stability of the film.

  12. Deposition of a-C:H films on UHMWPE substrate and its wear-resistance

    Science.gov (United States)

    Xie, Dong; Liu, Hengjun; Deng, Xingrui; Leng, Y. X.; Huang, Nan

    2009-10-01

    In prosthetic hip replacements, ultrahigh molecular weight polyethylene (UHMWPE) wear debris is identified as the main factor limiting the lifetime of the artificial joints. Especially UHMWPE debris from the joint can induce tissue reactions and bone resorption that may lead to the joint loosening. The diamond like carbon (DLC) film has attracted a great deal of interest in recent years mainly because of its excellent tribological property, biocompatibility and chemically inert property. In order to improve the wear-resistance of UHMWPE, a-C:H films were deposited on UHMWPE substrate by electron cyclotron resonance microwave plasma chemical vapor deposition (ECR-PECVD) technology. During deposition, the working gases were argon and acetylene, the microwave power was set to 800 W, the biased pulsed voltage was set to -200 V (frequency 15 kHz, duty ratio 20%), the pressure in vacuum chamber was set to 0.5 Pa, and the process time was 60 min. The films were analysed by X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, nano-indentation, anti-scratch and wear test. The results showed that a typical amorphous hydrogenated carbon (a-C:H) film was successfully deposited on UHMWPE with thickness up to 2 μm. The nano-hardness of the UHMWPE coated with a-C:H films, measured at an applied load of 200 μN, was increased from 10 MPa (untreated UHMWPE) to 139 MPa. The wear test was carried out using a ball (Ø 6 mm, SiC) on disk tribometer with an applied load of 1 N for 10000 cycles, and the results showed a reduction of worn cross-sectional area from 193 μm 2 of untreated UHMWPE to 26 μm 2 of DLC coated sample. In addition the influence of argon/acetylene gas flow ratio on the growth of a-C:H films was studied.

  13. Deposition of a-C:H films on UHMWPE substrate and its wear-resistance

    Energy Technology Data Exchange (ETDEWEB)

    Xie Dong [Key Laboratory for Advanced Technologies of Materials, Ministry of Education, School of Materials Science and Engineering, Southwest Jiaotong University, Chengdu 610031 (China); School of Physical Science and Technology, Southwest Jiaotong University, Chengdu 610031 (China); Liu Hengjun; Deng Xingrui [Key Laboratory for Advanced Technologies of Materials, Ministry of Education, School of Materials Science and Engineering, Southwest Jiaotong University, Chengdu 610031 (China); Leng, Y.X., E-mail: yxleng@263.net [Key Laboratory for Advanced Technologies of Materials, Ministry of Education, School of Materials Science and Engineering, Southwest Jiaotong University, Chengdu 610031 (China); Huang Nan [Key Laboratory for Advanced Technologies of Materials, Ministry of Education, School of Materials Science and Engineering, Southwest Jiaotong University, Chengdu 610031 (China)

    2009-10-15

    In prosthetic hip replacements, ultrahigh molecular weight polyethylene (UHMWPE) wear debris is identified as the main factor limiting the lifetime of the artificial joints. Especially UHMWPE debris from the joint can induce tissue reactions and bone resorption that may lead to the joint loosening. The diamond like carbon (DLC) film has attracted a great deal of interest in recent years mainly because of its excellent tribological property, biocompatibility and chemically inert property. In order to improve the wear-resistance of UHMWPE, a-C:H films were deposited on UHMWPE substrate by electron cyclotron resonance microwave plasma chemical vapor deposition (ECR-PECVD) technology. During deposition, the working gases were argon and acetylene, the microwave power was set to 800 W, the biased pulsed voltage was set to -200 V (frequency 15 kHz, duty ratio 20%), the pressure in vacuum chamber was set to 0.5 Pa, and the process time was 60 min. The films were analysed by X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, nano-indentation, anti-scratch and wear test. The results showed that a typical amorphous hydrogenated carbon (a-C:H) film was successfully deposited on UHMWPE with thickness up to 2 {mu}m. The nano-hardness of the UHMWPE coated with a-C:H films, measured at an applied load of 200 {mu}N, was increased from 10 MPa (untreated UHMWPE) to 139 MPa. The wear test was carried out using a ball (O 6 mm, SiC) on disk tribometer with an applied load of 1 N for 10000 cycles, and the results showed a reduction of worn cross-sectional area from 193 {mu}m{sup 2} of untreated UHMWPE to 26 {mu}m{sup 2} of DLC coated sample. In addition the influence of argon/acetylene gas flow ratio on the growth of a-C:H films was studied.

  14. Deposition of a-C:H films on UHMWPE substrate and its wear-resistance

    International Nuclear Information System (INIS)

    In prosthetic hip replacements, ultrahigh molecular weight polyethylene (UHMWPE) wear debris is identified as the main factor limiting the lifetime of the artificial joints. Especially UHMWPE debris from the joint can induce tissue reactions and bone resorption that may lead to the joint loosening. The diamond like carbon (DLC) film has attracted a great deal of interest in recent years mainly because of its excellent tribological property, biocompatibility and chemically inert property. In order to improve the wear-resistance of UHMWPE, a-C:H films were deposited on UHMWPE substrate by electron cyclotron resonance microwave plasma chemical vapor deposition (ECR-PECVD) technology. During deposition, the working gases were argon and acetylene, the microwave power was set to 800 W, the biased pulsed voltage was set to -200 V (frequency 15 kHz, duty ratio 20%), the pressure in vacuum chamber was set to 0.5 Pa, and the process time was 60 min. The films were analysed by X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, nano-indentation, anti-scratch and wear test. The results showed that a typical amorphous hydrogenated carbon (a-C:H) film was successfully deposited on UHMWPE with thickness up to 2 μm. The nano-hardness of the UHMWPE coated with a-C:H films, measured at an applied load of 200 μN, was increased from 10 MPa (untreated UHMWPE) to 139 MPa. The wear test was carried out using a ball (O 6 mm, SiC) on disk tribometer with an applied load of 1 N for 10000 cycles, and the results showed a reduction of worn cross-sectional area from 193 μm2 of untreated UHMWPE to 26 μm2 of DLC coated sample. In addition the influence of argon/acetylene gas flow ratio on the growth of a-C:H films was studied.

  15. Dichotomy in regioselectivity of Pd-catalyzed direct C-H arylation of protected uracils

    Czech Academy of Sciences Publication Activity Database

    Čerňová, Miroslava; Hocek, Michal

    Praha : Institute of Organic Chemistry and Biochemistry AS CR, v. v. i., 2011 - (Hocek, M.), s. 314-316 ISBN 978-80-86241-37-1. - (Collection Symposium Series. 12). [ Chemistry of Nucleic Acid Components /15./. Český Krumlov (CZ), 05.06.2011-10.06.2011] R&D Projects: GA MŠk(CZ) LC06077 Institutional research plan: CEZ:AV0Z40550506 Keywords : direct C-H arylation * uracils * pyrimidines * palladium Subject RIV: CC - Organic Chemistry

  16. Palladium-catalysed norbornene-mediated C-H functionalization of arenes

    Science.gov (United States)

    Ye, Juntao; Lautens, Mark

    2015-11-01

    The Catellani reaction -- a palladium-catalysed C-H functionalization reaction mediated by norbornene -- was first reported in 1997. The capacity to functionalize both the ortho and ipso positions of aryl halides in a single transformation held great appeal. We reported an annulative Catellani reaction in 2000. Since then, our two groups have explored the synthetic utility of this reaction and dramatic progress has been made by a number of groups in the past five years. Whereas the original Catellani reaction uses Pd(0) catalysts, recent studies have shown that Pd(II) catalysts can be used in combination with norbornene to effect (1) direct 2-alkylation of indoles and pyrroles and (2) selective meta-C-H functionalization of arenes bearing commonly used ortho-directing groups, thereby opening new avenues for future research. We describe the most recent developments concerning the Pd-catalysed norbornene-mediated C-H functionalization of arenes, including applications in natural products synthesis. We outline challenges and future opportunities.

  17. Thermal shock and thermal cycling behaviour of amorphous a-C:H films on molybdenum substrates

    International Nuclear Information System (INIS)

    The thermal behaviour of a-C:H films (a stands for amorphous) deposited by the TEXTOR carbonization technique on molybdenum substrates was investigated in high power electron beam testing device for single and multiple shot sequences. The stationary thermal behaviour was also measured. The results for single shot testing are presented in a threshold damage diagram and show that the stability of a-C:H films on molybdenum is superior to that on steel. At higher or repeated loadings the films are converted gradually to molybdenum carbide. AES and SIMS depth profiling was used to investigate the concentration profiles and interface compositions of the films after various heat treatments. Their 1-h thermal stability on molybdenum extends to approximately 700 degree C in a stationary test. Results show that a-C:H films on molybdenum should be effective in shielding the molybdenum substrate from the plasma in a fusion device as long as the stated loading limits are not exceeded. (author)

  18. Catalytic conversion of light alkanes

    Energy Technology Data Exchange (ETDEWEB)

    Lyons, J.E.

    1992-06-30

    The second Quarterly Report of 1992 on the Catalytic Conversion of Light Alkanes reviews the work done between April 1, 1992 and June 31, 1992 on the Cooperative Agreement. The mission of this work is to devise a new catalyst which can be used in a simple economic process to convert the light alkanes in natural gas to oxygenate products that can either be used as clean-burning, high octane liquid fuels, as fuel components or as precursors to liquid hydrocarbon uwspomdon fuel. During the past quarter we have continued to design, prepare, characterize and test novel catalysts for the mild selective reaction of light hydrocarbons with air or oxygen to produce alcohols directly. These catalysts are designed to form active metal oxo (MO) species and to be uniquely active for the homolytic cleavage of the carbon-hydrogen bonds in light alkanes producing intermediates which can form alcohols. We continue to investigate three molecular environments for the active catalytic species that we are trying to generate: electron-deficient macrocycles (PHASE I), polyoxometallates (PHASE II), and regular oxidic lattices including zeolites and related structures as well as other molecular surface structures having metal oxo groups (PHASE I).

  19. Catalytic cracking process

    Science.gov (United States)

    Lokhandwala, Kaaeid A.; Baker, Richard W.

    2001-01-01

    Processes and apparatus for providing improved catalytic cracking, specifically improved recovery of olefins, LPG or hydrogen from catalytic crackers. The improvement is achieved by passing part of the wet gas stream across membranes selective in favor of light hydrocarbons over hydrogen.

  20. Catalytic distillation structure

    Science.gov (United States)

    Smith, Jr., Lawrence A.

    1984-01-01

    Catalytic distillation structure for use in reaction distillation columns, a providing reaction sites and distillation structure and consisting of a catalyst component and a resilient component intimately associated therewith. The resilient component has at least about 70 volume % open space and being present with the catalyst component in an amount such that the catalytic distillation structure consist of at least 10 volume % open space.

  1. Palladium(ii)-catalyzed C-C and C-O bond formation for the synthesis of C1-benzoyl isoquinolines from isoquinoline N-oxides and nitroalkenes.

    Science.gov (United States)

    Li, Jiu-Ling; Li, Wei-Ze; Wang, Ying-Chun; Ren, Qiu; Wang, Heng-Shan; Pan, Ying-Ming

    2016-08-01

    C1-Benzoyl isoquinolines can be generated via a palladium(ii)-catalyzed C-C and C-O coupling of isoquinoline N-oxides with aromatic nitroalkenes. The reaction proceeds through remote C-H bond activation and subsequent intramolecular oxygen atom transfer (OAT). In this reaction, the N-O bond was designed as a directing group in the C-H bond activation as well as the source of an oxygen atom. PMID:27443150

  2. 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. PMID:26788794

  3. Diffusion bonding

    Science.gov (United States)

    Anderson, Robert C.

    1976-06-22

    1. A method for joining beryllium to beryllium by diffusion bonding, comprising the steps of coating at least one surface portion of at least two beryllium pieces with nickel, positioning a coated surface portion in a contiguous relationship with an other surface portion, subjecting the contiguously disposed surface portions to an environment having an atmosphere at a pressure lower than ambient pressure, applying a force upon the beryllium pieces for causing the contiguous surface portions to abut against each other, heating the contiguous surface portions to a maximum temperature less than the melting temperature of the beryllium, substantially uniformly decreasing the applied force while increasing the temperature after attaining a temperature substantially above room temperature, and maintaining a portion of the applied force at a temperature corresponding to about maximum temperature for a duration sufficient to effect the diffusion bond between the contiguous surface portions.

  4. Rhodium mediated bond activation: from synthesis to catalysis

    Energy Technology Data Exchange (ETDEWEB)

    Ho, Hung-An [Iowa State Univ., Ames, IA (United States)

    2012-01-01

    Recently, our lab has developed monoanionic tridentate ligand, ToR, showing the corresponding coordination chemistry and catalyst reactivity of magnesium, zirconium, zinc and iridium complexes. This thesis details synthetic chemistry, structural study and catalytic reactivity of the ToR-supported rhodium compounds. Tl[ToR] has been proved to be a superior ligand transfer agent for synthesizing rhodium complexes. The salt metathesis route of Tl[ToM] with [Rh(μ-Cl)(CO)]2 and [Rh(μ- Cl)(COE)]2 gives ToMRh(CO)2 (2.2) and ToMRhH(β3-C8H13) (3.1) respectively while Tl[ToM] with [Rh(μ-Cl)(CO)]2 affords ToPRh(CO)2 (2.3). 2.2 reacts with both strong and weak electrophiles, resulting in the oxazoline N-attacked and the metal center-attacked compounds correspondingly. Using one of the metal center-attacked electrophiles, 2.3 was demonstrated to give high diastereoselectivity. Parallel to COE allylic C-H activation complex 3.1, the propene and allylbenzene allylic C-H activation products have also been synthesized. The subsequent functionalization attempts have been examined by treating with Brønsted acids, Lewis acids, electrophiles, nucleophiles, 1,3-dipolar reagents and reagents containing multiple bonds able to be inserted. Various related complexes have been obtained under these conditions, in which one of the azide insertion compounds reductively eliminates to give an allylic functionalization product stoichiometrically. 3.1 reacts with various primary alcohols to give the decarbonylation dihydride complex ToMRh(H)2CO (4.1). 4.1 shows catalytic reactivity for primary alcohol decarbonylation under a photolytic condition. Meanwhile, 2.2 has been found to be more reactive than 4.1 for catalytic alcohol decarbonylation under the same condition. Various complexes and primary

  5. A Dynamic Supramolecular System Exhibiting Substrate Selectivity in the Catalytic Epoxidation of Olefins

    DEFF Research Database (Denmark)

    Jonsson, Stefan; Odille, Fabrice G. J.; Norrby, Per-Ola;

    2005-01-01

    A dynamic supramolecular system involving hydrogen bonding between a Mn(III) salen catalyst and a Zn(II) porphyrin receptor exhibits selectivity for pyridine appended cis-beta-substituted styrene derivatives over phenyl appended derivatives in a catalytic epoxidation reaction.......A dynamic supramolecular system involving hydrogen bonding between a Mn(III) salen catalyst and a Zn(II) porphyrin receptor exhibits selectivity for pyridine appended cis-beta-substituted styrene derivatives over phenyl appended derivatives in a catalytic epoxidation reaction....

  6. Mechanistic Insight into the Intramolecular Benzylic C-H Nitrene Insertion Catalyzed by Bimetallic Paddlewheel Complexes: Influence of the Metal Centers.

    Science.gov (United States)

    Zhang, Xuepeng; Xu, Huiying; Liu, Xueping; Phillips, David Lee; Zhao, Cunyuan

    2016-05-17

    The intramolecular benzylic C-H amination catalyzed by bimetallic paddlewheel complexes was investigated by using density functional theory calculations. The metal-metal bonding characters were investigated and the structures featuring either a small HOMO-LUMO gap or a compact SOMO energy scope were estimated to facilitate an easier one-electron oxidation of the bimetallic center. The hydrogen-abstraction step was found to occur through three manners, that is, hydride transfer, hydrogen migration, and proton transfer. The imido N species are more preferred in the Ru-Ru and Pd-Mn cases whereas coexisting N species, namely, singlet/triplet nitrene and imido, were observed in the Rh-Rh and Pd-Co cases. On the other hand, the triplet nitrene N species were found to be predominant in the Pd-Ni and Pd-Zn systems. A concerted asynchronous mechanism was found to be modestly favorable in the Rh-Rh-catalyzed reactions whereas the Pd-Co-catalyzed reactions demonstrated a slight preference for a stepwise pathway. Favored stepwise pathways were seen in each Ru-Ru- and Pd-Mn-catalyzed reactions and in the triplet nitrene involved Pd-Ni and Pd-Zn reactions. The calculations suggest the feasibility of the Pd-Mn, Pd-Co, and Pd-Ni paddlewheel complexes as being economical alternatives for the expensive dirhodium/diruthenium complexes in C-H amination catalysis. PMID:27061588

  7. Effect of the charge localization in the C+-H+ fragmentation pathway of the ethyne dication

    International Nuclear Information System (INIS)

    The C+-H+ channel in the fragmentation of the ethyne dication following inner-shell ionization has been studied by Auger electron-ion-ion coincidence spectroscopy. The ion-ion coincidence map shows a peculiar feature which corresponds to the emission of both the H+ and C+ ions in the same direction. The analysis of the data, complemented by ab initio calculations, suggests an interpretation in terms of a two-step, asynchronous concerted reaction, in which the charge of the ethynyl intermediate ion localizes on the terminal carbon atom.

  8. Kinetics of Hydrocarbon formation in a- C:H Film deposition plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Cal, E. de la; Tabares, F. L.

    1993-07-01

    The formation of C2 and Cp hydrocarbons during the PACVD of a-C:H films from admixtures of methane with H2 and He has been investigated by mass spectrometry under several deposition condition. The time evolution of the observed species indicates that the formation mechanisms of ethylene and acetylene are sensitive to the conditions of the wall during the growing of the film. Acetylene are sensitive to the conditions of the wall during the growing of the film. Acetylene formation was found to be directly related to the formation of the film on top of the carburized metal. (Author) 12 refs.

  9. Production of iron carbide using the metastable Fe-C-H-O system

    Energy Technology Data Exchange (ETDEWEB)

    Conejo, A.N.; Estrada, R.S.; Rodriguez, R.A. [Instituto Tecnologico Morelia (Mexico)

    2003-04-01

    The production of iron carbide without the formation of free carbon was explored using a metastable thermodynamic approach. Phase stability diagrams, at constant pressure and constant temperature, indicating the phase fields for the condensed phases in total equilibrium with a reactant gas phase were employed as the initial point analysis of the present study. With the aid of this information it was possible to identify the phase fields corresponding to metastable iron carbide in a ternary diagram (C-H-O). Experimental evidence confirms the validity of this information. The metastable diagrams are proposed to be used as a method to control the production of iron carbide in the industrial practice. (orig.)

  10. Kinetics of Hydrocarbon formation in a-C:H film deposition plasmas

    International Nuclear Information System (INIS)

    The formation of C2 and C3 hydrocarbons during the PACVD of a-C-H films from admixtures of methane with H2 and He has been investigated by mass spectrometry under several deposition condition. The time evolution of the observed species indicates that the formation mechanism of ethylene and acetylene are sensitive to the conditions of the wall during the growing of the film. Acetylene are sensitive to the conditions of the wall during the growing of the carburized metal. (Author)

  11. Formal Gold- and Rhodium-Catalyzed Regiodivergent C-H Alkynylation of 2-Pyridones.

    Science.gov (United States)

    Li, Yunyun; Xie, Fang; Li, Xingwei

    2016-01-15

    Formal regiodivergent C-H alkynylation of 2-pyridones bearing different N-substituents has been realized under Au(I) and Rh(III) catalysis using a hypervalent iodine alkyne reagent. When catalyzed by Au(I), the alkynylation occurred at the most electron-rich 5-position via an electrophilic alkynylation pathway. The selectivity was switched to the 6-position under assistance of an N-chelation group when a Rh(III) catalyst was employed. A rhodacylic complex has been isolated as a key intermediate. PMID:26709449

  12. Compositional, structural and optical properties of Si-rich a-SiC:H thin films deposited by ArF-LCVD

    Energy Technology Data Exchange (ETDEWEB)

    Lopez, E. [Dpto. Fisica Aplicada, Universidad de Vigo, Campus Lagoas-Marcosende, 36310 Vigo (Spain)]. E-mail: fani@uvigo.es; Chiussi, S. [Dpto. Fisica Aplicada, Universidad de Vigo, Campus Lagoas-Marcosende, 36310 Vigo (Spain); Kosch, U. [Dpto. Fisica Aplicada, Universidad de Vigo, Campus Lagoas-Marcosende, 36310 Vigo (Spain); Gonzalez, P. [Dpto. Fisica Aplicada, Universidad de Vigo, Campus Lagoas-Marcosende, 36310 Vigo (Spain); Serra, J. [Dpto. Fisica Aplicada, Universidad de Vigo, Campus Lagoas-Marcosende, 36310 Vigo (Spain); Serra, C. [CACTI, Universidad de Vigo, Campus Lagoas-Marcosende, 36310 Vigo (Spain); Leon, B. [Dpto. Fisica Aplicada, Universidad de Vigo, Campus Lagoas-Marcosende, 36310 Vigo (Spain)

    2005-07-30

    Silicon-rich amorphous hydrogenated silicon carbon (a-SiC:H) films with C content up to 23% have been grown on Si and Corning glass substrates using ArF laser induced chemical vapor deposition (ArF-LCVD). This technique allows tailoring film composition by controlling deposition parameters such as precursor gas mixture (disilane and ethylene diluted in helium) and substrate temperature (180-400 deg. C). The influence of both parameters on composition and bonding were studied by Fourier transform infrarred (FTIR) and X-Ray photoelectron spectroscopy (XPS). The optical gap of these semiconductors deposited at 250 deg. C varied from 1.6 to 2.4 eV and was determined by UV-vis spectroscopy. An additional analysis by profilometry and atomic force microscopy (AFM) have been done for determining the deposition rate and the roughness (rms < 6 nm) of the films as well as their surface morphology.

  13. Pi Bond Orders and Bond Lengths

    Science.gov (United States)

    Herndon, William C.; Parkanyi, Cyril

    1976-01-01

    Discusses three methods of correlating bond orders and bond lengths in unsaturated hydrocarbons: the Pauling theory, the Huckel molecular orbital technique, and self-consistent-field techniques. (MLH)

  14. Catalytic Synthesis Lactobionic Acid

    Directory of Open Access Journals (Sweden)

    V.G. Borodina

    2014-07-01

    Full Text Available Gold nanoparticles are obtained, characterized and deposited on the carrier. Conducted catalytic synthesis of lactobionic acid from lactose. Received lactobionic acid identify on the IR spectrum.

  15. Catalytic distillation process

    Science.gov (United States)

    Smith, Jr., Lawrence A.

    1982-01-01

    A method for conducting chemical reactions and fractionation of the reaction mixture comprising feeding reactants to a distillation column reactor into a feed zone and concurrently contacting the reactants with a fixed bed catalytic packing to concurrently carry out the reaction and fractionate the reaction mixture. For example, a method for preparing methyl tertiary butyl ether in high purity from a mixed feed stream of isobutene and normal butene comprising feeding the mixed feed stream to a distillation column reactor into a feed zone at the lower end of a distillation reaction zone, and methanol into the upper end of said distillation reaction zone, which is packed with a properly supported cationic ion exchange resin, contacting the C.sub.4 feed and methanol with the catalytic distillation packing to react methanol and isobutene, and concurrently fractionating the ether from the column below the catalytic zone and removing normal butene overhead above the catalytic zone.

  16. Chelation-assisted Pd-catalysed ortho-selective oxidative C-H/C-H cross-coupling of aromatic carboxylic acids with arenes and intramolecular Friedel-Crafts acylation: one-pot formation of fluorenones.

    Science.gov (United States)

    Sun, Denan; Li, Bijin; Lan, Jingbo; Huang, Quan; You, Jingsong

    2016-03-01

    Pd-Catalysed ortho-selective oxidative C-H/C-H cross-coupling of aromatic carboxylic acids with arenes and subsequent intramolecular Friedel-Crafts acylation has been accomplished for the first time through a chelation-assisted C-H activation strategy. Starting from the readily available substrates, a variety of fluorenone derivatives are obtained in one pot. The direct use of naturally occurring carboxylic acid functionalities as directing groups avoids unnecessary steps for installation and removal of an extra directing group. PMID:26861768

  17. Ion beam analysis of a-C:H films on alloy steel substrate

    International Nuclear Information System (INIS)

    An a-C:H thin film deposited by plasma immersion ion implantation and deposition on alloy steel (16MnCr5) was analyzed using a self-consistent ion beam analysis technique. In the self-consistent analysis, the results of each individual technique are combined in a unique model, increasing confidence and reducing simulation errors. Self-consistent analysis, then, is able to improve the regular ion beam analysis since several analyses commonly used to process ion beam data still rely on handling each spectrum independently. The sample was analyzed by particle-induced x-ray emission (for trace elements), elastic backscattering spectrometry (for carbon), forward recoil spectrometry (for hydrogen) and Rutherford backscattering spectrometry (for film morphology). The self-consistent analysis provided reliable chemical information about the film, despite its “heavy” substrate. As a result, we could determine precisely the H/C ratio, contaminant concentration and some morphological characteristics of the film, such as roughness and discontinuities. - Highlights: • Self-consistent approach of ion beam analysis was used to characterize an a-C:H film. • The self-consistent analysis provided a unequivocal and reliable model of the sample. • Morphological aspects of the film were assessed with the ion beam analysis

  18. The role of C-H$\\ldots$ interaction in the stabilization of benzene and adamantane clusters

    Indian Academy of Sciences (India)

    R Mahesh Kumar; M Elango; R Parthasarathi; Dolly Vijay; V Subramanian

    2012-01-01

    In this investigation, a systematic attempt has been made to understand the interaction between adamantane and benzene using both ab initio and density functional theory methods. C-H$\\ldots$ type of interaction between C-H groups of adamantane and cloud of benzene is found as the important attraction for complex formation. The study also reveals that the methylene (-CH2) and methine (-CH) groups of adamantane interact with benzene resulting in different geometrical structures. And it is found that the former complex is stronger than the later. The diamondoid structure of adamantane enables it to interact with a maximum of four benzene molecules, each one along the four faces. The stability of the complex increases with increase in the number of benzene molecules. The energy decomposition analysis of adamantane-benzene complexes using DMA approach shows that the origin of the stability primarily arises from the dispersive interaction. The theory of atoms in molecules (AIM) supports the existence of weak interaction between the two systems. The electrostatic topography features provide clues for the mode of interaction of adamantane with benzene.

  19. Novel Stable Compounds in the C-H-O Ternary System at High Pressure.

    Science.gov (United States)

    Saleh, Gabriele; Oganov, Artem R

    2016-01-01

    The chemistry of the elements is heavily altered by high pressure, with stabilization of many new and often unexpected compounds, the emergence of which can profoundly change models of planetary interiors, where high pressure reigns. The C-H-O system is one of the most important planet-forming systems, but its high-pressure chemistry is not well known. Here, using state-of-the-art variable-composition evolutionary searches combined with quantum-mechanical calculations, we explore the C-H-O system at pressures up to 400 GPa. Besides uncovering new stable polymorphs of high-pressure elements and known molecules, we predicted the formation of new compounds. A 2CH4:3H2 inclusion compound forms at low pressure and remains stable up to 215 GPa. Carbonic acid (H2CO3), highly unstable at ambient conditions, was predicted to form exothermically at mild pressure (about 1 GPa). As pressure rises, it polymerizes and, above 314 GPa, reacts with water to form orthocarbonic acid (H4CO4). This unexpected high-pressure chemistry is rationalized by analyzing charge density and electron localization function distributions, and implications for general chemistry and planetary science are also discussed. PMID:27580525

  20. Catalytic Coanda combustion

    Energy Technology Data Exchange (ETDEWEB)

    Coleman, J.D.; Smith, A.G.; Kopmels, M.

    1992-09-16

    A catalytic reaction is enhanced by the use of the Coanda effect to maximise contact between reactant and catalyst. A device utilising this principle comprises a Coanda surface which directs the flow of fuel from a slot to form a primary jet which entrains the surrounding ambient air and forms a combustible mixture for reaction on a catalytic surface. The Coanda surface may have an internal or external nozzle which may be axi-symmetric or two-dimensional. (author)

  1. Catalytic Deoxygenation of Fatty Acids: Elucidation of the Inhibition Process

    NARCIS (Netherlands)

    Hollak, S.A.W.; Jong, de K.P.; Es, van D.S.

    2014-01-01

    Catalytic deoxygenation of unsaturated fatty acids in the absence of H2 is known to suffer from significant catalyst inhibition. Thus far, no conclusive results have been reported on the cause of deactivation. Here we show that CC double bonds present in the feed or the products dramatically reduce

  2. Catalytic ignition of light hydrocarbons

    Institute of Scientific and Technical Information of China (English)

    K. L. Hohn; C.-C. Huang; C. Cao

    2009-01-01

    Catalytic ignition refers to phenomenon where sufficient energy is released from a catalytic reaction to maintain further reaction without additional extemai heating. This phenomenon is important in the development of catalytic combustion and catalytic partial oxidation processes, both of which have received extensive attention in recent years. In addition, catalytic ignition studies provide experimental data which can be used to test theoretical hydrocarbon oxidation models. For these reasons, catalytic ignition has been frequently studied. This review summarizes the experimental methods used to study catalytic ignition of light hydrocarbons and describes the experimental and theoretical results obtained related to catalytic ignition. The role of catalyst metal, fuel and fuel concentration, and catalyst state in catalytic ignition are examined, and some conclusions are drawn on the mechanism of catalytic ignition.

  3. Palladium/norbornene catalysis for selective aromatic functionalization via C-H activation

    OpenAIRE

    Fontana, Marco

    2015-01-01

    The subject of this PhD thesis is the study of new processes in homogeneous catalysis for the synthesis of selectively substituted compounds containing the biaryl unit. The methodology, discovered in our laboratory, utilizes simple and readily available starting materials to form complex molecular structures under mild conditions. It takes advantage of the catalytic system based on palladium and norbornene. The metal, the strained olefin and an aryl halide work in a cooperative way to build u...

  4. Effect of Ar/CH4 Mixture Ratio on Properties of Ag/C:H Nanocomposite Prepared by DC Sputtering

    OpenAIRE

    E. Mohsen Soltani; Ghorannevis, Z.; M. Shirazi

    2013-01-01

    Ag/C:H films were deposited by DC sputtering method on Si substrates with different Ar/CH4 gas mixture ratios. Effect of Ar/CH4 gas mixture ratios was investigated on optical and structural properties of Ag/C:H films by FTIR spectroscopy analysis, X-Ray diffractometry (XRD), scanning electron microscopy (SEM), and atomic force microscopy (AFM), respectively. In order to evaluate the effect of gas flow ratio on the optical and structural properties of Ag/C:H films, Ar/CH4 gas ratio was changed...

  5. Diversity-Oriented Synthesis of Substituted Benzo[b]thiophenes and Their Hetero-Fused Analogues through Palladium-Catalyzed Oxidative C-H Functionalization/Intramolecular Arylthiolation.

    Science.gov (United States)

    Acharya, Anand; Kumar, S Vijay; Ila, Hiriyakkanavar

    2015-11-16

    An efficient, high yielding route to multisubstituted benzo[b]thiophenes has been developed through palladium-catalyzed intramolecular oxidative C-H functionalization-arylthiolation of enethiolate salts of α-aryl-β-(het)aryl/alkyl-β-mercaptoacrylonitriles/acrylates or acrylophenones. The overall strategy involves a one-pot, two-step process in which enethiolate salts [generated in situ through base-mediated condensation of substituted arylacetonitriles, deoxybenzoins, or arylacetates with (het)aryl (or alkyl) dithioates] are subjected to intramolecular C-H functionalization-arylthiolation under the influence of a palladium acetate (or palladium chloride)/cupric acetate catalytic system and tetrabutylammonium bromide as additive in N,N-dimethylformamide (DMF) as solvent. In a few cases, the yields of benzo[b]thiophenes were better in a two-step process by employing the corresponding enethiols as substrates. In a few examples, Pd(OAc)2 (or PdCl2) catalyst in the presence of oxygen was found to be more efficient than cupric acetate as reoxidant, furnishing benzothiophenes in improved yields by avoiding formation of side products. The method is compatible with a diverse range of substituents on the aryl ring as well as on the 2- and 3-positions of the benzothiophene scaffold. The protocol could also be extended to the synthesis of a raloxifene precursor and a tubulin polymerization inhibitor in good yields. The versatility of this newly developed method was further demonstrated by elaborating it for the synthesis of substituted thieno-fused heterocycles such as thieno[2,3-b]thiophenes, thieno[2,3-b]indoles, thieno[3,2-c]pyrazole, and thieno[2,3-b]pyridines in high yields. A probable mechanism involving intramolecular electrophilic arylthiolation via either a Pd-S adduct or palladacycle intermediate has been proposed on the basis of experimental studies. PMID:26429766

  6. 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

    International Nuclear Information System (INIS)

    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 surface characterization was followed using atomic force microscopy (AFM) topography images, surface morphology parameters, height distribution histograms and bearing ratio curves with hybrid parameters. The AFM analysis directly showed that the a-C:H/SiOx/PVP and a-C:H:N/SiOx/PVP composite films represent different morphologies with characteristic surface textures. Surface adhesive properties were evaluated by measuring the force required to separate the AFM tip from the surface by means of AFM force-distance curves. The variance in adhesion force detected was lower for a-C:H/SiOx/PVP composite films due to lower structural homogeneity of the surfaces. Fourier transform infrared spectroscopy analysis was performed to study the blend behavior of PVP upon a-C:H/SiOx and a-C:H:N/SiOx direct ion beam deposition. It was determined that interfacial interactions of PVP with the direct ion beam induced changes in the carbonyl group of the PVP and are dependent on the carrier gas used for the synthesis of the amorphous hydrogenated carbon films. - Highlights: ► Polyvinylpyrrolidone (PVP) surface was modified with diamond-like carbon (DLC). ► Hall-type closed drift ion beam source was used for synthesis of DLC films. ► Surface morphological, adhesive properties and blend behavior were studied. ► Depending on thickness of PVP different surface textures were obtained. ► Changes in carbonyl group of PVP upon modification with DLC were observed

  7. 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, Vladimir; 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.

  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. PMID:20025109

  9. Recommended Thermal Rate Coefficients for the C + H$_3^+$ Reaction and Some Astrochemical Implications

    CERN Document Server

    Vissapragada, S; Miller, K A; O'Connor, A P; de Ruette, N; Urbain, X; Savin, D W

    2016-01-01

    We have incorporated our experimentally derived thermal rate coefficients for C + H$_3^+$ forming CH$^+$ and CH$_2^+$ into a commonly used astrochemical model. We find that the Arrhenius-Kooij equation typically used in chemical models does not accurately fit our data and use instead a more versatile fitting formula. At a temperature of 10 K and a density of 10$^4$ cm$^{-3}$, we find no significant differences in the predicted chemical abundances, but at higher temperatures of 50, 100, and 300 K we find up to factor of 2 changes. Additionally, we find that the relatively small error on our thermal rate coefficients, $\\sim15\\%$, significantly reduces the uncertainties on the predicted abundances compared to those obtained using the currently implemented Langevin rate coefficient with its estimated factor of 2 uncertainty.

  10. Rapid thermal annealing of Amorphous Hydrogenated Carbon (a-C:H) films

    Science.gov (United States)

    Alterovitz, Samuel A.; Pouch, John J.; Warner, Joseph D.

    1987-01-01

    Amorphous hydrogenated carbon (a-C:H) films were deposited on silicon and quartz substrates by a 30 kHz plasma discharge technique using methane. Rapid thermal processing of the films was accomplished in nitrogen gas using tungsten halogen light. The rapid thermal processing was done at several fixed temperatures (up to 600 C), as a function of time (up to 1800 sec). The films were characterized by optical absorption and by ellipsometry in the near UV and the visible. The bandgap, estimated from extrapolation of the linear part of a Tauc plot, decreases both with the annealing temperature and the annealing time, with the temperature dependence being the dominating factor. The density of states parameter increases up to 25 percent and the refractive index changes up to 20 percent with temperature increase. Possible explanations of the mechanisms involved in these processes are discussed.

  11. Erosion of a-C:H in the afterglow of ammonia plasma

    Science.gov (United States)

    Drenik, Aleksander; Mourkas, Angelos; Zaplotnik, Rok; Primc, Gregor; Mozetič, Miran; Panjan, Peter; Alegre, Daniel; Tabarés, Francisco L.

    2016-07-01

    Amorphous hydrogenated carbon (a-C:H) deposits were eroded in the afterglow of a NH3 plasma, created with an inductively coupled RF generator in pure NH3 at the gas pressure of 50 Pa. The plasma system was characterised by optical emission spectroscopy and mass spectrometry, and the erosion process was monitored in-situ with a laser interferometry system. Based on the mass spectrometry measurements, the degree of dissociation of the NH3 molecules was estimated at 90% at the highest generator forward power in the discharge region, however the densities of N and H atoms were significantly smaller at the location of the sample holder. The erosion rates were found to increase with surface temperature and forward generator power. In the high dissociation regime, the composition of the afterglow and the reaction products highlight the role of N atoms in the erosion process.

  12. R.E.A.C.H. to Teach: Making Patient and Family Education "Stick".

    Science.gov (United States)

    Cutilli, Carolyn Crane

    2016-01-01

    Healthcare professionals teach patients and families about their health every day. Regulatory and accreditation organizations mandate patient and family education to promote better health outcomes. And recently, financial rewards for healthcare organizations are being tied to patient satisfaction (Hospital Consumer Assessment of Healthcare Providers and Systems-HCAHPS). A University of Pennsylvania Health System group of staff and patients, devoted to excellence in patient and family education, developed the graphic "R.E.A.C.H. to Teach." The purpose of the graphic is to make evidence-based practice (EBP) for patient and family education "stick" with staff. The group used concepts from the marketing book, Made to Stick, to demonstrate how to develop effective staff and patient and family education. Ideas (education) that survive ("stick") have the following attributes: simple, unexpected, concrete, credible, emotional, and narrative (story). This article demonstrates how to apply these principles and EBP to patient and family education. PMID:27441879

  13. Gas avalanche pixel detectors with amorphous silicon carbide (a-Si:C:H) overcoating

    International Nuclear Information System (INIS)

    Performance of the gas avalanche pixel detectors of square and circular geometry, with and without semiconducting surface coating, was characterized in terms of gas gain and active region. Although the electric field profile of the square geometry cannot be radially uniform, a 200 microm pitch detector of this type exhibited a maximum gain of ∼ 12,000 which is comparable to that of the circular counterpart. Due to the existence of the anode bus lines passing under the cathodes, there is a defocusing effect of the drift field lines converging to the anodes, resulting in inactive regions where electrons produced from gas ionization are not collected at the anodes. Variation of the count rate with the drift field was measured to probe these defocusing effects. The p-type a-Si:C:H surface coating was effective in reducing these inactive regions

  14. C-H arylation of azaheterocycles: a direct ligand-free and Cu-catalyzed approach using diaryliodonium salts.

    Science.gov (United States)

    Kumar, Dalip; Pilania, Meenakshi; Arun, V; Pooniya, Savita

    2014-09-01

    An efficient and high yielding Cu-catalyzed direct C-H arylation of azaheterocycles including oxadiazoles, thiadiazoles, benzoxazoles and benzothiazoles has been achieved by employing easily accessible diaryliodonium salts. PMID:25017573

  15. Functionalized alkynyl-chlorogermanes: hydrometallation, Ge-Cl bond activation, Ge-H bond formation and chlorine-tert-butyl exchange via a transient germyl cation.

    Science.gov (United States)

    Honacker, Christian; Qu, Zheng-Wang; Tannert, Jens; Layh, Marcus; Hepp, Alexander; Grimme, Stefan; Uhl, Werner

    2016-04-14

    Treatment of alkynyl-arylchlorogermanes ArylnGe(Cl)(C[triple bond, length as m-dash]C-(t)Bu)3-n (n = 1, 2) with HM(t)Bu2 (M = Al, Ga) yielded mixed Al or Ga alkenyl-alkynylchlorogermanes via hydrometallation reactions. Intramolecular interactions between the Lewis-basic Cl atoms and the Lewis-acidic Al or Ga atoms afforded MCGeCl heterocycles. The endocyclic M-Cl distances were significantly lengthened compared to the starting compounds and indicated Ge-Cl bond activation. Dual hydrometallation succeeded only with HGa(t)Bu2. One Ga atom of the product was involved in a Ga-Cl bond, while the second one had an interaction to a C-H bond of a phenyl group. In two cases treatment of chlorogermanes with two equivalents of HAl(t)Bu2 resulted in hydroalumination of one alkynyl group and formation of unprecedented Ge-H functionalized germanes, Aryl-Ge(H)(C[triple bond, length as m-dash]C-(t)Bu)[C(Al(t)Bu2)[double bond, length as m-dash]C(H)-(t)Bu] (Aryl = mesityl, triisopropylphenyl). The Al atoms of these compounds interacted with the α-C atoms of the alkynyl groups. Ph(Cl)Ge(C[triple bond, length as m-dash]C-(t)Bu)[C(Al(t)Bu2}[double bond, length as m-dash]C(H)-(t)Bu] reacted in an unusual Cl/(t)Bu exchange to yield the tert-butylgermane Ph((t)Bu)Ge(C[triple bond, length as m-dash]C-(t)Bu)[C{Al((t)Bu)(Cl)}[double bond, length as m-dash]C(H)-(t)Bu]. Quantum chemical calculations suggested the formation of a germyl cation as a transient intermediate. PMID:26610394

  16. Deposition of a-C:H films on inner surface of high-aspect-ratio microchannel

    Science.gov (United States)

    Hirata, Yuki; Choi, Junho

    2016-08-01

    Hydrogenated amorphous carbon (a-C:H) films were prepared on inner surface of 100-μm-width microchannel by using a bipolar-type plasma based ion implantation and deposition. The microchannel was fabricated using a silicon plate, and two kinds of microchannels were prepared, namely, with a bottom layer (open at one end) and without a bottom layer (open at both ends). The distribution of thickness and hardness of films was evaluated by SEM and nanoindentation measurements, respectively, and the microstructures of films were evaluated by Raman spectroscopy. Furthermore, the behavior of ions and radicals was analyzed simultaneously by combining the calculation methods of Particle-In-Cell/Monte Carlo Collision and Direct Simulation Monte Carlo to investigate the coating mechanism for the microchannel. It was found that the film thickness decreased as the depth of the coating position increased in the microchannels where it is open at one end. The uniformity of the film thickness improved by increasing the negative pulse voltage because ions can arrive at the deeper part of the microchannel. In addition, the hardness increased as the depth of the coating position increased. This is because the radicals do not arrive at the deeper part of the microchannel, and the incident proportion of ions relative to that of radicals increases, resulting in a high hardness due to the amorphization of the film. The opening area of the microchannel where the aspect ratio is very small, radicals dominate the incident flux, whereas ions prevail over radicals above an aspect ratio of about 7.5. On the other hand, in the microchannels that are open at both ends, there were great improvements in uniformity of the film thickness, hardness, and the film structure. The a-C:H films were successfully deposited on the entire inner surface of a microchannel with an aspect ratio of 20.

  17. Accurate NMR determination of C-H or N-H distances for unlabeled molecules.

    Science.gov (United States)

    Nishiyama, Y; Malon, M; Potrzebowski, M J; Paluch, P; Amoureux, J P

    2016-02-01

    Cross-Polarization with Variable Contact-time (CP-VC) is very efficient at ultra-fast MAS (νR ≥ 60 kHz) to measure accurately the dipolar interactions corresponding to C-H or N-H short distances, which are very useful for resonance assignment and for analysis of dynamics. Here, we demonstrate the CP-VC experiment with (1)H detection. In the case of C-H distances, we compare the CP-VC signals with direct ((13)C) and indirect ((1)H) detection and find that the latter allows a S/N gain of ca. 2.5, which means a gain of ca. 6 in experimental time. The main powerful characteristics of CP-VC methods are related to the ultra-fast spinning speed and to the fact that most of the time only the value of the dipolar peak separation has to be used to obtain the information. As a result, CP-VC methods are: (i) easy to set up and to use, and robust with respect to (ii) rf-inhomogeneity thus allowing the use of full rotor samples, (iii) rf mismatch, and (iv) offsets and chemical shift anisotropies. It must be noted that the CP-VC 2D method with indirect (1)H detection requires the proton resolution and is thus mainly applicable to small or perdeuterated molecules. We also show that an analysis of the dynamics can even be performed, with a reasonable experimental time, on unlabeled samples with (13)C or even (15)N natural abundance. PMID:26169913

  18. Catalytic arylation methods from the academic lab to industrial processes

    CERN Document Server

    Burke, Anthony J

    2014-01-01

    A current view of the challenging field of catalytic arylation reactions. Clearly structured, the chapters in this one-stop resource are arranged according to the reaction type, and focus on novel, efficient and sustainable processes, rather than the well-known and established cross-coupling methods.The entire contents are written by two authors with academic and industrial expertise to ensure consistent coverage of the latest developments in the field, as well as industrial applications, such as C-H activation, iron and gold-catalyzed coupling reactions, cycloadditions or novel methodologies

  19. Catalytic coherence transformations

    Science.gov (United States)

    Bu, Kaifeng; Singh, Uttam; Wu, Junde

    2016-04-01

    Catalytic coherence transformations allow the otherwise impossible state transformations using only incoherent operations with the aid of an auxiliary system with finite coherence that is not being consumed in any way. Here we find the necessary and sufficient conditions for the deterministic and stochastic catalytic coherence transformations between a pair of pure quantum states. In particular, we show that the simultaneous decrease of a family of Rényi entropies of the diagonal parts of the states under consideration is a necessary and sufficient condition for the deterministic catalytic coherence transformations. Similarly, for stochastic catalytic coherence transformations we find the necessary and sufficient conditions for achieving a higher optimal probability of conversion. We thus completely characterize the coherence transformations among pure quantum states under incoherent operations. We give numerous examples to elaborate our results. We also explore the possibility of the same system acting as a catalyst for itself and find that indeed self-catalysis is possible. Further, for the cases where no catalytic coherence transformation is possible we provide entanglement-assisted coherence transformations and find the necessary and sufficient conditions for such transformations.

  20. Catalytic asymmetric formal synthesis of beraprost

    Science.gov (United States)

    Kobayashi, Yusuke; Kuramoto, Ryuta

    2015-01-01

    Summary The first catalytic asymmetric synthesis of the key intermediate for beraprost has been achieved through an enantioselective intramolecular oxa-Michael reaction of an α,β-unsaturated amide mediated by a newly developed benzothiadiazine catalyst. The Weinreb amide moiety and bromo substituent of the Michael adduct were utilized for the C–C bond formations to construct the scaffold. All four contiguous stereocenters of the tricyclic core were controlled via Rh-catalyzed stereoselective C–H insertion and the subsequent reduction from the convex face. PMID:26734111

  1. Enantioselective Allylic C-H Oxidation of Terminal Olefins to Isochromans by Palladium(II)/Chiral Sulfoxide Catalysis.

    Science.gov (United States)

    Ammann, Stephen E; Liu, Wei; White, M Christina

    2016-08-01

    The enantioselective synthesis of isochroman motifs has been accomplished by palladium(II)-catalyzed allylic C-H oxidation from terminal olefin precursors. Critical to the success of this goal was the development and utilization of a novel chiral aryl sulfoxide-oxazoline (ArSOX) ligand. The allylic C-H oxidation reaction proceeds with the broadest scope and highest levels of asymmetric induction reported to date (avg. 92 % ee, 13 examples with greater than 90 % ee). PMID:27376625

  2. Convergent Synthesis of Diverse Nitrogen Heterocycles via Rh(III)-Catalyzed C-H Conjugate Addition/Cyclization Reactions.

    Science.gov (United States)

    Weinstein, Adam B; Ellman, Jonathan A

    2016-07-01

    The development of Rh(III)-catalyzed C-H conjugate addition/cyclization reactions that provide access to synthetically useful fused bi- and tricyclic nitrogen heterocycles is reported. A broad scope of C-H functionalization substrates and electrophilic olefin coupling partners is effective, and depending on the nature of the directing group, cyclic imide, amide, or heteroaromatic products are obtained. An efficient synthesis of a pyrrolophenanthridine alkaloid natural product, oxoassoanine, highlights the utility of this method. PMID:27337641

  3. Ru-catalysed C-H silylation of unprotected gramines, tryptamines and their congeners.

    Science.gov (United States)

    Devaraj, K; Sollert, C; Juds, C; Gates, P J; Pilarski, L T

    2016-04-30

    Selective Ru-catalysed C2-H silylation of heteroarenes is presented. The transformation works with or without directing group assistance and requires no protecting groups. Gramines and tryptamines may be converted efficiently whilst avoiding deleterious elimination side-reactions. Mechanistic studies reveal an unusual activation of the indole C4-H bond by an electron-rich metal. PMID:27050747

  4. 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.

  5. The C--H Stretching Features at 3.2--3.5 Micrometer of Polycyclic Aromatic Hydrocarbons with Aliphatic Sidegroups

    CERN Document Server

    Yang, Xuejuan; Glaser, Rainer; Zhong, Jianxin

    2016-01-01

    The so-called unidentified infrared emission (UIE) features at 3.3, 6.2, 7.7, 8.6, and 11.3 micrometer are ubiquitously seen in a wide variety of astrophysical regions. The UIE features are characteristic of the stretching and bending vibrations of aromatic hydrocarbon materials, e.g., polycyclic aromatic hydrocarbon (PAH) molecules. The 3.3 micrometer aromatic C--H stretching feature is often accompanied by a weaker feature at 3.4 micrometer. The latter is often thought to result from the C--H stretch of aliphatic groups attached to the aromatic systems. The ratio of the observed intensity of the 3.3 micrometer aromatic C--H feature to that of the 3.4 micrometer aliphatic C--H feature allows one to estimate the aliphatic fraction of the UIE carriers, provided that the intrinsic oscillator strengths of the 3.3 micrometer aromatic C--H stretch (A3.3) and the 3.4 micrometer aliphatic C--H stretch (A3.4) are known. While previous studies on the aliphatic fraction of the UIE carriers were mostly based on the A3.4...

  6. Effects of metal elements in catalytic growth of carbon nanotubes/graphene: A first principles DFT study

    International Nuclear Information System (INIS)

    Graphical abstract: - Highlights: • Role of metals in the catalytic growth of CNTs or graphene was studied using DFT. • The results explain why Ni-based catalyst is suitable for growing CNTs. • Cu based alloys, e.g. Cu8Ni, are found appropriate catalyst for graphene synthesis. - Abstract: Role of metals in the catalytic Chemical Vapor Deposition (CVD) growth of carbon nanotubes (CNTs) or graphene was investigated using DFT. Crucial processes involved in the growth of CNTs/graphene: methane dissociation to produce C, C diffusion and nucleation kinetics were studied on the (1 1 1) surface of different transition metals, i.e., Fe, Co, Ni, and Cu. Based on the DFT calculation results, the present study explains why Ni-based catalyst is a suitable CVD substrate for growing CNTs: it has a moderate reactivity towards methane dissociation; low energy barrier for C atom surface diffusion, which makes C to diffuse easily to the metal/CNTs edges and contribute to CNTs growth; relatively high nucleation barriers, making it more resistant for deactivation caused by the cover of carbon clusters. Meanwhile, this study also shows that Cu may be an appropriate catalyst for graphene synthesis due to the particularly low diffusion and nucleation barriers of C atoms on Cu, which suggest that C atoms tend to be more uniformly distributed and nucleate easily on the Cu surface. Key limitation of Cu is the low reactivity of this metal towards methane dissociation. Since Fe and Ni are very reactive towards C-H bond breaking, Cu based alloys, e.g. Cu8Ni, were proposed as a suitable catalyst for graphene production

  7. Effects of metal elements in catalytic growth of carbon nanotubes/graphene: A first principles DFT study

    Energy Technology Data Exchange (ETDEWEB)

    Li, Jingde; Croiset, Eric; Ricardez-Sandoval, Luis, E-mail: laricard@uwaterloo.ca

    2014-10-30

    Graphical abstract: - Highlights: • Role of metals in the catalytic growth of CNTs or graphene was studied using DFT. • The results explain why Ni-based catalyst is suitable for growing CNTs. • Cu based alloys, e.g. Cu{sub 8}Ni, are found appropriate catalyst for graphene synthesis. - Abstract: Role of metals in the catalytic Chemical Vapor Deposition (CVD) growth of carbon nanotubes (CNTs) or graphene was investigated using DFT. Crucial processes involved in the growth of CNTs/graphene: methane dissociation to produce C, C diffusion and nucleation kinetics were studied on the (1 1 1) surface of different transition metals, i.e., Fe, Co, Ni, and Cu. Based on the DFT calculation results, the present study explains why Ni-based catalyst is a suitable CVD substrate for growing CNTs: it has a moderate reactivity towards methane dissociation; low energy barrier for C atom surface diffusion, which makes C to diffuse easily to the metal/CNTs edges and contribute to CNTs growth; relatively high nucleation barriers, making it more resistant for deactivation caused by the cover of carbon clusters. Meanwhile, this study also shows that Cu may be an appropriate catalyst for graphene synthesis due to the particularly low diffusion and nucleation barriers of C atoms on Cu, which suggest that C atoms tend to be more uniformly distributed and nucleate easily on the Cu surface. Key limitation of Cu is the low reactivity of this metal towards methane dissociation. Since Fe and Ni are very reactive towards C-H bond breaking, Cu based alloys, e.g. Cu{sub 8}Ni, were proposed as a suitable catalyst for graphene production.

  8. Oxidative coupling between C(sp(2))-H and C(sp(3))-H bonds of indoles and cyclic ethers/cycloalkanes.

    Science.gov (United States)

    Yang, Qingjing; Choy, Pui Ying; Wu, Yinuo; Fan, Baomin; Kwong, Fuk Yee

    2016-02-24

    Cross-dehydrogenative-coupling (CDC) between C-H/C-H bonds of indoles and cyclic ethers/cycloalkanes is made viable through a simple transition-metal-free pathway. With the aid of only di-tert-butyl peroxide, a number of inactive cyclic ethers and cycloalkanes can be directly coupled with indole derivatives in satisfactory yields. PMID:26842403

  9. Bipyridine- and phenanthroline-based metal-organic frameworks for highly efficient and tandem catalytic organic transformations via directed C-H activation

    Energy Technology Data Exchange (ETDEWEB)

    Manna, Kuntal [Univ. of Chicago, Chicago, IL (United States); Zhang, Teng [Univ. of Chicago, Chicago, IL (United States); Greene, Francis X. [Univ. of Chicago, Chicago, IL (United States); Lin, Wenbin [Univ. of Chicago, Chicago, IL (United States)

    2015-02-16

    We report here the synthesis of a series of robust and porous bipyridyl- and phenanthryl-based metal–organic frameworks (MOFs) of UiO topology (BPV-MOF, mBPV-MOF, and mPT-MOF) and their postsynthetic metalation to afford highly active single-site solid catalysts. While BPV-MOF was constructed from only bipyridyl-functionalized dicarboxylate linker, both mBPV- and mPT-MOF were built with a mixture of bipyridyl- or phenanthryl-functionalized and unfunctionalized dicarboxylate linkers. The postsynthetic metalation of these MOFs with [Ir(COD)(OMe)]2 provided Ir-functionalized MOFs (BPV-MOF-Ir, mBPV-MOF-Ir, and mPT-MOF-Ir), which are highly active catalysts for tandem hydrosilylation of aryl ketones and aldehydes followed by dehydrogenative ortho-silylation of benzylicsilyl ethers as well as C–H borylation of arenes using B₂pin₂. Both mBPV-MOF-Ir and mPT-MOF-Ir catalysts displayed superior activities compared to BPV-MOF-Ir due to the presence of larger open channels in the mixed-linker MOFs. Impressively, mBPV-MOF-Ir exhibited high TONs of up to 17000 for C–H borylation reactions and was recycled more than 15 times. The mPT-MOF-Ir system is also active in catalyzing tandem dehydrosilylation/dehydrogenative cyclization of N-methylbenzyl amines to azasilolanes in the absence of a hydrogen acceptor. Importantly, MOF-Ir catalysts are significantly more active (up to 95 times) and stable than their homogeneous counterparts for all three reactions, strongly supporting the beneficial effects of active site isolation within MOFs. This work illustrates the ability to increase MOF open channel sizes by using the mixed linker approach and shows the enormous potential of developing highly active and robust single-site solid catalysts based on MOFs containing nitrogen-donor ligands for important organic transformations.

  10. J.C.H. de Meijere (1866-1947, een voorzichtig geneticus en evolutiebioloog

    Directory of Open Access Journals (Sweden)

    W.J. van der Schoor

    1991-04-01

    Full Text Available

    J.C.H. de Meijere (1866-1947, a cautious geneticist and evolutionary biologist

    After the success of Hugo de Vries' 'mutationism' during the socalled 'Eclipse of Darwinism' (see Bowler, 1983, Dutch biologists in the 20's and 30's had little interest in evolutionary theory. A remarkable exception was the entomologist J.C.H. de Meijere, who thought technical zoology and (1921-1936 genetics at Amsterdam University. De Meijere's career as a systematist, morphologist and (at the same time geneticist contradicts G.E. Allen's 'revolt from morphology' hypothesis, following which a generation conflict was involved in the rise of experimental biology (see Allen, 1975. Although he had been trained in the nineteenth-century 'classical' descriptive tradition, his early articles on Mendelian genetics (1910-1915 showed distinctly 'experimental'-analytical features concerning their problem-definition. He did not carry out genetic experiments himself, due to a lack of time.

    In this paper I have analysed De Meijere's work on phylogenetic morphology, genetics and evolutionary biology. As a morphologist, De Meijere fits perfectly in the pattern of Dutch academical zoology of this period (see Theunissen and Donath, 1986. As a geneticist, he focussed on transmission genetics. He adopted Morgan's concept of gene mutation but at the same time he refused to reject neo-Lamarckian inheritance.

    His opinions on evolutionary issues were eclectic and somewhat cautious. He held a pluralistic view on the mechanisms of evolution, including Morgan mutation, 'moderate' Darwinian natural selection and neo-Lamarckian inheritance of acquired characters. Population genetics was absent in his writings.

    De Meijere's opinions on evolution united elements of descriptive and experimental traditions in biology, but this did not result in an evolutionary synthesis in a neo- Darwinian or any other sense. This stresses the importance of

  11. Catalytic methanol dissociation

    International Nuclear Information System (INIS)

    Results of the methanol dissociation study on copper/potassium catalyst with alumina support at various temperatures are presented. The following gaseous and liquid products at. The catalytic methanol dissociation is obtained: hydrogen, carbon monoxide, carbon dioxide, methane, and dimethyl ether. Formation rates of these products are discussed. Activation energies of corresponding reactions are calculated

  12. Catalytic Phosphination and Arsination

    Institute of Scientific and Technical Information of China (English)

    Kwong Fuk Yee; Chan Kin Shing

    2004-01-01

    The catalytic, user-friendly phosphination and arsination of aryl halides and triflates by triphenylphosphine and triphenylarsine using palladium catalysts have provided a facile synthesis of functionalized aryl phosphines and arsines in neutral media. Modification of the cynaoarisne yielded optically active N, As ligands which will be screened in various asymmetric catalysis.

  13. Monolithic catalytic igniters

    Science.gov (United States)

    La Ferla, R.; Tuffias, R. H.; Jang, Q.

    1993-01-01

    Catalytic igniters offer the potential for excellent reliability and simplicity for use with the diergolic bipropellant oxygen/hydrogen as well as with the monopropellant hydrazine. State-of-the-art catalyst beds - noble metal/granular pellet carriers - currently used in hydrazine engines are limited by carrier stability, which limits the hot-fire temperature, and by poor thermal response due to the large thermal mass. Moreover, questions remain with regard to longevity and reliability of these catalysts. In this work, Ultramet investigated the feasibility of fabricating monolithic catalyst beds that overcome the limitations of current catalytic igniters via a combination of chemical vapor deposition (CVD) iridium coatings and chemical vapor infiltration (CVI) refractory ceramic foams. It was found that under all flow conditions and O2:H2 mass ratios tested, a high surface area monolithic bed outperformed a Shell 405 bed. Additionally, it was found that monolithic catalytic igniters, specifically porous ceramic foams fabricated by CVD/CVI processing, can be fabricated whose catalytic performance is better than Shell 405 and with significantly lower flow restriction, from materials that can operate at 2000 C or higher.

  14. Hydrogen bonded C-H···Y (Y = O, S, Hal) molecular complexes: A natural bond orbital analysis

    Science.gov (United States)

    Isaev, A. N.

    2016-03-01

    Hydrogen bonded C-H···Y complexes formed by H2O, H2S molecules, hydrogen halides, and halogen-ions with methane, halogen substituted methane as well as with the C2H2 and NCH molecules were studied at the MP2/aug-cc-pVDZ level. The structure of NBOs corresponding to lone pair of acceptor Y, n Y, and vacant anti-σ-bond C-H of proton donor was analyzed and estimates of second order perturbation energy E(2) characterizing donor-acceptor n Y → σ C-H * charge-transfer interaction were obtained. Computational results for complexes of methane and its halogen substituted derivatives show that for each set of analogous structures, the EnY→σ*C-H (2) energy tends to grow with an increase in the s-component percentage in the lone pair NBO of acceptor Y. Calculations for different C···Y distances show that the equilibrium geometries of complexes lie in the region where the E(2) energy is highest and it changes symbatically with the length of the covalent E-H bond when the R(C···Y) distance is varied. The performed analysis allows us to divide the hydrogen bonded complexes into two groups, depending on the pattern of overlapping for NBOs of the hydrogen bridge.

  15. Carbon dioxide as a carbon source in organic transformation: carbon-carbon bond forming reactions by transition-metal catalysts.

    OpenAIRE

    Tsuji, Yasushi; Fujihara, Tetsuaki

    2012-01-01

    Recent carbon-carbon bond forming reactions of carbon dioxide with alkenes, alkynes, dienes, aryl zinc compounds, aryl boronic esters, aryl halides, and arenes having acidic C-H bonds are reviewed in which transition-metal catalysts play an important role.

  16. Studies of beauty baryon decays to D0ph- and Λc+h- final states

    Science.gov (United States)

    Aaij, R.; Adeva, B.; Adinolfi, M.; Adrover, C.; Affolder, A.; Ajaltouni, Z.; Albrecht, J.; Alessio, F.; Alexander, M.; Ali, S.; Alkhazov, G.; Alvarez Cartelle, P.; Alves, A. A.; Amato, S.; Amerio, S.; Amhis, Y.; Anderlini, L.; Anderson, J.; Andreassen, R.; Andreotti, M.; Andrews, J. E.; Appleby, R. B.; Aquines Gutierrez, O.; Archilli, F.; Artamonov, A.; Artuso, M.; Aslanides, E.; Auriemma, G.; Baalouch, M.; Bachmann, S.; Back, J. J.; Badalov, A.; Balagura, V.; Baldini, W.; Barlow, R. J.; Barschel, C.; Barsuk, S.; Barter, W.; Batozskaya, V.; Bauer, Th.; Bay, A.; Beddow, J.; Bedeschi, F.; Bediaga, I.; Belogurov, S.; Belous, K.; Belyaev, I.; Ben-Haim, E.; Bencivenni, G.; Benson, S.; Benton, J.; Berezhnoy, A.; Bernet, R.; Bettler, M.-O.; van Beuzekom, M.; Bien, A.; Bifani, S.; Bird, T.; Bizzeti, A.; Bjørnstad, P. M.; Blake, T.; Blanc, F.; Blouw, J.; Blusk, S.; Bocci, V.; Bondar, A.; Bondar, N.; Bonivento, W.; Borghi, S.; Borgia, A.; Bowcock, T. J. V.; Bowen, E.; Bozzi, C.; Brambach, T.; van den Brand, J.; Bressieux, J.; Brett, D.; Britsch, M.; Britton, T.; Brook, N. H.; Brown, H.; Bursche, A.; Busetto, G.; Buytaert, J.; Cadeddu, S.; Calabrese, R.; Callot, O.; Calvi, M.; Calvo Gomez, M.; Camboni, A.; Campana, P.; Campora Perez, D.; Carbone, A.; Carboni, G.; Cardinale, R.; Cardini, A.; Carranza-Mejia, H.; Carson, L.; Carvalho Akiba, K.; Casse, G.; Castillo Garcia, L.; Cattaneo, M.; Cauet, Ch.; Cenci, R.; Charles, M.; Charpentier, Ph.; Cheung, S.-F.; Chiapolini, N.; Chrzaszcz, M.; Ciba, K.; Cid Vidal, X.; Ciezarek, G.; Clarke, P. E. L.; Clemencic, M.; Cliff, H. V.; Closier, J.; Coca, C.; Coco, V.; Cogan, J.; Cogneras, E.; Collins, P.; Comerma-Montells, A.; Contu, A.; Cook, A.; Coombes, M.; Coquereau, S.; Corti, G.; Couturier, B.; Cowan, G. A.; Craik, D. C.; Cruz Torres, M.; Cunliffe, S.; Currie, R.; D'Ambrosio, C.; Dalseno, J.; David, P.; David, P. N. Y.; Davis, A.; De Bonis, I.; De Bruyn, K.; De Capua, S.; De Cian, M.; De Miranda, J. M.; De Paula, L.; De Silva, W.; De Simone, P.; Decamp, D.; Deckenhoff, M.; Del Buono, L.; Déléage, N.; Derkach, D.; Deschamps, O.; Dettori, F.; Di Canto, A.; Dijkstra, H.; Dogaru, M.; Donleavy, S.; Dordei, F.; Dorosz, P.; Dosil Suárez, A.; Dossett, D.; Dovbnya, A.; Dupertuis, F.; Durante, P.; Dzhelyadin, R.; Dziurda, A.; Dzyuba, A.; Easo, S.; Egede, U.; Egorychev, V.; Eidelman, S.; van Eijk, D.; Eisenhardt, S.; Eitschberger, U.; Ekelhof, R.; Eklund, L.; El Rifai, I.; Elsasser, Ch.; Falabella, A.; Färber, C.; Farinelli, C.; Farry, S.; Ferguson, D.; Fernandez Albor, V.; Ferreira Rodrigues, F.; Ferro-Luzzi, M.; Filippov, S.; Fiore, M.; Fiorini, M.; Fitzpatrick, C.; Fontana, M.; Fontanelli, F.; Forty, R.; Francisco, O.; Frank, M.; Frei, C.; Frosini, M.; Furfaro, E.; Gallas Torreira, A.; Galli, D.; Gandelman, M.; Gandini, P.; Gao, Y.; Garofoli, J.; Garosi, P.; Garra Tico, J.; Garrido, L.; Gaspar, C.; Gauld, R.; Gersabeck, E.; Gersabeck, M.; Gershon, T.; Ghez, Ph.; Gibson, V.; Giubega, L.; Gligorov, V. V.; Göbel, C.; Golubkov, D.; Golutvin, A.; Gomes, A.; Gordon, H.; Grabalosa Gándara, M.; Graciani Diaz, R.; Granado Cardoso, L. A.; Graugés, E.; Graziani, G.; Grecu, A.; Greening, E.; Gregson, S.; Griffith, P.; Grillo, L.; Grünberg, O.; Gui, B.; Gushchin, E.; Guz, Yu.; Gys, T.; Hadjivasiliou, C.; Haefeli, G.; Haen, C.; Hafkenscheid, T. W.; Haines, S. C.; Hall, S.; Hamilton, B.; Hampson, T.; Hansmann-Menzemer, S.; Harnew, N.; Harnew, S. T.; Harrison, J.; Hartmann, T.; He, J.; Head, T.; Heijne, V.; Hennessy, K.; Henrard, P.; Hernando Morata, J. A.; van Herwijnen, E.; Heß, M.; Hicheur, A.; Hicks, E.; Hill, D.; Hoballah, M.; Hombach, C.; Hulsbergen, W.; Hunt, P.; Huse, T.; Hussain, N.; Hutchcroft, D.; Hynds, D.; Iakovenko, V.; Idzik, M.; Ilten, P.; Jacobsson, R.; Jaeger, A.; Jans, E.; Jaton, P.; Jawahery, A.; Jing, F.; John, M.; Johnson, D.; Jones, C. R.; Joram, C.; Jost, B.; Jurik, N.; Kaballo, M.; Kandybei, S.; Kanso, W.; Karacson, M.; Karbach, T. M.; Kenyon, I. R.; Ketel, T.; Khanji, B.; Klaver, S.; Kochebina, O.; Komarov, I.; Koopman, R. F.; Koppenburg, P.; Korolev, M.; Kozlinskiy, A.; Kravchuk, L.; Kreplin, K.; Kreps, M.; Krocker, G.; Krokovny, P.; Kruse, F.; Kucharczyk, M.; Kudryavtsev, V.; Kurek, K.; Kvaratskheliya, T.; La Thi, V. N.; Lacarrere, D.; Lafferty, G.; Lai, A.; Lambert, D.; Lambert, R. W.; Lanciotti, E.; Lanfranchi, G.; Langenbruch, C.; Latham, T.; Lazzeroni, C.; Le Gac, R.; van Leerdam, J.; Lees, J.-P.; Lefèvre, R.; Leflat, A.; Lefrançois, J.; Leo, S.; Leroy, O.; Lesiak, T.; Leverington, B.; Li, Y.; Li Gioi, L.; Liles, M.; Lindner, R.; Linn, C.; Lionetto, F.; Liu, B.; Liu, G.; Lohn, S.; Longstaff, I.; Lopes, J. H.; Lopez-March, N.; Lu, H.; Lucchesi, D.; Luisier, J.; Luo, H.; Luppi, E.; Lupton, O.; Machefert, F.; Machikhiliyan, I. V.; Maciuc, F.; Maev, O.; Malde, S.; Manca, G.; Mancinelli, G.; Maratas, J.; Marconi, U.; Marino, P.; Märki, R.; Marks, J.; Martellotti, G.; Martens, A.; Martín Sánchez, A.; Martinelli, M.; Martinez Santos, D.; Martins Tostes, D.; Martynov, A.; Massafferri, A.; Matev, R.; Mathe, Z.; Matteuzzi, C.; Maurice, E.; Mazurov, A.; McCann, M.; McCarthy, J.; McNab, A.; McNulty, R.; McSkelly, B.; Meadows, B.; Meier, F.; Meissner, M.; Merk, M.; Milanes, D. A.; Minard, M.-N.; Molina Rodriguez, J.; Monteil, S.; Moran, D.; Morawski, P.; Mordà, A.; Morello, M. J.; Mountain, R.; Mous, I.; Muheim, F.; Müller, K.; Muresan, R.; Muryn, B.; Muster, B.; Naik, P.; Nakada, T.; Nandakumar, R.; Nasteva, I.; Needham, M.; Neubert, S.; Neufeld, N.; Nguyen, A. D.; Nguyen, T. D.; Nguyen-Mau, C.; Nicol, M.; Niess, V.; Niet, R.; Nikitin, N.; Nikodem, T.; Nomerotski, A.; Novoselov, A.; Oblakowska-Mucha, A.; Obraztsov, V.; Oggero, S.; Ogilvy, S.; Okhrimenko, O.; Oldeman, R.; Onderwater, G.; Orlandea, M.; Otalora Goicochea, J. M.; Owen, P.; Oyanguren, A.; Pal, B. K.; Palano, A.; Palutan, M.; Panman, J.; Papanestis, A.; Pappagallo, M.; Pappalardo, L.; Parkes, C.; Parkinson, C. J.; Passaleva, G.; Patel, G. D.; Patel, M.; Patrignani, C.; Pavel-Nicorescu, C.; Pazos Alvarez, A.; Pearce, A.; Pellegrino, A.; Penso, G.; Pepe Altarelli, M.; Perazzini, S.; Perez Trigo, E.; Pérez-Calero Yzquierdo, A.; Perret, P.; Perrin-Terrin, M.; Pescatore, L.; Pesen, E.; Pessina, G.; Petridis, K.; Petrolini, A.; Picatoste Olloqui, E.; Pietrzyk, B.; Pilař, T.; Pinci, D.; Playfer, S.; Plo Casasus, M.; Polci, F.; Polok, G.; Poluektov, A.; Polycarpo, E.; Popov, A.; Popov, D.; Popovici, B.; Potterat, C.; Powell, A.; Prisciandaro, J.; Pritchard, A.; Prouve, C.; Pugatch, V.; Puig Navarro, A.; Punzi, G.; Qian, W.; Rachwal, B.; Rademacker, J. H.; Rakotomiaramanana, B.; Rangel, M. S.; Raniuk, I.; Rauschmayr, N.; Raven, G.; Redford, S.; Reichert, S.; Reid, M. M.; dos Reis, A. C.; Ricciardi, S.; Richards, A.; Rinnert, K.; Rives Molina, V.; Roa Romero, D. A.; Robbe, P.; Roberts, D. A.; Rodrigues, A. B.; Rodrigues, E.; Rodriguez Perez, P.; Roiser, S.; Romanovsky, V.; Romero Vidal, A.; Rotondo, M.; Rouvinet, J.; Ruf, T.; Ruffini, F.; Ruiz, H.; Ruiz Valls, P.; Sabatino, G.; Saborido Silva, J. J.; Sagidova, N.; Sail, P.; Saitta, B.; Salustino Guimaraes, V.; Sanmartin Sedes, B.; Santacesaria, R.; Santamarina Rios, C.; Santovetti, E.; Sapunov, M.; Sarti, A.; Satriano, C.; Satta, A.; Savrie, M.; Savrina, D.; Schiller, M.; Schindler, H.; Schlupp, M.; Schmelling, M.; Schmidt, B.; Schneider, O.; Schopper, A.; Schune, M.-H.; Schwemmer, R.; Sciascia, B.; Sciubba, A.; Seco, M.; Semennikov, A.; Senderowska, K.; Sepp, I.; Serra, N.; Serrano, J.; Seyfert, P.; Shapkin, M.; Shapoval, I.; Shcheglov, Y.; Shears, T.; Shekhtman, L.; Shevchenko, O.; Shevchenko, V.; Shires, A.; Silva Coutinho, R.; Sirendi, M.; Skidmore, N.; Skwarnicki, T.; Smith, N. A.; Smith, E.; Smith, E.; Smith, J.; Smith, M.; Sokoloff, M. D.; Soler, F. J. P.; Soomro, F.; Souza, D.; Souza De Paula, B.; Spaan, B.; Sparkes, A.; Spradlin, P.; Stagni, F.; Stahl, S.; Steinkamp, O.; Stevenson, S.; Stoica, S.; Stone, S.; Storaci, B.; Stracka, S.; Straticiuc, M.; Straumann, U.; Subbiah, V. K.; Sun, L.; Sutcliffe, W.; Swientek, S.; Syropoulos, V.; Szczekowski, M.; Szczypka, P.; Szilard, D.; Szumlak, T.; T'Jampens, S.; Teklishyn, M.; Tellarini, G.; Teodorescu, E.; Teubert, F.; Thomas, C.; Thomas, E.; van Tilburg, J.; Tisserand, V.; Tobin, M.; Tolk, S.; Tomassetti, L.; Tonelli, D.; Topp-Joergensen, S.; Torr, N.; Tournefier, E.; Tourneur, S.; Tran, M. T.; Tresch, M.; Tsaregorodtsev, A.; Tsopelas, P.; Tuning, N.; Ubeda Garcia, M.; Ukleja, A.; Ustyuzhanin, A.; Uwer, U.; Vagnoni, V.; Valenti, G.; Vallier, A.; Vazquez Gomez, R.; Vazquez Regueiro, P.; Vázquez Sierra, C.; Vecchi, S.; Velthuis, J. J.; Veltri, M.; Veneziano, G.; Vesterinen, M.; Viaud, B.; Vieira, D.; Vilasis-Cardona, X.; Vollhardt, A.; Volyanskyy, D.; Voong, D.; Vorobyev, A.; Vorobyev, V.; Voß, C.; Voss, H.; de Vries, J. A.; Waldi, R.; Wallace, C.; Wallace, R.; Wandernoth, S.; Wang, J.; Ward, D. R.; Watson, N. K.; Webber, A. D.; Websdale, D.; Whitehead, M.; Wicht, J.; Wiechczynski, J.; Wiedner, D.; Wiggers, L.; Wilkinson, G.; Williams, M. P.; Williams, M.; Wilson, F. F.; Wimberley, J.; Wishahi, J.; Wislicki, W.; Witek, M.; Wormser, G.; Wotton, S. A.; Wright, S.; Wu, S.; Wyllie, K.; Xie, Y.; Xing, Z.; Yang, Z.; Yuan, X.; Yushchenko, O.; Zangoli, M.; Zavertyaev, M.; Zhang, F.; Zhang, L.; Zhang, W. C.; Zhang, Y.; Zhelezov, A.; Zhokhov, A.; Zhong, L.; Zvyagin, A.; LHCb Collaboration

    2014-02-01

    Decays of beauty baryons to the D0ph- and Λc+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 Λb0→D0pK- and Λb0→Λc+K- are observed, and their branching fractions are measured with respect to the decays Λb0→D0pπ- and Λb0→Λc+π-. In addition, the first observation is reported of the decay of the neutral beauty-strange baryon Ξb0 to the D0pK- final state, and a measurement of the Ξb0 mass is performed. Evidence of the Ξb0→Λc+K- decay is also reported.

  17. Transport Coefficients of Ar/C/H/O/N Systems Thermal Plasma at Atmospheric Pressure

    International Nuclear Information System (INIS)

    The transport coefficients of thermal plasma composed of Ar/C/H/O/N elements are presented in the temperature range from 1000 to 15000 K. Several chemical composition calculations with different proportions of the elements lead us to retain 35 major species. We have characterized 595 interactions the between these species and derived the collision integrals necessary for the calculation of transport coefficients by Chapman-Enskog method. The following approximation orders have been used: 3rd for electrical conductivity and electrons translation thermal conductivity, 2nd for heavy particles translation thermal conductivity and 1st for viscosity, reaction and internal thermal conductivity. The development of thermal plasma processes lead to the use of plasma gases or gases mixtures more and more complexes. If data concerning the transport coefficients of simple gases like argon, hydrogen, oxygen or nitrogen or some binary mixtures like argon-hydrogen, argon-oxygen or oxygen-nitrogen can be early found in literature, those concerning ternary mixtures or more are not available. Ar/H/O and N brought together and C is added permitting to take into account hydrocarbons. First ours results for simple gases or gases mixtures are compared with recently published data of the literature and finally we present the transport coefficients of oxygen-nitrogen-methane, and argon-steam mixtures.

  18. Thermal effects on the Ga+ ion beam induced structural modification of a-SiC:H

    International Nuclear Information System (INIS)

    The effects of implantation temperature and post-implantation thermal annealing on the Ga+ ion beam induced optical contrast formation in hydrogenated silicon-carbon alloy (a-SiC:H) films and underlying structural modifications have been studied. The optical contrast formed (between implanted and unimplanted regions of the film material) has been made use of in the form of optical pattern formation by computer-operated Ga+-focused ion beam. Possible applications of this effect in the area of submicron lithography and high-density optical data storage have been suggested with regard to the most widely spread focused micro-beam systems based on Ga+ liquid metal ion sources. The implanted samples were structurally analysed using vibrational spectroscopies, like Raman and infra-red (IR) spectroscopy, to define optimum implantation conditions. The precise role of implantation temperature effects, i.e. the target temperature during Ga+ ion irradiation, on the structural modification obtainable has been therefore a key part of this study. Appropriate post-implantation annealing treatments were also studied, since these are expected to offer further benefits in reducing the required ion dose and enhancing the optical contrast, thus increasing the cost-effectiveness of the method.

  19. Modeling the Complete Catalytic Cycle of Aspartoacylase.

    Science.gov (United States)

    Kots, Ekaterina D; Khrenova, Maria G; Lushchekina, Sofya V; Varfolomeev, Sergei D; Grigorenko, Bella L; Nemukhin, Alexander V

    2016-05-12

    The complete catalytic cycle of aspartoacylase (ASPA), a zinc-dependent enzyme responsible for cleavage of N-acetyl-l-aspartate, is characterized by the methods of molecular modeling. The reaction energy profile connecting the enzyme-substrate (ES) and the enzyme-product (EP) complexes is constructed by the quantum mechanics/molecular mechanics (QM/MM) method assisted by the molecular dynamics (MD) simulations with the QM/MM potentials. Starting from the crystal structure of ASPA complexed with the intermediate analogue, the minimum-energy geometry configurations and the corresponding transition states are located. The stages of substrate binding to the enzyme active site and release of the products are modeled by MD calculations with the replica-exchange umbrella sampling technique. It is shown that the first reaction steps, nucleophilic attack of a zinc-bound nucleophilic water molecule at the carbonyl carbon and the amide bond cleavage, are consistent with the glutamate-assisted mechanism hypothesized for the zinc-dependent hydrolases. The stages of formation of the products, acetate and l-aspartate, and regeneration of the enzyme are characterized for the first time. The constructed free energy diagram from the reactants to the products suggests that the enzyme regeneration, but not the nucleophilic attack of the catalytic water molecule, corresponds to the rate-determining stage of the full catalytic cycle of ASPA. PMID:27089954

  20. Cross Shear Roll Bonding

    DEFF Research Database (Denmark)

    Bay, Niels; Bjerregaard, Henrik; Petersen, Søren. B;

    1994-01-01

    The present paper describes an investigation of roll bonding an AlZn alloy to mild steel. Application of cross shear roll bonding, where the two equal sized rolls run with different peripheral speed, is shown to give better bond strength than conventional roll bonding. Improvements of up to 20......-23% in bond strength are found and full bond strength is obtained at a reduction of 50% whereas 65% is required in case of conventional roll bonding. Pseudo cross shear roll bonding, where the cross shear effect is obtained by running two equal sized rolls with different speed, gives the same results....

  1. Catalytic reduction of NO by methane using a Pt/C/polybenzimidazole/Pt/C fuel cell

    DEFF Research Database (Denmark)

    Petrushina, Irina; Cleemann, Lars Nilausen; Refshauge, Rasmus;

    2007-01-01

    The catalytic NO reduction by methane was studied using a (NO,CH4,Ar),Pt|polybenzimidazole(PBI)–H3PO4|Pt,(H2,Ar) fuel cell at 135 and 165°C. It has been found that, without any reducing agent (like CH4), NO can be electrochemically reduced in the (NO, Ar), Pt/C|PBI–H3PO4|Pt/C, (H2,Ar) fuel cell...

  2. Ruthenium-Catalyzed Direct and Selective C-H Cyanation of N-(Hetero)aryl-7-azaindoles.

    Science.gov (United States)

    Mishra, Aniket; Vats, Tripta Kumari; Deb, Indubhusan

    2016-08-01

    An efficient, highly regioselective, and scalable ruthenium-catalyzed o-aryl C-H mono-cyanation of N-aryl-7-azaindoles to form N-(2-cyanoaryl)-7-azaindoles has been developed through N-directed ortho C-H activation using N-cyano-N-phenyl-p-toluenesulfonamide as cyanating reagent in the presence of AgOTf and NaOAc in DCE. A range of substrates has furnished cyanated azaindoles in good to excellent yields under the simple reaction conditions. Involvement of C-H metalation has been supported by a kinetic study. This methodology provides easy access to a class of pharmaceutically significant molecules and their precursors. PMID:27408980

  3. Structural and mechanical properties of nc-TiC/a-C:H nanocomposite film prepared by dual plasma technique

    International Nuclear Information System (INIS)

    Nanocomposite nc-TiC/a-C:H film, with an unusual combination of superhardness, high elastic modulus and high elastic recovery, are prepared by using the dual plasma technique. The effects of the filter coil current on the compositional, structural and mechanical properties of the nc-TiC/a-C:H films have been investigated. X-ray photoelectron spectroscopy (XPS) and Raman analyses show that deposition rate, composition and nanostructure of the nc-TiC/a-C:H films could be changed by varying the filter coil current. Fortunately, by selecting the proper value for the filter coil current, 2.5 A, one could remarkably enhance mechanical properties of films such as the superhardness (66.4 GPa), the high elastic modulus (510 GPa) and the high elastic recovery (83.3%)

  4. Wire bonding in microelectronics

    CERN Document Server

    Harman, George G

    2010-01-01

    Wire Bonding in Microelectronics, Third Edition, has been thoroughly revised to help you meet the challenges of today's small-scale and fine-pitch microelectronics. This authoritative guide covers every aspect of designing, manufacturing, and evaluating wire bonds engineered with cutting-edge techniques. In addition to gaining a full grasp of bonding technology, you'll learn how to create reliable bonds at exceedingly high yields, test wire bonds, solve common bonding problems, implement molecular cleaning methods, and much more. Coverage includes: Ultrasonic bonding systems and technologies, including high-frequency systems Bonding wire metallurgy and characteristics, including copper wire Wire bond testing Gold-aluminum intermetallic compounds and other interface reactions Gold and nickel-based bond pad plating materials and problems Cleaning to improve bondability and reliability Mechanical problems in wire bonding High-yield, fine-pitch, specialized-looping, soft-substrate, and extreme-temperature wire bo...

  5. Paramagnetic states in {mu}c-SiC:H thin films prepared by Hot-Wire CVD at low temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Xiao, Lihong; Astakhov, Oleksandr; Carius, Reinhard; Finger, Friedhelm [IEF-5 Photovoltaik, Forschungszentrum Juelich (Germany); Chen, Tao [IEF-5 Photovoltaik, Forschungszentrum Juelich (Germany); State Key Lab of Silicon Materials, Zhejiang University, Hangzhou, Zhejiang (China); Wang, Haiyan [IEF-5 Photovoltaik, Forschungszentrum Juelich (Germany); School of Physical Engineering, Zhengzhou University, Henan (China); Stutzmann, Martin [Walter Schottky Institut, Technische Universitaet Muenchen, Garching (Germany)

    2010-04-15

    The relationship between the structure, electrical conductivity and paramagnetic states in microcrystalline hydrogenated silicon carbide ({mu}c-SiC:H) prepared by HWCVD is investigated. The study includes undoped and Al-doped (p -type) {mu}c-SiC:H of different crystalline volume fraction (I{sub C}{sup IR}). High densities of paramagnetic states are observed in undoped material over a wide range of crystallinity whereas the conductivity increases by 10 orders of magnitude up to 10{sup -2} S/cm as the material becomes more crystalline. This dramatic increase of the conductivity attributed to unintentional n -type doping has a clear effect on the ESR spectrum which changes from a broad featureless resonance in the low crystallinity material to a sharp line with a pair of distinct satellites in highly crystalline n -type {mu}c-SiC:H. Al-doping results in compensation and then effective p -type doping in {mu}c-SiC:H at higher doping concentration. Al-doping seems to hinder the crystalline growth in p -type {mu}c-SiC:H. For I{sub C}{sup IR} {<=} 20% the spin resonance signature is a broad (peak-to-peak linewidth {delta}H{sub pp}{approx}30 G) featureless slightly asymmetric line at g {approx} 2.01. The nature and behavior of the ESR spectra in different types of {mu}c-SiC:H are investigated with respect to the Fermi level position and crystalline volume fraction (copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  6. Study on the HPHT synthetic diamond crystal from Fe-C(H)system and its significance

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Investigations of crystal habit,micro-topographic imaging,micro-composition and micro-structural analysis of HPHT synthetic diamonds from the Fe-C(H)system indicate that most of them have an octahedral habit.The crystals grow mainly layer-to-layer from center to periphery.HPHT synthetic diamond is smaller in size than naturel diamond because it only goes through nucleation and growth in the early stage.In the middle and late stages,due to the coalescence of diamond grains related to differences of surface energy,the growth of HPHT synthetic diamond iS limited.The active energy (E) of transforming single nitrogen into a nitrogen-pair is lowered and the time of transforming single nitrogen into a nitrogen-pair is shortened because of the existence of hydrogen.Therefore,aggregate nitrogen(A-centers)may exist in synthetic diamond from HPHT and explosive detonation processes.It needs further discussion on a worldwide view that the time of natural diamond formation extrectad from nitrogen aggregation is some hundred million years.Consideration of the way in which Surface energy influences the growth of diamond can help to understand some of the remaining issues(e.g.growth mechanism,etc.)in the HPHT synthetic process and effectively explain the formation of naturel diamond in terms of HPHT thermodynamic theory.Especially,it is important to pay more attention to the influence of hydrogen on surface energy in that hydrogen may be a"bridge"for explaining the formation of HPHT synthetic and natural diamond.

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

    OpenAIRE

    Strondl, C.; Carvalho, NM; de Hosson, JTM; Krug, TG

    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 W-C:H coatings, the deposition energy has been varied by changing the ion current density and the bias voltage on the substrate. The aim of the investigation has been to study the changes in the mic...

  8. Gold-catalysed facile access to indene scaffolds via sequential C-H functionalization and 5-endo-dig carbocyclization.

    Science.gov (United States)

    Ma, Ben; Wu, Ziang; Huang, Ben; Liu, Lu; Zhang, Junliang

    2016-08-01

    A concise synthesis of functionalized indene derivatives via the gold(i)-catalysed cascade C-H functionalization/conia-ene type reaction of electron-rich aromatics with o-alkynylaryl α-diazoesters has been developed. In this transformation, the gold catalyst not only catalysed the formation of the zwitterionic intermediate via intermolecular C-H functionalization but promoted the subsequent intramolecular 5-endo-dig cyclization via activation of alkynes. The reaction is characterized by high chemo- and site-selectivity, readily available starting materials, nice functional-group tolerance and mild reaction conditions. PMID:27373228

  9. Catalytic thermal barrier coatings

    Science.gov (United States)

    Kulkarni, Anand A.; Campbell, Christian X.; Subramanian, Ramesh

    2009-06-02

    A catalyst element (30) for high temperature applications such as a gas turbine engine. The catalyst element includes a metal substrate such as a tube (32) having a layer of ceramic thermal barrier coating material (34) disposed on the substrate for thermally insulating the metal substrate from a high temperature fuel/air mixture. The ceramic thermal barrier coating material is formed of a crystal structure populated with base elements but with selected sites of the crystal structure being populated by substitute ions selected to allow the ceramic thermal barrier coating material to catalytically react the fuel-air mixture at a higher rate than would the base compound without the ionic substitutions. Precious metal crystallites may be disposed within the crystal structure to allow the ceramic thermal barrier coating material to catalytically react the fuel-air mixture at a lower light-off temperature than would the ceramic thermal barrier coating material without the precious metal crystallites.

  10. On Bond Portfolio Management

    OpenAIRE

    Vladislav Kargin

    2002-01-01

    This paper describes a new method of bond portfolio optimization based on stochastic string models of correlation structure in bond returns. The paper shows how to approximate correlation function of bond returns, compute the optimal portfolio allocation using Wiener-Hopf factorization, and check whether a collection of bonds presents arbitrage opportunities.

  11. Multicenter bonds, bond valence and bond charge apportion

    International Nuclear Information System (INIS)

    In the same way that the valence of an atom issues from the definition of bond index, we shoe here that the three-center bond index lends itself to the definition of a bond valence. Within the charge of a bond, we show that its self-charge (i.e., the amount of electron kept by the atoms involved in the bond) is parted in a such a way that the more electronegative atom tends to allot more electronic charge than the other atom. We give examples of these quantities and discuss the results for different kinds of chemical systems. We also show some results for four-center indices and report six-center indices for hexagonal rings. (author). 54 refs., 4 figs., 8 tabs

  12. NUV/VIS sensitive multicolor thin film detector based on a-SiC:H/a-Si:H/μc-SiGeC:H alloys with an in-situ structured transparent conductive oxide front contact without etching

    International Nuclear Information System (INIS)

    An innovative family of hydrogenated amorphous silicon (a-Si:H) multicolor p–i–n photo sensors, sensitive in the VIS and the near UV spectrum, is presented. Typical values of the quantum efficiency at 350 nm and 580 nm are 5.4% and 54.7%, respectively, with − 0.4 V and − 12 V bias. Electro-optical studies were performed to explore the effect of combining linearly graded a-SiGe:H/μc-SiGeC:H layers with linearly graded a‐SiC:H-layers. The devices presented additionally contain a buried a-Si:H region. Low-reflective aluminum doped zinc oxide (ZnO:Al) back contacts improve the spectral color separation. μτ-products and absorption coefficients of graded absorbers were determined. Discrete absorbers were substituted by a linear graded a-SiC:H absorption zone in the top structure, an interior a-Si:H region and a graded a-SiGe:H/a-SiC:H alloy combination. In this paper we demonstrate a reduction of interference fringes and operation at low bias voltages, combined with a highly precise adjustment of the spectral sensitivity, even in the near UV-spectrum. The device dynamic range exceeds 50 dB at 1000 lx white-light illumination. As the deposited upper layers adopt the roughness of μc-SiGeC:H clusters in the rear absorber, we present an in-situ structured front contact without etching ZnO:Al. - Highlights: ► Structuring zinc oxide anode without etching ► UV/VIS amorphous silicon sensor ► Microcrystalline narrow gap absorber ► Significant color separation improvement

  13. NUV/VIS sensitive multicolor thin film detector based on a-SiC:H/a-Si:H/{mu}c-SiGeC:H alloys with an in-situ structured transparent conductive oxide front contact without etching

    Energy Technology Data Exchange (ETDEWEB)

    Bablich, A., E-mail: andreas.bablich@uni-siegen.de; Boehm, M., E-mail: m.boehm@t-online.de

    2012-10-01

    An innovative family of hydrogenated amorphous silicon (a-Si:H) multicolor p-i-n photo sensors, sensitive in the VIS and the near UV spectrum, is presented. Typical values of the quantum efficiency at 350 nm and 580 nm are 5.4% and 54.7%, respectively, with - 0.4 V and - 12 V bias. Electro-optical studies were performed to explore the effect of combining linearly graded a-SiGe:H/{mu}c-SiGeC:H layers with linearly graded a-SiC:H-layers. The devices presented additionally contain a buried a-Si:H region. Low-reflective aluminum doped zinc oxide (ZnO:Al) back contacts improve the spectral color separation. {mu}{tau}-products and absorption coefficients of graded absorbers were determined. Discrete absorbers were substituted by a linear graded a-SiC:H absorption zone in the top structure, an interior a-Si:H region and a graded a-SiGe:H/a-SiC:H alloy combination. In this paper we demonstrate a reduction of interference fringes and operation at low bias voltages, combined with a highly precise adjustment of the spectral sensitivity, even in the near UV-spectrum. The device dynamic range exceeds 50 dB at 1000 lx white-light illumination. As the deposited upper layers adopt the roughness of {mu}c-SiGeC:H clusters in the rear absorber, we present an in-situ structured front contact without etching ZnO:Al. - Highlights: Black-Right-Pointing-Pointer Structuring zinc oxide anode without etching Black-Right-Pointing-Pointer UV/VIS amorphous silicon sensor Black-Right-Pointing-Pointer Microcrystalline narrow gap absorber Black-Right-Pointing-Pointer Significant color separation improvement.

  14. Ultraviolet laser deposition of graphene thin films without catalytic layers

    KAUST Repository

    Sarath Kumar, S. R.

    2013-01-09

    In this letter, the formation of nanostructured graphene by ultraviolet laser ablation of a highly ordered pyrolytic graphite target under optimized conditions is demonstrated, without a catalytic layer, and a model for the growth process is proposed. Previously, graphene film deposition by low-energy laser (2.3 eV) was explained by photo-thermal models, which implied that graphene films cannot be deposited by laser energies higher than the C-C bond energy in highly ordered pyrolytic graphite (3.7 eV). Here, we show that nanostructured graphene films can in fact be deposited using ultraviolet laser (5 eV) directly over different substrates, without a catalytic layer. The formation of graphene is explained by bond-breaking assisted by photoelectronic excitation leading to formation of carbon clusters at the target and annealing out of defects at the substrate.

  15. A HYDROGEN BONDING ASSISTED CATALYST SCREENED OUT VIA COMBINATORIAL CHEMISTRY STRATEGY

    Institute of Scientific and Technical Information of China (English)

    XUMancai; OUZhize; 等

    2000-01-01

    Possibilities for enhancement of catalytic reaction rate by combining phase transfer catalysis and hydrogen bonding of the catalyst with the substrate and reagent were studied.A phase transfer catalyst library with sixty polystyrene-supported quaternary ammonium salt catalysts was synthesized.The reduction of acetophenone by NaBH4 was used as the probing reaction to select out the ost active catalyst in the library by using iterative method.which was the gel-type triethanolamine aminsating strongly asic anion exchange resin with the crosslinking degeree of 2% A hydrogen bonding assisted catalytic mechanism was proposed to explain the high catalytic activity of the catalyst.

  16. 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.

  17. Spin-forbidden and spin-allowed cyclopropenone (c-H2C3O) formation in interstellar medium

    International Nuclear Information System (INIS)

    Three proposed mechanisms of cyclopropenone (c-H2C3O) formation from neutral species are studied using high-level electronic structure methods in combination with nonadiabatic transition state and collision theories to deduce the likelihood of each reaction mechanism under interstellar conditions. The spin-forbidden reaction involving the singlet electronic state of cyclopenylidene (c-C3H2) and the triplet state of atomic oxygen is studied using nonadiabatic transition state theory to predict the rate constant for c-H2C3O formation. The spin-allowed reactions of c-C3H2 with molecular oxygen and acetylene with carbon monoxide were also investigated. The reaction involving the ground electronic states of acetylene and carbon monoxide has a very large reaction barrier and is unlikely to contribute to c-H2C3O formation in interstellar medium. The spin-forbidden reaction of c-C3H2 with atomic oxygen, despite the high probability of nonadiabatic transition between the triplet and singlet states, was found to have a very small rate constant due to the presence of a small (3.8 kcal mol–1) reaction barrier. In contrast, the spin-allowed reaction between c-C3H2 and molecular oxygen is found to be barrierless, and therefore can be an important path to the formation of c-H2C3O molecule in interstellar environment.

  18. Rh(iii)-catalyzed C-H activation/cyclization of oximes with alkenes for regioselective synthesis of isoquinolines.

    Science.gov (United States)

    Chen, Renjie; Qi, Jifeng; Mao, Zhenjun; Cui, Sunliang

    2016-07-14

    A Rh(iii)-catalyzed C-H activation/cyclization of oximes and alkenes for facile and regioselective access to isoquinolines has been developed. This protocol features mild reaction conditions and easily accessible starting materials, and has been applied to the concise synthesis of moxaverine. A kinetic isotope effect study was conducted and a plausible mechanism was proposed. PMID:27273816

  19. An overview on the applications of `Doyle catalysts’ in asymmetric cyclopropanation, cyclopropenation and C-H insertion reactions

    Indian Academy of Sciences (India)

    Thomas J Colacot

    2000-06-01

    The chiral dirhodium(II) carboxamidates are a unique class of chiral catalysts useful for asymmetric inter- and intramolecular cyclopropanation, cyclopropenation and C-H insertion reactions with excellent enantioselectivities. The broad applications of these catalysts in organic syntheses are briefly reviewed.

  20. Simulation of the Efficiency of a-SiC:H/a-Si:H Tandem Multilayer Solar Cells

    CERN Document Server

    Muminov, Khikmat Kh

    2016-01-01

    In this paper we carried out theoretical study of the general issues related to the efficiency of SiC:H/a-Si:H single- and multi-junction tandem solar cells. Implementation of numerical simulations by the use of AMPS-1D program of one-dimensional analysis of microelectronic and photonic structures for the analysis of hydrogenated silicon solar cells allowed us to formulate the optimal design of new kind of multi-junction tandem solar cells, providing its most efficient operation. The numerical analysis of SiC:H/a-Si:H single-junction solar cell whith doped i-layer used as the intermediate absorbing layer (a -Si: H) placed between layers of p-type (a-SiC: H) and n-type (a-Si: H) has been conducted. It has been established that after optimizing the solar cell parameters its highest efficiency of 19.62% is achieved at 500 nm thickness of i-layer. The optimization of the newly developed multi-junction structure of a-SiC:H/a-Si:H tandem solar cell has been conducted. It has been shown numerically that its highest ...

  1. Direct Arylation of Pyrroles via Indirect Electroreductive C-H Functionalization Using Perylene Bisimide as an Electron-Transfer Mediator.

    Science.gov (United States)

    Sun, Guoquan; Ren, Shuya; Zhu, Xinhai; Huang, Manna; Wan, Yiqian

    2016-02-01

    The indirect electroreductive coupling of aryl halides and pyrroles was successfully conducted using a catalytic amount of perylene bisimide as a mediator in 1-ethyl-3-methylimidazolium bis((trifluoromethyl)sulfonyl)imide ([EMIM]NTf2)/DMSO. PMID:26800089

  2. To rebound or dissociate? This is the mechanistic question in C-H hydroxylation by heme and nonheme metal-oxo complexes.

    Science.gov (United States)

    Cho, Kyung-Bin; Hirao, Hajime; Shaik, Sason; Nam, Wonwoo

    2016-03-01

    Enzymatic reactions that involve C-H bond activation of alkanes by high-valent iron-oxo species can be explained by the rebound mechanism (RM). Hydroxylation reactions of alkane substrates effected by the reactive compound I (Cpd I) species of cytochrome P450 enzymes are good examples. There was initially little doubt that the rebound paradigm could be carried over in the same form to the arena of synthetic nonheme high-valent iron-oxo or other metal-oxo complexes. However, the active reaction centres of these synthetic systems are not well-caged, in contrast to the active sites of enzymes; therefore, the relative importance of the radical dissociation pathway can become prominent. Indeed, accumulating experimental and theoretical evidence shows that introduction of the non-rebound mechanism (non-RM) is necessary to rationalise the different reactivity patterns observed for synthetic nonheme complexes. In this tutorial review, we discuss several specific examples involving the non-RM while making frequent comparisons to the RM, mainly from the perspective of computational chemistry. We also provide a technical guide to DFT calculations of RM and non-RM and to the interpretations of computational outcomes. PMID:26690848

  3. Density functional theory study of O-H and C-H bond scission of methanol catalyzed by a chemisorbed oxygen layer on Cu(111)

    Science.gov (United States)

    Li, Jonathan; Zhou, Guangwen

    2016-04-01

    Using the density-functional theory within the generalized gradient approximation, we have studied the partial oxidation of methanol on a Cu(111) surface covered with a chemisorbed oxygen layer that resembles a Cu2O layer. Adsorption energies and geometries were computed for methanol, methoxy, hydroxymethyl and formaldehyde on both clean Cu(111) and Cu2O/Cu(111) and electronic structures were computed for the reaction intermediates on Cu2O/Cu(111). We also calculated the energy barrier for partial oxidation of methanol to formaldehyde on Cu2O/Cu(111). These results show that the Cu2O monolayer slightly lowers the stability of each of the surface adsorbates and the oxygen strongly promotes hydrogen dissociation by lowering the energy barrier of methanol decomposition and causing the spontaneous dissociation of methanol into methoxy.

  4. C-H and H-H Bond Activation via Ligand Dearomatization/Rearomatization of a PN3P-Rhodium(I) Complex

    KAUST Repository

    Huang, Kuo-Wei

    2015-04-13

    A neutral complex PN3P-Rh(I)Cl (2) was prepared from a reaction of the PN3P pincer ligand (1) with [Rh(COD)Cl]2 (COD = 1,5-cyclooctadiene). Upon treatment with a suitable base, H–H and Csp2–H activation reactions can be achieved through the deprotonation/reprotonation of one of the N–H arms and dearomatization/rearomatization of the central pyridine ring with the oxidation state of Rh remaining I.

  5. Active groups for oxidative activation of C-H bond in C{sub 2}-C{sub 5} paraffins on V-P-O catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Zazhigalov, V.A. [AN Ukrainskoj SSR, Kiev (Ukraine). Inst. Fizicheskoj Khimii

    1998-12-31

    For the first time in scientific literature, in our joint work with Dr. G. Ladwig in 1978 it was established phase portraite of the oxide vanadium-phosphorus system within wide range of P/V ratios from 0.5 to 3.2. Some later those data were confirmed. By investigation of the properties of individual vanadium-phosphorus phases it was also shown that the active component of such catalysts in n-butane oxidation was vanadyl pyrophosphate phase (VO){sub 2}Pr{sub 2}O{sub 7}. From then the conclusion has been evidenced by numerous publications and at present it has been out of doubt practically all over the world. It was hypothized that the unique properties of (VO){sub 2}P{sub 2}O{sub 7} in the reaction of n-butane oxidation could be explained by the presence of paired vanadyl groups and nearness of the distances between neighbouring vanadyl pairs and that between the first and fourth carbon atoms in n-butane molecule. The molecule activation occured at the latter atoms by proton abstraction. A comparison of the results on n-butane and butenes oxidation over vanadyl pyrophosphate allowed to conclude that the paraffin oxidation did not take place due to the molecule dehydrogenation process at the first stage of its conversion. Up to now, more than 100 papers related to paraffins oxidation over vanadyl pyrophosphate and the physico-chemical properties of the catalyst have been published. The process of n-butane oxidation is realized in practice. But still, the question about the nature of active sites of the catalyst and the reaction mechanism remains open and provokes further investigations. The present paper deals with our opinion about the problem and the experimental results supporting it. (orig.)

  6. Magnetism, chemical bonding and hyperfine properties in the nanoscale antiferromagnet [Fe(O Me)2(O2 C C H2 Cl)]10

    International Nuclear Information System (INIS)

    The electronic and magnetic properties of the nanometer-size antiferromagnet (the ferric wheel molecule) are investigated with the first-principles spin-polarized Discrete Variational Method, in the framework of Density Functional theory. Magnetic moments, densities of the states and charge and spin-density maps are obtained. The Moessbauer hyperfine parameters Isomer shift, Quadrupole Splitting and Hyperfine Field are obtained from the calculations and compared to reported experimental values when available. (author). 33 refs., 8 figs., 4 tabs

  7. Control of the intermolecular coupling of dibromotetracene on Cu(110) by the sequential activation of C-Br and C-H bonds.

    Science.gov (United States)

    Ferrighi, Lara; Píš, Igor; Nguyen, Thanh Hai; Cattelan, Mattia; Nappini, Silvia; Basagni, Andrea; Parravicini, Matteo; Papagni, Antonio; Sedona, Francesco; Magnano, Elena; Bondino, Federica; Di Valentin, Cristiana; Agnoli, Stefano

    2015-04-01

    Dibromotetracene molecules are deposited on the Cu(110) surface at room temperature. The complex evolution of this system has been monitored at different temperatures (i.e., 298, 523, 673, and 723 K) by means of a variety of complementary techniques that range from STM and temperature-programmed desorption (TPD) to high-resolution X-ray spectroscopy (XPS) and near-edge X-ray absorption fine structure spectroscopy (NEXAFS). State-of-the-art density-functional calculations were used to determine the chemical processes that take place on the surface. After deposition at room temperature, the organic molecules are transformed into organometallic monomers through debromination and carbon-radical binding to copper adatoms. Organometallic dimers, trimers, or small oligomers, which present copper-bridged molecules, are formed by increasing the temperature. Surprisingly, further heating to 673 K causes the formation of elongated chains along the Cu(110) close-packed rows as a consequence of radical-site migration to the thermodynamically more stable molecule heads. Finally, massive dehydrogenation occurs at the highest temperature followed by ring condensation to nanographenic patches. This study is a paradigmatic example of how intermolecular coupling can be modulated by the stepwise control of a simple parameter, such as temperature, through a sequence of domino reactions. PMID:25711882

  8. Indole cyanation via C-H bond activation under catalysis of Ru(Ⅲ)-exchanged NaY zeolite (RuY) as a recyclable catalyst

    Institute of Scientific and Technical Information of China (English)

    Alireza Khorshidi

    2012-01-01

    Selective 3-cyanation of indoles was achieved under heterogeneous catalysis of Ru(Ⅲ)-exchanged NaY zeolite (RuY) as a recyclable catalyst,in combination with K4[Fe(CN)6] as a nontoxic,slow cyanide releasing agent.Under the aforementioned conditions,good yields of the desired products were obtained.

  9. Cobalt-Catalyzed Cyclization of N-Methoxy Benzamides with Alkynes using an Internal Oxidant through C-H/N-O Bond Activation.

    Science.gov (United States)

    Sivakumar, Ganesan; Vijeta, Arjun; Jeganmohan, Masilamani

    2016-04-18

    The cyclization of substituted N-methoxy benzamides with alkynes in the presence of an easily affordable cobalt complex and NaOAc provides isoquinolone derivatives in good to excellent yields. The cyclization reaction is compatible with a range of functional group-substituted benzamides, as well as ester- and alcohol-substituted alkynes. The cobalt complex [Co(III) Cp*(OR)2 ] (R=Me or Ac) serves as an efficient catalyst for the cyclization reaction. Later, isoquinolone derivatives were converted into 1-chloro and 1-bromo substituted isoquinoline derivatives in excellent yields in the presence of POCl3 or PBr3 . PMID:26951887

  10. Glass-aluminium bonded joints ; testing, comparing and designing for the ATP

    NARCIS (Netherlands)

    Richemont, S.A.J. de; Veer, F.A.

    2007-01-01

    This article presents the research to the bonded joints of the All Transparent Pavilion (ATP), an experimental project built in November 2004 at the faculty of Architecture in Delft. The pavilion is designed to use structural glass elements, bonded with Delo Photobond GB 368, a photo-catalytic trans

  11. Catalytic reforming process

    Energy Technology Data Exchange (ETDEWEB)

    Absil, R.P.; Huss, A. Jr.; McHale, W.D.; Partridge, R.D.

    1989-06-13

    This patent describes a catalytic reforming process which comprises contacting a naphtha range feed with a low acidity extrudate comprising an intermediate and/or a large pore acidic zeolite bound with a low acidity refractory oxide under reforming conditions to provide a reaction product of increased aromatic content, the extrudate having been prepared with at least an extrusion-facilitating amount of a low acidity refractory oxide in colloidal form and containing at least one metal species selected from the platinum group metals.

  12. A bait and switch hapten strategy generates catalytic antibodies for phosphodiester hydrolysis

    OpenAIRE

    Wentworth, Paul; Liu, Yunqi; Wentworth, Anita D.; Fan, Ping; Foley, Matthew J.; Janda, Kim D.

    1998-01-01

    General base catalysis supplied by the histidine-12 (H-12) residue of ribonuclease (RNase) A has long been appreciated as a major component of the catalytic power of the enzyme. In an attempt to harness the catalytic power of a general base into antibody catalysis of phosphodiester bond hydrolysis, the quaternary ammonium phosphate 1 was used as a bait and switch hapten. Based on precedence, it was rationalized that this positively charged hapten could induce a counter-charged residue in the ...

  13. Hydrogen bonded supramolecular structures

    CERN Document Server

    Li, Zhanting

    2015-01-01

    This book covers the advances in the studies of hydrogen-bonding-driven supramolecular systems  made over the past decade. It is divided into four parts, with the first introducing the basics of hydrogen bonding and important hydrogen bonding patterns in solution as well as in the solid state. The second part covers molecular recognition and supramolecular structures driven by hydrogen bonding. The third part introduces the formation of hollow and giant macrocycles directed by hydrogen bonding, while the last part summarizes hydrogen bonded supramolecular polymers. This book is designed to b

  14. Novel Catalytic Membrane Reactors

    Energy Technology Data Exchange (ETDEWEB)

    Stuart Nemser, PhD

    2010-10-01

    There are many industrial catalytic organic reversible reactions with amines or alcohols that have water as one of the products. Many of these reactions are homogeneously catalyzed. In all cases removal of water facilitates the reaction and produces more of the desired chemical product. By shifting the reaction to right we produce more chemical product with little or no additional capital investment. Many of these reactions can also relate to bioprocesses. Given the large number of water-organic compound separations achievable and the ability of the Compact Membrane Systems, Inc. (CMS) perfluoro membranes to withstand these harsh operating conditions, this is an ideal demonstration system for the water-of-reaction removal using a membrane reactor. Enhanced reaction synthesis is consistent with the DOE objective to lower the energy intensity of U.S. industry 25% by 2017 in accord with the Energy Policy Act of 2005 and to improve the United States manufacturing competitiveness. The objective of this program is to develop the platform technology for enhancing homogeneous catalytic chemical syntheses.

  15. Microstructure of a-C:H films prepared on a microtrench and analysis of ions and radicals behavior

    International Nuclear Information System (INIS)

    Amorphous carbon films (a-C:H) were prepared on a microtrench (4-μm pitch and 4-μm depth), and the uniformity of film thickness and microstructure of the films on the top, sidewall, and bottom surfaces of the microtrench were evaluated by scanning electron microscopy and Raman spectroscopy. The a-C:H films were prepared by bipolar-type plasma based ion implantation and deposition (bipolar PBII&D), and the negative pulse voltage, which is the main parameter dominating the film structure, was changed from −1.0 to −15 kV. Moreover, the behavior of ions and radicals was analyzed simultaneously by combining the calculation methods of Particle-In-Cell/Monte Carlo Collision (PIC-MCC) and Direct Simulation Monte Carlo (DSMC) to investigate the coating mechanism for the microtrench. The results reveal that the thickness uniformity of a-C:H films improves with decreasing negative pulse voltage due to the decreasing inertia of incoming ions from the trench mouth, although the film thickness on the sidewall tends to be much smaller than that on the top and bottom surfaces of the trench. The normalized flux and the film thickness show similar behavior, i.e., the normalized flux or thickness at the bottom surface increases at low negative pulse voltages and then saturates at a certain value, whereas at the sidewall it monotonically decreases with increasing negative voltage. The microstructure of a-C:H films on the sidewall surface is very different from that on the top and bottom surfaces. The film structure at a low negative pulse voltage shifts to more of a polymer-like carbon (PLC) structure due to the lower incident energy of ions. Although the radical flux on the sidewall increases slightly, the overall film structure is not significantly changed because this film formation at a low negative voltage is originally dominated by radicals. On the other hand, the flux of radicals is dominant on the sidewall in the case of high negative pulse voltage, resulting in a

  16. Hard TiCx/SiC/a-C:H nanocomposite thin films using pulsed high energy density plasma focus device

    International Nuclear Information System (INIS)

    Highlights: •The energetic ions and electron beams are used to synthesize TiCx/SiC/a-C:H films. •As-deposited crystalline and hard nanocomposite TiCx/SiC/a-C:H films are synthesized. •Very high average deposition rates of 68 nm/shot are achieved using dense plasma focus. •The maximum hardness of 22 GPa is achieved at the surface of the film. -- Abstract: Thin films of TiCx/SiC/a-C:H were synthesized on Si substrates using a complex mix of high energy density plasmas and instability accelerated energetic ions of filling gas species, emanated from hot and dense pinched plasma column, in dense plasma focus device. The conventional hollow copper anode of Mather type plasma focus device was replaced by solid titanium anode for synthesis of TiCx/SiC/a-C:H nanocomposite thin films using CH4:Ar admixture of (1:9, 3:7 and 5:5) for fixed 20 focus shots as well as with different number of focus shots with fixed CH4:Ar admixture ratio 3:7. XRD results showed the formation of crystalline TiCx/SiC phases for thin film synthesized using different number of focus shots with CH4:Ar admixture ratio fixed at 3:7. SEM results showed that the synthesized thin films consist of nanoparticle agglomerates and the size of agglomerates depended on the CH4:Ar admixture ratio as well as on the number of focus shots. Raman analysis showed the formation of polycrystalline/amorphous Si, SiC and a-C for different CH4:Ar ratio as well as for different number of focus shots. The XPS analysis confirmed the formation of TiCx/SiC/a-C:H composite thin film. Nanoindentation results showed that the hardness and elastic modulus values of composite thin films increased with increasing number of focus shots. Maximum values of hardness and elastic modulus at the surface of the composite thin film were found to be about 22 and 305 GPa, respectively for 30 focus shots confirming the successful synthesis of hard composite TiCx/SiC/a-C:H coatings

  17. Microstructure of a-C:H films prepared on a microtrench and analysis of ions and radicals behavior

    Energy Technology Data Exchange (ETDEWEB)

    Hirata, Yuki; Choi, Junho, E-mail: choi@mech.t.u-tokyo.ac.jp [Department of Mechanical Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan)

    2015-08-28

    Amorphous carbon films (a-C:H) were prepared on a microtrench (4-μm pitch and 4-μm depth), and the uniformity of film thickness and microstructure of the films on the top, sidewall, and bottom surfaces of the microtrench were evaluated by scanning electron microscopy and Raman spectroscopy. The a-C:H films were prepared by bipolar-type plasma based ion implantation and deposition (bipolar PBII&D), and the negative pulse voltage, which is the main parameter dominating the film structure, was changed from −1.0 to −15 kV. Moreover, the behavior of ions and radicals was analyzed simultaneously by combining the calculation methods of Particle-In-Cell/Monte Carlo Collision (PIC-MCC) and Direct Simulation Monte Carlo (DSMC) to investigate the coating mechanism for the microtrench. The results reveal that the thickness uniformity of a-C:H films improves with decreasing negative pulse voltage due to the decreasing inertia of incoming ions from the trench mouth, although the film thickness on the sidewall tends to be much smaller than that on the top and bottom surfaces of the trench. The normalized flux and the film thickness show similar behavior, i.e., the normalized flux or thickness at the bottom surface increases at low negative pulse voltages and then saturates at a certain value, whereas at the sidewall it monotonically decreases with increasing negative voltage. The microstructure of a-C:H films on the sidewall surface is very different from that on the top and bottom surfaces. The film structure at a low negative pulse voltage shifts to more of a polymer-like carbon (PLC) structure due to the lower incident energy of ions. Although the radical flux on the sidewall increases slightly, the overall film structure is not significantly changed because this film formation at a low negative voltage is originally dominated by radicals. On the other hand, the flux of radicals is dominant on the sidewall in the case of high negative pulse voltage, resulting in a

  18. Electronic Structure and Bonding in Complex Biomolecule

    Science.gov (United States)

    Ouyang, Lizhi

    2005-03-01

    For over a century vitamin B12 and its enzyme cofactor derivates have persistently attracted research efforts for their vital biological role, unique Co-C bonding, rich red-ox chemistry, and recently their candidacies as drug delivery vehicles etc. However, our understanding of this complex metalorganic molecule's efficient enzyme activated catalytic power is still controversial. We have for the first time calculated the electronic structure, Mulliken effective charge and bonding of a whole Vitamin B12 molecule without any structural simplification by first- principles approaches based on density functional theory using structures determined by high resolution X-ray diffraction. A partial density of states analysis shows excellent agreement with X-ray absorption data and has been used successfully to interpret measured optical absorption spectra. Mulliken bonding analysis of B12 and its derivatives reveal noticeable correlations between the two axial ligands which could be exploited by the enzyme to control the catalytic process. Our calculated X-ray near edge structure of B12 and its derivates using Slater's transition state theory are also in good agreement with experiments. The same approach has been applied to other B12 derivatives, ferrocene peptides, and recently DNA molecules.

  19. 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...

  20. Hydrogen bonds in 1-indanone: Charge density analysis and simulation of the inelastic neutron scattering spectrum in solid phase

    International Nuclear Information System (INIS)

    The influence of the intermolecular interactions on the vibrational dynamics of 1-indanone has been checked by simulating the INS spectrum from molecular and DFT periodic calculations, showing that, even in the case of weak hydrogen bonds, those modes associated with lower energy transfer are affected in the solid state. The electron charge distribution of solid 1-indanone has also been studied from a DFT periodic calculation. In order to obtain some insight into the intermolecular interactions Bader's atoms in molecules theory has been used. After a careful analysis of the topological properties of the calculated electron density, bond paths, critical points and other related properties, most of the C-H...π and C-H...O weak hydrogen bonds predicted in the experimental X-ray structure are confirmed. In addition some new H?H interactions were found. Furthermore, a natural bond orbital analysis was performed describing each hydrogen bond as donor-acceptor interactions

  1. Catalytic Oxidation of Methane into Methanol over Copper-Exchanged Zeolites with Oxygen at Low Temperature.

    Science.gov (United States)

    Narsimhan, Karthik; Iyoki, Kenta; Dinh, Kimberly; Román-Leshkov, Yuriy

    2016-06-22

    The direct catalytic conversion of methane to liquid oxygenated compounds, such as methanol or dimethyl ether, at low temperature using molecular oxygen is a grand challenge in C-H activation that has never been met with synthetic, heterogeneous catalysts. We report the first demonstration of direct, catalytic oxidation of methane into methanol with molecular oxygen over copper-exchanged zeolites at low reaction temperatures (483-498 K). Reaction kinetics studies show sustained catalytic activity and high selectivity for a variety of commercially available zeolite topologies under mild conditions (e.g., 483 K and atmospheric pressure). Transient and steady state measurements with isotopically labeled molecules confirm catalytic turnover. The catalytic rates and apparent activation energies are affected by the zeolite topology, with caged-based zeolites (e.g., Cu-SSZ-13) showing the highest rates. Although the reaction rates are low, the discovery of catalytic sites in copper-exchanged zeolites will accelerate the development of strategies to directly oxidize methane into methanol under mild conditions. PMID:27413787

  2. C-H arylations of 1,2,3-triazoles by reusable heterogeneous palladium catalysts in biomass-derived γ-valerolactone.

    Science.gov (United States)

    Tian, Xu; Yang, Fanzhi; Rasina, Dace; Bauer, Michaela; Warratz, Svenja; Ferlin, Francesco; Vaccaro, Luigi; Ackermann, Lutz

    2016-07-28

    C-H arylations were accomplished with a user-friendly heterogeneous palladium catalyst in the biomass-derived γ-valerolactone (GVL) as an environmentally-benign reaction medium. The user-friendly protocol was characterized by ample substrate scope and high functional group tolerance in the C-H arylation of 1,2,3-triazoles, and the palladium catalyst could be recycled and reused in the C-H activation process. PMID:27419251

  3. Bonding silicones with epoxies

    Energy Technology Data Exchange (ETDEWEB)

    Tira, J.S.

    1980-01-01

    It is shown that silicones, both room temperature vulcanizing (RTV) and millable rubber (press cured) can be successfully bonded to other materials using plasma treatment and epoxy adhesives. The plasma treatment using dry air atmosphere increases the surface energy of the silicone and thus provides a lower water contact angle. This phenomenon allows the epoxy adhesive to wet the silicone surface and ultimately bond. Bond strengths are sufficiently high to result in failures in the silicone materials rather than the adhesive bond.

  4. Australia's Bond Home Bias

    OpenAIRE

    Mishra, Anil V; Umaru B. Conteh

    2014-01-01

    This paper constructs the float adjusted measure of home bias and explores the determinants of bond home bias by employing the International Monetary Fund's high quality dataset (2001 to 2009) on cross-border bond investment. The paper finds that Australian investors' prefer investing in countries with higher economic development and more developed bond markets. Exchange rate volatility appears to be an impediment for cross-border bond investment. Investors prefer investing in countries with ...

  5. Performance of microstrip gas chambers with conductive surface coating of doped amorphous silicon carbide (a-Si:C:H)

    International Nuclear Information System (INIS)

    A new technique involves the use of doped amorphous silicon carbide (a-Si:C:H) as a conductive surface coating in the fabrication of microstrip gas chambers, to eliminate the effect of charge accumulation on the substrate surface. The performance of these detectors made in this way has been tested, measuring gas gains with respect to several operating parameters such as time, anode voltage (Va), backplane voltage (Vb), and drift voltage (Vd). Doped a-Si:C:H film is a conductive surface coating that works well, and is an attractive alternative to other surface treatments of the substrate, because its resistivity can be easily controlled over a wide range by doping, it has a naturally good radiation hardness, and large areas can be coated at relatively low cost. (orig.)

  6. Hot reactions in the systems 11C/H2O(l), 11C/H2O-NH3(l) and 13N/H2O(g)

    International Nuclear Information System (INIS)

    The chemical reactions of hot 11C with liquid water and a water ammonia mixture of mass ratio 3:1 and of 13N with water vapour were studied at T = 295 K. 11C was generated by the nuclear processes 16O(p,α,pn)11C and 14N(p,α)11C. 13N was produced via the 16O(p,α)13N nuclear reaction. The proton radiation dose was varied from D* = 2.8x10-3 to 0.28 eV per target molecule for the system 11C/H2O(l), from D* = 2.2 to 32 eV for the system 11C/H2O-NH3(l) and from D* = 0.13 to 6.2 eV for the system 13N/H2O(g), in order to follow radiolytic changes of the reaction products. Products of the system 11C/H2O(l) were 11CO2 (98-100% radiochemical yield) and 11CO (max. 1.5%). For the system 11C/H2O-NH3(l) six products (11CO2, 11CO, H11COOH, 11CH2O, 11CH3OH and 11CH4) were observed at radiation doses up to D* = 32 eV. In the system 13N/H2O(g) five products were detected: 13NO2, 13NO, 13NN, 13NNO and some 13NH3. 13NO is the main product at lowest doses with radiochemical yields exceeding 45%. With increasing radiolysis 13NO is changed to 13NO2. At higher doses 13NN becomes the main product. The system 11C/H2O-NH3(l) seems to bear some importance for the production of labelled precursors for the synthesis of radiopharmaceuticals. The interesting products 11CH2O and 11CH3OH are still formed under intensive irradiation which is necessary for the production of high radioactivities for nuclear medical application. (orig./RB)

  7. Carboxylate-Assisted Iridium-Catalyzed C-H Amination of Arenes with Biologically Relevant Alkyl Azides.

    Science.gov (United States)

    Zhang, Tao; Hu, Xuejiao; Wang, Zhen; Yang, Tiantian; Sun, Hao; Li, Guigen; Lu, Hongjian

    2016-02-24

    An iridium-catalyzed C-H amination of arenes with a wide substrate scope is reported. Benzamides with electron-donating and -withdrawing groups and linear, branched, and cyclic alkyl azides are all applicable. Cesium carboxylate is crucial for both reactivity and regioselectivity of the reactions. Many biologically relevant molecules, such as amino acid, peptide, steroid, sugar, and thymidine derivatives can be introduced to arenes with high yields and 100 % chiral retention. PMID:26712274

  8. Performance of microdot (MDOT) detectors with conductive coating of doped amorphous silicon carbide (a-Si:C:H)

    International Nuclear Information System (INIS)

    A conductive coating of doped amorphous silicon carbide (a-Si:C:H) has been used in the fabrication of microdot (MDOT) detectors, to minimize the defocusing, away from the anodes, of the drifting primary electrons. This defocusing is caused by the existence of the readout line passing below the insulating layer. The defocusing effect and other effects of the conductive coating on the performance of these detectors fabricated in this way have been investigated

  9. Malaysia : Bond Market Development

    OpenAIRE

    International Monetary Fund; World Bank

    2013-01-01

    This paper pertains to the bond market development in Malaysia, and provides an overview of the market scenario in the country. Malaysia has been successful in developing the capital markets, particularly bond markets, in the recent past. Now, it faces the challenge of how to improve broader access and efficiency of the bond market. A high degree of investor concentration, dominated by gov...

  10. Chemical bond fundamental aspects of chemical bonding

    CERN Document Server

    Frenking, Gernot

    2014-01-01

    This is the perfect complement to ""Chemical Bonding - Across the Periodic Table"" by the same editors, who are two of the top scientists working on this topic, each with extensive experience and important connections within the community. The resulting book is a unique overview of the different approaches used for describing a chemical bond, including molecular-orbital based, valence-bond based, ELF, AIM and density-functional based methods. It takes into account the many developments that have taken place in the field over the past few decades due to the rapid advances in quantum chemica

  11. Superhard nanocomposite nc-TiC/a-C:H film fabricated by filtered cathodic vacuum arc technique

    International Nuclear Information System (INIS)

    Superhard nanocomposite nc-TiC/a-C:H films, with an excellent combination of high elastic recovery, low friction coefficient and good H/E ratio, were prepared by filtered cathodic vacuum arc technique using the C2H2 gas as the precursor. The effect of C2H2 flow rate on the microstructure, phase composition, mechanical and tribological properties of nanocomposite nc-TiC/a-C:H films have been investigated by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), energy disperse spectroscopy (EDS), microindentation and tribotester measurements. It was observed that the C2H2 flow rate significantly affected the Ti content and hardness of films. Furthermore, by selecting the proper value for C2H2 flow rate, 20 sccm, one can deposit the nanocomposite film nc-TiC/a-C:H with excellent properties such as superhardness (66.4 GPa), high elastic recovery (83.3%) and high H/E ratio (0.13)

  12. Evolution of random catalytic networks

    Energy Technology Data Exchange (ETDEWEB)

    Fraser, S.M. [Santa Fe Inst., NM (United States); Reidys, C.M. [Santa Fe Inst., NM (United States)]|[Los Alamos National Lab., NM (United States)

    1997-06-01

    In this paper the authors investigate the evolution of populations of sequences on a random catalytic network. Sequences are mapped into structures, between which are catalytic interactions that determine their instantaneous fitness. The catalytic network is constructed as a random directed graph. They prove that at certain parameter values, the probability of some relevant subgraphs of this graph, for example cycles without outgoing edges, is maximized. Populations evolving under point mutations realize a comparatively small induced subgraph of the complete catalytic network. They present results which show that populations reliably discover and persist on directed cycles in the catalytic graph, though these may be lost because of stochastic effects, and study the effect of population size on this behavior.

  13. Molecular Simulation of Naphthenic Acid Removal on Acidic Catalyst (Ⅰ) Mechanism of Catalytic Decarboxylation

    Institute of Scientific and Technical Information of China (English)

    Fu Xiaoqin; Dai Zhenyu; Tian Songbai; Hou Suandi; Wang Xieqing

    2008-01-01

    In this paper, the charge distribution, the chemical bond order and the reactive performance of carboxylic acid model compounds on acidic catalyst were investigated by using molecular simulation technology. The simulation results showed that the bond order of C-O was higher than that of C-C,and C-C bond connected to the carbon atom in the carboxyl radical had the lowest bond order. The charge distributions of model naphthenic acids were similar in characteristics that the negative charges were concentrated on carboxyls. According to the simulation results, the mechanisms of catalytic decarboxylation over acidic solid catalyst were proposed, and a new route was put forward regarding removal of the naphthenic acid from crude oil through catalytic decarboxylation.

  14. Catalytic Combustion of Gasified Waste

    Energy Technology Data Exchange (ETDEWEB)

    Kusar, Henrik

    2003-09-01

    This thesis concerns catalytic combustion for gas turbine application using a low heating-value (LHV) gas, derived from gasified waste. The main research in catalytic combustion focuses on methane as fuel, but an increasing interest is directed towards catalytic combustion of LHV fuels. This thesis shows that it is possible to catalytically combust a LHV gas and to oxidize fuel-bound nitrogen (NH{sub 3}) directly into N{sub 2} without forming NO{sub x} The first part of the thesis gives a background to the system. It defines waste, shortly describes gasification and more thoroughly catalytic combustion. The second part of the present thesis, paper I, concerns the development and testing of potential catalysts for catalytic combustion of LHV gases. The objective of this work was to investigate the possibility to use a stable metal oxide instead of noble metals as ignition catalyst and at the same time reduce the formation of NO{sub x} In paper II pilot-scale tests were carried out to prove the potential of catalytic combustion using real gasified waste and to compare with the results obtained in laboratory scale using a synthetic gas simulating gasified waste. In paper III, selective catalytic oxidation for decreasing the NO{sub x} formation from fuel-bound nitrogen was examined using two different approaches: fuel-lean and fuel-rich conditions. Finally, the last part of the thesis deals with deactivation of catalysts. The various deactivation processes which may affect high-temperature catalytic combustion are reviewed in paper IV. In paper V the poisoning effect of low amounts of sulfur was studied; various metal oxides as well as supported palladium and platinum catalysts were used as catalysts for combustion of a synthetic gas. In conclusion, with the results obtained in this thesis it would be possible to compose a working catalytic system for gas turbine application using a LHV gas.

  15. Catalytic activity of nuclease P1: Experiment and theory

    International Nuclear Information System (INIS)

    Nuclease P1 from Penicillium citrinum is a zinc dependent glyco-enzyme that recognizes single stranded DNA and RNA as substrates and hydrolyzes the phosphate ester bond. Nuclease Pl seems to recognize particular conformations of the phosphodiester backbone and shows significant variation in the rate of hydrolytic activity depending upon which nucleosides are coupled by the phosphodiester bond. The efficiency of nuclease Pl in hydrolyzing the phosphodiester bonds of a substrate can be altered by modifications to one of the substrate bases induced by ionizing radiation or oxidative stress. Measurements have been made of the effect of several radiation induced lesions on the catalytic rate of nuclease Pl. A model of the structure of the enzyme has been constructed in order to better understand the binding and activity of this enzyme on various ssDNA substrates

  16. Antibody catalysis of peptide bond formation.

    OpenAIRE

    Jacobsen, J R; Schultz, P. G.

    1994-01-01

    An antibody generated against a neutral phosphonate diester transition-state (TS not equal to) analog catalyzes the formation of an amide bond between a phenylalanyl amino group and an acyl azide derived from L-alanine. The antibody is selective for L- vs. D-alanine and does not catalyze the hydrolysis of the acyl azide to an appreciable degree. A rate acceleration of 10,000-fold relative to the uncatalyzed reaction is observed. The antibody may achieve its catalytic efficiency both by acting...

  17. Unsteady catalytic processes and sorption-catalytic technologies

    International Nuclear Information System (INIS)

    Catalytic processes that occur under conditions of the targeted unsteady state of the catalyst are considered. The highest efficiency of catalytic processes was found to be ensured by a controlled combination of thermal non-stationarity and unsteady composition of the catalyst surface. The processes based on this principle are analysed, in particular, catalytic selective reduction of nitrogen oxides, deep oxidation of volatile organic impurities, production of sulfur by the Claus process and by hydrogen sulfide decomposition, oxidation of sulfur dioxide, methane steam reforming and anaerobic combustion, selective oxidation of hydrocarbons, etc.

  18. Ruthenium-Immobilized Periodic Mesoporous Organosilica: Synthesis, Characterization, and Catalytic Application for Selective Oxidation of Alkanes.

    Science.gov (United States)

    Ishito, Nobuhiro; Kobayashi, Hirokazu; Nakajima, Kiyotaka; Maegawa, Yoshifumi; Inagaki, Shinji; Hara, Kenji; Fukuoka, Atsushi

    2015-10-26

    Periodic mesoporous organosilica (PMO) is a unique material that has a crystal-like wall structure with coordination sites for metal complexes. A Ru complex, [RuCl2 (CO)3 ]2 , is successfully immobilized onto 2,2'-bipyridine (BPy) units of PMO to form a single-site catalyst, which has been confirmed by various physicochemical analyses. Using NaClO as an oxidant, the Ru-immobilized PMO oxidizes the tertiary C-H bonds of adamantane to the corresponding alcohols at 57 times faster than the secondary C-H bonds, thereby exhibiting remarkably high regioselectivity. Moreover, the catalyst converts cis-decalin to cis-9-decalol in a 63 % yield with complete retention of the substrate stereochemistry. The Ru catalyst can be separated by simple filtration and reused without loss of the original activity and selectivity for the oxidation reactions. PMID:26330333

  19. The pseudohydrogen bond structures between 2-F-epoxy-butane and three kinds of bimolecular

    International Nuclear Information System (INIS)

    The weak intermolecular interactions between 2-F-epoxy-butane and Iminazole, Thiazole and Oxazole were theoretically discussed by using density functional B3LYP (Becke, three-parameter, Lee- Yang-Parr)/6-311++G** and HF (Hartree Fock)/6-311++G** methods. The results showed that both the N…H conventional hydrogen bond and C-F…H-C pseudohydrogen bond (PHB) structures are coexisting in the three complexes. The weak intermolecular interactions energies indicate the relative stabilities of the three complexes are proportionable. The calculated results showed that the stretch vibrational frequency of C-H bond (electronic acceptor) presents blue shift, but that of C-F bond, which is intensely related to F group (electronic donor), presents red shift. Electron density topological properties demonstrates that the covalent and ionic characteristics of the C-F…H-C pseudohydrogen bond are proportional to that of convention hydrogen bond. (authors)

  20. Catalytic production of biodiesel

    Energy Technology Data Exchange (ETDEWEB)

    Theilgaard Madsen, A.

    2011-07-01

    The focus of this thesis is the catalytic production of diesel from biomass, especially emphasising catalytic conversion of waste vegetable oils and fats. In chapter 1 an introduction to biofuels and a review on different catalytic methods for diesel production from biomass is given. Two of these methods have been used industrially for a number of years already, namely the transesterification (and esterification) of oils and fats with methanol to form fatty acid methyl esters (FAME), and the hydrodeoxygenation (HDO) of fats and oils to form straight-chain alkanes. Other possible routes to diesel include upgrading and deoxygenation of pyrolysis oils or aqueous sludge wastes, condensations and reductions of sugars in aqueous phase (aqueous-phase reforming, APR) for monofunctional hydrocarbons, and gasification of any type of biomass followed by Fischer-Tropsch-synthesis for alkane biofuels. These methods have not yet been industrialised, but may be more promising due to the larger abundance of their potential feedstocks, especially waste feedstocks. Chapter 2 deals with formation of FAME from waste fats and oils. A range of acidic catalysts were tested in a model fat mixture of methanol, lauric acid and trioctanoin. Sulphonic acid-functionalised ionic liquids showed extremely fast convertion of lauric acid to methyl laurate, and trioctanoate was converted to methyl octanoate within 24 h. A catalyst based on a sulphonated carbon-matrix made by pyrolysing (or carbonising) carbohydrates, so-called sulphonated pyrolysed sucrose (SPS), was optimised further. No systematic dependency on pyrolysis and sulphonation conditions could be obtained, however, with respect to esterification activity, but high activity was obtained in the model fat mixture. SPS impregnated on opel-cell Al{sub 2}O{sub 3} and microporous SiO{sub 2} (ISPS) was much less active in the esterification than the original SPS powder due to low loading and thereby low number of strongly acidic sites on the

  1. Weak bond screening system

    Science.gov (United States)

    Chuang, S. Y.; Chang, F. H.; Bell, J. R.

    Consideration is given to the development of a weak bond screening system which is based on the utilization of a high power ultrasonic (HPU) technique. The instrumentation of the prototype bond strength screening system is described, and the adhesively bonded specimens used in the system developmental effort are detailed. Test results obtained from these specimens are presented in terms of bond strength and level of high power ultrasound irradiation. The following observations were made: (1) for Al/Al specimens, 2.6 sec of HPU irradiation will screen weak bond conditions due to improper preparation of bonding surfaces; (2) for composite/composite specimens, 2.0 sec of HPU irradiation will disrupt weak bonds due to under-cured conditions; (3) for Al honeycomb core with composite skin structure, 3.5 sec of HPU irradiation will disrupt weak bonds due to bad adhesive or oils contamination of bonding surfaces; and (4) for Nomex honeycomb with Al skin structure, 1.3 sec of HPU irradiation will disrupt weak bonds due to bad adhesive.

  2. Ligand-Promoted Borylation of C(sp(3))-H Bonds with Palladium(II) Catalysts.

    Science.gov (United States)

    He, Jian; Jiang, Heng; Takise, Ryosuke; Zhu, Ru-Yi; Chen, Gang; Dai, Hui-Xiong; Dhar, T G Murali; Shi, Jun; Zhang, Hao; Cheng, Peter T W; Yu, Jin-Quan

    2016-01-11

    A quinoline-based ligand effectively promotes the palladium-catalyzed borylation of C(sp(3))-H bonds. Primary β-C(sp(3))-H bonds in carboxylic acid derivatives as well as secondary C(sp(3))-H bonds in a variety of carbocyclic rings, including cyclopropanes, cyclobutanes, cyclopentanes, cyclohexanes, and cycloheptanes, can thus be borylated. This directed borylation method complements existing iridium(I)- and rhodium(I)-catalyzed C-H borylation reactions in terms of scope and operational conditions. PMID:26611496

  3. Non-Pincer-Type Mononuclear Scandium Alkylidene Complexes: Synthesis, Bonding, and Reactivity.

    Science.gov (United States)

    Wang, Chen; Zhou, Jiliang; Zhao, Xuefei; Maron, Laurent; Leng, Xuebing; Chen, Yaofeng

    2016-01-22

    The first non-pincer-type mononuclear scandium alkylidene complexes were synthesized and structurally characterized. These complexes exhibited short Sc-C bond lengths and even one of the shortest reported to date (2.1134(18) Å). The multiple character of the Sc-C bond was highlighted by a DFT calculation. This was confirmed by experimental reactivity study where the complex underwent [2+1] cycloaddition with elemental selenium and [2+2] cycloaddition with imine. DFT calculation also revealed a strong nucleophilic behavior of the alkylidene complex that was experimentally demonstrated by the C-H bond activation of phenylacetylene. PMID:26617412

  4. XPS study of target poisoning during the plasma assisted deposition of a-C:H/Au thin films

    International Nuclear Information System (INIS)

    The X-ray photoelectron spectroscopic (XPS) study of the target poisoning during the deposition of a-C:H/Au using combined radio frequency (RF) powered magnetron sputtering at 100 W and plasma-assisted chemical vapor deposition (PACVD) with a mass flow ratio of 0.5 between CH4 and at is made by Gampp. In this paper we extend this study to both RF and bipolar pulsed (BPP) powered magnetron sputtering in gas mixtures of different values of CH4/Ar mass flow ratio. Elemental compositions of deposited a-C:H/Au layers have been determined by in situ X-ray photoelectron spectroscopy. To determine the elemental content of a sample, the integration over Au 4f7/2, C 1s and 0 1s core level signals (oxygen shows up as an impurity of max. 1 at.%) was used. One may generally conclude that the character of target poisoning process is steep and step-like in time regardless of the type of magnetron power supply, i.e. that it is inherent to the deposition of a-C:H/Au using present deposition setup. Therefore, in the attempts to obtain stable and reproducible deposition conditions and homogeneous coatings, the target had to be driven to the certain degree of poisoning. This is done by conditioning in pure CH4 (covering) and in pure Ar plasma (cleaning) subsequently and alternatively, until the desired Au content is reached. Then, for deposition purposes, a CH4/Ar gas mixture was selected so that steady state of target covering and cleaning is sustained

  5. The cheap preparation technology of A-, μC-SiC:H films for thin film solar cells

    International Nuclear Information System (INIS)

    We propose the use of a cheap liquid methyltrichlorosilane (MTCS) as a precursor in the modified plasma enhanced- chemical-vapor-deposition (PECVD) system with a very high frequency (VHF) discharge for preparing high quality hydrogenated amorphous silicon carbide (αSi1-xCx:H) films with the large carbon content. This method allows to control the composition and the morphology of the films in the region of 0.3< x<0.7. The monocrystalline fraction, consisting of 3C-SiC crystallites in an amorphous network (μc-SiC:H), is revealed in the films with the composition of about 0.5. (Author)

  6. 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.

  7. The cheap preparation technology of A-, mC-SiC:H films for thin film solar cells

    International Nuclear Information System (INIS)

    We propose the use of a cheap liquid methyltriclorosilane (MTCS) as a precursor in the modified plasma-enhanced-chemical-vapor-deposition (PECVD) system with a very high frequency (VHF) discharge for preparing high quality hydrogenated amorphous silicon carbide (a-Si1-xCx:H) films with the large carbon content. This method allows to control the composition and the morphology of the films in the region of 0.3< x<0.7. The monocrystalline fraction, consisting of 3C-SiC crystallites in an amorphous network (mc-SiC:H), is reveled in the films with the composition of about 0.5. (Author)

  8. Immigration process in catalytic medium

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The longtime behavior of the immigration process associated with a catalytic super-Brownian motion is studied. A large number law is proved in dimension d≤3 and a central limit theorem is proved for dimension d=3.

  9. Bond Markets in Africa

    OpenAIRE

    Yibin Mu; Peter Phelps; Janet Gale Stotsky

    2013-01-01

    African bond markets have been steadily growing in recent years, but nonetheless remain undeveloped. African countries would benefit from greater access to financing and deeper financial markets. This paper compiles a unique set of data on corporate bond markets in Africa. It then applies an econometric model to analyze the key determinants of African government securities market and corporate bond market capitalization. Government securities market capitalization is directly related to bette...

  10. Build America Bonds

    OpenAIRE

    Andrew Ang; Vineer Bhansali; Yuhang Xing

    2010-01-01

    Build America Bonds (BABs) are a new form of municipal financing introduced in 2009. Investors in BAB municipal bonds receive interest payments that are taxable, but issuers receive a subsidy from the U.S. Treasury. The BAB program has succeeded in lowering the cost of funding for state and local governments with BAB issuers obtaining finance 54 basis points lower, on average, compared to issuing regular municipal bonds. For institutional investors, BAB issue yields are 116 basis points highe...

  11. Two-dimensional supramolecular networks via C-H$\\cdots$Cl and N-H$\\cdots$Cl interactions utilizing bidentate neutral pyridine amide coordinated MnIICl2 tectons

    Indian Academy of Sciences (India)

    Wilson Jacob; Rabindranath Mukherjee

    2008-09-01

    Reaction of -(phenyl)-2-pyridinecarboxamide (HL1) and -(-tolyl)-2-pyridinecarboxamide (HL2) ligands with MnCl2.4H2O affords complexes [(HL1)2MnCl2] 1 and [(HL2)2MnCl2] 2. The structures of 1 and 2 were determined by three-dimensional X-ray crystallography revealing that the MnII ions assume distorted octahedral geometry with coordination by two HL1/HL2 ligands providing two pyridine N and two amide O and two chloride ions. Notably, secondary interactions [C-H$\\cdots$Cl (pyridine 3-H hydrogen) and N-H$\\cdots$Cl (amide NH hydrogen)] triggered by MnII-coordinated chloride ions acting as hydrogen bonding acceptors generate self-complementary dimeric tectons, which lead to 2D supramolecular architectures.

  12. Catalytic DNA with phosphatase activity

    OpenAIRE

    Chandrasekar, Jagadeeswaran; Silverman, Scott K.

    2013-01-01

    Catalytic DNA sequences (deoxyribozymes, DNA enzymes, or DNAzymes) have been identified by in vitro selection for various catalytic activities. Expanding the limits of DNA catalysis is an important fundamental objective and may facilitate practical utility of catalysts that can be obtained from entirely unbiased (random) sequence populations. In this study, we show that DNA can catalyze Zn2+-dependent phosphomonoester hydrolysis of tyrosine and serine side chains (i.e., exhibit phosphatase ac...

  13. The Bond Market's q

    OpenAIRE

    Thomas Philippon

    2006-01-01

    I propose an implementation of the q-theory of investment using bond prices instead of equity prices. Credit risk makes corporate bond prices sensitive to future asset values, and q can be inferred from bond prices. The bond market's q performs much better than the usual measure in standard investment equations. With aggregate data, the fit is three times better, cash flows are driven out and the implied adjustment costs are reduced by more than an order of magnitude. The new measure also imp...

  14. Copper wire bonding

    CERN Document Server

    Chauhan, Preeti S; Zhong, ZhaoWei; Pecht, Michael G

    2014-01-01

    This critical volume provides an in-depth presentation of copper wire bonding technologies, processes and equipment, along with the economic benefits and risks.  Due to the increasing cost of materials used to make electronic components, the electronics industry has been rapidly moving from high cost gold to significantly lower cost copper as a wire bonding material.  However, copper wire bonding has several process and reliability concerns due to its material properties.  Copper Wire Bonding book lays out the challenges involved in replacing gold with copper as a wire bond material, and includes the bonding process changes—bond force, electric flame off, current and ultrasonic energy optimization, and bonding tools and equipment changes for first and second bond formation.  In addition, the bond–pad metallurgies and the use of bare and palladium-coated copper wires on aluminum are presented, and gold, nickel and palladium surface finishes are discussed.  The book also discusses best practices and re...

  15. Hydrogen bonding and anaesthesia

    Science.gov (United States)

    Sándorfy, C.

    2004-12-01

    General anaesthetics act by perturbing intermolecular associations without breaking or forming covalent bonds. These associations might be due to a variety of van der Waals interactions or hydrogen bonding. Neurotransmitters all contain OH or NH groups, which are prone to form hydrogen bonds with those of the neurotransmitter receptors. These could be perturbed by anaesthetics. Aromatic rings in amino acids can act as weak hydrogen bond acceptors. On the other hand the acidic hydrogen in halothane type anaesthetics are weak proton donors. These two facts together lead to a probable mechanism of action for all general anaesthetics.

  16. A synthetic, catalytic and theoretical investigation of an unsymmetrical SCN pincer palladacycle.

    Science.gov (United States)

    Roffe, Gavin W; Boonseng, Sarote; Baltus, Christine B; Coles, Simon J; Day, Iain J; Jones, Rhiannon N; Press, Neil J; Ruiz, Mario; Tizzard, Graham J; Cox, Hazel; Spencer, John

    2016-04-01

    The SCN ligand 2-{3-[(methylsulfanyl)methyl]phenyl}pyridine, 1, has been synthesized starting from an initial Suzuki-Miyaura (SM) coupling between 3-((hydroxymethyl)phenyl)boronic acid and 2-bromopyridine. The C-H activation of 1 with in situ formed Pd(MeCN)4(BF4)2 has been studied and leads to a mixture of palladacycles, which were characterized by X-ray crystallography. The monomeric palladacycle LPdCl 6, where L-H = 1, has been synthesized, and tested in SM couplings of aryl bromides, where it showed moderate activity. Density functional theory and the atoms in molecules (AIM) method have been used to investigate the formation and bonding of 6, revealing a difference in the nature of the Pd-S and Pd-N bonds. It was found that S-coordination to the metal in the rate determining C-H bond activation step leads to better stabilization of the Pd(II) centre (by 13-28 kJ mol(-1)) than with N-coordination. This is attributed to the electron donating ability of the donor atoms determined by Bader charges. The AIM analysis also revealed that the Pd-N bonds are stronger than the Pd-S bonds influencing the stability of key intermediates in the palladacycle formation reaction pathway. PMID:27152207

  17. CATALYTIC AND ADSORPTION PROPERTIES OF Al- AND Ti-MCM-41 SYNTHESIZED AT ROOM TEMPERATURE

    OpenAIRE

    Silva, Tiago N.; Lopes, José Madeira; Ribeiro, Fernando Ramôa; Carrott, Manuela Ribeiro; Galacho, Cristina; Sousa, Maria José; Carrott, Peter

    2002-01-01

    Aluminosilicate and titanosilicate MCM-41 were synthesized using a room temperature method. A preliminary catalytic evaluation was performed in the promotion of the 1-butene double bond isomerization, which was successful in probing differences in the acidity of the samples prepared.

  18. Multifunctional catalytic platform for peroxidase mimicking, enzyme immobilization and biosensing.

    Science.gov (United States)

    Maroneze, Camila Marchetti; Dos Santos, Glauco P; de Moraes, Vitoria B; da Costa, Luiz P; Kubota, Lauro Tatsuo

    2016-03-15

    A hybrid platform based on ionic liquid-based alkoxysilane functionalized mesoporous silica was applied for the synthesis of supported Pt nanoparticles with peroxidase-like catalytic activity. The positively charged groups (imidazolium) chemically bonded to the surface provide dual-functionality as ion-exchangers to the hybrid material, firstly used for the in situ synthesis of the highly dispersed Pt nanostructures and, secondly, for the immobilization of biological species aiming biosensing purposes. The peroxidase-like catalytic activity of the SiO2/Imi/Pt material was evaluated towards the H2O2-mediated oxidation of a chromogenic peroxidase substrate (TMB), allowing the colorimetric detection of H2O2. Finally, to further explore the practical application of this nanomaterial-based artificial system, glucose oxidase (GOx) was immobilized on the catalytic porous platform and a bioassay for the colorimetric determination of glucose was successfully conducted as a model system. The enzyme-like catalytic properties of the SiO2/Imi/Pt as well as its ability to immobilize and keep active biological entities on the porous structure indicate that this hybrid porous platform is potentially useful for the development of biosensing devices. PMID:26499871

  19. Weak C-H$\\cdots$F-C interactions in carboxylate anion binding: Synthesis, spectroscopic and X-ray structural studies of [Co(phen)2CO3]2 (C7H3O2FCl)Cl$\\cdots$11H2O and [Co(phen)2CO3](C7H3NO4Cl)$\\cdot$6H2O

    Indian Academy of Sciences (India)

    A Singh; R P Sharma; T Aree; P Venugopalan

    2010-09-01

    Two new complex salts containing 2,5-substituted benzoate ions, [Co(phen)2CO3]2 (C7H3O2FCl)Cl$\\cdot$11H2O (1) and [Co(phen)2CO3](C7H3NO4Cl)$\\cdot$6H2O (2) (where phen = 1,10-phenanthroline, C7H3O2FCl = 2-chloro-5-fluorobenzoate (cfbz) and C7H3NO4Cl = 2-chloro-5-nitrobenzoate(cnbz)) were synthesized by reacting carbonatobis(1,10-phenanthroline)cobalt(III) chloride with appropriate salts in aqueous medium. A detailed packing analysis has been undertaken to delineate the role of second sphere C-H$\\cdots$F and C-H$\\cdots$O interactions amid other heteroatom interactions. The complex salts have been characterized by elemental analyses, spectroscopic studies (IR, UV/Visible, multinuclear NMR), conductance and solubility product measurements. Single crystal X-ray structure determination revealed ionic structures of both the complex salts having discrete ions along with lattice water molecules. Crystal lattice is stabilized by a variety of hydrogen bonding interactions, i.e. O-H$\\cdots$O, C-H$\\cdots$O and C-H$\\cdots$F involving second sphere coordination besides - interaction. Furthermore, packing analyses reveal that C-H…F interactions can manifest even in the presence of a large number of heteroatom interactions.

  20. Modeling of the gas-phase chemistry in C-H-O gas mixtures for diamond chemical vapor deposition

    Science.gov (United States)

    Petherbridge, James R.; May, Paul W.; Ashfold, Michael N. R.

    2001-05-01

    The boundaries of the diamond deposition region in the C-H-O (Bachmann) atomic phase composition diagram have been reproduced successfully for 38 different C, H, and O containing gas mixtures using the CHEMKIN computer package, together with just two criteria—a minimum mole fraction of methyl radicals [CH3] and a limiting value of the [H]/[C2H2] ratio. The diamond growth/no-growth boundary coincides with the line along which the input mole fractions of C and O are equal. For every gas mixture studied, no-growth regions are found to coincide with a negligible (<10-10) mole fraction of CH3 radicals, while for gas mixtures lying within the diamond growth region the CH3 mole fraction is ˜10-7. Each no-growth→diamond growth boundary is seen to be accompanied by a 2-3 order of magnitude step in CH3 mole fraction. The boundary between diamond and nondiamond growth is less clearly defined, but can be reproduced by assuming a critical, temperature dependent [H]/[C2H2] ratio (0.2, in the case that Tgas=2000 K) that reflects the crucial role of H atoms in the etching of nondiamond phases. The analysis allows prediction of the composition process window for good quality diamond growth for all stable input gas mixtures considered in this study.

  1. Reactively co-sputter deposited a-C:H/Cr thin films: Material characteristics and optical properties

    International Nuclear Information System (INIS)

    Various chromium-containing amorphous hydrogenated carbon (a-C:H/Cr) coatings were deposited on oxygen-free copper and silicon substrates for use as solar selective absorber coatings. The deposition was performed using a magnetron co-sputter deposition method under various methane/Ar ratios, ranging from 0 to 8%. The obtained films were characterized using glazing incident X-ray diffraction, scanning electron microscopy, high-resolution transmission electron microscopy, secondary ion mass spectrometer, and X-ray photoelectron spectroscopy. The optical absorptance and emittance at 100 °C were determined using UV–vis-NIR spectroscopy and Fourier transform infrared spectrometry, respectively. Effects of the material characteristics on the optical properties are reported and discussed. - Highlights: ► a-C:H/Cr coatings were prepared using reactive magnetron co-sputtering deposition. ► Cr exists as crystallites having diameters in between 1 to 2 nm. ► Coating prepared with 3% methane in the gas fed exhibits the best optical absorptance

  2. Direct catalytic cross-coupling of organolithium compounds

    Science.gov (United States)

    Giannerini, Massimo; Fañanás-Mastral, Martín; Feringa, Ben L.

    2013-08-01

    Catalytic carbon-carbon bond formation based on cross-coupling reactions plays a central role in the production of natural products, pharmaceuticals, agrochemicals and organic materials. Coupling reactions of a variety of organometallic reagents and organic halides have changed the face of modern synthetic chemistry. However, the high reactivity and poor selectivity of common organolithium reagents have largely prohibited their use as a viable partner in direct catalytic cross-coupling. Here we report that in the presence of a Pd-phosphine catalyst, a wide range of alkyl-, aryl- and heteroaryl-lithium reagents undergo selective cross-coupling with aryl- and alkenyl-bromides. The process proceeds quickly under mild conditions (room temperature) and avoids the notorious lithium halogen exchange and homocoupling. The preparation of key alkyl-, aryl- and heterobiaryl intermediates reported here highlights the potential of these cross-coupling reactions for medicinal chemistry and material science.

  3. KINETIC ANALYSIS OF THE CATALYTIC DECOMPOSITION OF HYDRAZINE

    Directory of Open Access Journals (Sweden)

    J.E. de MEDEIROS

    1998-06-01

    Full Text Available The bond-order conservation method was used to study the catalytic decomposition of N2H4. Variation in the activation energy, E, of the most relevant steps was calculated as a function of the enthalpy of adsorption of N, QN, between 0 and 1250 kJmol-1. Results suggest that below QN = 520 kJmol-1 the catalytic decomposition of N2H4 produces mostly N2 and H2. Above QN = 520 kJmol-1, NH3 and N2 are the main products. Near QN = 520 kJmol-1 N2, H2 and NH3 are obtained, in agreement with experimental results on different metals.

  4. The mechanism of catalytic methylation of 2-phenylpyridine using di-tert-butyl peroxide.

    Science.gov (United States)

    Sharma, Akhilesh K; Roy, Dipankar; Sunoj, Raghavan B

    2014-07-14

    The mechanism of palladium chloride-catalyzed direct methylation of arenes with peroxides is elucidated by using the energetics computed at the M06 density functional theory. The introduction of a methyl group by tert-butyl peroxides at the ortho-position of a prototypical 2-phenyl pyridine, a commonly used substrate in directed C-H functionalization reactions, is examined in detail by identifying the key intermediates and transition states involved in the reaction sequence. Different possibilities that differ in terms of the site of catalyst coordination with the substrate and the ensuing mechanism are presented. The important mechanistic events involved are (a) an oxidative or a homolytic cleavage of the peroxide O-O bond, (b) C-H bond activation, (c) C-C bond activation, and (d) reductive elimination involving methyl transfer to the aromatic ring. We have examined both radical and non-radical pathways. In the non-radical pathway, the lowest energy pathway involves C-H bond activation prior to the coordination of the peroxide to palladium, which is subsequently followed by the O-O bond cleavage of the peroxide and the C-C bond activation. Reductive elimination in the resulting intermediate leads to the vital C-C bond formation between methyl and aryl carbon atoms. In the non-radical pathway, the C-C bond activation is higher in energy and has been identified as the rate-limiting step of this reaction. In the radical pathway, however, the activation barrier for the C-C bond cleavage is lower than for the peroxide O-O bond cleavage. A combination of a radical pathway up to the formation of a palladium methyl intermediate and a subsequent non-radical pathway has been identified as the most favored pathway for the title reaction. The predicted mechanism is in good agreement with the experimental observations on PdCl2 catalyzed methylation of 2-phenyl pyridine using tert-butyl peroxide. PMID:24875675

  5. Conceptual chemistry approach towards the support effect in supported vanadium oxides : Valence bond calculations on the ionicity of vanadium catalysts

    NARCIS (Netherlands)

    Fievez, Tim; De Proft, Frank; Geerlings, Paul; Weckhuysen, Bert M.; Havenith, Remco W. A.

    2011-01-01

    The concept of bond ionicity, obtained via a valence bond analysis, is invoked in the interpretation of the catalytic activity of supported vanadium oxides, in analogy with previous work conducted within the framework of conceptual DFT. For a set of model clusters representing the vanadium oxide sup

  6. Comparison of Gold Bonding with Mercury Bonding

    NARCIS (Netherlands)

    Kraka, Elfi; Filatov, Michael; Cremer, Dieter

    2009-01-01

    Nine AuX molecules (X = H, O, S, Se, Te, F, Cl, Br, I), their isoelectronic HgX(+) analogues, and the corresponding neutral HgX diatomics have been investigated using NESC (Normalized Elimination of the Small Component) and B3LYP theory to determine relativistic effects for bond dissociation energie

  7. Molecular dynamics simulation of liquid methanol. II. Unified assignment of infrared, raman, and sum frequency generation vibrational spectra in methyl C-H stretching region

    Science.gov (United States)

    Ishiyama, Tatsuya; Sokolov, Vladimir V.; Morita, Akihiro

    2011-01-01

    Vibrational spectra of methyl C-H stretching region are notoriously complicated, and thus a theoretical method of systematic assignment is strongly called for in condensed phase. Here we develop a unified analysis method of the vibrational spectra, such as infrared (IR), polarized and depolarized Raman, and ssp polarized sum frequency generation (SFG), by flexible and polarizable molecular dynamics simulation. The molecular model for methanol has been developed by charge response kernel model to allow for analyzing the methyl C-H stretching vibrations. The complicated spectral structure by the Fermi resonance has been unraveled by empirically shifting potential parameters, which provides clear information on the coupling mechanism. The analysis confirmed that for the IR, polarized Raman, and SFG spectra, two-band structure at about 2830 and 2950 cm^{-1} results from the Fermi resonance splitting of the methyl C-H symmetric stretching and bending overtones. In the IR spectrum, the latter, higher-frequency band is overlapped with prominent asymmetric C-H stretching bands. In the depolarized Raman spectrum, the high frequency band at about 2980 cm^{-1} is assigned to the asymmetric C-H stretching mode. In the SFG spectrum, the two bands of the splitted symmetric C-H stretching mode have negative amplitudes of imaginary nonlinear susceptibility χ ^{(2)}, while the higher-frequency band is partly cancelled by positive imaginary components of asymmetric C-H stretching modes.

  8. The problem of dose in homeopaty: evaluation of the effect of high dilutions of Arsenicum album 30cH on rats intoxicasted with arsenic

    Directory of Open Access Journals (Sweden)

    Maria Imaculada Lima Montebelo

    2011-09-01

    Full Text Available Background: Although scientific studies have confirmed the action of homeopathic high dilutions in living organisms an endless debate on the choice of the most fitting dilution, the frequency of administration and the dose (amount of medicine still remains. Aims: This study sought to assess the in vivo effect of 2 different concentrations of Arsenicum album 30cH in order to elucidate some problems in the homeopathic notion of dose. Methods: Male Wistar rats previously intoxicated with sodium arsenate by peritoneal injection were treated with undiluted Ars 30cH and Ars 30cH in 1% solution administered by oral route. Atomic absorption spectroscopy was employed to measure the levels of arsenic retained in the animals as well as the amounts eliminated through urine. Urine samples were collected before and after and during treatment. A positive control group (intoxicated animals and negative control group (non-intoxicated animals were administered only the vehicle used to prepare the medicine (ethanol. Results: The groups treated with undiluted Ars 30cH and Ars 30cH in 1% solution eliminated significant amounts of arsenic through urine when compared to the control groups. The group treated with undiluted Ars 30cH eliminated significantly higher amounts of arsenic than the group treated with the same medicine in 1% solution. Conclusion: These results suggest that undiluted Ars 30cH was more effective than in 1% solution in this experimental model.

  9. Opto-electronic properties of P-doped nc-Si-QD/a-SiC:H thin films as foundation layer for all-Si solar cells in superstrate configuration

    Science.gov (United States)

    Kar, Debjit; Das, Debajyoti

    2016-07-01

    With the advent of nc-Si solar cells having improved stability, the efficient growth of nc-Si i-layer of the top cell of an efficient all-Si solar cell in the superstrate configuration prefers nc-Si n-layer as its substrate. Accordingly, a wide band gap and high conducting nc-Si alloy material is a basic requirement at the n-layer. Present investigation deals with the development of phosphorous doped n-type nanocrystalline silicon quantum dots embedded in hydrogenated amorphous silicon carbide (nc-Si-QD/a-SiC:H) hetero-structure films, wherein the optical band gap can be widened by the presence of Si-C bonds in the amorphous matrix and the embedded high density tiny nc-Si-QDs could provide high electrical conductivity, particularly in P-doped condition. The nc-Si-QDs simultaneously facilitate further widening of the optical band gap by virtue of the associated quantum confinement effect. A complete investigation has been made on the electrical transport phenomena involving charge transfer by tunneling and thermionic emission prevailing in n-type nc-Si-QD/a-SiC:H thin films. Their correlation with different phases of the specific heterostructure has been carried out for detailed understanding of the material, in order to improve its device applicability. The n-type nc-Si-QD/a-SiC:H films exhibit a thermally activated electrical transport above room temperature and multi-phonon hopping (MPH) below room temperature, involving defects in the amorphous phase and the grain-boundary region. The n-type nc-Si-QD/a-SiC:H films grown at ˜300 °C, demonstrating wide optical gap ˜1.86-1.96 eV and corresponding high electrical conductivity ˜4.5 × 10-1-1.4 × 10-2 S cm-1, deserve to be an effective foundation layer for the top nc-Si sub-cell of all-Si solar cells in n-i-p structure with superstrate configuration.

  10. (±)Methanodibenzodiazocine tethered [C-H]+ functional site: Study towards benzoin condensation and Baylis-Hillman reactions

    Indian Academy of Sciences (India)

    Arruri Sathyanarayana; Ganesan Prabusankar

    2015-05-01

    New heterocyclic ring systems consisting of (±) methanodibenzodiazocine and imidazolium/benzimidazolium salts were synthesized in very good yield. Subsequently, these halide salts were subjected to the anion exchange reaction with KPF6 to yield the corresponding azolium salts in excellent yield. The possible applications of these newly prepared salts were investigated in homogeneous catalysis. Remarkable changes in the catalytic activity were observed by varying the bulkiness of N-substituent at imidazole. Catalytic activity of these newly prepared salts was tested for the benzoin condensation reaction. Exclusive formation of benzoin products were observed in good yield. Similarly, the dimerization of cyclohexen-1-one to Baylis-Hillman type product, 2-(3-oxocyclohexyl)-2-cyclohexen-1-one was studied.

  11. POLYMER-SUPPORTED LEWIS ACID CATALYSTS. VI. POLYSTYRENE-BONDED STANNIC CHLORIDE CATALYST

    Institute of Scientific and Technical Information of China (English)

    RAN Ruicheng; FU Diankui

    1991-01-01

    A polystyrene-bonded stannic chloride catalyst was synthesized by the method of lithium polystyryl combined with stannic chloride. This catalyst is a polymeric organometallic compound containing 0.25 mmol Sn(IV)/g catalyst. The catalyst showed sufficient stability and catalytic activity in organic reaction such as esterification, acetalation and ketal formation, and it could be reused many times without losing its catalytic activity.

  12. Coupled valence bond theory

    NARCIS (Netherlands)

    Havenith, R.W.A.

    2005-01-01

    In this Letter, the formulation and implementation of a parallel response property code for non-orthogonal, valence bond wave-functions are described. Test calculations on benzene and cyclobutadiene show that the polarisability and magnetisability tensors obtained using valence bond theory are compa

  13. Bonded labour in Pakistan

    OpenAIRE

    Ercelawn, Aly; Nauman, Muhammad

    2001-01-01

    Examines the continuing prevalence of debt bondage in the 1990s despite the introduction of national legislation banning the practice. Makes recommendations to the Government and the international community for actions to be taken to eliminate bonded labour and provide rehabilitation for freed workers. Includes texts of Land Reforms Regulations, 1972, the Sindh Tenancy Act, 1950 and the Bonded Labour System (Abolition) Act, 1992.

  14. The samurai bond market

    OpenAIRE

    Frank Packer; Elizabeth Reynolds

    1997-01-01

    Issuance in the samurai bond market has more than tripled over the past several years. Some observers have attributed this growth to a systematic underestimation of credit risk in the market. A detailed review of credit quality, ratings differences, and initial issue pricing in the samurai bond market, however, turns up little evidence to support this concern.

  15. Money and Nominal Bonds

    OpenAIRE

    Marchesiani, Alessandro; Senesi, Pietro

    2007-01-01

    This paper studies an economy with trading frictions, ex post heterogeneity and nominal bonds in a model à la Lagos and Wright (2005). It is shown that a strictly positive interest rate is a sufficient condition for the allocation with nominal bonds to be welfare improving. This result comes from the protection against the inflation tax.

  16. Hydrogen bonding in polyanilines

    Energy Technology Data Exchange (ETDEWEB)

    Bahceci, S. (Department of Chemistry, Middle East Technical University, Ankara 06531 (Turkey)); Toppare, L. (Department of Chemistry, Middle East Technical University, Ankara 06531 (Turkey)); Yurtsever, E. (Department of Chemistry, Middle East Technical University, Ankara 06531 (Turkey))

    1994-11-29

    Hydrogen bonding between poly(bisphenol A carbonate) (PC) and polyaniline (PAn) is analyzed using semi-empirical quantum methodology. Fully optimized AM1 molecular orbital calculations are reported for various aniline structures (monomer, dimer and trimer), the monomer of the PC and the hydrogen-bonded model of PAn-PC oligomer. ((orig.))

  17. Characterization of a-SiC:H as a window material for p-i-n a-Si solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Tawada, Y.; Hamakawa, Y.; Kondo, M.; Nishimura, K.; Okamoto, H.; Tsuge, K.

    1982-01-01

    Films of a-SiC:H were settled by method of plasma breakdown of a mixture of silane with methane (SM) or silane with ethylene (SET). For optical and optical-electron measurements, films of a-SiC:H were applied to a substrate made of glass or monocrystalline Si. Photoelectrical properties were studied on solar cells with structure glass/Sn0/sub 2//p-a-SiC:H/5-n-aSi:H/Al in which a layer of a-SiC:H of thickness 10 mm was alloyed by B. With increase in the width of the forbidden zone of a-SiC:H from 1.75 to 2.15 eV, current density of short circuiting of the solar cell rises from 10.5 to 12.5 mA/cm/sub 2/, if a-SiC:H was obtained from SM, and roughly from 9 to 10.5 mA/cm/sub 2/ if from SET. The photoelectromotive force changes in this case approximately from 0.8 to 0.9 V. The jump in potential on the boundary of the valent zone in the p-i-heterotransition, where a-SiC:H was obtained from the SET limits the collection of light-generated holes from the i-layer. The film of a-Si-C:H obtained from the SET contains C mainly in the form of C/sup 2/H/sup 5/ groups, while a-SiC:H from CM is an amorphous alloy close to the ideal with small quantity of the CH/sup 3/ groups.

  18. Shape Bonding method

    Science.gov (United States)

    Pontius, James T. (Inventor)

    2010-01-01

    The present invention is directed to a method of bonding at least two surfaces together. The methods step of the present invention include applying a strip of adhesive to a first surface along a predefined outer boundary of a bond area and thereby defining a remaining open area there within. A second surface, or gusset plate, is affixed onto the adhesive before the adhesive cures. The strip of adhesive is allowed to cure and then a second amount of adhesive is applied to cover the remaining open area and substantially fill a void between said first and second surfaces about said bond area. A stencil may be used to precisely apply the strip of adhesive. When the strip cures, it acts as a dam to prevent overflow of the subsequent application of adhesive to undesired areas. The method results in a precise bond area free of undesired shapes and of a preferred profile which eliminate the drawbacks of the prior art bonds.

  19. Water's Hydrogen Bond Strength

    CERN Document Server

    Chaplin, Martin

    2007-01-01

    Water is necessary both for the evolution of life and its continuance. It possesses particular properties that cannot be found in other materials and that are required for life-giving processes. These properties are brought about by the hydrogen bonded environment particularly evident in liquid water. Each liquid water molecule is involved in about four hydrogen bonds with strengths considerably less than covalent bonds but considerably greater than the natural thermal energy. These hydrogen bonds are roughly tetrahedrally arranged such that when strongly formed the local clustering expands, decreasing the density. Such low density structuring naturally occurs at low and supercooled temperatures and gives rise to many physical and chemical properties that evidence the particular uniqueness of liquid water. If aqueous hydrogen bonds were actually somewhat stronger then water would behave similar to a glass, whereas if they were weaker then water would be a gas and only exist as a liquid at sub-zero temperature...

  20. Selective Catalytic Synthesis Using the Combination of Carbon Dioxide and Hydrogen: Catalytic Chess at the Interface of Energy and Chemistry.

    Science.gov (United States)

    Klankermayer, Jürgen; Wesselbaum, Sebastian; Beydoun, Kassem; Leitner, Walter

    2016-06-20

    The present Review highlights the challenges and opportunities when using the combination CO2 /H2 as a C1 synthon in catalytic reactions and processes. The transformations are classified according to the reduction level and the bond-forming processes, covering the value chain from high volume basic chemicals to complex molecules, including biologically active substances. Whereas some of these concepts can facilitate the transition of the energy system by harvesting renewable energy into chemical products, others provide options to reduce the environmental impact of chemical production already in today's petrochemical-based industry. Interdisciplinary fundamental research from chemists and chemical engineers can make important contributions to sustainable development at the interface of the energetic and chemical value chain. The present Review invites the reader to enjoy this exciting area of "catalytic chess" and maybe even to start playing some games in her or his laboratory. PMID:27237963

  1. Silver-Free Palladium-Catalyzed sp(3) and sp(2) C-H Alkynylation Promoted by a 1,2,3-Triazole Amine Directing Group.

    Science.gov (United States)

    Ye, Xiaohan; Xu, Chang; Wojtas, Lukasz; Akhmedov, Novruz G; Chen, Hao; Shi, Xiaodong

    2016-06-17

    Triazole amine was identified as an effective directing group in promoting C-H alkynylation under silver-free conditions. No other external oxidant was required, and the alkynylation products were received in good to excellent yields. X-ray crystallographic analysis confirmed a direct C-H activation intermediate. Other typical directing groups, including pyridine amine (PIP) and 8-aminoquinoline (QA), gave almost no reaction under identical conditions, which highlighted the unique reactivity of the triazole directing group in direct C-H functionalization. PMID:27267908

  2. Carbon–heteroatom bond formation catalysed by organometallic complexes

    OpenAIRE

    Hartwig, John F.

    2008-01-01

    At one time the synthetic chemist’s last resort, reactions catalysed by transition metals are now the preferred method for synthesizing many types of organic molecule. A recent success in this type of catalysis is the discovery of reactions that form bonds between carbon and heteroatoms (such as nitrogen, oxygen, sulphur, silicon and boron) via complexes of transition metals with amides, alkoxides, thiolates, silyl groups or boryl groups. The development of these catalytic processes has been ...

  3. Catalytic reduction of NO by methane using a Pt/C/polybenzimidazole/Pt/C fuel cell

    OpenAIRE

    Petrushina, Irina; Cleemann, Lars Nilausen; Refshauge, Rasmus; Bjerrum, Niels; Bandur, Viktor

    2007-01-01

    The catalytic NO reduction by methane was studied using a (NO,CH4,Ar),Pt|polybenzimidazole(PBI)–H3PO4|Pt,(H2,Ar) fuel cell at 135 and 165°C. It has been found that, without any reducing agent (like CH4), NO can be electrochemically reduced in the (NO, Ar), Pt/C|PBI–H3PO4|Pt/C, (H2,Ar) fuel cell with participation of H+ or electrochemically produced hydrogen. When added, methane partially suppresses the electrochemical reduction of NO. Methane outlet concentration monitoring has shown the CH4 ...

  4. Fundamental studies of the mechanism of catalytic reactions with catalysts effective in the gasification of carbon solids and the oxidative coupling of methane. Quarterly report, April 1, 1994--June 30, 1994

    Energy Technology Data Exchange (ETDEWEB)

    Iglesia, E.; Perry, D.L.; Heinemann, H.

    1994-06-01

    Catalytic gasification work has been completed and no other work is planned in the general area of catalytic gasification of coals and chars has operated without a post-doctoral fellow because of budget limitations during the first two quarters of FY1994. Dr. S. Sundararajan joined the group in April 1994 and will be assigned to the project throughout the remaining of the fiscal year. Results published by Hamakawa, et al. in The Journal of the Electrochemical Society have confirmed the concept of methane coupling via a membrane reactor. These findings confirm our previous conclusion that thinner membranes and increased surface activity for C-H bond activation at low temperatures are required in order to reach commercially attractive rates of reaction. The initial analysis of a theoretical model comparing the membrane and cyclic processes has been completed. The results indicate that perovskite membranes on the order of 50 microns will be needed for the membrane operation to be superior to a cyclic one. Two techniques, laser ablation and spin-coating/sol-gel chemistry are being tried to prepare the thin membranes described above. Studies of the magnetochemical properties of the calcium-nickel-potassium oxide powdered catalysts have been concluded and a manuscript describing the work has been completed. Synchrotron x-ray fluorescence microprobe data for calcium-nickel-potassium films have been analyzed and an abstract of the results has been submitted for presentation at the Fall Meeting of the Materials Research Society. Initial films of strontium-zirconium oxide, using yttria-stabilized zirconia as a buffer layer, have been fabricated using pulsed laser deposition. X-ray diffraction data have been obtained for several of the strontium-zirconium-yttrium oxide films.

  5. Fields, particles and analyticity: recent results or 30 goldberg (ER) variations on B.A.C.H

    International Nuclear Information System (INIS)

    As it is known, Axiomatic Field Theory (A) implies double analyticity of the η-point functions in space-time and energy-momentum Complex Variables (C), with various interconnections by Fourier-Laplace analysis. When the latter is replaced by. Harmonic Analysis (H) on spheres and hyperboloids, a new kind of double analyticity results from (A) (i.e. from locality, spectral condition, temperateness and invariance): complex angular momentum is thereby introduced (a missing chapter in (A)). Exploitation of Asymptotic Completeness via Bethe-Salpeter-type equations (B) leads to new developments of the previous theme on (A, C, H) (complex angular momentum) and of other themes on (A,C) (crossing, Haag-Swieca property etc...). Various aspects of (A) + (B) have been implemented in Constructive Field Theory (composite spectrum, asymptotic properties etc...) by a combination of specific techniques and of model-independent methods

  6. Grain-size effect on the preferred orientation of TiC/α-C:H thin films

    International Nuclear Information System (INIS)

    The grain-size effect on the preferred orientation has been revealed in TiC/α-C:H nanocomposite films grown by magnetron sputtering, in which the grain size of TiC can be adjusted through changing C content in films. The finding is that the preferred orientation of films is significantly affected by the grain size, and the crystallographic orientation changes from face-centered cubic (fcc) TiC(1 1 1) to (2 0 0) as the grain size of nanocrystallite TiC decreases from ∼22.3 to ∼4.7 nm. This size-dependent preferred orientation is explained via thermodynamic calculations, from which the size-dependent Gibbs free energies are found to be a key factor that controls the texture development in thin films if the grain size in films is sufficient small.

  7. Kinetic model of C/H/N/O emissions in laser-induced breakdown spectroscopy of organic compounds

    International Nuclear Information System (INIS)

    A kinetic model to predict the relative intensities of the atomic C/H/N/O emission lines in laser-induced breakdown spectroscopy (LIBS) has been developed for organic compounds. The model includes a comprehensive set of chemical processes involving both neutral and ionic chemistry and physical excitation and de-excitation of atomic levels affecting the neutral, ionic, and excited-state species concentrations. The relative excited-state atom concentrations predicted by this modeling are compared with those derived from the observed LIBS intensities for 355 nm ns laser irradiation of residues of two organic compounds on aluminum substrate. The model reasonably predicts the relative excited-state concentrations, as well as their time profiles. Comparison of measured and computed concentrations has also allowed an estimation of the degree of air entrainment.

  8. 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. PMID:19277084

  9. Surface morphology and grain analysis of successively industrially grown amorphous hydrogenated carbon films (a-C:H) on silicon

    Energy Technology Data Exchange (ETDEWEB)

    Catena, Alberto [Department of Physics, University of Koblenz-Landau, 56070 Koblenz (Germany); McJunkin, Thomas [Department of Physics, The Ohio State University, 43210 Columbus, Ohio (United States); Agnello, Simonpietro; Gelardi, Franco M. [Department of Physics and Chemistry, University of Palermo, 90100 Palermo (Italy); Wehner, Stefan [Department of Physics, University of Koblenz-Landau, 56070 Koblenz (Germany); Fischer, Christian B., E-mail: chrbfischer@uni-koblenz.de [Department of Physics, University of Koblenz-Landau, 56070 Koblenz (Germany)

    2015-08-30

    Graphical abstract: - Highlights: • Two different a-C:H coatings in various thicknesses on Si (1 0 0) have been studied. • For both types no significant difference in surface morphology is detectable. • The grain number with respect to their height appears randomly distributed. • In average no grain higher than 14 nm and larger than 0.05 μm{sup 2} was observed. • A height to area correlation confines all detected grains to a limited region. - Abstract: Silicon (1 0 0) has been gradually covered by amorphous hydrogenated carbon (a-C:H) films via an industrial process. Two types of these diamond-like carbon (DLC) coatings, one more flexible (f-DLC) and one more robust (r-DLC), have been investigated. Both types have been grown by a radio frequency plasma-enhanced chemical vapor deposition (RF-PECVD) technique with acetylene plasma. Surface morphologies have been studied in detail by atomic force microscopy (AFM) and Raman spectroscopy has been used to investigate the DLC structure. Both types appeared to have very similar morphology and sp{sup 2} carbon arrangement. The average height and area for single grains have been analyzed for all depositions. A random distribution of grain heights was found for both types. The individual grain structures between the f- and r-type revealed differences: the shape for the f-DLC grains is steeper than for the r-DLC grains. By correlating the average grain heights to the average grain areas for all depositions a limited region is identified, suggesting a certain regularity during the DLC deposition mechanisms that confines both values. A growth of the sp{sup 2} carbon entities for high r-DLC depositions is revealed and connected to a structural rearrangement of carbon atom hybridizations and hydrogen content in the DLC structure.

  10. Surface morphology and grain analysis of successively industrially grown amorphous hydrogenated carbon films (a-C:H) on silicon

    International Nuclear Information System (INIS)

    Graphical abstract: - Highlights: • Two different a-C:H coatings in various thicknesses on Si (1 0 0) have been studied. • For both types no significant difference in surface morphology is detectable. • The grain number with respect to their height appears randomly distributed. • In average no grain higher than 14 nm and larger than 0.05 μm2 was observed. • A height to area correlation confines all detected grains to a limited region. - Abstract: Silicon (1 0 0) has been gradually covered by amorphous hydrogenated carbon (a-C:H) films via an industrial process. Two types of these diamond-like carbon (DLC) coatings, one more flexible (f-DLC) and one more robust (r-DLC), have been investigated. Both types have been grown by a radio frequency plasma-enhanced chemical vapor deposition (RF-PECVD) technique with acetylene plasma. Surface morphologies have been studied in detail by atomic force microscopy (AFM) and Raman spectroscopy has been used to investigate the DLC structure. Both types appeared to have very similar morphology and sp2 carbon arrangement. The average height and area for single grains have been analyzed for all depositions. A random distribution of grain heights was found for both types. The individual grain structures between the f- and r-type revealed differences: the shape for the f-DLC grains is steeper than for the r-DLC grains. By correlating the average grain heights to the average grain areas for all depositions a limited region is identified, suggesting a certain regularity during the DLC deposition mechanisms that confines both values. A growth of the sp2 carbon entities for high r-DLC depositions is revealed and connected to a structural rearrangement of carbon atom hybridizations and hydrogen content in the DLC structure

  11. Catalytic activity of Au nanoparticles

    DEFF Research Database (Denmark)

    Larsen, Britt Hvolbæk; Janssens, Ton V.W.; Clausen, Bjerne;

    2007-01-01

    Au is usually viewed as an inert metal, but surprisingly it has been found that Au nanoparticles less than 3–5 nm in diameter are catalytically active for several chemical reactions. We discuss the origin of this effect, focusing on the way in which the chemical activity of Au may change with par......Au is usually viewed as an inert metal, but surprisingly it has been found that Au nanoparticles less than 3–5 nm in diameter are catalytically active for several chemical reactions. We discuss the origin of this effect, focusing on the way in which the chemical activity of Au may change...... with particle size. We find that the fraction of low-coordinated Au atoms scales approximately with the catalytic activity, suggesting that atoms on the corners and edges of Au nanoparticles are the active sites. This effect is explained using density functional calculations....

  12. Catalytic distillation water recovery subsystem

    Science.gov (United States)

    Budininkas, P.; Rasouli, F.

    1985-01-01

    An integrated engineering breadboard subsystem for the recovery of potable water from untreated urine based on the vapor phase catalytic ammonia removal was designed, fabricated and tested. Unlike other evaporative methods, this process catalytically oxidizes ammonia and volatile hydrocarbons vaporizing with water to innocuous products; therefore, no pretreatment of urine is required. Since the subsystem is fabricated from commercially available components, its volume, weight and power requirements are not optimized; however, it is suitable for zero-g operation. The testing program consists of parametric tests, one month of daily tests and a continuous test of 168 hours duration. The recovered water is clear, odorless, low in ammonia and organic carbon, and requires only an adjustment of its pH to meet potable water standards. The obtained data indicate that the vapor phase catalytic ammonia removal process, if further developed, would also be competitive with other water recovery systems in weight, volume and power requirements.

  13. Engineering reactors for catalytic reactions

    Indian Academy of Sciences (India)

    Vivek V Ranade

    2014-03-01

    Catalytic reactions are ubiquitous in chemical and allied industries. A homogeneous or heterogeneous catalyst which provides an alternative route of reaction with lower activation energy and better control on selectivity can make substantial impact on process viability and economics. Extensive studies have been conducted to establish sound basis for design and engineering of reactors for practising such catalytic reactions and for realizing improvements in reactor performance. In this article, application of recent (and not so recent) developments in engineering reactors for catalytic reactions is discussed. Some examples where performance enhancement was realized by catalyst design, appropriate choice of reactor, better injection and dispersion strategies and recent advances in process intensification/ multifunctional reactors are discussed to illustrate the approach.

  14. Corporate Bonds in Denmark

    DEFF Research Database (Denmark)

    Tell, Michael

    2015-01-01

    Corporate financing is the choice between capital generated by the corporation and capital from external investors. However, since the financial crisis shook the markets in 2007–2008, financing opportunities through the classical means of financing have decreased. As a result, corporations have...... to think in alternative ways such as issuing corporate bonds. A market for corporate bonds exists in countries such as Norway, Germany, France, the United Kingdom and the United States, while Denmark is still behind in this trend. Some large Danish corporations have instead used foreign corporate bonds...

  15. Transversely Compressed Bonded Joints

    DEFF Research Database (Denmark)

    Hansen, Christian Skodborg; Schmidt, Jacob Wittrup; Stang, Henrik

    2012-01-01

    The load capacity of bonded joints can be increased if transverse pressure is applied at the interface. The transverse pressure is assumed to introduce a Coulomb-friction contribution to the cohesive law for the interface. Response and load capacity for a bonded single-lap joint was derived using...... non-linear fracture mechanics. The results indicated a good correlation between theory and tests. Furthermore, the model is suggested as theoretical base for determining load capacity of bonded anchorages with transverse pressure, in externally reinforced concrete structures....

  16. The Halogen Bond

    Science.gov (United States)

    2016-01-01

    The halogen bond occurs when there is evidence of a net attractive interaction between an electrophilic region associated with a halogen atom in a molecular entity and a nucleophilic region in another, or the same, molecular entity. In this fairly extensive review, after a brief history of the interaction, we will provide the reader with a snapshot of where the research on the halogen bond is now, and, perhaps, where it is going. The specific advantages brought up by a design based on the use of the halogen bond will be demonstrated in quite different fields spanning from material sciences to biomolecular recognition and drug design. PMID:26812185

  17. Enantioselective S - H and C - H insertions with optically active Rh(II) and Cu(II) catalysts. Asymmetric catalysis, 58

    International Nuclear Information System (INIS)

    The substrates for the S - H insertion reaction were azibutanone 2 and thiophenol 3. Methyl 2-diazo-3-oxo-heptane-carboxylate 26 was used as the substrate in an intramolecular C - H insertion. Both reactions were carried out enantioselectively in the presence of optically active rhodium(II) and copper(II) catalysts. For the S - H insertion optical inductions up to 13,8 %ee and for the C - H insertion up to 14 %ee were achieved. (Authors)

  18. Structural basis for the discrepancy of spectral behavior in C-H stretching band between steroids and long chain hydrocarbon compounds

    Institute of Scientific and Technical Information of China (English)

    徐怡庄; 陶靖; 许振华; 翁诗甫; 徐建平; 吴瑾光; 徐端夫; 徐光宪

    1999-01-01

    The discrepancies of the spectral behavior for the C-H stretching band between some long chain hydrocarbon compounds and steroids were investigated. At low temperature, the C-H stretching bands exhibit complex fine structure in steroids but remain simple in long chain hydrocarbon compounds. MM3 molecular mechanics calculation indicates that, for long chain hydrocarbon compounds, the C-H groups vibrate with large scale coupling. There exist a few bands where the C-H groups vibrate in synchronous and inphase mode. Thus the variations of dipole moment for these bands are enhanced and the intensities are obviously stronger than others and cover other band in the spectra. This is just the reason why the C-H stretching bands are simple even at low temperature environment. Nevertheless, for the steroids, the C-H stretching bands vibrate with local coupling mode. The synchronous enhancement effect does not occur, the differences of intensities for various modes are not as large as those in long chain hydrocarbo

  19. Potential of Cat-CVD deposited a-SiC:H as diffusion barrier layer on low-k HSQ films for ULSI

    International Nuclear Information System (INIS)

    Cu diffusion in the spin-on hydrogen silsesquioxane (HSQ) is a major obstacle in the low-k plus Cu technology for future ULSI devices. We have optimized the process conditions for the spin-on HSQ low-k films. Subsequent metallization with Al and Cu shows a higher leakage current for Cu contact. We have employed Cat-CVD to deposit a-SiC:H films of different thickness on HSQ and studied their effect on the leakage current with both Al and Cu electrodes. The films were deposited using silane (SiH4) and acetylene (C2H2) gases. Also, an independent determination of the dielectric constant of the Cat-CVD a-SiC:H layer has been carried out from the C-V measurements on Al/c-Si/a-SiC:H/Al structure. The electrical characteristics of the Al/c-Si/HSQ + a-SiC:H/Cu structures show almost two orders of magnitude lower leakage current compared with Al/c-Si/HSQ/Cu, indicating very good barrier properties of the a-SiC:H material. Moreover, the low dielectric value observed for a-SiC:H compares favorably to other diffusion barrier materials

  20. Effective Binding of Methane Using a Weak Hydrogen Bond.

    Science.gov (United States)

    Henley, Alice; Bound, Michelle; Besley, Elena

    2016-05-26

    The weak hydrogen bond is an important type of noncovalent interaction, which has been shown to contribute to stability and conformation of proteins and large biochemical membranes, stereoselectivity, crystal packing, and effective gas storage in porous materials. In this work, we systematically explore the interaction of methane with a series of functionalized organic molecules specifically selected to exhibit a weak hydrogen bond with methane molecules. To enhance the strength of hydrogen bond interactions, the functional groups include electron-enriched sites to allow sufficient polarization of the C-H bond of methane. The binding between nine functionalized benzene molecules and methane has been studied using the second order Møller-Plesset perturbation theory to reveal that benzenesulfonic acid (C6H5-SO3H) and phenylphosphonic acid (C6H5-PO3H2) have the greatest potential for efficient methane capture through hydrogen bonding interactions. Both acids exhibit efficient binding potential with up to three methane molecules. For additional insight, the atomic charge distribution associated with each binding site is presented. PMID:27148999

  1. Bond dissociation & electronegativity equalization

    OpenAIRE

    Verstraelen, Toon; Ayers, Paul W.; Van Speybroeck, Veronique; Waroquier, Michel

    2012-01-01

    It is well known that the Electrongativity Equalization Mtehod (EEM) fails to describe the charge distribution upon bond dissocation. In this presentation, the bond dissocation is studied with the Atom-Condensed Kohn-Sham DFT approximated to second order (ACKS2). After reviewing the basic equations, a two-fragment system is studied in the dissociation limit. The limiting behavior of the Coulomb interaction (1/r) and the Kohn-Sham matrix elements (exponentially decaying) are plugged into the e...

  2. Anodic bonded graphene

    OpenAIRE

    Balan, Adrian; Kumar, Rakesh; Boukhicha, Mohamed; Beyssac, Olivier; Bouillard, Jean-Claude; Taverna, Dario; Sacks, William; Marangolo, Massimiliano; Lacaze, Emmanuelle; Escoffier, Walter; Poumirol, Jean-Marie; Shukla, Abhay

    2010-01-01

    Abstract We show how to prepare graphene samples on a glass substrate with the anodic bonding method. In this method, a graphite precursor in flake form is bonded to a glass substrate with the help of an electrostatic field and then cleaved off to leave few layer graphene on the substrate. Now that several methods are available for producing graphene, the relevance of our method is in its simplicity and practicality for producing graphene samples of about 100 ?m lateral dimensions. This me...

  3. Handbook of wafer bonding

    CERN Document Server

    Ramm, Peter; Taklo, Maaike M V

    2011-01-01

    Written by an author and editor team from microsystems companies and industry-near research organizations, this handbook and reference presents dependable, first-hand information on bonding technologies.In the first part, researchers from companies and institutions around the world discuss the most reliable and reproducible technologies for the production of bonded wafers. The second part is devoted to current and emerging applications, including microresonators, biosensors and precise measuring devices.

  4. Significantly shorter Fe-S bond in cytochrome P450-I is consistent with greater reactivity relative to chloroperoxidase

    Science.gov (United States)

    Krest, Courtney M.; Silakov, Alexey; Rittle, Jonathan; Yosca, Timothy H.; Onderko, Elizabeth L.; Calixto, Julio C.; Green, Michael T.

    2015-09-01

    Cytochrome P450 (P450) and chloroperoxidase (CPO) are thiolate-ligated haem proteins that catalyse the activation of carbon hydrogen bonds. The principal intermediate in these reactions is a ferryl radical species called compound I. P450 compound I (P450-I) is significantly more reactive than CPO-I, which only cleaves activated C-H bonds. To provide insight into the differing reactivities of these intermediates, we examined CPO-I and P450-I using variable-temperature Mössbauer and X-ray absorption spectroscopies. These measurements indicate that the Fe-S bond is significantly shorter in P450-I than in CPO-I. This difference in Fe-S bond lengths can be understood in terms of variations in the hydrogen-bonding patterns within the ‘cys-pocket’ (a portion of the proximal helix that encircles the thiolate ligand). Weaker hydrogen bonding in P450-I results in a shorter Fe-S bond, which enables greater electron donation from the axial thiolate ligand. This observation may in part explain P450's greater propensity for C-H bond activation.

  5. Catalytic properties of niobium compounds

    International Nuclear Information System (INIS)

    The catalytic activity and selectivity of niobium compounds including oxides, salts, organometallic compounds and others are outlined. The application of these compounds as catalysts to diversified reactions is reported. The nature and action of niobium catalysts are characteristic and sometimes anomalous, suggesting the necessity of basic research and the potential use as catalysts for important processes in the chemical industry. (Author)

  6. Bond Length and Bond Order in One of the Shortest Cr-Cr Bonds

    OpenAIRE

    La Macchia, Giovanni; Aquilante, Francesco; Veryazov, Valera; Roos, Bjorn O.; Gagliardi, Laura

    2008-01-01

    Multiconfigurational quantum chemical calculations on the R-diimines dichromium compound confirm that the Cr-Cr bond, 1.80 A, is among the shortest Cr (I)-Cr (I) bonds. However, the bond between the two Cr atoms is only a quadruple bond rather than a quintuple bond. The reason why the bond is so short has to be attributed to the strain in the NCCN ligand moieties.

  7. Heteropoly acid promoted Cu and Fe catalysts for the selective catalytic reduction of NO with ammonia

    DEFF Research Database (Denmark)

    Putluru, Siva Sankar Reddy; Mossin, Susanne L.; Riisager, Anders; Fehrmann, Rasmus

    2011-01-01

    were studied and compared with the catalytic activity for the selective catalytic reduction (SCR) of NO with ammonia. The SCR activities and acidity values of heteropoly acid promoted catalysts were found to be much higher than unpromoted catalysts. The influence of potassium poisons on the SCR...... activity and acidity was lower for promoted catalysts than for unpromoted catalysts. In the heteropoly acid promoted catalysts the SCR active Cu and Fe metals were protected from potassium poisons by bonding of the potassium to the Brønsted acid centres. Thus heteropoly acid promoted catalysts might be...... suitable for biomass fired power plant SCR applications....

  8. Romanian government bond market

    Directory of Open Access Journals (Sweden)

    Cornelia POP

    2012-12-01

    Full Text Available The present paper aims to present the level of development reached by Romanian government bond market segment, as part of the country financial market. The analysis will be descriptive (the data series available for Romania are short, based on the secondary data offered by the official bodies involved in the process of issuing and trading the Romanian government bonds (Romanian Ministry of Public Finance, Romanian National Bank and Bucharest Stock Exchange, and also on secondary data provided by the Federation of European Stock Exchanges.To enhance the market credibility as a benchmark, a various combination of measures is necessary; among these measures are mentioned: the extension of the yield curve; the issuance calendars in order to improve transparency; increasing the disclosure of information on public debt issuance and statistics; holding regular meetings with dealers, institutional investors and rating agencies; introducing a system of primary dealers; establishing a repurchase (repo market in the government bond market. These measures will be discussed based on the evolution presented inside the paper.The paper conclude with the fact that, until now, the Romanian government bond market did not provide a benchmark for the domestic financial market and that further efforts are needed in order to increase the government bond market transparency and liquidity.

  9. Synthesis of dihydrophenanthridines by a sequence of Ugi-4CR and palladium-catalyzed intramolecular C-H functionalization

    Directory of Open Access Journals (Sweden)

    2008-04-01

    Full Text Available BackgroundSmall polyfunctionalized heterocyclic compounds play important roles in the drug discovery process and in the isolation and structural identification of biological macromolecules. It is expected that ready access to diverse sets of heterocycles can not only help improving the known biological and pharmacokinetic properties of drugs, but also assist the discovery of molecules that exhibit biological effects beyond those associated with previously known macromolecules. By virtue of their inherent convergence, high productivity, their exploratory and complexity-generating power, multicomponent reactions (MCRs are undoubtedly well suited for creating molecular diversity. The combination of MCRs with an efficient post-functionalization reaction has proven to be an efficient strategy to increase the skeleton diversity.ResultsThe Ugi reaction of an o-iodobenzaldehyde (2, an aniline (3, an isocyanide (4, and a carboxylic acid (5 afforded α-acetamido-α-phenylacetamide (6 in good to excellent yields. The palladium-catalyzed intramolecular C-H functionalization of these adducts under ligandless conditions provided the functionalized dihydrophenanthridines (1.ConclusionHighly functionalized dihydrophenanthridines are synthesized in only two steps from readily accessible starting materials in good to excellent overall yields.

  10. Mutremdamide A and koshikamides C-H, peptide inhibitors of HIV-1 entry from different Theonella species.

    Science.gov (United States)

    Plaza, Alberto; Bifulco, Giuseppe; Masullo, Milena; Lloyd, John R; Keffer, Jessica L; Colin, Patrick L; Hooper, John N A; Bell, Lori J; Bewley, Carole A

    2010-07-01

    A new sulfated cyclic depsipeptide, termed mutremdamide A, and six new highly N-methylated peptides, termed koshikamides C-H, were isolated from different deep-water specimens of Theonella swinhoei and Theonella cupola. Their structures were determined using extensive 2D NMR, ESI, or CDESI and QTOF-MS/MS experiments and absolute configurations established by quantum mechanical calculations, advanced Marfey's method, and chiral HPLC. Mutremdamide A displays a rare 2-amino-3-(2-hydroxyphenyl)propanoic acid and a new N(delta)-carbamoyl-beta-sulfated asparagine. Koshikamides C-E are linear undecapeptides, and koshikamides F-H are 17-residue depsipeptides containing a 10-residue macrolactone. Koshikamides F and G differ from B and H in part by the presence of the conjugated unit 2-(3-amino-5-oxopyrrolidin-2-ylidene)propanoic acid. Cyclic koshikamides F and H inhibited HIV-1 entry at low micromolar concentrations while their linear counterparts were inactive. The Theonella collections studied here are distinguished by co-occurrence of mutremdamide A, koshikamides, and theonellamides, the combination of which appears to define a new Theonella chemotype that can be found in deeper waters. PMID:20402515

  11. Anti-thrombotic activity and chemical characterization of steroidal saponins from Dioscorea zingiberensis C.H. Wright.

    Science.gov (United States)

    Li, Hua; Huang, Wen; Wen, Yanqing; Gong, Guohua; Zhao, Qingbing; Yu, Gang

    2010-12-01

    Steroidal saponins have long attracted scientific attention, due to their structural diversity and significant biological activities. Total steroidal saponins (TSS) extracted from the rhizomes of Dioscorea zingiberensis C.H. Wright (DZW) constitute an effective treatment for cardiovascular disease. However, the active constituents contained in DZW rhizomes and their pharmacological properties are not fully understood. The aim of this work is to determine and quantify the active constituents in DZW rhizomes using fingerprint technique, and evaluate its anti-thrombotic activity using inferior vena cava ligation thrombosis rat model and pulmonary thrombosis mice model after being gavaged with TSS for 1 or 2weeks. In the study, a chemical fingerprint method was firstly established and validated to quantify and standardize TSS from DZW rhizomes including parvifloside, protodeltonin, protodioscin, protogracillin, zingiberensis saponin, deltonin, dioscin and trillin. TSS extracted from DZW rhizomes were showed to have the inhibitions on platelet aggregation (PAG) and thrombosis, and prolong activated partial thromboplastin time (APTT), thrombin time (TT), and prothrombin time (PT) in a dose-dependent manner in rats. TSS also prolonged the bleeding time and clotting time in a dose-dependent manner in mice. The results indicate that TSS could inhibit thrombosis by both improving the anticoagulation activity and inhibiting PAG action, suggesting that TSS from DZW rhizomes have the potential to reduce the risk of cardiovascular diseases by anti-thrombotic action. PMID:20659537

  12. A novel β-glucosidase from Aspergillus fumigates releases diosgenin from spirostanosides of Dioscorea zingiberensis C. H. Wright (DZW).

    Science.gov (United States)

    Lei, Jing; Niu, Hai; Li, Tianhong; Huang, Wen

    2012-03-01

    A β-glucosidase effectively releasing diosgenin from spirostanosides of Dioscorea zingiberensis C. H. Wright (DZW), named AfG, was purified from a strain of Aspergillus fumigates. The molecular weight of AfG was 113 kDa. Analysis of protein fragments by ESI-Q-TOF indicated that AfG was a β-glucosidase. The circular dichroism spectrum suggested that the main secondary structure of AfG in Milli-Q water was α-helixes. Atomic force microscopy revealed that it was a globular protein. AfG maintained high activity from pH 3.6 to 5.0 and from 50 to 90°C. With the strong heat stability, AfG retained 55% of its original activity at 65°C for 120 h. AfG utilized muti-3-O-glycosides of various steroidal saponins from DZW as substrate, such as trillin, diosgenin diglucoside, dioscin, deltonin and gracillin, to yield diosgenin, suggesting the possibility of producing diosgenin from total saponins of DZW using a single enzyme. PMID:22805852

  13. Effect of Ion Irradiation on the Structural Properties and Hardness of a-C:H:Si:O:F Films

    Science.gov (United States)

    Rangel, Elidiane C.; da Cruz, Nilson C.; Rangel, Rita C. C.; Landers, Richard; Durrant, Steven F.

    2015-03-01

    Amorphous carbon-based thin films, a-C:H:Si:O:F, were obtained by plasma immersion ion implantation and deposition (PIIID) from mixtures of hexamethyldisiloxane, sulfur hexafluoride and argon. For PIIID the sample holder was biased with negative 25 kV pulses at 60 Hz. The main system parameter was the proportion of SF6 in the reactor feed, RSF. To allow comparison to growth without intentional ion implantation, some films were also grown by plasma enhanced chemical vapor deposition (PECVD). The objectives were to investigate the effects of fluorine incorporation and ion implantation on the film's chemical structure, and principally on the surface contact angle, hardness and friction coefficient. Infrared and X-ray photo-electron spectroscopic analyses revealed that the films are essentially amorphous and polymer-like, and that fluorine is incorporated for any non-zero value of RSF. Choice of RSF influences film composition and structure but ion implantation also plays a role. Depending on RSF, hydrophilic or hydrophobic films may be produced. Ion implantation is beneficial while fluorine incorporation is detrimental to hardness. For ion implanted films the friction coefficient falls about one third as RSF is increased from 0 to 60%. Films prepared by PIIID without fluorine incorporation present fairly low friction coefficients and hardnesses greater than those of conventional polymers.

  14. TEXT tf coil bonding system

    International Nuclear Information System (INIS)

    An extensive bond test program was conducted prior to manufacturing and bonding the toroidal field (TF) coils for the Texas Experimental Tokamak (TEXT). The bonding materials consisted of fiberglass cloth with pre-impregnated, 'B' staged Hexcel F-159 resin. Approximately 100 double lap bond samples were constructed to test quality, strength, and repeatability of the bonds. The variables investigated included surface machining methods, surface preparations, bond sample size (planform area), bonding pressure, bonding temperature, and the number of laminations bonded simultaneously. Double lap shear tests conducted at room temperature resulted in ultimate shear strengths for all variables in the range of 3000 to 7000 psi with an average value of 5650 psi. Fatigue tests were also conducted to demonstrate bond integrity over the anticipated cycle lifetime of the TEXT machine (10/sup 6/ cycles) under simulated worst case conditions. 2 refs

  15. Infrared and Raman Spectroscopy from Ab Initio Molecular Dynamics and Static Normal Mode Analysis: The C-H Region of DMSO as a Case Study

    Energy Technology Data Exchange (ETDEWEB)

    Fischer, Sean A.; Ueltschi, Tyler W.; El-Khoury, Patrick Z.; Mifflin, Amanda L.; Hess, Wayne P.; Wang, Hongfei; Cramer, Christopher J.; Govind, Niranjan

    2016-03-03

    Carbon-hydrogen (C-H) vibration modes serve as key probes in the chemical iden- tication of hydrocarbons and in vibrational sum-frequency generation (SFG) spec- *troscopy of hydrocarbons at the liquid/gas interface. Their assignments pose a chal- lenge from a theoretical viewpoint. In this work, we present a detailed study of the C-H stretching region of dimethyl sulfoxide (DMSO) using a new Gaussian basis set- based ab initio molecular dynamics (AIMD) module that we have implemented in the NWChem computational chemistry program. By combining AIMD simulations and static normal mode analysis, we interpret experimental infrared and Raman spectra and explore the role of anharmonic effects in this system. Our anharmonic normal mode analysis of the in-phase and out-of-phase symmetric C-H stretching modes chal- lenges the previous experimental assignment of the shoulder in the symmetric C-H stretching peak as an overtone or Fermi resonance. In addition, our AIMD simulations also show signicant broadening of the in-phase symmetric C-H stretching resonance, which suggests that the experimentally observed shoulder is due to thermal broadening of the symmetric stretching resonance.

  16. Isolation and Characterization of Well-Defined Silica-Supported Azametallacyclopentane: A Key Intermediate in Catalytic Hydroaminoalkylation Reactions

    KAUST Repository

    Hamzaoui, Bilel

    2015-09-25

    Intermolecular catalytic hydroaminoalkylation of unactivated alkene occurs with silica-supported azazirconacyclopropane [[TRIPLE BOND]Si[BOND]O[BOND]Zr(HNMe2)(η2-NMeCH2)(NMe2)]. Mechanistic studies were conducted using surface organometallic chemistry (SOMC) concepts to identify the key surface intermediates. The azametallacyclopentene intermediate {[TRIPLE BOND]Si[BOND]O[BOND]Zr(HNMe2)[η2-NMeCH2CH(Me)CH2](NMe2)} was isolated after treating with 1-propylene and characterized by FT-IR spectroscopy, elemental analysis, 1H 13C HETCOR, DARR SS-NMR and DQ TQ SS-NMR. The regeneration of the catalyst was conducted by dimethylamine protonolysis to yield the pure amine.

  17. Insulation bonding test system

    Science.gov (United States)

    Beggs, J. M.; Johnston, G. D.; Coleman, A. D.; Portwood, J. N.; Saunders, J. M.; Redmon, J. W.; Porter, A. C. (Inventor)

    1984-01-01

    A method and a system for testing the bonding of foam insulation attached to metal is described. The system involves the use of an impacter which has a calibrated load cell mounted on a plunger and a hammer head mounted on the end of the plunger. When the impacter strikes the insulation at a point to be tested, the load cell measures the force of the impact and the precise time interval during which the hammer head is in contact with the insulation. This information is transmitted as an electrical signal to a load cell amplifier where the signal is conditioned and then transmitted to a fast Fourier transform (FFT) analyzer. The FFT analyzer produces energy spectral density curves which are displayed on a video screen. The termination frequency of the energy spectral density curve may be compared with a predetermined empirical scale to determine whether a igh quality bond, good bond, or debond is present at the point of impact.

  18. The Illiquidity of Corporate Bonds

    OpenAIRE

    Bao, Jack; Pan, Jun; Wang, Jiang

    2011-01-01

    This paper examines the illiquidity of corporate bonds and its asset-pricing implications. Using transactions data from 2003 to 2009, we show that the illiquidity in corporate bonds is substantial, significantly greater than what can be explained by bid–ask spreads. We establish a strong link between bond illiquidity and bond prices. In aggregate, changes in market-level illiquidity explain a substantial part of the time variation in yield spreads of high-rated (AAA through A) bonds, overshad...

  19. Anodic bonded graphene

    Energy Technology Data Exchange (ETDEWEB)

    Balan, Adrian; Kumar, Rakesh; Boukhicha, Mohamed; Beyssac, Olivier; Bouillard, Jean-Claude; Taverna, Dario; Sacks, William; Shukla, Abhay [Universite Pierre et Marie Curie-Paris 6, CNRS-UMR7590, Institut de Mineralogie et de Physique des Milieux Condenses, 140 rue de Lourmel, Paris, F-75015 France (France); Marangolo, Massimiliano; Lacaze, Emanuelle; Gohler, Roger [Universite Pierre et Marie Curie-Paris 6, CNRS-UMR7588, Institut des Nanosciences de Paris, 140 rue de Lourmel, Paris, F-75015 France (France); Escoffier, Walter; Poumirol, Jean-Marie, E-mail: abhay.shukla@upmc.f [Laboratoire National des Champs Magnetiques Intenses, INSA UPS CNRS, UPR 3228, Universite de Toulouse, 143 avenue de Rangueil, 31400 Toulouse (France)

    2010-09-22

    We show how to prepare graphene samples on a glass substrate with the anodic bonding method. In this method, a graphite precursor in flake form is bonded to a glass substrate with the help of an electrostatic field and then cleaved off to leave few layer graphene on the substrate. Now that several methods are available for producing graphene, the relevance of our method is in its simplicity and practicality for producing graphene samples of about 100 {mu}m lateral dimensions. This method is also extensible to other layered materials. We discuss some detailed aspects of the fabrication and results from Raman spectroscopy, local probe microscopy and transport measurements on these samples.

  20. The Trouble With Bonds

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    @@ In early June,global financial markets gyrated downwards in the wake of central banks'tough language on inflation.At one point bond prices reflected expectations of four rate hikes by the US Federal Reserve (Fed) in the next 12 months.As a result,the dollar firmed,oil prices stabilized,and yield curves flattened around the world.If all these inflation-fighting measures are real,the situation bodes well for bonds.But,I think otherwise.

  1. Concurrent Formation of Carbon-Carbon Bonds and Functionalized Graphene by Oxidative Carbon-Hydrogen Coupling Reaction.

    Science.gov (United States)

    Morioku, Kumika; Morimoto, Naoki; Takeuchi, Yasuo; Nishina, Yuta

    2016-01-01

    Oxidative C-H coupling reactions were conducted using graphene oxide (GO) as an oxidant. GO showed high selectivity compared with commonly used oxidants such as (diacetoxyiodo) benzene and 2,3-dichloro-5,6-dicyano-p-benzoquinone. A mechanistic study revealed that radical species contributed to the reaction. After the oxidative coupling reaction, GO was reduced to form a material that shows electron conductivity and high specific capacitance. Therefore, this system could concurrently achieve two important reactions: C-C bond formation via C-H transformation and production of functionalized graphene. PMID:27181191

  2. Catalytic Fast Pyrolysis: A Review

    Directory of Open Access Journals (Sweden)

    Theodore Dickerson

    2013-01-01

    Full Text Available Catalytic pyrolysis is a promising thermochemical conversion route for lignocellulosic biomass that produces chemicals and fuels compatible with current, petrochemical infrastructure. Catalytic modifications to pyrolysis bio-oils are geared towards the elimination and substitution of oxygen and oxygen-containing functionalities in addition to increasing the hydrogen to carbon ratio of the final products. Recent progress has focused on both hydrodeoxygenation and hydrogenation of bio-oil using a variety of metal catalysts and the production of aromatics from bio-oil using cracking zeolites. Research is currently focused on developing multi-functional catalysts used in situ that benefit from the advantages of both hydrodeoxygenation and zeolite cracking. Development of robust, highly selective catalysts will help achieve the goal of producing drop-in fuels and petrochemical commodities from wood and other lignocellulosic biomass streams. The current paper will examine these developments by means of a review of existing literature.

  3. Bond orientation properties in lipid molecules of membranes: molecular dynamics simulations

    International Nuclear Information System (INIS)

    Atomistic molecular dynamics simulations have been carried out for 16 different fully hydrated phosphatidylcholine lipid bilayers, having 16 or 18 carbon atoms in fully saturated sn − 1 chain and from 18 to 22 carbon atoms in sn − 2 chain with different degree of unsaturation, with the purpose to investigate the effect of unsaturation on physical properties of lipid bilayers. Special attention has been paid to profiles of C-C and C-H bond order parameters of lipid molecules and the orientational fluctuations of these bond vectors. It was shown that the study of anisotropy degree of bond orientations probability distributions allows distinguishing extended regions with different types of angular fluctuations of bonds in a membrane formed by lipid molecules with unsaturated chains.

  4. Combined catalytic converter and afterburner

    Energy Technology Data Exchange (ETDEWEB)

    Ma, T.T.-H.

    1994-11-30

    This patent describes the combined use of a catalytic converter and afterburner. An afterburner chamber and a catalyst matrix are disposed in series within a casing. A combustible premixed charge is ignited in the afterburner chamber before it enters the catalyst matrix. This invention overcomes the problem encountered in previous designs of some of the premixed charge passing unreacted through the device unless a very long afterburner chamber is used. (UK)

  5. Investigations for designing catalytic recombiners

    International Nuclear Information System (INIS)

    In case of a severe accident in pressurised water reactors (PWR) a high amount of hydrogen up to about 20,000 m3 might be generated and released into the containments. The mixture consisting of hydrogen and oxygen may either burn or detonate, if ignited. In case of detonation the generated shock wave may endanger the components of the plant or the plant itself. Consequently, effective removal of hydrogen is required. The fact that hydrogen and oxygen react exo-thermally on catalytically acting surfaces already at low temperatures generating steam and heat is made use of in catalytic recombiners. They consist of substrates coated with catalyst (mainly platinum or palladium) which are arranged inside a casing. Being passively acting measures, recombiners do not need any additional energy supply. Experimental investigations on catalytic hydrogen recombination are conducted at FZJ (Forschungszentrum Juelich) using three test facilities. The results yield insight in the development potential of contemporary recombiner systems as well as of innovative systems. Detailed investigations on a recombiner section show strong temperature gradients over the surface of a catalytically coated sample. Dependent on the flow velocity, ignition temperature may be reached at the leading edge already at an inlet hydrogen concentration of about 5 vol.-%. The thermal strain of the substrate leads to considerable detachment of catalyst particles probably causing unintended ignition of the flammable mixture. Temperature peaks can be prevented effectively by leaving the first part of the plate uncoated. In order to avoid overheating of the catalyst elements of a recombiner even at high hydrogen concentrations a modular system of porous substrates is proposed. The metallic substrates are coated with platinum at low catalyst densities thus limiting the activity of the single specimen. A modular arrangement of these elements provides high recombination rates over a large hydrogen concentration

  6. Transition metal and rare earth quad-doped photovoltaic phosphate glasses toward raising a-SiC:H solar cell performance

    Science.gov (United States)

    Song, P.; Zhang, C. M.; Zhu, P. F.

    2016-01-01

    Efficiency enhancement of a hydrogenated amorphous-silicon carbide (a-SiC:H) solar cell using downshifting and upconversion of photovoltaic (PV) glasses doped with transition metal (TM) ions and rare earth (RE) ions are investigated. P2O5-Li2O-Al2O3-Sb2O3-MnO-Yb2O3-Er2O3 glass doped with Sb3+-Mn2+-Yb3+-Er3+ ions is prepared and the PV glass is placed on an a-SiC:H solar cell. The performance of the cell in combination with the PV glass is simulated and measured, and the results show that the theoretical and experimental efficiencies are both enhanced compared to the bare one. The potential of TM-RE quad-doped glasses for improving the efficiency of a-SiC:H PV modules are explored.

  7. Transition metal and rare earth quad-doped photovoltaic phosphate glasses toward raising a-SiC:H solar cell performance

    International Nuclear Information System (INIS)

    Efficiency enhancement of a hydrogenated amorphous-silicon carbide (a-SiC:H) solar cell using downshifting and upconversion of photovoltaic (PV) glasses doped with transition metal (TM) ions and rare earth (RE) ions are investigated. P2O5-Li2O-Al2O3-Sb2O3-MnO-Yb2O3-Er2O3 glass doped with Sb3+-Mn2+-Yb3+-Er3+ ions is prepared and the PV glass is placed on an a-SiC:H solar cell. The performance of the cell in combination with the PV glass is simulated and measured, and the results show that the theoretical and experimental efficiencies are both enhanced compared to the bare one. The potential of TM-RE quad-doped glasses for improving the efficiency of a-SiC:H PV modules are explored. (paper)

  8. Flax Fiber - Interfacial Bonding

    Science.gov (United States)

    Measured flax fiber physical and chemical properties potentially impact bonding and thus stress transfer between the matrix and fiber within composites. These first attempts at correlating flax fiber quality and biofiber composites contain the initial steps towards identifying key flax fiber charac...

  9. Bonds Between Atoms.

    Science.gov (United States)

    Holden, Alan

    The field of inquiry into how atoms are bonded together to form molecules and solids crosses the borderlines between physics and chemistry encompassing methods characteristic of both sciences. At one extreme, the inquiry is pursued with care and rigor into the simplest cases; at the other extreme, suggestions derived from the more careful inquiry…

  10. Thread bonds in molecules

    CERN Document Server

    Ivlev, B

    2015-01-01

    Unusual chemical bonds are proposed. Each bond is almost covalent but is characterized by the thread of a small radius $\\sim 0.6\\times 10^{-11}$cm, between two nuclei in a molecule. The main electron density is concentrated outside the thread as in a covalent bond. The thread is formed by the electron wave function which has a tendency to be singular on it. The singularity along the thread is cut off by electron "vibrations" due to the interaction with zero point electromagnetic oscillations. The electron energy has its typical value of (1-10)eV. Due to the small tread radius the uncertainty of the electron momentum inside the thread is large resulting in a large electron kinetic energy $\\sim 1 MeV$. This energy is compensated by formation of a potential well due to the reduction of the energy of electromagnetic zero point oscillations. This is similar to formation of a negative van der Waals potential. Thread bonds are stable and cannot be created or destructed in chemical or optical processes.

  11. Theoretical investigation of efficiency of a p-a-SiC:H/i-a-Si:H/n-{mu}c-Si solar cell

    Energy Technology Data Exchange (ETDEWEB)

    Deng Qingwen; Wang Xiaoliang; Xiao Hongling; Ma Zeyu; Zhang Xiaobin; Hou Qifeng; Li Jinmin [Materials Science Center, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083 (China); Wang Zhanguo, E-mail: daven@semi.ac.c [Key Laboratory of Semiconductor Materials Science, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083 (China)

    2010-10-15

    A solar cell with a novel structure is investigated by means of the analysis of microelectronic and photonic structure (AMPS). The power conversion efficiency is investigated with the variations in interface recombination velocity, thicknesses of p-type layer, intrinsic layer, n-type layer, and doping density. Results show that it is available and preferable in theory to employ a-SiC:H as a window layer in p-a-SiC:H/i-a-Si:H/n-{mu}c-Si solar cells, and provide a new approach to improving the power conversion efficiency of amorphous silicon solar cells. (semiconductor materials)

  12. Additional Value of CH4 Measurement in a Combined 13C/H2 Lactose Malabsorption Breath Test: A Retrospective Analysis

    OpenAIRE

    Els Houben; Vicky De Preter; Jaak Billen; Marc Van Ranst; Kristin Verbeke

    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 brea...

  13. cis-Dichloroplatinum(II) complexes tethered to dibenzo[c,h][1,6]naphthyridin-6-ones: synthesis and cytotoxicity in human cancer cell lines in vitro.

    Science.gov (United States)

    Desbois, Nicolas; Pertuit, David; Moretto, Johnny; Cachia, Claire; Chauffert, Bruno; Bouyer, Florence

    2013-11-01

    A novel family of cisplatin-type complexes tethered to dibenzo[c,h][1,6]naphthyridin-6-one topoisomerase inhibitor via a polymethylene chain and their nonplatinated counterparts were prepared. Their potential cytotoxicity was assessed in three human colorectal cancer cell lines HCT 116, SW480 and HT-29 and compared to the reference molecules cisplatin and oxaliplatin. Platinated compounds were poorly active whilst nonplatinated dibenzo[c,h][1,6]naphthyridin-6-one moieties exhibited higher cytotoxic properties than cisplatin and oxaliplatin whatever the length of the polymethylene chain; molecules containing the tri- and hexamethylene chain length were the most cytotoxic. PMID:24095763

  14. Results of the independent radiological verification survey at the former C.H. Schnoor and Company Site, 644 Garfield Street, Springdale, Pennsylvania (CPV001)

    Energy Technology Data Exchange (ETDEWEB)

    Murray, M.E.; Brown, K.S.; Foley, R.D. [and others

    1995-09-01

    At the request of the U.S. Department of Energy (DOE), a team from Oak Ridge National Laboratory (ORNL) conducted an independent radiological verification survey at the former C. H. Schnoor and Company Site in Springdale, Pennsylvania. The survey was performed from August to October of 1994. The purpose of the survey was to verify that the site was remediated to levels below DOE guidelines from FUSRAP sites. Results of the independent radiological verification survey at the former C. H. Schnoor and Company Site confirm that the residual uranium contamination at the site is below DOE FUSRAP guidelines for unrestricted use.

  15. Interface modification effect between p-type a-SiC:H and ZnO:Al in p-i-n amorphous silicon solar cells

    OpenAIRE

    Baek, Seungsin; Lee, Jeong Chul; Lee, Youn-Jung; Iftiquar, Sk Md; Kim, Youngkuk; Park, Jinjoo; Yi, Junsin

    2012-01-01

    Aluminum-doped zinc oxide (ZnO:Al) [AZO] is a good candidate to be used as a transparent conducting oxide [TCO]. For solar cells having a hydrogenated amorphous silicon carbide [a-SiC:H] or hydrogenated amorphous silicon [a-Si:H] window layer, the use of the AZO as TCO results in a deterioration of fill factor [FF], so fluorine-doped tin oxide (Sn02:F) [FTO] is usually preferred as a TCO. In this study, interface engineering is carried out at the AZO and p-type a-SiC:H interface to obtain a b...

  16. Pd-Catalyzed C-H Alkylation of Arenes Using PyrDipSi, a Transformable and Removable Silicon-Tethered Directing Group.

    Science.gov (United States)

    Sarkar, Dhruba; Gevorgyan, Vladimir

    2016-08-01

    An efficient Pd-catalyzed ortho-C-H alkylation reaction of arenes using a transformable and removable Si-tethered pyridyldiisopropylsilyl (PyrDipSi) directing group has been developed. In addition, the PyrDipSi directing group allows for an efficient sequential double-fold C-H alkylation/oxygenation of arenes to produce meta-alkylated phenols. This directing group can easily be removed or converted into valuable functionalities, such as aryl, iodo, boronic ester, or phenol. PMID:27272930

  17. Enzyme:substrate hydrogen bond shortening during the acylation phase of serine protease catalysis.

    Science.gov (United States)

    Fodor, Krisztián; Harmat, Veronika; Neutze, Richard; Szilágyi, László; Gráf, László; Katona, Gergely

    2006-02-21

    Atomic resolution (bonds between the enzyme and the substrate changed during catalysis. The well-conserved hydrogen bonds of antiparallel beta-sheet between the enzyme and the substrate become significantly shorter in the transition from a Michaelis complex analogue (Pontastacus leptodactylus (narrow-fingered crayfish) trypsin (CFT) in complex with Schistocerca gregaria (desert locust) trypsin inhibitor (SGTI) at 1.2 A resolution) to an acyl-enzyme intermediate (N-acetyl-Asn-Pro-Ile acyl-enzyme intermediate of porcine pancreatic elastase at 0.95 A resolution) presumably synchronously with the nucleophilic attack on the carbonyl carbon atom of the scissile peptide bond. This is interpreted as an active mechanism that utilizes the energy released from the stronger hydrogen bonds to overcome the energetic barrier of the nucleophilic attack by the hydroxyl group of the catalytic serine. In the CFT:SGTI complex this hydrogen bond shortening may be hindered by the 27I-32I disulfide bridge and Asn-15I of SGTI. The position of the catalytic histidine changes slightly as it adapts to the different nucleophilic attacker during the transition from the Michaelis complex to the acyl-enzyme state, and simultaneously its interaction with Asp-102 and Ser-214 becomes stronger. The oxyanion hole hydrogen bonds provide additional stabilization for acyl-ester bond in the acyl-enzyme than for scissile peptide bond of the Michaelis complex. Significant deviation from planarity is not observed in the reactive bonds of either the Michaelis complex or the acyl-enzyme. In the Michaelis complex the electron distribution of the carbonyl bond is distorted toward the oxygen atom compared to other peptide bonds in the structure, which indicates the polarization effect of the oxyanion hole. PMID:16475800

  18. Convertible bond valuation focusing on Chinese convertible bond market

    OpenAIRE

    Yang, Ke

    2010-01-01

    This paper mainly discusses the methods of valuation of convertible bonds in Chinese market. Different from common convertible bonds in European market, considering the complicate features of Chinese convertible bond, this paper represents specific pricing approaches for pricing convertible bonds with different provisions along with the increment of complexity of these provisions. More specifically, this paper represents the decomposing method and binomial tree method for pricing both of Non-...

  19. Synthesis and properties of epoxydized cooligomers obtained from petroleum resins synthesized by heterogeneous catalytic oligomerization

    OpenAIRE

    Voronchak, Taras; Nykulyshyn, Irena; Pikh, Zorian; Rypka, Anna

    2012-01-01

    Synthesis of cooligomers with epoxy groups was studied. They were synthesized by epoxidation of unsaturated petroleum resins obtained by heterogeneous catalytic oligomerization of liquid pyrolysis products С9 fraction. The degree of unsaturated bonds conversion and the selectivity of epoxidation process were calculated. The properties of epoxydized cooligomers were determined and analyzed. The structurization of synthesized products in the composition of composites with epoxy resin ED-20 ...

  20. DuraFoil{sup TM} ICR-a new material for catalytic converter substrates

    Energy Technology Data Exchange (ETDEWEB)

    Sukonnik, I.M.; Chang, S.; Jha, B. [Texas Instruments, Inc., Attleboro, MA (United States)

    1997-12-31

    A new type of FeCrAl material for catalytic converter substrate applications, DuraFoil{sup TM} ICR, has been developed by solid state bonding of strip layers of steel and aluminum. Such clad material is further rolled to intermediate gauge and then subjected to a thermal in situ reaction to form a solid solution material. Such monolithic material is subsequently thermomechanically processed to foil gauges. The combination of roll bonding followed by thermo-mechanical processing to produce FeCrAl foil for metallic catalytic converter substrate offers many metallurgical and economic advantages over conventional ingot metallurgy practice. The fact that thermal diffusion was performed at the intermediate gauge prior to reaching the final foil thickness gives material properties for use in the wider design range of catalytic converters. In its simplest form, the requirements for a catalytic converter substrate (foil material) are dictated by four major factors: oxidation resistance; shape stability; formability (applicable ductility); and compatibility with typical substrate processing technologies such as brazing and washcoating. To this end, the microstructures, mechanical properties, chemical homogeneity, surface chemistry and morphology of two DuraFoil{sup TM} new grades foil materials, i.e., ICR-H (hard) and ICR-F (soft), were characterized. This study has shown those superior properties, desirable formability can be achieved from diffusion-made material. (orig.)

  1. Tunable Molecular MoS2 Edge-Site Mimics for Catalytic Hydrogen Production.

    Science.gov (United States)

    Garrett, Benjamin R; Polen, Shane M; Click, Kevin A; He, Mingfu; Huang, Zhongjie; Hadad, Christopher M; Wu, Yiying

    2016-04-18

    Molybdenum sulfides represent state-of-the-art, non-platinum electrocatalysts for the hydrogen evolution reaction (HER). According to the Sabatier principle, the hydrogen binding strength to the edge active sites should be neither too strong nor too weak. Therefore, it is of interest to develop a molecular motif that mimics the catalytic sites structurally and possesses tunable electronic properties that influence the hydrogen binding strength. Furthermore, molecular mimics will be important for providing mechanistic insight toward the HER with molybdenum sulfide catalysts. In this work, a modular method to tune the catalytic properties of the S-S bond in MoO(S2)2L2 complexes is described. We studied the homogeneous electrocatalytic hydrogen production performance metrics of three catalysts with different bipyridine substitutions. By varying the electron-donating abilities, we present the first demonstration of using the ligand to tune the catalytic properties of the S-S bond in molecular MoS2 edge-site mimics. This work can shed light on the relationship between the structure and electrocatalytic activity of molecular MoS2 catalysts and thus is of broad importance from catalytic hydrogen production to biological enzyme functions. PMID:27022836

  2. Quantum Mechanical Study on the Blue-Shifting Hydrogen-Bond between 3-Aminophenol and CHX3 (X F, Cl)

    International Nuclear Information System (INIS)

    Intermolecular bonding between 3-aminophenol and two halomethanes, namely fluoroform and chloroform, was quantum mechanically investigated. Several low-energy structures are found, and all geometries within 1 kcal/mol show π-hydrogen bonds between the aromatic ring and the hydrogen atom of the halomethane. The C H stretching frequency of halomethane involved in the π-hydrogen bond is blue-shifted, and the amount of blue shift is the largest with the most stable isomer and decreases with decreasing stability. Binding energy, infrared intensity, and dipole moment as a function of relative stability are also reported. This study forms another example of a blue-shifting hydrogen bond, or an anti-hydrogen bond

  3. Iridium-catalysed ortho-H/D and -H/T exchange under basic conditions: C-H activation of unprotected tetrazoles.

    Science.gov (United States)

    Kerr, William J; Lindsay, David M; Reid, Marc; Atzrodt, Jens; Derdau, Volker; Rojahn, Patrick; Weck, Remo

    2016-05-10

    The first examples of selective ortho-directed C-H activation with unprotected 2-aryltetrazoles are described. A new base-assisted protocol for iridium(i) hydrogen isotope exchange catalysis allows access to ortho-deuterated and tritiated tetrazoles, including the tetrazole-containing pharmaceutical, Valsartan. Preliminary mechanistic studies are also presented. PMID:27115235

  4. Follow-up of radiopharmaceuticals out of globally harmonized system (G.H.S.) at the C.H.U. of Grenoble

    International Nuclear Information System (INIS)

    The improvement and the secure of the radiopharmaceutical circuit in the service of nuclear medicine of the Grenoble C.H.U. are a permanent concern and a true team work between the doctors and the pharmacists. The implementation of cards allowed to optimize the radiopharmaceuticals management by avoiding expenses in relation with the non given drugs. (N.C.)

  5. 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

  6. Additional Value of CH4 Measurement in a Combined 13C/H2 Lactose Malabsorption Breath Test: A Retrospective Analysis

    Directory of Open Access Journals (Sweden)

    Els Houben

    2015-09-01

    Full Text Available 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.

  7. 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.)

  8. Rhodium-Catalyzed Highly Regioselective C-H Arylation of Imidazo[1,2-a]pyridines with Aryl Halides and Triflates

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Yi; He, Lin [Guandong Pharmaceutical Univ., Zhongshan (China); Yin, Guoqiang; Wu, Guojie; Cui, Yingde [Zhongkai Univ. of Agriculture and Engineering, Guangzhou (China)

    2013-08-15

    A convenient Rh-catalyzed C-H arylation of imidazo[1,2-a]pyridines with a variety of aryl halides or triflates has been reported. This process afforded a range of biaryl compounds in excellent yields and showed high activity and broad scope.

  9. Interface modification effect between p-type a-SiC:H and ZnO:Al in p-i-n amorphous silicon solar cells.

    Science.gov (United States)

    Baek, Seungsin; Lee, Jeong Chul; Lee, Youn-Jung; Iftiquar, Sk Md; Kim, Youngkuk; Park, Jinjoo; Yi, Junsin

    2012-01-01

    Aluminum-doped zinc oxide (ZnO:Al) [AZO] is a good candidate to be used as a transparent conducting oxide [TCO]. For solar cells having a hydrogenated amorphous silicon carbide [a-SiC:H] or hydrogenated amorphous silicon [a-Si:H] window layer, the use of the AZO as TCO results in a deterioration of fill factor [FF], so fluorine-doped tin oxide (Sn02:F) [FTO] is usually preferred as a TCO. In this study, interface engineering is carried out at the AZO and p-type a-SiC:H interface to obtain a better solar cell performance without loss in the FF. The abrupt potential barrier at the interface of AZO and p-type a-SiC:H is made gradual by inserting a buffer layer. A few-nanometer-thick nanocrystalline silicon buffer layer between the AZO and a-SiC:H enhances the FF from 67% to 73% and the efficiency from 7.30% to 8.18%. Further improvements in the solar cell performance are expected through optimization of cell structures and doping levels. PMID:22257671

  10. 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

    2005-01-01

    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

  11. Domestic Bond Market Development

    OpenAIRE

    Jonathan A. Batten; Szilagyi, Peter G.

    2007-01-01

    A two-tiered approach to financial market development aimed at both bank and bond market reform would also be complementary to longer term economic development, provided services could be delivered through efficient financial and legal institutions (Chakraborty and Ray 2006) and there was strong protection for investors and sound fiscal and monetary policy management by government (Burger and Warnock 2006b). Historically, local issuers tend to issue in the major currencies (U.S. dollars, yen,...

  12. Kinetics of heterogeneous catalytic reactions

    CERN Document Server

    Boudart, Michel

    2014-01-01

    This book is a critical account of the principles of the kinetics of heterogeneous catalytic reactions in the light of recent developments in surface science and catalysis science. Originally published in 1984. The Princeton Legacy Library uses the latest print-on-demand technology to again make available previously out-of-print books from the distinguished backlist of Princeton University Press. These paperback editions preserve the original texts of these important books while presenting them in durable paperback editions. The goal of the Princeton Legacy Library is to vastly increase acc

  13. Molecular catalytic coal liquid conversion

    Energy Technology Data Exchange (ETDEWEB)

    Stock, L.M.; Yang, Shiyong [Univ. of Chicago, IL (United States)

    1995-12-31

    This research, which is relevant to the development of new catalytic systems for the improvement of the quality of coal liquids by the addition of dihydrogen, is divided into two tasks. Task 1 centers on the activation of dihydrogen by molecular basic reagents such as hydroxide ion to convert it into a reactive adduct (OH{center_dot}H{sub 2}){sup {minus}} that can reduce organic molecules. Such species should be robust withstanding severe conditions and chemical poisons. Task 2 is focused on an entirely different approach that exploits molecular catalysts, derived from organometallic compounds that are capable of reducing monocyclic aromatic compounds under very mild conditions. Accomplishments and conclusions are discussed.

  14. Studies of Catalytic Model Systems

    DEFF Research Database (Denmark)

    Holse, Christian

    the Cu/ZnO nanoparticles is highly relevant to industrial methanol synthesis for which the direct interaction of Cu and ZnO nanocrystals synergistically boost the catalytic activity. The dynamical behavior of the nanoparticles under reducing and oxidizing environments were studied by means of ex situ...... observed by XPS as the nanoparticles are reduced. The Cu/ZnO nanoparticles are tested on a  µ-reactor platform and prove to be active towards methanol synthesis, making it an excellent model system for further investigations into activity depended morphology changes....

  15. Catalytic Spectrophotometric Determination of Chromium

    OpenAIRE

    STOYANOVA, Angelina Miltcheva

    2005-01-01

    The catalytic effect of chromium(III) and chromium(VI) on the oxidation of sulfanilic acid by hydrogen peroxide was studied. The reaction was followed spectrophotometrically by measuring the absorbance of the reaction product at 360 nm. Under the optimum conditions 2 calibration graphs (for chromium(III) up to 100 ng mL-1, and for chromium(VI) up to 200 ng mL-1) were obtained, using the ``fixed time'' method with detection limits of 4.9 ng mL-1 and 3.8 ng mL-1, respectively...

  16. Catalytic Combustion of Ethyl Acetate

    OpenAIRE

    ÖZÇELİK, Tuğba GÜRMEN; ATALAY, Süheyda; ALPAY, Erden

    2007-01-01

    The catalytic combustion of ethyl acetate over prepared metal oxide catalysts was investigated. CeO, Co2O3, Mn2O3, Cr2O3, and CeO-Co2O3 catalysts were prepared on monolith supports and they were tested. Before conducting the catalyst experiments, we searched for the homogeneous gas phase combustion reaction of ethyl acetate. According to the homogeneous phase experimental results, 45% of ethyl acetate was converted at the maximum reactor temperature tested (350 °C). All the prepare...

  17. Estimating the temperature of a catalytic converter

    Energy Technology Data Exchange (ETDEWEB)

    Ma, T.T.-H.

    1994-11-02

    A method is described for estimating the temperature in a catalytic converter used in the exhaust system of an internal combustion engine. Pressure sensors monitor the flow resistance across the catalytic converter to provide an indication of the temperature inside. This feedback system allows heating devices to be switched off and thus avoid overheating, while maintaining the catalytic converter's efficiency by assuring that it does not operate below its light off temperature. (UK)

  18. Estimating the temperature of a catalytic converter

    Energy Technology Data Exchange (ETDEWEB)

    Ma, T.T.-H.

    1994-11-02

    A method of estimating the temperature of a catalytic converter used in the exhaust system of an internal combustion engine is described. Heated exhaust gas oxygen (HEGO) sensors are placed upstream and downstream of the catalytic converter. The temperature of the catalytic converter shortly after start-up is measured by monitoring the resistance of the HEGO sensor's heating element. The downstream sensor is used for mixture control and to double check results of the upstream sensor. (UK)

  19. Integration of European Bond Markets

    OpenAIRE

    Christiansen, Charlotte

    2012-01-01

    I investigate the time variation in the integration of EU government bond markets. The integration is measured by the explanatory power of European factor portfolios for the individual bond markets for each year. The integration of the government bond markets is stronger for EMU than non-EMU members and stronger for old than new EU members. The integration is weaker for the sovereign debt crisis countries than for other countries. The integration of the EU bond markets is decreasing over time...

  20. Doseringsutrustningen SafeBond Electronic

    OpenAIRE

    Bodegren, Patrik

    2003-01-01

    This thesis for the Master of Science degree was performed at Oppunda Electronics AB. The assignment was to further develop an existing prototype of a dispensing equipment. The dispensing equipment doses a kind of glue, bonding which dentist use to mend teeth. The dispensing equipment is adjusted to dose 12 micro litres of bonding. With the dispensing equipment SafeBond Electronic the user can reduce the bonding consumption with approximately 50 percent. Furthermore will the handling of the b...

  1. Contribution to the study of the 31P, 1H spin spin coupling constant N. M. R. in three co-ordinated phosphorus compounds. Influence of the bond orientation and of the nature of the substituent around the phosphorus atom

    International Nuclear Information System (INIS)

    In order to investigate the influence of the configuration at the phosphorus atom and the influence of the substituents attached to the phosphorus atom on the JPH spin spin coupling constant, we have performed the NMR spectrum analysis of some three coordinated organo-phosphorus compounds. The studied coupling constants are 3JPH through P-O-C-H and P-C-C-H fragments and 2JPH through P-C-H fragment. The results clearly show that on the NMR time scale, in all the studied compounds (1,3,2-dioxaphospholanes, 1,3,2-dioxaphosphorinanes, 3-phospha-cyclopentene and 4-phosphorinanone) there is no inversion of the bonds around phosphorous. This conclusion held also for secondary phosphines. For a given geometry of the bonds joining the P and H atoms, and a given disposition of the bonds around the phosphorus atom, there is only a little influence of the nature of the substituents on the JPH spin coupling constants. The geometrical dependence of the 3JPH cannot be explained by a 'Karplus law'. There is an influence of the bond disposition around phosphorus. In the case of the 2JP-C-H, one can plot a curve 2JP-C-H = f(α) (0≤ α ≤ 180), α denote the dihedral angle of the two plane defined the first one by the P, C and H atoms, and the second one by the P-C bond together with the three-fold axis of the bond around phosphorus assuming a regular pyramidal arrangement. The function 2JP-C-H = f(α) has two maxima, one for α = 0 degrees and the other for α = 180 degrees, and also a minimum for α = 110 degrees. (author)

  2. Nanostructured Catalytic Reactors for Air Purification Project

    Data.gov (United States)

    National Aeronautics and Space Administration — This SBIR Phase II project proposes the development of lightweight compact nanostructured catalytic reactors for air purification from toxic gaseous organic...

  3. Nanostructured Catalytic Reactors for Air Purification Project

    Data.gov (United States)

    National Aeronautics and Space Administration — This SBIR Phase I project proposes the development of lightweight compact nanostructured catalytic reactors for air purification from toxic gaseous organic...

  4. Hamiltonian formulation of bond graphs

    NARCIS (Netherlands)

    Golo, Goran; Schaft, van der Arjan; Breedveld, Peter C.; Maschke, Bernhard M.; Johansson, R.; Rantzer, A.

    2003-01-01

    This paper deals with the mathematical formulation of bond graphs. It is proven that the power continuous part of bond graphs, the junction structure, can be associated with a Dirac structure and that the equations describing a bond graph model correspond to a port Hamiltonian system. The conditions

  5. catena-Poly[[(pentaaqua)(4-nitrobenzoato-O,O')barium(II)] (-4-nitrobenzoato-O,O')]: A barium(II) coordination polymer showing O-H$\\cdots$O and C-H$\\cdots$O interactions

    Indian Academy of Sciences (India)

    Bikshandarkoil R Srinivasan; Jyoti V Sawant; Sarvesh C Sawant; Pallepogu Raghavaiah

    2007-11-01

    The reaction of barium carbonate with 4-nitrobenzoic acid (4-nbaH) results in the formation of a Ba(II) coordination polymer, catena-poly[[(pentaaqua)(4-nitrobenzoato-O,O')barium(II)](-4-nitrobenzoato-O,O')] 1. The polymeric compound [[Ba(H2O)5(4-nba-O,O')](-4-nba-O,O')] 1 was characterized by elemental analysis, IR and UV-Vis spectra, weight loss studies, X-ray powder diffraction and its structure determined. In 1 five water molecules are coordinated to the central metal and one of the 4-nba ligands is bonded to Ba(II) in a bidentate manner (4-nba-O,O') through the carboxylate O atoms. The [(pentaaqua)(4-nitrobenzoato-O,O')barium(II)] units are linked into an infinite one-dimensional chain along -axis with the aid of the second 4-nba anion, which functions as a bridging bidentate (-4-nba-O,O') ligand. This results in nine coordination around each Ba(II) ion in the coordination polymer. A long Ba$\\cdots$Ba distance of 6.750(1) Å is observed between adjacent Ba(II) ions in the chain and the oxygen atoms of the carboxylate group and the nitro functionalities of the 4-nba ligand are involved in several O-H$\\cdots$O and C-H$\\cdots$O interactions.

  6. Catalytic converters in the fireplace

    International Nuclear Information System (INIS)

    In addition to selecting the appropriate means of heating and using dry fuel, the amount of harmful emissions contained by flue gases produced by fireplaces can be reduced by technical means. One such option is to use an oxidising catalytic converter. Tests at TTS Institute's Heating Studies Experimental Station have focused on two such converters (dense and coarse) mounted in light-weight iron heating stoves. The ability of the dense catalytic converter to oxidise carbon monoxide gases proved to be good. The concentration of carbon monoxide in the flue gases was reduced by as much as 90 %. Measurements conducted by VTT (Technical Research Centre of Finland) showed that the conversion of other gases, e.g. of methane, was good. The exhaust resistance caused by the dense converter was so great as to necessitate the mounting of a fluegas evacuation fan in the chimney for the purpose of creating sufficient draught. When relying on natural draught, the dense converter requires a chimney of at least 7 metres and a by-pass connection while the fire is being lit. In addition, the converter will have to be constructed to be less dense and this will mean that it's capability to oxidise non-combusted gases will be reduced. The coarse converter did not impair the draught but it's oxidising property was insufficient. With the tests over, the converter was not observed to have become blocked up by impurities

  7. Catalytic reforming feed characterisation technique

    Energy Technology Data Exchange (ETDEWEB)

    Larraz Mora, R.; Arvelo Alvarez, R. [Univ. of La Laguna, Chemical Engineering Dept., La Laguna (Spain)

    2002-09-01

    The catalytic reforming of naphtha is one of the major refinery processes, designed to increase the octane number of naphtha or to produce aromatics. The naphtha used as catalytic reformer feedstock usually contains a mixture of paraffins, naphthenes, and aromatics in the carbon number range C{sub 6} to C{sub 10}. The detailed chemical composition of the feed is necessary to predict the aromatics and hydrogen production as well as the operation severity. The analysis of feed naphtha is usually reported in terms of its ASTM distillation curve and API or specific gravity. Since reforming reactions are described in terms of lumped chemical species (paraffins, naphthenes and aromatics), a feed characterisation technique should be useful in order to predict reforming operating conditions and detect feed quality changes. Unfortunately online analyzer applications as cromatography or recently introduced naphtha NMR [1] are scarce in most of refineries. This work proposes an algorithmic characterisation method focusing on its main steps description. The method could help on the subjects previously described, finally a calculation example is shown. (orig.)

  8. ASEAN+3 Bond Market Guides

    OpenAIRE

    Asian Development Bank (ADB)

    2012-01-01

    The ASEAN+3 Bond Market Guide contains the comprehensive reports of the ASEAN+3 Bond Market Forum Sub-Forum 1 (SF1) and Sub-Forum 2 (SF2). The SF1 report (Volume 1) analyzes the harmonization and standardization of the existing bond markets in the ASEAN+3. It also contains the individual market guides of 11 economies under the ASEAN+3 Bond Market Forum (ABMF). The SF2 report (Volume 2) provides an overview of the ASEAN+3 bond markets and their infrastructures, as well as issues confronted by ...

  9. Optimal Investment in Structured Bonds

    DEFF Research Database (Denmark)

    Jessen, Pernille; Jørgensen, Peter Løchte

    The paper examines the role of structured bonds in the optimal portfolio of a small retail investor. We consider the typical structured bond essentially repacking an exotic option and a zero coupon bond, i.e. an investment with portfolio insurance. The optimal portfolio is found when the investment...... opportunities consist of a risky reference fund, a risk-free asset and a structured bond. Key model elements are the trading strategy and utility function of the investor. Our numerical results indicate structured bonds do have basis for consideration in the optimal portfolio. The product holdings are...

  10. Surface and catalytic properties of doped tin oxide nanoparticles

    Science.gov (United States)

    Wang, Chien-Tsung; Lai, De-Lun; Chen, Miao-Ting

    2010-10-01

    Mixed oxides composed of Zn-Sn, Ti-Sn and V-Sn were prepared by a co-precipitation method and evaluated as catalysts for methanol oxidation in an ambient fixed-bed reactor. Surface analysis by X-ray photoelectron spectroscopy (XPS) revealed an electronic interaction between dopant and Sn atoms in the oxide structure and showed the formation of surface states associated with the dopants. Oxygen vacancies were present on the Zn-doped oxide, and the oxidation of methanol to carbon oxides was favored. The Ti-doped oxide exhibited a favorable selectivity to dimethyl ether, related to the oxygen anions near Ti centers. Vanadium dopants not only dramatically increased the catalytic activity but also promoted the partial oxidation of methanol to formaldehyde. Results demonstrate that the bridging dopant-O-Sn bond acts as active sites and influences product distribution.

  11. Catalytic ring opening of decalin. Biofunctional versus hydrogenolytic pathways

    Energy Technology Data Exchange (ETDEWEB)

    Weitkamp, J.; Rabl, S.; Haas, A.; Santi, D. [Stuttgart Univ. (Germany). Inst. of Chemical Technology; Ferrari, M.; Calemma, V. [Eni R and M Div., San Donato Milanese (Italy)

    2010-12-30

    Ir/silica, Pt/La-X and Rh/H-Beta were prepared and tested in the hydroconversion of cisdecalin at different temperatures. The catalytic tests were carried out under hydrogen in a high-pressure flow-type apparatus at 5.2 MPa. On the three catalysts open-chain decane yields up to 20 % were achieved, which is much higher than the yields reported so far in the literature. Pt/La-X and Rh/H-Beta behave as bifunctional catalysts with a high tendency for skeletal isomerization. On these catalysts the so-called paring reaction via carbenium ions occurs, leading to iso-butane and methylcyclopentane as main hydrocracked products. On Ir/SiO{sub 2}, carbon-carbon bond cleavage occurs through hydrogenolysis on the noble metal without prior isomerization. As a consequence the product spectrum is less complex than on the bifunctional catalysts which makes the system particularly amenable to mechanistic studies. (orig.)

  12. Catalytic synthesis of ammonia-a "never-ending story"?

    Science.gov (United States)

    Schlögl, Robert

    2003-05-01

    Nitrogen atoms are essential for the function of biological molecules and thus are and important component of fertilizers and medicaments. Bonds to nitrogen also find nonbiological uses in dyes, explosives, and resins. The synthesis of all these materials requires ammonia as an activated nitrogen building block. This situation is true for natural processes and the chemical industry. Knowledge of the various techniques for the preparation of ammonia is thus of fundamental importance for chemistry. The Haber-Bosch synthesis was the first heterogeneous catalytic system employed in the chemical industry and is still in use today. Understanding the mechanism and the translation of the knowledge into technical perfection has become a fundamental criterion for scientific development in catalysis research. PMID:12746811

  13. Chemical activation of molecules by metals: Experimental studies of electron distributions and bonding

    International Nuclear Information System (INIS)

    The formal relationship between measured molecular ionization energies and thermodynamic bond dissociation energies has been developed into a single equation which unifies the treatment of covalent bonds, ionic bonds, and partially ionic bonds. This relationship has been used to clarify the fundamental thermodynamic information relating to metal-hydrogen, metal-alkyl, and metal-metal bond energies. We have been able to obtain a direct observation and measurement of the stabilization energy provided by the agostic interaction of the C-H bond with the metal. The ionization energies have also been used to correlate the rates of carbonyl substitution reactions of (η5-C5H4X)Rh(CO)2 complexes, and to reveal the electronic factors that control the stability of the transition state. The extent that the electronic features of these bonding interactions transfer to other chemical systems is being investigated in terms of the principle of additivity of ligand electronic effects. Specific examples under study include metal- phosphines, metal-halides, and metallocenes. Especially interesting has been the recent application of these techniques to the characterization of the soccer-ball shaped C60 molecule, buckminsterfullerene, and its interaction with a metal surface. The high-resolution valence ionizations in the gas phase reveal the high symmetry of the molecule, and studies of thin films of C60 reveal weak intermolecular interactions. Scanning tunneling and atomic force microscopy reveal the arrangement of spherical molecules on gold substrates, with significant delocalization of charge from the metal surface. 21 refs

  14. Sepia 200cH at 1:1000 dilution ameliorates salt stress in cowpea seedlings but its medium 90% ethanol proves ineffective at the same dilution

    Directory of Open Access Journals (Sweden)

    Sandhimita Mondal

    2012-12-01

    Full Text Available Soil salinity severely affects crop yield all over the world. In a recent study we observed that Natrum mur 200cH, a homeopathic remedy, improved growth in germinating cowpea seeds. In the present study we have tested another remedy Sepia, which is complementary to Natrum mur, on cowpea seedlings under salt stress. Cowpea seedlings grown over moist filter paper in petridishes were divided into 4 groups: (1 control in sterile water, (2 in 50mM NaCl solution, (3 seeds pretreated with 90% ethanol diluted with water 1:100 and then transferred to 50mM NaCl solution, (4 seeds pretreated with Sepia 200cH diluted with water 1:100 and transferred to 50mM NaCl solution. In another experiment the groups were same, but the dilution of 90% ethanol and Sepia 200cH was 1:1000 instead of 1:100. The purpose was to further reduce the ethanol content in both the drug and its vehicle 90% ethanol, so that the alcohol effect is minimized or abolished. The data were analysed by ANOVA followed by t-test. Sepia 200cH at both 1:100 and 1:1000 dilutions significantly increased growth, sugar, chlorophyll, protein and water content in seedlings as compared to the untreated salt-stressed group. The effect with the1000th dilution of Sepia 200cH was more pronounced than with its 100th dilution. The vehicle 90% ethanol at 1:100 dilution produced some positive effect on the seedlings, but the 1000th dilution of the vehicle produced no such effect. It is, therefore, concluded that Sepia 200cH could ameliorate salt stress in cowpea seedlings and that the 1000th dilution is more effective than its 100th dilution. The alcohol effect is totally eliminated with the 1000th dilution of 90% ethanol. Thus the 1000th dilution could retain the drug effect and eliminate the vehicle effect.

  15. Isotopic Effects on Covalent Bond Confined in a Penetrable Sphere.

    Science.gov (United States)

    Sarsa, Antonio; Alcaraz-Pelegrina, José M; Le Sech, Claude

    2015-11-12

    A model of confinement of the covalent bond by a finite potential beyond the Born-Oppenheimer approximation is presented. A two-electron molecule is located at the center of a penetrable spherical cavity. The Schrödinger equation has been solved by using the diffusion Monte Carlo method. Total energies, internuclear distances, and vibrational frequencies of the confined molecular system have been obtained. Even for confining potentials of a few electronvolts, a noticeable increase in the bond energy and the nuclear vibrational frequency is observed, and the internuclear distance is lowered. The gap between the zero point energy of different molecular isotopes increases with confinement. The confinement of the electron pair might play a role in chemical reactivity, providing an alternative explanation for the tunnel effect, when large values of primary kinetic isotopic effect are observed. The Swain-Schaad relation is still verified when confinement changes the zero point energy. A semiquantitative illustration is proposed using the data relative to an hydrogen transfer involving a C-H cleavage catalyzed by the bovine serum amine oxidase. Changes on the confining conditions, corresponding to a confinement/deconfinement process, result in a significant decrease in the activation energy of the chemical transformation. It is proposed that confinement/deconfinement of the electron-pair bonding by external electrostatic forces inside the active pocket of an enzyme could be one of the basic mechanisms of the enzyme catalysis. PMID:26484576

  16. Catalytic hydrolysis for the degradation of organophosphorus pesticides in water

    International Nuclear Information System (INIS)

    The kinetic studies of catalytic hydrolysis revealed that the concentration of two kinds of organophosphorus pesticides (omethoate and methidathion) in solution apparently decays according to the second order reaction. It was found that the rate constant value was highest at strong acidic conditions and it continued to decrease as the pH of the solution was increased. At basic conditions the rate constant value decreased to minimum. Manganese dioxide under acidic conditions converted into Mn/sup 2+/ ions and then these ions in water form hexaaquomanganese (II) ion. This hexaaquomanganese (II ion then adsorbed itself on the S or O atom of the organophosphorus compound and thus weakens the bond between P-S. This reaction facilitated the attack of H/sub 2/O or OH/sup -/ ion and thus enhanced the efficiency of hydrolysis. It was studied that methidathion hydrolyzed more efficiently than omethoate The rate constants of catalytic hydrolysis were increased with increasing the amount of MnO/sub 2/. It was found that the pesticides had undergone adsorption on catalyst in the first few minutes and there was the rapid drop of total phosphorus concentration. The decrease of total phosphorus adsorption with increasing pH was also observed. After the addition of alkaline earth metal cations (Ca/sup 2+/ and Mg/sup 2+/) along with magnesium, the enhancement in the efficiency of hydrolysis at near neutral conditions occurred. (author)

  17. Resonant active sites in catalytic ammonia synthesis: A structural model

    Science.gov (United States)

    Cholach, Alexander R.; Bryliakova, Anna A.; Matveev, Andrey V.; Bulgakov, Nikolai N.

    2016-03-01

    Adsorption sites Mn consisted of n adjacent atoms M, each bound to the adsorbed species, are considered within a realistic model. The sum of bonds Σ lost by atoms in a site in comparison with the bulk atoms was used for evaluation of the local surface imperfection, while the reaction enthalpy at that site was used as a measure of activity. The comparative study of Mn sites (n = 1-5) at basal planes of Pt, Rh, Ir, Fe, Re and Ru with respect to heat of N2 dissociative adsorption QN and heat of Nad + Had → NHad reaction QNH was performed using semi-empirical calculations. Linear QN(Σ) increase and QNH(Σ) decrease allowed to specify the resonant Σ for each surface in catalytic ammonia synthesis at equilibrium Nad coverage. Optimal Σ are realizable for Ru2, Re2 and Ir4 only, whereas other centers meet steric inhibition or unreal crystal structure. Relative activity of the most active sites in proportion 5.0 × 10- 5: 4.5 × 10- 3: 1: 2.5: 3.0: 1080: 2270 for a sequence of Pt4, Rh4, Fe4(fcc), Ir4, Fe2-5(bcc), Ru2, Re2, respectively, is in agreement with relevant experimental data. Similar approach can be applied to other adsorption or catalytic processes exhibiting structure sensitivity.

  18. Acoustics of automotive catalytic converter assemblies

    Science.gov (United States)

    Dickey, Nolan S.; Selamet, Ahmet; Parks, Steve J.; Tallio, Kevin V.; Miazgowicz, Keith D.; Radavich, Paul M.

    2003-10-01

    In an automotive exhaust system, the purpose of the catalytic converter is to reduce pollutant emissions. However, catalytic converters also affect the engine and exhaust system breathing characteristics; they increase backpressure, affect exhaust system acoustic characteristics, and contribute to exhaust manifold tuning. Thus, radiated sound models should include catalytic converters since they can affect both the source characteristics and the exhaust system acoustic behavior. A typical catalytic converter assembly employs a ceramic substrate to carry the catalytically active noble metals. The substrate has numerous parallel tubes and is mounted in a housing with swelling mat or wire mesh around its periphery. Seals at the ends of the substrate can be used to help force flow through the substrate and/or protect the mat material. Typically, catalytic converter studies only consider sound propagation in the small capillary tubes of the substrate. Investigations of the acoustic characteristics of entire catalytic converter assemblies (housing, substrate, seals, and mat) do not appear to be available. This work experimentally investigates the acoustic behavior of catalytic converter assemblies and the contributions of the separate components to sound attenuation. Experimental findings are interpreted with respect to available techniques for modeling sound propagation in ceramic substrates.

  19. Understanding catalytic biomass conversion through data mining

    NARCIS (Netherlands)

    E.J. Ras; B. McKay; G. Rothenberg

    2010-01-01

    Catalytic conversion of biomass is a key challenge that we chemists face in the twenty-first century. Worldwide, research is conducted into obtaining bulk chemicals, polymers and fuels. Our project centres on glucose valorisation via furfural derivatives using catalytic hydrogenation. We present her

  20. Intermolecular C-H activation with an Ir-METAMORPhos piano-stool complex--multiple reaction steps at a reactive ligand.

    Science.gov (United States)

    Oldenhof, S; Lutz, M; van der Vlugt, J I; Reek, J N H

    2015-10-21

    Substrate activation by means of a reactive ligand is a topic of much interest. Herein we describe a stoichiometric anti-Markovnikov C-N bond formation involving ligand reactivity in multiple steps along the reaction coordinate, including ligand assisted substrate (de)protonation and C-N bond formation, as illustrated by a combined experimental, spectroscopic and computational study. This affords a highly unusual four-membered iridacycle bearing an exo-cyclic C=C double bond. PMID:26329519