2875-94-7Relevant academic research and scientific papers
FTIR matrix-isolation study of the reaction products of vanadium atoms with propene: Observation of allylvanadium hydride as a precursor to sacrificial hydrogenation of propene
Thompson, Matthew G. K.,Walker, Stephen W. C.,Parnis, J. Mark
, p. 7317 - 7323 (2011)
Vanadium atoms have been reacted with different partial pressures of propene in Ar under matrix-isolation conditions, and the products have been observed using Fourier transform infrared (FTIR) spectroscopy. Under dilute propene in Ar conditions, new features are observed in the IR spectra corresponding to a C-H insertion product, identified here as H-V-(η3-allyl). Use of d3-propene (CD 3-CH=CH2) demonstrates that the initial V-atom insertion occurs at the methyl group of the propene molecule, and DFT calculations have been used to support the identity of the initial product. Upon increasing the partial pressure of propene, additional features corresponding to propane (C3H8) are observed, with the hydrogen-atom source for the observed hydrogenation demonstrated to be additional propene units. Analysis of a systematic increase in the partial pressure of propene in the system demonstrates that the yield of propane correlates with the decrease of the allyl product, demonstrating the H-V(allyl) species as a reactive intermediate in the overall hydrogenation process. An overall mechanism is proposed to rationalize the formation of the insertion product and ultimately the products of hydrogenation, which agrees with previous gas-phase and matrix-isolation work involving propene and the related system, ethene.
A Simple High Energy Conformer Trapping Technique. Axial Phenylcyclohexane, NMR Spectra, and Thermodynamics
Squillacote, Michael E.,Neth, Joann M.
, p. 198 - 202 (1987)
The axial conformer of phenylcyclohexane has been observed for the first time by using a unique but simple high-temperature cryogenic trapping technique.Thermodynamic and NMR spectral data have been obtained for this high-energy conformer, which is shown
A Comparative Analysis of the CO-Reducing Activities of MoFe Proteins Containing Mo- and V-Nitrogenase Cofactors
Lee, Chi Chung,Tanifuji, Kazuki,Newcomb, Megan,Liedtke, Jasper,Hu, Yilin,Ribbe, Markus W.
, p. 649 - 653 (2018/04/16)
The Mo and V nitrogenases are structurally homologous yet catalytically distinct in their abilities to reduce CO to hydrocarbons. Here we report a comparative analysis of the CO-reducing activities of the Mo- and V-nitrogenase cofactors (i.e., the M and V clusters) upon insertion of the respective cofactor into the same, cofactor-deficient MoFe protein scaffold. Our data reveal a combined contribution from the protein environment and cofactor properties to the reactivity of nitrogenase toward CO, thus laying a foundation for further mechanistic investigation of the enzymatic CO reduction, while suggesting the potential of targeting both the protein scaffold and the cofactor species for nitrogenase-based applications in the future.
Hydrogen/Deuterium-Exchange Reactions of Methane with Aromatics and Cyclohexane Catalyzed by a Nanoscopic Aluminum Chlorofluoride
Calvo, Beatriz,Braun, Thomas,Kemnitz, Erhard
, p. 403 - 406 (2017/12/26)
H/D-exchange reactions between methane and deuterated solvents such as [D6]benzene and [D12]cyclohexane were heterogeneously catalyzed by nanoscopic aluminum chlorofluoride (ACF=AlClxF3?x, x≈0.05–0.3) under very mild conditions. 13C NMR spectroscopy experiments at labeled methane revealed the formation of all isotopologues. AlCl3, AlBr3, HS-AlF3, γ-Al2O3, and γ-Al2O3 preheated at 700 °C did not show any H/D-exchange reaction of methane or [D6]benzene. Mechanistically, electrophilic activation of methane was suggested at the ACF surface.
Tracing the hydrogen source of hydrocarbons formed by vanadium nitrogenase
Lee, Chi Chung,Hu, Yilin,Ribbe, Markus W.
experimental part, p. 5545 - 5547 (2011/07/08)
Hydrocarbons from CO: The vanadium-nitrogenase-catalyzed reduction of carbon monoxide involves the adenosine triphosphate (ATP)-dependent protonation of CO and the subsequent formation of C - C bonds, leading to the production of small hydrocarbons, such as C2H4, C2H 6, C3H6, and C3H8 (see picture). Isotope-substitution studies monitored by GC-MS analysis show that protons are the source of hydrogen for the CO reduction. Copyright
Reactions of Cyclopropane and Deuterium over Supported Metal Catalysts
Brown, Ronald,Kemball, Charles
, p. 3815 - 3822 (2007/10/02)
The reaction of cyclopropane and deuterium has been studied at low temperatures over a number of supported metal catalysts.The main reaction was normally ring-opening, yielding a mixture of isotopic propanes which were analysed mass-spectrometrically and by deuterium NMR spectroscopy.The patterns of isotopic propanes varied substancially with the nature of the metal and provided information about the types of adsorbed intermediates involved in the mechanism of the reactions. The rection of propene and deuterium was also followed over supported platinum catalysts.In contrast to the results with cyclopropane, exchange of propene occured and the propanes formed from propene were markedly different from those from cyclopropane, reflecting differences in the mechanism of the reactions. Evidence of dual-function catalysis was obtained using alumina-supported iridium with cyclopropane and deuterium; exchange took place on the support and ring-opening on the metal.Similar dual functionality was observed for reactions of methylcylopropane or 1,1-dimethylcyclopropane with deuterium over the same Ir/Al2O3 catalyst.As a consequence of the present work, the high selectivity for the exchange of primary hydrogen atoms in various hydrocarbons over Ir/Al2O3 is now considered to be a function of the support rather than of the metal.
Ionization of Normal Alkanes: Enthalpy, Entropy, Structural, and Isotope Effects
Meot-Ner (Mautner), M.,Sieck, L.W.,Ausloos, P.
, p. 5342 - 5348 (2007/10/02)
Enthalpies and entropies of ionization (ΔHi0, ΔSi0) of C4 to C11 normal alkanes were determined from charge-transfer equilibrium measurement between 300 and 420 K by using photoionization high-pressure mass spectrometry.Large negative ΔSi0 values are observed in C7 and larger n-alkanes, from -4.7 cal mol-1 K-1 (-19.6 J mol-1 K-1) in heptane to -13.9 cal mol-1 K-1 (-58.1 J mol-1 K-1) in undecane; in contrast, ΔSi0 of C4-C7 n-alkanes is negligible. ΔHi0 values range from 10.35 eV (997.6 kJ mol-1) (butane) to 9.45 eV (910.9 kJ mol-1) (undecane); the incremental ΔHi0 values also suggest the occurence of an effect that stabilizes C7 and higher but not the lower molecular ions.Analogy with disubstituted alkanes suggests that the negative ΔSi0 values and excess stabilization in C7 and higher alkane ions are due to constrained cyclic conformations which result from noncovalent intramolecular bonding between the terminal -C2H5 groups in the large, flexible molecular ions.These effects are more pronounced in n-alkanes than in 2-methylalkanes.Isotope effects on ΔHi0 as measured by the equilibrium constant K290 for n-CmD2m+2+ + n-CmH2m+2 ->/+ + n-CmD2m+2 are significant for ethane (k291 = 4.5) but decrease with increasing m: in propane K290 = 3.2 and in hexane and octane K291 = 1.0.However, the isotope effects in cyclic alkanes are much larger than in corresponding normal alkanes: in cyclohexane, K321 = 3.3 compared with that in n-hexane, were K320 = 1.0.
