2143-68-2Relevant academic research and scientific papers
Competition between hydrogen and deuterium abstraction by methyl radicals in isotopomerically mixed methanol glasses
Doba, Takahisa,Ingold, K. U.,Lusztyk, Janusz,Siebrand, Willem,Wildman, Timothy A.
, p. 2962 - 2970 (1993)
Rate parameters are reported for hydrogen and deuterium abstraction of methyl radicals embedded in glassy mixtures of CH3OH and CD3OD.The mole fraction of CH3OH in these isotopomeric mixture is 0, 0.05, 0.075, 0.10, 0.15, or 1.The nonexponential time dependence of the radical concentration is analyzed in terms of distributions of first-order rate constants.For the isotopomerically pure matrices, lognormal distributions describe the decay satisfactorily.The large difference between characteristic H and D transfer rate constants indicates tunneling.In the mixtures, there is competition between H and D abstraction processes which depends on the local structure about a radical, so that the corresponding rate parameters contain information about this structure.On the basis of earlier work , the analysis begins with the assumption that the structure about a radical resembles one of the crystalline phases of methanol.The entire set of decay curves is described by a (disordered) β-phase structure in which the radical replaces a methanol molecule and is located near the position associated with a methyl group.However, this static picture is inadequate because the radical can diffuse through the glass on the time scale of the kinetic measurements.Diffusion allows the radical to encounter more CH3OH molecules than would be expected for the static structure on a statistical basis - the effective mole fraction of CH3OH in the mixtures is higher than the analytical concentration.For the xH = 0.05 mixture, we estimate that on the average the radical encounters approximately 26 methanol molecules before abstraction occurs.This corresponds to diffusion over roughly 1100pm through the lattice.
ESR Spectroscopic Detection of Methoxyl Radicals Formed in the Photochemical Gas-Phase Reaction of Methane and Water
Migita, Catharina T.,Chaki,. Satoshi,Ogura, Kotaro
, p. 6368 - 6370 (1989)
During the photolysis of methane-water gas mixtures, a radical has been trapped by both α-phenyl-N-tert-butylnitrone and 5,5-dimethyl-1-pyrroline 1-oxide.The analysis of the ESR parameters along with the control experiments and the determination of reaction products strongly suggests the detection of methoxyl radical.It is revealed that the yield of methanol and methoxyl radical depends on the initial concentration of methane and the reaction temperature, and the observed difference between their yields is mainly ascribed to the reaction CH3O. + CH4 --> CH3OH + .CH3, which is favorable at higher concentration of initial methane and at higher reaction temperature.Furthermore, the preferential trapping of the methoxyl radical by the spin traps is discussed.
Kinetics and Mechanism of the Reaction of CH3 and CH3O with ClO and OClO at 298 K
Biggs, Peter,Canosa-Mas, Carlos E.,Fracheboud, Jean-Marc,Marston, George,Shallcross, Dudley E.,Wayne, Richard P.
, p. 3045 - 3054 (1995)
A discharge-flow system equipped with a laser-induced fluorescence cell to detect the methoxyl radical and a quadrupole mass spectrometer to detect both the chlorine monoxide and chlorine dioxide radicals has been used to measure the rate constants for the reactions CH3 + ClO -> products (1) CH3O + ClO -> products (2) CH3 + OClO -> products (3) CH3O + OClO -> products (4) at T 298 K and P = 1-3 Torr.The observed products of these reactions are CH3O for reaction (1), HOCl for reaction (2), and CH3O and ClO for reaction (3).For reaction (4), CH3OCl is a possible product.The rate constants derived for reactions (1)-(4) are: k1 = (1.3 +/- 0.4)E-10 cm3 molecule -1 s-1; k2 = (1.3 +/- 0.3)E-11 cm3 molecule-1 s-1; k3 = (1.6 +/- 0.3)E-11 cm3 molecule-1 s-1; k4 = (1.5 +/- 0.5)E-12 cm3 molecule-1 s-1.The likely mechanism for (1)-(4) are briefly discussed.
Kinetics of the Methoxy Radical Decomposition Reaction: Theory and Experiment
Page, M.,Lin, M. C.,He, Yisheng,Choudhury, T. K.
, p. 4404 - 4408 (1989)
The rate constant for the unimolecular decomposition of the methoxy radical, CH3O + M --> CH2O + H + M, is determined both theoretically and experimentally.In the theoretical calculations, potential energy surface information is obtained from ab initio multiconfiguration SCF and multireference configuration interaction calculations using basis sets of up to triple-ζ plus polarization quality.The zero point corrected forward and reverse barriers are calculated to be 25.6 and 8.0 kcal/mol, respectively.RRKM rate calculations are performed incorporating a quantum correction due to tunneling through an Eckart barrier fit to represent the MRCI/TZP energetics and the shape of the MC-SCF/DZP vibrationally adiabatic potential energy curve in the saddle pont region.The calculated values compare closely with experimental data derived from kinetic modeling of CO formation rates measured in the thermal decomposition of methyl nitrate at 550-700 K in a static cell and at 1060-1620 K in shock waves.
Kinetic studies of the reactions CH3+NO2→products, CH3O+NO2→products, and OH+CH3C(O)CH3→CH3C(O)OH+CH3, over a range of temperature and pressure
Wollenhaupt, Matthias,Crowley, John N.
, p. 6429 - 6438 (2000)
The title reactions were investigated using pulsed laser photolysis combined with pulsed laser induced fluorescence detection of CH3O to determine the rate coefficients for CH3+NO2→products (3) and CH3O+NO2→products (5) as a function of temperature and pressure, and to estimate the yield of CH3 (and thus the yield of CH3C(O)OH) from the reaction of OH with CH3C(O)CH3 (2) at two different temperatures. Reaction 3 has both bimolecular and termolecular components: a simplified falloff parametrization with Fcent = 0.6 gives k3b0 = (3.2±1.3)×10-28(T/297)-0.3 cm6 s-1 and k3b∞ = (4.3±0.4)×10-11(T/297)-1.2 cm3 s-1 with CH3NO2 the likely product. The rate constant for the bimolecular reaction pathway to form CH3O+NO (3a) was found to be 1.9×10-11 cm-3 s-1. The low- and high-pressure limiting rate coefficients for reaction between CH3O and NO2 to form CH3ONO2 (5b) were derived as k5b0 = (5.3±0.3)×10-29(T/297)-4.4 cm6 s-1 and k5b∞ = (1.9±0.05)×10-11(T/297)-1.9 cm3 s-1, respectively. Although the final result is associated with some experimental uncertainty, we find that CH3 is formed in the reaction between OH and CH3C(O)CH3 at ≈50% yield at room temperature and 30% at 233 K.
Chemiluminescence Studies of the Reaction between O(3P) Atoms and Methyl Ioide
Kwong, Bess C. L.,Tse, R. S.
, p. 823 - 827 (1994)
The reaction between O(3P) atoms and CH3I was studied in a fast discharge-flow system.A threshold behavior with respect to the ratio of initial reactant concentrations in the chemiluminescence due to I2 (B2Π0+u -> X1Σ+g) was observed.The reactions in Chart 1 were considered significant in our interpretation.Fitting of temporal profiles produced an order of magnitude for k1 of 1010 cm3 mol-1 s-1 at room temperature.Chemiluminescence from OH(A2Σ -> X2Π)(0,0), OH(X)(2->1,1->0), CO(X)(1->0), and CO2(X)(v3=1->0) was also observed, in common with observations of O(3P) reactions with hydrocarbons.
Competing pathways for methoxy decomposition on oxygen-covered Mo(110)
Queeney,Friend
, p. 6067 - 6074 (1998)
The reactions of methanol (CH3OH) are investigated on a range of oxygen overlayers on Mo(110), with θO from ～0.5 to >1 ML, using a combination of vibrational spectroscopies and temperature-programmed reaction. Infrared spectroscopy identifies a common, tilted methoxy intermediate at high temperature on all overlayers studied; electron energy loss spectroscopy shows that this intermediate decomposes to deposit oxygen exclusively in high-coordination sites. While C-O bond scission to evolve gas-phase methyl radicals is the only reaction observed for methoxy on highly oxidized Mo(110), on the surface oxygen overlayers competition between dehydrogenation and methyl evolution is highly sensitive to oxygen coverage. The enhanced selectivity for hydrocarbon formation from methanol reaction on oxygen-modified Mo(110) relative to the clean surface is attributed to inhibition of dehydrogenation pathways rather than to marked changes in the C-O bond potential of methoxy.
Kinetics of the Reactions of CH3O and CD3O with NO
McCaulley, James A.,Moyle, Alfred M.,Golde, Michael F.,Anderson, Stuart M.,Kaufman, Frederick
, p. 4001 - 4009 (1990)
The kinetics of the reactions of CH3O and CD3O with NO have been studiedusing a discharge flow reactor.CH3O and CD3O were detected using laser-excited fluorescence (LEF) near 300 nm.Total rate coefficients for the reaction of CH3O with NO were measured as a function of temperature (220-473 K) and presure (0.75-5.0 Torr) of He or Ar.Total rate coefficients for the CD3O + NO reaction were measured at ca. 294 K over the pressure range 0.75-5.0 Torr He.Using molecular-beam mass spectrometry, the CH3ONO zield of the CH3O + NO reaction was measured at 297 K (0.5 and 1.0 percentTorr) and 223 K (1.0 Torr), showing that disproportionation to H2CO + HNO is the major channel at low pressures.These results were combined to obtain the following expressions for the disproportionation and low-pressure recombination rate coefficients.For the CH3O + NO reaction, kDISP=(1.3 +/- 0,4) x 10-12 exp cm3s-1, kolll=(1.8 +/- 1.3) x 10-29 (Τ/300)-(3.2+/-0.5) cm6 s-1.For the CD3O + NO reaction at 294 +/- 2 K, kDISP =(3.0 +/- 0.4) x 10-12 cm3 s-1, and kolll = (2.5 +/- 0.4) x 10-29 cm6 s-1.While the uncertainty associated with the measured rate coefficients is ca. +/- l5percent, the product channel-specific rate coefficients obtained from these expressions are less certain, ca. +/- 50percent.Using MBMS, the CH3NO2 yield of the CH3 + NO2 reaction was measured at 297 K )0.5 and 1.0 Torr) and 223 K (1.0 Torr).Combined with the previously reported rate coefficient, these results indicate a low-pressure, third-order recombination rate coefficient of (6 +/- 2) x 10 -29cm 6 s-1 in He at 297 K.
High-temperature shock tube study of the reactions CH3 + OH → products and CH3OH + Ar → products
Vasudevan, Venkatesh,Cook, Robert D.,Hanson, Ronald K.,Bowman, Craig T.,Golden, David M.
, p. 488 - 495 (2008)
The reaction between methyl and hydroxyl radicals has been studied in reflected shock wave experiments using narrow-linewidth OH laser absorption. OH radicals were generated by the rapid thermal decomposition of tert-butyl hydroperoxide. Two different species were used as CH3 radical precursors, azomethane and methyl iodide. The overall rate coefficient of the CH3 + OH reaction was determined in the temperature range 1081-1426 K under conditions of chemical isolation. The experimental data are in good agreement with a recent theoretical study of the reaction. The decomposition of methanol to methyl and OH radicals was also investigated behind reflected shock waves. The current measurements are in good agreement with a recent experimental study and a master equation simulation.
Near-infrared cavity ring-down spectroscopic study of the reaction of methylperoxy radical with nitrogen monoxide
Enami, Shinichi,Yamanaka, Takashi,Kawasaki, Masahiro
body text, p. 80 - 81 (2009/11/30)
Time-resolved near-infrared cavity ring-down spectroscopy was applied to the kinetics of the gas-phase reaction of CH3O2 with NO at 100 Torr total pressure and 298 K. After flash photolysis of the CH 4/Cl2/Osub
