Pressure dependence of the rate constant of the reaction atomic hydrogen + methyl radicals .fwdarw. methane

1977 ◽  
Vol 81 (21) ◽  
pp. 1982-1984 ◽  
Author(s):  
Jung-Tsang Cheng ◽  
Chuin-Tih Yeh
Keyword(s):  
Rate Constant ◽  
Pressure Dependence ◽  
Atomic Hydrogen ◽  
Methyl Radicals

Mercury-photosensitized decomposition of dimethyl ether. Part III. The combination of radicals

1967 ◽  
Vol 45 (22) ◽  
pp. 2775-2783 ◽  
Author(s):  
Leon F. Loucks
Keyword(s):  
Dimethyl Ether ◽  
Rate Constant ◽  
Pressure Dependence ◽  
Rate Coefficient ◽  
Methyl Radicals ◽  
Methyl Ethyl ◽  
Methyl Radical ◽  
Unimolecular Decomposition ◽  
Third Body ◽  
Methyl Ethyl Ether

As part of the study of the mercury-photosensitized decomposition of dimethyl ether, the combination of methyl radicals has been investigated in the temperature range 200 to 300 °C and at pressures between 3 and 300 mm Hg. For pressures of less than 100 mm the second-order rate coefficient for the combination of methyl radicals shows a pressure dependence. The pressure dependence agrees qualitatively with that observed by others, but occurs at somewhat higher pressures. Calculations for the Kassel equation using the Arrhenius parameters for ethane decomposition and fitted to the pressure dependence of the methyl radical combination show that the number of effective modes for ethane decomposition is 8 or 9. Carbon dioxide was found to be a quite ineffective third body for energy transfer. The results for the mercury-photosensitized decomposition of dimethyl ether have also been analyzed to obtain information about the combination of methyl radicals with methoxymethyl radicals. The combination of these radicals becomes pressure dependent at pressures less than about 15 mm. Kassel integrations based on the rate constant [Formula: see text]for the unimolecular decomposition of methyl ethyl ether at the C—C bond, and fitted to the observed pressure dependence of the combination reaction, lead to s = 10 for these reactions.The rate constant for the abstraction of a hydrogen atom by a methyl radical from dimethyl ether was found to be [Formula: see text]

Direct rate constant measurements for atomic hydrogen + methane .fwdarw. methyl + hydrogen, 897-1729 K, using the flash photolysis-shock tube technique

1991 ◽  
Vol 95 (2) ◽  
pp. 674-681 ◽  
Author(s):  
M. J. Rabinowitz ◽  
J. W. Sutherland ◽  
P. M. Patterson ◽  
R. B. Klemm
Keyword(s):  
Shock Tube ◽  
Rate Constant ◽  
Atomic Hydrogen ◽  
Flash Photolysis

ChemInform Abstract: Comment: A Reevaluation of the Rate Constant for Abstraction of Hydrogen from Isobutane by Methyl Radicals

ChemInform ◽  
1990 ◽  
Vol 21 (33) ◽  
Author(s):  
H.-X. ZHANG ◽  
M. H. BACK
Keyword(s):  
Rate Constant ◽  
Methyl Radicals

The reaction of hydrogen atoms with ethylene

1970 ◽  
Vol 316 (1527) ◽  
pp. 575-591 ◽  
Keyword(s):  
Hydrogen Atom ◽  
Rate Constant ◽  
Recombination Reaction ◽  
Methyl Radicals ◽  
Methyl Radical ◽  
Hydrogen Atoms ◽  
Ethyl Radical ◽  
Cracking Reaction ◽  
Computer Calculations ◽  
First Time

A detailed study has been made of the products from the reaction between hydrogen atoms and ethylene in a discharge-flow system at 290 ± 3 K. Total pressures in the range 8 to 16 Torr (1100 to 2200 Nm -2 ) of argon were used and the hydrogen atom and ethylene flow rates were in the ranges 5 to 10 and 0 to 20 μ mol s -1 , respectively. In agreement with previous work, the main products are methane and ethane ( ~ 95%) together with small amounts of propane and n -butane, measurements of which are reported for the first time. A detailed mechanism leading to formation of all the products is proposed. It is shown that the predominant source of ethane is the recombination of two methyl radicals, the rate of recombination of a hydrogen atom with an ethyl radical being negligible in comparison with the alternative, cracking reaction which produces two methyl radicals. A set of rate constants for the elementary steps in this mechanism has been derived with the aid of computer calculations, which gives an excellent fit with the experimental results. In this set, the values of the rate constant for the addition of a hydrogen atom to ethylene are at the low end of the range of previously measured values but are shown to lead to a more reasonable value for the rate constant of the cracking reaction of a hydrogen atom with an ethyl radical. It is shown that the recombination reaction of a hydrogen atom with a methyl radical, the source of methane, is close to its third-order region.

Curve-crossing collisions of excited lead atoms in flames

1981 ◽  
Vol 376 (1767) ◽  
pp. 545-564 ◽  
Keyword(s):  
Rate Constant ◽  
Atomic Hydrogen ◽  
Negative Temperature Coefficient ◽  
Negative Temperature ◽  
Model Systems ◽  
Attractive Potential ◽  
Hydrogen Atoms ◽  
Lennard Jones ◽  
Increasing Temperature ◽  
Curve Crossing

Lead atoms, present as a trace additive in a series of premixed H 2 –N 2 –O 2 flames, were excited to the 7 3 P o 1 state by 405.8 nm radiation from a nitrogen-pumped dye laser. Rate constants for spin-orbit relaxation to the 7 3 P o 0 state were obtained separately for collisions with atomic hydrogen and for collisions with the bulk flame gas, by measuring the relative intensities of fluorescence at 364.0 and 368.3 nm as a function of distance from the reaction zone in each flame. For hydrogen atoms the rate constant is typically 1 x 10 -9 cm 3 molecule -1 s -1 , decreasing with increasing temperature; for the bulk flame gas the rate constant is typically 1 x 10 -11 cm 3 molecule -1 s -1 , increasing with increasing temperature. Numerical calculations for model systems, with the use of Morse and Lennard-Jones potentials to describe the interaction of the colliding species, show that the negative temperature coefficient found for atomic hydrogen can be attributed to the crossing of attractive potential curves, corresponding to bound excited states of PbH.

Temperature and Pressure Dependence of the Rate Constant for the HO2+ NO Reaction

1996 ◽  
Vol 100 (10) ◽  
pp. 4026-4031 ◽  
Author(s):  
John V. Seeley ◽  
Roger F. Meads ◽  
Matthew J. Elrod ◽  
Mario J. Molina
Keyword(s):  
Rate Constant ◽  
Pressure Dependence ◽  
Temperature And Pressure
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