Df. Davidson et al., A SHOCK-TUBE STUDY OF METHYL-METHYL REACTIONS BETWEEN 1200 AND 2400 K, International journal of chemical kinetics, 27(12), 1995, pp. 1179-1196
The methyl-methyl reaction was studied in a shock tube using uv narrow
line laser absorption to measure time-varying concentration profiles o
f CH3. Methyl radicals were rapidly formed initially by pyrolysis of v
arious precursors, azomethane, ethane, or methyl iodide, dilute in arg
on. The contributions of the various product channels, C2H6, C2H5 + H,
C2H4 + H-2, and CH2 + CH4, were examined by varying reactant mixtures
and temperature. The measured rate coefficients for recombination to
C2H6 between 1200 and 1800 K are accurately fit using the unimolecular
rate coefficients reported by Wagner and Wardlaw (1988). The rate coe
fficient for the C2H5 + H channel was found to be 2.4 (+/-0.5) x 10(13
) exp(-6480/T) [cm(3)/mol-s] between 1570 and 1780 K, and is in agreem
ent with the value reported by Frank and Braun-Unkhoff (1988). No evid
ence of a contribution by the C2H4 + H-2 channel was found in ethane/m
ethane/argon mixtures, although methyl profiles in these mixtures shou
ld be particularly sensitive to this channel. An upper limit of approx
imately 10(11) [cm(3)/mol-s] over the range 1700 to 2200 K-was inferre
d for the rate coefficient of the C2H4 + H-2 channel. Between 1800 and
2200 K, methyl radicals are also rapidly removed by CH3 + H double ri
ght arrow (CH2)-C-1 + H-2. In this temperature range, the reverse reac
tion was found to have a rate coefficient of 1.3 (+/- 0.3) X 10(14) [c
m(3)/mol-s], which is 1.8 times the room-temperature value. (C) 1995 J
ohn Wiley & Sons, Inc.