Nitromethane dissociation: Implications for the CH3+NO2 reaction

The thermal decomposition of nitromethane under highly diluted conditions i n shock tubes has been analyzed in terms of a detailed chemical kinetic mod el. The experimental data were adopted from Glanzer and Tree, Hsu and Lin, and Zhang and Bauer, respectively; they cover the temperature range 1000-14 00 K and pressures from 0.5 to 6.0 bar. Based on these results, rate consta nts for the reactions CH3NO2(+M)half arrow right over half arrow left CH3 NO2(+M) (R1) and CH3 + NO2 half arrow right over half arrow left CH3O + NO (R14) have been re-examined. The high and low pressure limits for reaction (R1) determined by Glanzer an d Tree have been shown to be consistent with more recent shock tube data, p rovided a center broadening parameter is introduced to describe the fall-of f behavior. Our reinterpretation of the shock tube results of Glanzer and T ree together with room temperature measurements indicate that the rate cons tant for (R14) decreases slightly with temperature, as k(14) = 4.0.10(13)T( -0.2) cm(3)mol(-1)s(-1). At high temperatures and atmospheric pressure this reaction is more than an order of magnitude faster than recombination of C H, and NO, to form nitromethane. Based on the available data for the forwar d and reverse rate of reaction (R1) a value of 66.7 +/- 2.0 cal/(mol K) for the entropy S-0.298 of CH3NO2 is estimated. (C) 1999 lohn Wiley G Sons, In c. Int J Chem Kinet 31: 591-602, 1999.