Nitromethane dissociation: Implications for the CH3 + NO2 reaction

Abstract

The thermal decomposition of nitromethane under highly diluted conditions in shock tubes has been analyzed in terms of a detailed chemical kinetic model. The experimental data were adopted from Glanzer and Troe, Hsu and Lin, and Zhang and Bauer, respectively; they cover the temperature range 1000–1400 K and pressures from 0.5 to 6.0 bar. Based on these results, rate constants for the reactions CH3NO2(+M) ⇌ CH3 + NO2(+M) (R1) and CH3 + NO2 ⇌ CH3O + NO (R14) have been re-examined. The high and low pressure limits for reaction (R1) determined by Glanzer and Troe have been shown to be consistent with more recent shock tube data, provided a center broadening parameter is introduced to describe the fall-off behavior. Our reinterpretation of the shock tube results of Glanzer and Troe together with room temperature measurements indicate that the rate constant for (R14) decreases slightly with temperature, as k14 = 4.0 · 1013T−0.2 cm3mol−1s−1. At high temperatures and atmospheric pressure this reaction is more than an order of magnitude faster than recombination of CH3 and NO2 to form nitromethane. Based on the available data for the forward and reverse rate of reaction (R1) a value of 66.7 ± 2.0 cal/(mol K) for the entropy S0,298 of CH3NO2 is estimated. © 1999 John Wiley & Sons, Inc. Int J Chem Kinet 31: 591–602, 1999