The reaction of OH and OD with nitromethane and OD with perdeuteronitromethane

Abstract

Laser photolysis/laser-induced fluorescence (LIF) is employed to investigate the kinetics of the reactions, OH+CH 3NO 2, OD+CH 3NO 2, and OD+CD 3NO 2 over the temperature range 296–671 K. Photolysis of nitromethane at 266 nm generates OH or OD radicals. Rate constants are independent of pressure over the range 100–300 Torr. The following Arrhenius equations are calculated: k =(1.1±0.4)x10 −12 exp[−(2730±290 cal/mol)/ RT] cm 3 s −1 for OH, OD+CH 3NO 2 and k =(5.3±2.4)×10 −13 exp[−(2860±340 cal/mol)/ RT] cm 3 s −1 for OD+CD 3NO 2. A hydrogen atom abstraction mechanism is supported by evidence from isotopic studies, transition-state theory calculations, absence of pressure effects, known energetics, and measured activation energies. Transition-state theory (TST) calculations predict non-Arrhenius behavior as temperatures approach the combustion regime. The TST calculation is fit by the equation, k = 4.37 × 10 −20 T 2.4 exp(− 340/T) cm 3 s −1 over the temperature range 200–2000 K.