Mechanism of Decomposition of Nitroaromatics. Laser-Powered Homogeneous Pyrolysis of Substituted Nitrobenzenes

摘要

Laser-powered homogeneous pyrolysis (LPHP) has been used to study the gas-phase thermal decomposition of nitrobenzene (NB), m-dinitrobenzene (m-DNB), p-nitrotoluene (p-NT), o-nitrotoluene (o-NT), and 2,4-dinitrotoluene (2,4-DNT) under conditions where surface-catalyzed reactions are precluded. The Arrhenius parameters have been determined by comparative rate measurements relative to cyclohexene decomposition and the reaction mechanisms have been established. In all cases, the rate-limiting step is the homolysis of the Ar-NO2 bond. The measured Arrhenius parameters for homolysis range from log A = 14.5 to 16.4 and E sub a from 67.0 to 70.0 kcal/mol. The C-NO2 bond dissociation energies (kcal/mol) and values of log k (S superscript-1) have been derived from these results.