Theoretical study of nitro-nitrite rearrangement of nitramide

Abstract

ROBERTA P. SAXON and MEGUMU YOSHIMINE. Can. J . Chem. 70, 572 (1992). Calculations designed to characterize the transition state and determine the barrier height for rearrangement of nitromethane to methyl nitrite are reported. Structures of CH,NO,, C H 3 0 N 0 , dissociation products, CH3 + NOz and CH,O + NO, and the transition state for nitro-nitrite rearrangement have been optimized at the MCSCF/4-31G level. The geometry of the transition state may be approximately described as separated CH3 and NO, species with extremely long C-N and C 4 bond lengths, 3.396 and 3.654 A, respectively. Energies have been obtained by large-scale multireference singleand double-excitation CI calculations (6-3 lG:+ basis). The transition state is calculated to lie 56.7 kcal/mol above nitromethane (with zero-point energy). A C-N bond dissociation energy of 51.7 kcal/mol is obtained. Results are compared with the infrared multiphoton dissociation experiment of Wodtke, Hintsa, and Lee.