Theoretical study of nitro-nitrite rearrangement of NH₂NO₂

Abstract

Calculations designed to determine the barrier height for nitro-nitrite rearrangement in N-NO2 compounds are reported. Structures of NH2NO2, the four isomers of NH2ONO, dissociation products, and the transition state for nitro-nitrite rearrangement have been optimized at the MCSCF/4-31G level. The wave function of the transition state is characterized by two singly occupied orbitals and the geometry may be approximately described as separated NH2 and NO2 species with an N-N bond length of 2.845 Å. Energies have been obtained by large-scale multireference single- and double-excitation CI calculations (6-31G* basis). The transition state is predicted to lie with (without) zero-point energy 40.70 (46.68) kcal/mol above NH2NO2, 0.15 kcal/mol above (0.87 kcal/mol below) the NH2 + NO2 asymptote and 22.03 (26.71) kcal/mol above the H-trans, NONO-cis NH2ONO isomer, to which it leads. From these results, isomerization is expected to be competitive with N-NO2 bond scission, as observed in recent experiments on thermal decomposition of dimethylnitramine [Stewart, Jeffries, Zellweger, McMillen, and Golden, J. Phys. Chem., in press]. © 1989 American Chemical Society.