Gaussian‐2 and density functional studies of H 2 NNO 2 dissociation, inversion, and isomerization

Several computational approaches, including Gaussian‐2 (G2) and nonlocal density functional theory ( DFT‐GGA ), have been used to calculate the energy requirements for (a) H 2 NNO 2 dissociation (through NN bond scission), (b) inversion of the amine group, and (c) isomerization through the nitro‐nitrite rearrangement. Taking zero‐point energies into account, the G2 predictions are 53.6 kcal/mole for the dissociation energy and 1.5 kcal/mole for the inversion barrier. The corresponding DFT‐QGA values are 48.4 and 0.9 kcal/mole, and an activation energy of 48.7 kcal/mole for the nitro‐nitrite rearrangement. The DFF‐OGA results indicate that dissociation and rearrangement should be competitive for H 2 N‐NO 2 . The same conclusion was reached earlier by Saxon and Yoshimine on the basis of MRCISD/6‐3lG* calculations, although their computed energy requirements differ from the present ones by approximately 8 kcal/mole. © 1992 John Wiley & Sons, Inc.