Valence bond and molecular orbital studies of three N2O isomers, and valence bond representations for some azide decompositions

The results of STO-6G valence bond calculations with Lewis-type valence bond structures are reported for the S=0 spin ground states of the linear NNO (C-infinityv) and NON (D-infinityh) isomers of N2O. It is calculated that the singlet diradical character of the NON isomer is substantially larger than for the NNO isomer. The results of B3LYP/6-31G(d) density functional calculations are also reported for the C-infinityv and D-infinityh ground states, the single-determinant approximations to the lowest-energy S=1 spin excited states of these two isomers, and for the triangular C-2v isomer. The calculated bond lengths are in accord with qualitative valence bond considerations. Valence bond formulations of mechanisms for O(N-3)(2)-->N2O+2N(2) and C-6(CH2N3)(6)-->3C(2)+3H(2)+6HCN+ 6N(2) decompositions are presented. These formulations exploit the singlet diradical character present in the azide substituents. The results of further molecular orbital calculations for the O(N-3)(2) decomposition are also provided.