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

Abstract.

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 _{∞ v}) and NON (D _{∞ h}) 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 _{∞ v} and D _{∞ h} 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(N₃)₂→N₂O+2N₂ and C₆(CH₂N₃)₆→3C₂+3H₂+6HCN+6N₂ 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(N₃)₂ decomposition are also provided.