A theoretical investigation by the MNDO method of the explosive complexes of hydroxide ion with 1,3,5-trinitrobenzene and 4,6-dinitrobenzofuroxan

Abstract

The theoretical study of the covalent sigma adducts of hydroxide ion with 1,3,5-trinitrobenzene (TNB) and 4,6-dinitrobenzofuroxan (DNBF), a “super-electrophile”, using the MNDO method, is reported. The two MNDO optimized structures show remarkable similarities to the crystal structures of the methoxide ion adduct of 1,3,5-trinitrobenzene and the ethoxide ion adduct of 7-ethoxy-4,6-dinitrobenzofurazan, respectively. Any differences between the “gas phase” and the crystal structures can be accounted for by the interactions which are expected to occur between the oxygens of the nitro group para to the sp 3 carbon and the metal gegenion in the crystal. The calculated charge densities in the TNB·OH − and DNBF·OH − adducts show that while most of the negative charge in the adducts is borne by the NO 2 groups, and to a lesser extent on the furoxan moiety, the benzenoid ring also carries partial negative charge, in agreement with results of PPP calculations on related structures. The computed heats of formation are in accord with the lesser thermodynamic stability of the DNBF·OH − adduct compared to the TNB·OH − adduct.