The mechanism of the observed amine sensitization of nitromethane has been investigated by means of a density functional procedure (Becke-3 exchange, Lee, Yang and Parr correlation functionals and 6-31+G*basis set). Of the various possibilities examined, the most reasonable is that involving theaci(nitronate) ion in an activated form which can interact with the amine eventually to yield another amine and the nitrite ion. The key features of this process are firstly an activation barrier less than the C–NO2dissociation of nitromethane, secondly a net release of energy and thirdly products that can sustain the reaction.