Semi-empirical (AM1) calculations of the nitration of amines

The mechanism of amines nitration has been studied using the AMI method. Th e reaction involves a series of amines Me2NL (L being a leaving group) and the nitronium ion NO2+. Calculations carried out with 14 different electrop hilic leaving groups corresponding to 7 functionalities (L = H, CH2Ph, CHO, COR, X, SO2R, Si(CH3)(3)). In each case a complete potential energy diagra m is derived from the structure of reagents, products, reaction intermediat es and transition states. The first intermediate corresponds to a complex b etween NO2+ and L (if L has a Lewis basicity) or with the nitrogen atom (if L has no Lewis basicity). The last intermediate involves the leaving group LC and the group NO2 of the nitramine. The energy of activation depends up on the nature of the leaving group. The results are in good agreement with experimental reactivity data.