Abstract

Ab initio and DFT calculations reveal that both imidoyl and thioyl radicals add to the nitrogen end of methanimine through simultaneous SOMO-pi*imine, SOMO-piimine, SOMO-LPN and pi*radical-LPN interactions between the radical and the imine. At the CCSD(T)/cc-pVDZ//BHandHLYP/cc-pVTZ level of theory, barriers of 13.8 and 26.1 kJ mol-1 are calculated for the attack of the methylimidoyl radical at the carbon- and nitrogen- end of methanimine, respectively, indicating that the imidoyl radial has a preference for addition to the nitrogen end of imine. On the other hand, barriers of 25.1 and 13.4 kJ mol-1 are calculated at the same level of theory for the addition reaction of the methanethioyl radical at the carbon- and nitrogen- end of methanimine, respectively. Natural bond orbital (NBO) analysis at the BHandHLYP/6-311G** level of theory reveals that SOMO-pi*imine, SOMO-piimine, SOMO-LPN and pi*radical-LPN interactions are worth 111, 89, 115 and 17 kJ mol-1, respectively, in the transition state (4) for the reaction of methylimidoyl radical at the nitrogen end of methanimine; similar interactions are observed for the chemistry involving all the radicals studied here. These multi-component interactions are responsible for the unusual motion vectors associated with the transition states involved in these reactions.