Energy barriers to gas-phase unimolecular decomposition of mono- and dinitrotoluenes

Resumo

Alternative paths of gas-phase unimolecular decomposition of three nitrotoluenes and six dinitrotoluenes, in particular homolytic dissociation of the C–N bond, nitro–nitrite rearrangement, intramolecular hydrogen transfer from the methyl to nitro group with formation of isomeric aci-nitrotoluenes, and various paths involving formation of bicyclic intermediates, have been studied at the DFT B3LYP/6-31+G(2df,p) level of theory using GAUSSIAN 09 software package. The most energetically favorable path for o-nitrotoluene and 2,3-, 2,4-, 2,5-, and 2,6-dinitrotoluenes is the formation of aci-nitrotoluenes. The effect of the substrate structure on the competition between different mechanisms of these reactions has been analyzed.