Possible Thermally Induced Skeletal Isomerizations of Pyridine and Phosphinine

Based on the properties of the conjugated p-electron system in cyclic polyenes, possible steric and electronic structures of transition states in thermal isomerizations of pyridine and phosphinine in an oxygen-free atmosphere have been determined by DFT calculations using B3LYP functional and 6-31G* basis set. The degree of stabilization of the transition states depends on the level of p-electron conjugation. Schemes of the thermal isomerizations of pyridine and phosphinine have been constructed, and potential barriers to these transformations have been calculated. The study of the reactivities of pyridine and phosphinine in the thermal isomerization processes has revealed lower aromaticity of phosphinine compared to pyridine.