Ab initio molecular orbital study of valence isomers of pyridine

Abstract

Ab initio calculation at HF/6-31G*, HF/6-31G**, HF/6-311G**, HF/6-311++G**, RMP2-FC/6-31G*, and B3LYP/6-31G* levels of theory for geometry optimization and MP4(SDQ)/6-31G* for a single point total energy calculation are reported for pyridine ( 7) and eight valence isomers of pyridine ( 8– 15). The calculated energy difference (63.39 kcal mol −1) between pyridine and the most stable valence isomer of pyridine (3-aza-benzvalene, 8) is smaller than the difference (73.60 kcal mol −1) between benzene and Dewar benzene ( 3).