A computational study of the valence isomers of benzene and their group V hetero analogs

Abstract

Ab initio [HF, MP2 and up to CCSD(T)] and hybrid density functional B3LYP calculations were performed on benzene, group V heterobenzenes, (CH)5X (X = N, P and As), and their corresponding valence isomers. Six valence isomers of benzene and ten valence isomers of (CH)₅X have been identified and their structures, energetics, relative stabilities and their reactivities were studied. The stability ordering observed in phosphinine and arsabenzene isomers is very similar to that in the benzene isomers (benzene > benzvalene > Dewar benzene > prismane > bicyclopropenyl > trans-Dewar benzene). In the pyridine isomers, one of the bicyclopropenyl isomers (C2N) is computed to be more stable than the prismane isomer (P1N). The framework is the main factor determining the relative stabilities and the nature of the substituent is of secondary importance. Exactly the same trend in the relative energies is observed for phosphinine and arsabenzene isomers.