Theoretical Studies of the Electrocyclic Reaction Mechanisms of Hexatriene to Cyclohexadiene

Abstract

The potential energy surfaces for electrocyclic reactions of hexa-1,3,5-triene were calculated by ab initio molecular orbital methods. The transition states of two electrocyclic reaction pathways (conrotatory and disrotatory) for hexa-1,3,5-triene were obtained. Both transition states are a true transition state. The transition state of the disrotatory pathway is about 11 kcal/mol lower in energy than that of the conrotatory pathway. The reaction path through cis−trans isomerization from cZc-hexa-1,3,5-triene to cyclohexa-1,3-diene was proposed. The conrotatory and the disrotatory reaction pathways were also characterized by the CiLC-IRC method.