The contribution of ring conformational flexibility to the relative stability of isomeric cyclohexadienes

The relative stability of isomeric cyclohexadienes was studied using density functional theory (B3LYP) and second-order Møller–Plesset perturbational method (MP2). It was demonstrated that higher conformational flexibility of dihydrocycles in 1,4-isomer results in additional stabilization of this molecules with respect to 1,3-cyclohexadiene. This fact is caused by the presence of low-frequency vibrations in 1,4-dihydrocycle which are populated at room temperature.