Modeling (Prediction) of the Structure of Possible Transition States of Aromatic Hydrocarbons

Based on the properties of a conjugate p -electron system, a method is proposed for predicting possible spatial structures of aromatic hydrocarbons during their skeletal carbon transformation. The existence of predicted spatial structures is explained by the stabilizing effect of π-electron conjugation. The proposed method for predicting possible spatial structures was verified by DFT B3LYP/6-31G* and RHF/6-31G calculations including electron correlation at the MR4-SDTQ level on the example of benzene and hexafluorobenzene molecules. The proposed method gives stable results regardless of the methods used for calculating the electronic structure of molecules. It is found that of all the predicted spatial structures, one corresponds to the ground state, and the others correspond to transition states. The schemes of thermal isomerization of benzene and hexafluorobenzene, constructed with the potential barriers calculated by the Gonzales–Schlegel method, are consistent with the experimental data.