| Abstract: | The AM-1 method with full optimization of geometry was used to study several proposed isomerization mechanisms for dichloro- and difluorobenzenes on active centers as proton donors. Preferred positions of proton addition in dihalobenzenes were studied and protonation and activation energies for intramolecular migration of hydrogen and halogen atoms were determined. It was shown that the isomerization mechanisms are the same for dichloro-and difluorobenzenes and result from a 1,2-shift of the halogen. The activation energy for migration of a fluorine atom in difluorobenzenonium cations is substantially higher than for a chlorine atom in dichlorobenzenonium cations. The data obtained on the mechanism have experimental verification.A. N. Nesmeyanov Institute Heteroorganic Compounds, Russian Academy of Sciences, 117813 Moscow. N. D. Zelinskii Institute of Organic Chemistry, Russian Academy of Sciences, 117433 Moscow. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 3, pp. 731–737, March, 1992. |
