Calculation of the proton affinities of polychlorobenzenes and the activation energies of 1,2-hydrogen shifts in arenonium ions

The proton affinities of benzene, chlorobenzene and polychlorobenzenes with the common formula C₆Cl _n H_6–n (n=0–6) have been calculated by the AM1 method. The proton affinity averaged over the protonated isomers increases monotonically asn growing from 0 to 5, and then decreases when passing from pentato hexachlorobenzene. The energies of proton addition to the different positions in the polychlorobenzene molecules have been estimated. It has been found that unsubstituted carbon atoms are preferred for proton attack. The positions with the highest proton affinity are the carbon atoms with the largest negative charges. The activation energies of 1,2-hydrogen shifts in arenonium ions of the polychlorobenzenes have been calculated.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1213–1217, July, 1993.