Fragmentation of intermediate radical anions determines the main features of the hydrodefluorination of isomeric perfluoroxylenes. Quantum chemical substantiation

Abstract

Оn the basis of a quantum chemical analysis of potential energy surfaces (PESs) of intermediate radical anions (RAs), we give a theoretical interpretation for the emergence of unusual products of the reductive deflourination of perfluorinated xylenes under the action of Zn(Cu)-DMF-H2O, observed by V.I. Krasnov et al in 1997: in the case of ortho- and meta-isomers, the fluorine atoms of the aromatic ring are replaced by hydrogen atoms, while the fluorine atoms of trifluoromethyl groups are retained. Using a hybrid model combining the supermolecular approach with the polarizable continuum model to consider the effects of solvation, we performed DFT calculations of the sections of the PESs mentioned along the coordinates of fluoride ion elimination from different positions of the RAs. The calculation results show that an outcome of the competition between the aryl and alkyl C-F bonds to be broken is determined by a ratio of the corresponding activation barriers.