Mechanisms for reactions of halogenated compounds. Part 5. Orientating effects of fluorine substituents on nucleophilic substitution in naphthalene and other polycyclic systems

Abstract

Separate activating effects have been determined for fluorine atoms as substituents at ortho-positions and at sites in the remote ring, relative to the position of attack by methoxide in methanol, in polyfluoronaphthalenes. Fluorine activates at sites in the remote ring that are adjacent to the centres of high charge density in the transition state, but is slightly deactivating when attached directly to these sites. Fluorine at ortho-positions activates. These results enable a simple model, which accounts for orientation of nucleophilic aromatic substitution, to be extended to perfluoropolycyclic compounds.