Halide-induced elimination reactions

Abstract

A literature survey is made of halide-induced elimination reactions, covering the preparative, kinetic and mechanistic aspects. Preparative studies indicate that halide ion in a dipolar aprotic solvent is an ideal eliminating agent - it is mild, selective, stereospecific, clean and efficient. Whether the reaction follows the E2H or the E2C mechanism is not clear, but no compelling evidence for the E2C mechanism exists. A study is made of the DDT/halide reaction in acetone, and the results are somewhat different from earlier studies. The reason for this is not readily apparent. It is shown that nucleophilic attack by halide ion at Cα of the substrate is still possible, despite deactivation of that centre by electron-withdrawing chlorine atoms.