E1CB NATURE OF TRANSITION STATE IN ELIMINATION REACTION OF PHENETHYL SULPHOXIDES IN BASIC MEDIA

Rates of elimination were determined for a number of p-X-phenethyl methyl sulphoxides (X = H, Me, OMe, and Cl) with potassium 1,1-dimethylethoxide in 1,1-dimethylethanol; correlation against Hammett σ-constants gave a ρ-value of +4.4. The reaction was found to have a β-deuterium isotope effect of 2.7 and no exchange of the β-hydrogens in the substrate was detected during the elimination. The transition state for the reaction is suggested to have substantial carbanion character.