Kinetic study of E2 eliminations from 2-thienylethyl bromides and toluene-p-sulphonates promoted by sodium ethoxide in ethanol

Abstract

Kinetics of E2 elimination from 5-substituted 2-(2-thienyl)ethyl tosylates (ρ 2·23) and bromides (ρ 1·89) and from 2-(3-thienyl)ethyl bromide were studied in EtOH–EtONa at 50°. The transition state for these reactions appeared to be very close to that for the corresponding elimination from 2-phenylethyl derivatives. Values of σ_α(+0·26) and σ_β(–0·05) were calculated for the sulphur heteroatom. No significant conjugative interaction exists between sulphur and the negative charge which develops in the transition state of the reaction.