Heteroaromatic rings as substituents. Part II. Evaluation of the electrophilic substituent constants for 2- and 3-thienyl groups from the solvolysis of 2-chloro-2-(thienylphenyl)propanes in 90% aqueous acetone

Abstract

The rates of solvolysis of 2-chloro-2-{m(or p)-[2(or 3)-thienyl]phenyl}propanes have been measured in 90% aqueous acetone and the σ_p⁺ and σ_m⁺ constants for the 2- and 3-thienyl groups have been calculated by use of the Brown–Okamoto equation. Examination of the constants σ⁺(this work) and σ and σ^–(previously determined) shows that the thienyl groups exert a moderate electron-withdrawing inductive effect, and are able either to release or to withdraw electrons by a resonance effect, according to the type of reaction. The electron-releasing conjugative effect is markedly stronger than the electron-withdrawing effect. Both inductive and resonance effects are somewhat stronger for the 2-thienyl group.