Electrophilic substitution on the thiophen ring. Part III. Kinetics and mechanism of hydrogen exchange in acidic media

Abstract

Protodetritiation of 2- and 3-tritiothiophen in aqueous sulphuric and perchloric acids has been studied as a function of acidity and temperature. There is a linear relation between log k and –H₀ but the activation parameters are independent of acidity. General acid catalysis has been demonstrated in the protodetritiation of 5-methoxy-2-tritiothiophen. The relative reactivity of the 2- and 3-positions in thiophen appears to be a function of acidity. The mechanism of hydrogen exchange in thiophen is compared to that in benzene compounds.