Structure -Activity Correlation of Thiophene-2- Sulfonic Acid and Thiophene by Rapid Chlorination Kinetics using Hydrodynamic Voltammetry

V.T. Borkar*
Department of Chemistry, Nowrosjee Wadia College Research Centre, Affiliated to the Savitribai Phule Pune University, Pune, Maharashtra, India

A B S T R A C T
The rapid chlorination kinetics of thiophene-2-sulfonic acid by molecular chlorine in aqueous solution has been investigated employing hydrodynamic volatammetry. The specific reaction rate and energy of activation for the reaction were found to be respectively 18 M^-1s^-1 and 53 kJ mol^-1 at 24.5⁰C. These data complemented with those for the chlorination of thiophene obtained under identical conditions, quantitatively ascertained the markedly less reactivity of thiophene-2-sulfonic acid relative to thiophene in these reactions. The substituent effect of the sulfonic acid moiety has been proposed as the cause of the difference in the reactivity of the two substrates.
Keywords: Chlorination, hydrodynamic voltammetry, thiophene-2-sulfonic acid