Kinetics and thermodynamics of sulfuric acid-mediated cleavage of substituted diaryl sulfones

Abstract

The cleavage of di-p-tolyl sulfone with concentrated sulfuric acid has been shown to occur at elevated temperatures (>120°C). The products were confirmed as the corresponding sulfonic acids by gas chromatography-mass spectrometry analysis of the sulfonate ester derivatives. The cleavage reactions of a series of di-p-substituted diaryl sulfones with sulfuric acid have been studied. A method using a double end-point titration has been used to quantify the amounts of sulfonic acid formed as the reactions proceed. These data have been used to construct second-order rate plots over a range of temperatures and to determine rate constants for the cleavage reactions. The second-order rate plots showed good linearity. Activation energies were determined from Arrhenius plots of the second-order rate constants over a range of temperatures. The presence of electron-donating groups decreases the activation energy of the reaction, whereas the presence of electron-with-drawing groups increases the activation energy of the reaction.