Solvent hydrogen bonding and structural effects on nucleophilic substitution reactions. Part-7: Reaction of benzenesulphonyl chloride with substituted benzylamines in acetonitrile/dimethylsulfoxide mixtures

Substitution reactions of eleven para- and meta-substituted benzylamines with benzenesulphonyl chloride in different mole fractions of dimethylsulfoxide (HMSO) in acetonitrile (AcN) have been investigated conductometrically. The second order rate constants found to increase with an increase in the mole fraction of HMSO up to 0.5 mole fraction and beyond that it remained nearly constant. Multiple correlation analysis of the rate data via Kamlet-Taft's solvatochromic parameters revealed that the solvent H-bonding and dipolarity/polarizability plays a dominant role in governing the reactivity and also solvent-solvent interaction influenced the preferential solvation and consequently the rate of the reaction. A curved Hammett plot was obtained and a mechanism was proposed to account for this nonlinear behaviour observed.