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

Department of Chemistry, Gandhigram Rural University, Gandhigram-624 302, Tamilnadu, India E-mail : drkpelango@rediffmail.com Manuscript received 5 May 2009, revised 5 October 2009, accepted 31 December 2009 Substitution reactions or eleven para- and meta-substituted benzylamines with benzenesulphonyl chloride in different mole fractions of dimethylsulfoxide (DMSO) in acetonitrile (AcN) have been investigated conductometrically. The second order rate constants round to increase with an increase in the mole fraction of DMSO 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