Solvent hydrogen bonding and structural effects on the reaction of biphenyl and naphthalene sulphonyl chloride with para-substituted anilines in dime thy lfonnantide/ acetonitrile ntixtures

PG and Research Department of Chemistry, Thiagarajar College (Autonomous), Madurai-625 009,

Tamilnadu, India

E-mail : bukanch@yahoo.co.in

Manuscript received online O3 March 2012, revised 22 April 2012, accepted 24 April 2012

Substitution reactions of some of para-substituted anilines with biphenylsulphonyl chlolride and naphthalenesulphonyl chloride were carried out conductometrically in dimcthylformamide/acctonitrile mixtures. The correlation of second order rate constants with Hammett's substituent constants yil'lds a fairly linear straight line with a negative slope. The correlation of rate data with Kamlet-Taft's solvatochromic parameters is excel! cut (100R² = 97%) in both the substrates. The solvation model proposed is well supported by the solvatochromism exhibited by aniline in the solvent mixture under investigation. The molar extinction coefficient (ɛ_\(max\))of aniline varies appreciably up to ~25% with the change in composition of the mixture. The multivariate correlation analysis of ɛ_\(max\) (with \(α\), \(β\), \(π\)*) suggests that the solvation around NH₂ moiety of aniline through hydrogen bond donor (HBD) property is found to he dominant in the solvation process and consequently in altering the rate. The observation is that the dominance of HBD property in solvation is further confirmed by the cyclic voltammetric oxidation of aniline in the solvent mixture.