LSER and LFER in the reaction of benzimidazole with benzyl bromide

Abstract

The second order rate constants of the nucleophilic substitution reaction of benzyl bromide with benzimidazole have been obtained conductometrically in 11 different solvents in the

temperature range 303-318 K. The rate constants are correlated with the polarisability (<i>P</i>)<i> </i>of the solvent and hydrogen bond acceptor basicity (<i>β</i>) of tile solvent leading to a biparametric equation, log <i>k</i> = -7.86+20.23<i>P</i> + 1.45β (n = 11, <i>R </i>= 0.93, SE =0.08). Substituent effect on rate of the reaction suggests that both electron donating group (<i>p</i>-CH₃) and electron withdrawing groups (<i>p</i> -NO₂, <i>p</i>-Br) enhance the rate of the reaction compared to the unsubstituted compound. The substituted (<i>p</i> -NO₂, <i>p</i>-Br) and the unsubstituted compound form a linear free energy relationship.