A mechanistic approach to solvolysis of n-caproyl chloride (n-CH3(CH2)4 COCl) in solutions of acetone and acetonitrile with nucleophilic solvents

The study of the rate and rate constants in the alcoholysis of n-caproyl chloride in acetone and acetonitrile, reveals that SN2 mechanism is more favourable than SN1. A plot of logarithm of rate constant against the logarithm of molar concentration of alcohol gives a straight line with a slope close to 1.1 and that with respect to water is 1.5 both in acetone and acetonitrile. This shows that in addition to SN2 mechanism, Addition-Ionization mechanism is simultaneously operating. Moderately high enthalpy of activation favours an Addition-ionisation pathway. A large negative entropy of activation favours an SN2 mechanism. Studies on the effect of methanol, phenol and mercuric chloride on the hydrolysis also gave evidence for simultaneous involvement of SN2 and Addition-Ionization mechanism. However addition-ionisation mechanism is having greater contribution in aqueous acetonitrile than in aqueous acetone.