The kinetics of solvolysis of 1-(3-chloro-4-methylphenyl)- and 1-(3-chloro-4-t-butylphenyl)-1-methylethyl chlorides in aqueous acetone

Abstract

1-(3-Chloro-4-methylphenyl)- and 1-(3-chloro-4-t-butylphenyl)-1-methylethyl chloride have been prepared from the corresponding alcohols by action of hydrogen chloride. The alcohols were prepared by the reaction of methylmagnesium iodide with the ester of the corresponding disubstituted benzoic acid. The solvolysis rates of the two alkyl chlorides have been measured in 90% aqueous acetone at various temperatures. The energies of activation for the solvolysis reactions have been calculated. The results are compared with those obtained for cumyl chloride and its mono-substituted derivatives. The observed and calculated rate constants of solvolysis have been compared and it has been found that the observed rate constant for 1-(3-chloro-4-methylphenyl)-1-methylethyl chloride is 79% of the predicted value, while for 1-(3-chloro-4-t-butylphenyl)-1-methylethyl chloride it is 44%. This decrease in the observed rate constant as compared with the calculated value might be due to the steric interaction between the 3-Cl and 4-alkyl group. It also shows that the calculations of the rates of solvolysis of 3-chloro-p-alkylcumyl chlorides based upon additivity, underestimate the retarding effect of the chlorine substituent.