Correlations of relative rate constants for sulfonation of alkylbenzenes with molecular structure

Relative sulfonation rates of a series of linear alkylbenzenes are correlated with carbon numbers of the linear branches from which the alkyl groups are constituted. The trends are interpreted in terms of a composite steric parameter which reflects the degrees of freedom lost in forming the transition state. The results lend support to the argument that the entropy of activation is the main factor determining the relative reactivities of the different homologs and isomers in this reaction.