Second-order rate constants have been determined spectrophotometrically for nucleophilic substitution reactions of p-nitrophenyl benzoate with various anionic nucleophiles including 6 ${alpha}$ -effect nucleophiles. The logarithmic second-order rate constants for the aryloxides give a good Bronsted correlation with the respective basicity while the ones for p-chlorothiophenoxide and hydroxide exhibit significantly positive and negative deviations, respectivity, from the Bronsted linear line. The deviations are attributed to a solvation effect rather than a change in the reaction mechanism. The ${alpha}$-effect nucleophiles except highly basic ones demonstrate significantly higher nucleophilicity (the ${alpha}$ -effect) than would be predicted from the respective basicity. The effect of solvation and polarizability appears to be important for the ${alpha}$-effect as well as for the reaction rate.