Substituent Effects in Naphthalene. III. Saponification of 6- and 7-substituted Methyl 2-naphthoates and Application of the Hammett Equation

The rates of alkaline hydrolysis in 70% v/v aqueous dioxan at 25° have been determined for the 6- and 7-NO, 6- and 7-CN, 6- and 7-F, 6- and 7-Cl, 6- and 7-NMe, 6-Me and 6-OMe substituted methyl 2-naphthoates, methyl 2- naphthoate, m-NO, p-NO, p-Me substituted methyl benzoates, and methyl benzoate. An examination of the application of the Hammett equation reveals that this linear free energy relationship applies with high precision but that it yields different ρ values for different substituent-reaction centre dispositions. This may be a general feature for all aromatic systems although in many cases the differences are not larger than the experimental uncertainties