Rate coefficients have been determined for the reactions at 30° of diazodiphenylmethane with benzoic acid and with m-XC₆H₄·CO₂H (X = Me, Cl, or NO₂) in methanol, ethanol, propan-1-ol, propan-2-ol, 2-methylpropan-1-ol, 2-methylpropan-2-ol, 2-methylbutan-2-ol, 2-methoxyethanol, dioxan, ethyl acetate, acetone, dimethylformamide, or dimethyl sulphoxide. The reactions of benzoic acid and of m-chlorobenzoic acid in benzyl alcohol have also been studied. Log k₀ and Hammett ρ values have been evaluated for the reactions in the fourteen solvents. For benzoic acid, rate coefficients have also been determined for this reaction in butan-1-ol, butan-2-ol, 2-n-butoxyethanol, diethyl oxalate, or chloroform. The reactions of p-chlorobenzoic acid with diazodiphenylmethane have also been studied in selected solvents. For many of the solvents, log k for the reaction of diazodiphenylmethane with benzoic acid may be correlated fairly well with dielectric constant by the expression log k= 0·98 – 2·60/(0·916 + 0·084ε) but the effect of specific interactions is usually discernible. These are believed to involve solvation of the carboxylic proton and of the transition state of the reaction. Specific interactions are most marked in dipolar aprotic solvents such as acetone, dimethylformamide, and dimethyl sulphoxide, but it is also relevant to consider them for alcohols. Limited multiple correlations of log k with pairs of solvent parameters are discussed.

The Hammett ρ constant is correlated broadly with dielectric constant by the expression ρ= 0·60 + 2·40/(0·75 + 0·25ε), but again specific interactions are important.

The rate coefficients for p-chlorobenzoic acid reacting with diazodiphenylmethane indicate a solvent dependence of the Hammett σ value for p-CI.

Values for the ratio R, of the amount of diazodiphenylmethane consumed in esterification to the total consumed (esterification + etherification) are presented and discussed for the reactions with benzoic acid in a number of alcohols.