Additive substituent effects on the thermodynamic functions of proton ionization processes. Part III. Phenols with adjacent methyl and chloro-substituents

Abstract

Thermodynamic acidity constants of 4-chloro-3-methylphenol, 4-chloro-3,5-dimethylphenol, 3,4-dichlorophenol, and 3,4,5-trichlorophenol have been measured spectrophotometrically within the temperature range 5–60 °C and the standard enthalpies and entropies of proton ionization have been calculated. The results are discussed in terms of the general additivity hypothesis previously formulated and with reference to earlier studies of additive substituent effects.