Thermodynamic functions of ionization of t-butyl-substituted and methoxysubstituted phenols

Abstract

Thermodynamic ionization constants of 2-t-butylphenol, 3-t-butylphenol, 4-t-butylphenol, 3,5-di-t-butylphenol, and 3,5-dimethoxyphenol have been measured in aqueous solution by an e.m.f./spectrophotometric method within the temperature range 5-60°C and the thermodynamic functions of ionization ΔG₂₅, ΔH₂₅, ΔS25, and ΔC_p25 calculated. These results confirm the additivity of substituent effects noted previously for the ionization of 3,5-disubstituted phenols and indicate that this ionization process is relatively insensitive to steric effects.