Substituent effects on the thermodynamic functions of ionisation of phenols

The thermodynamic acidity constants of p-tert-butylphenol, eight 4-substltuted-2,6--dlmethylphenols, seven 4- substltuted-2,6-dlchlorophenols5 six 4-substltuted-2,6- dlbromophenols, 4-nltro-2,6-dllodophenol, and 4-formyl-2 5 6-dlmethoxyphenol have been measured over a wide range of temperature using an e.m.f./spectrophotometrlc technique. The thermodynamic functions ΔG°25 , ΔH° 25, and ΔS° 25 of proton Ionisation have been calculated using the Clarke and Glew procedure.