Determination of the Acidity Constants of Chlorinated Phenolic Compounds by Liquid Chromatography

The acidity constants of all chlorophenols, 15 chlorobiphenols, eight chloroguaiacols, seven chlorocatechols, and two chlorovanillins are measured on a prepacked reversed-phase column at 20°C in a 60% methanol solution by investigating the pH dependence of their capacity factors. Comparison of the results obtained in this work is made with those values that are found in the literature. The effect of substituents on the acidity constants is discussed in the light of Hammett's correlation of the substituent constants of different radicals. The effect of a changing medium upon the acidity constants is also examined.