Hydrogen bonding in some adducts of oxygen bases with acids. Part 7.—Thermodynamic study by infra-red spectroscopy of the association of chloroacetic acids with some oxygen bases

Abstract

The association between the chloroacetic acids (mono-, di-, and tri-) and a series of bases (dimethyl, dibenzyl, diphenyl sulphoxide, triphenylphosphine oxide, diphenyl selenoxide) in carbon tetrachloride was studied using the absorbance of the OH stretching band of the free acid. K_as, ΔG^o, ΔH^o and ΔS^o of association were derived from the spectrophotometric data. A linear relationship between ΔH^o and the pK_a of the acids was found. The thermodynamic quantities reflect also the basicity of the proton acceptors but not in a simple relation. The strongest hydrogen bond is formed between trichloroacetic acid and diphenyl selenoxide, –ΔH^o being ∼67 kJ/mol.