The thermodynamics of the acid dissociation of some amino-alcohols in water

Abstract

This paper reports the acid dissociation constants from 0° to 60° of the conjugate acids of the following six substituted 2-amino-ethanols: H₂N·CH₂·CHMe·OH, H₂N·CHEt·CH₂OH, H₂N·CMe₂·CH₂OH, H₂N·C(CH₂OH)₂Me, EtHN·CH₂·CH₂OH, and Et₂N·CH₂·CH₂OH. The data are analysed to obtain values of ΔG°, ΔH°, ΔS°, and ΔC_p° for the acid dissociations. These thermodynamic quantities are discussed in relation to the structure of the acids, and ion–solvent and molecule–solvent interactions. A novel method of comparing acid strengths is suggested and the change in energy of dissociation per OH group, calculated for zero entropy change, is found to be –1250 cal. mole^–1.