Complexation of lanthanoids(III) with aromatic carboxylic and α-hydroxycarboxylic acids in aqueous solution and chloroform

Abstract

The heats of complexation of lanthanoids(III) with several carboxylic acids in 0.1 M NaClO 4 solution and the formation constants of the adduct formation of lanthanoid(III) chelates with these acids in chloroform have been measured. The heat of complexation of lanthanoids(III) with the α-phenyllactate ion is found to be more exothermic with increasing atomic number than that with the α-hydroxyphenylacetate ion. The adduct formation constant of lanthanoid(III) chelates with α-phenyllactic acid decreases with increasing atomic number, but that with α-diphenylhydroxyacetic acid does not change. A similar trend was observed in the adduct formation with phenylacetic and diphenylacetic acids. These data are discussed in connection with the basicity of the ligand acids.