Ultrasonic Absorption Study of the Complex Formation of Zinc(II) Carboxylates in Aqueous Solution

Article abstract of DOI:10.1021/j100358a022

Ultrasonic absorption of aqueous zinc(II) formate, acetate, and propionate is measured in the metal-rich concentration regions with a pulse technique over the frequency range 3-260 MHz.The single relaxations observed in all cases are attributed to the complex formation of zinc(II) carboxylates via the Eigen-Tamm mechanism of stepwise association.The reaction parameters are determined from the concentration dependences of the relaxation frequency and amplitude.Both the association constant of outer-sphere complex and the rate constant of ligand substitution indicate ligand dependences; the former is larger while the latter is smaller with the higher carboxylate.However, the uncertainties involved in these reaction parameters prevent the elucidation of the above feature.The volume changes of the outer-sphere complexing are substantially less than those of the ligand substitution; the volume change of the latter is larger for the higher carboxylate.