Kinetics and thermodynamics of complex formation between aluminium(III) and citric acid in aqueous solution

Abstract

By stopped-flow and pressure-jump relaxation measurements, equilibrium and rate constants for the formation of aluminium citrate complexes have been determined at 293.7 K. For the monodentate complex, AlH₂Cit²⁺, the bidentate complex, AlHCit⁺, and the tridentate complex, AlCit, the stability constants are (8.2 ± 1.5)× 10², (3.6 ± 1.6)× 10⁶ and (5.3 ± 2.3)× 10¹⁰ dm³ mol^–1, respectively. The rate constants for the formation of the monodentate and the bidentate complexes are (5.4 ± 0.5)× 10³ and 80 ± 10 dm³ mol^–1 s^–1, respectively.