Chelation of aqueous iron(III) by 2-acetyl-1,3-cyclohexanedione and beer ageing

Fe(III) is present in alcoholic drinks, such as wine and beer, and it is well known that this metal ion may affect beer fermentation, stability and quality. From a study of the complexation of 2-acetyl-1,3-cyclohexanedione with Fe(III)in aqueous solution, thermodynamic and kinetic parameters were obtained. Kinetics and equilibria in aqueous 1:1 chelation were investigated spectrophotometrically in aqueous solution at 25 °C and ionic strength of 0.5 mol dm−3 NaClO4. The mechanism proposed to account for the kinetic data involves a double reversible pathway, where both Fe3+ and Fe(OH)2+ react with the enol tautomer of the ligand. Some comparative analyses with the homologous iron(III) 2-acetylcyclohexanonate were established and the effect of previously cited changes during beer ageing considered.