RATE CONSTANTS AND EQUILIBRIA OF MONOCHELATE FORMATION OF IRON(III) WITH 2-ACETYLCYCLOHEXANONE

Kinetics and equilibria in aqueous 1:1 chelation of iron(III) by 2-ace tylcyclohexanone have been investigated spectrophotometrically in aque ous solution at 25 degrees C and 0.5 mol dm(-3) NaClO4. In conjunction with earlier work, the results suggest that the deprotonation rate of the keto tautomer of 2-acetylcyclohexanone has a minimum value when c ompared with 1,3-dicarbonylic ligands of similar structure. The mechan ism proposed to account for the kinetic data involves pathways in whic h both Fe3+ and Fe(OH)(2+) react with the enol tautomer of the ligand. The relative rates of complex formation are shown to depend not only on the metal species involved but also on ligand structure factors suc h as steric hindrances, ring strain and intramolecular hydrogen bondin g.