Influence of Calcium Ions on the Mechanism of Oxime Formation from Acetoin

Article abstract of DOI:10.1246/bcsj.69.1639

The effect of calcium ions on the reaction of acetoin with hydroxylamine was studied. This reaction proceeds by a two-step mechanism: the attack of hydroxylamine on the carbonyl compound to give a tetrahedral addition intermediate, and the dehydration of this intermediate to form the oxime. The presence of calcium ions decreases the value of the equilibrium constant of the tetrahedral addition intermediate formation, but increases the overall rate constant of the reaction when dehydration is the rate-determining step. Evidence suggests that the effect of calcium ions is through the formation of a complex with the hydroxyl groups of the tetrahedral addition intermediate, facilitating the dehydration step of the reaction.