Kinetics and mechanism for oxime formation from benzoylformic acid: Electrostatic interactions in the dehydration of carbinolamines

Abstract

The evidence establishes that oxime formation from benzoylformic acid in the pH range from 0.25 to 5.5 occurs with acid-catalyzed dehydration of carbinolamines derived from the acid and its anion. The pH-rate profile shows in order of decreasing pH in two regions: (1) In the pH range from 5.5 to ∼2.2 the second-order rate constants are linearly dependent on the concentration of hydronium ion and (2) from pH ∼2.2 to 0.25 the rate constants deviate slightly from the line of slope = −1. This slight deviation is a consequence of the very similar values of limiting rate constants of the two forms of the substrate. Electrostatic interactions between charged carbinolamines and hydronium ions are analyzed. C 2008 Wiley Periodicals, Inc. Int J Chem Kinet 40: [554][555][556][557][558] 2008