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

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 ( I I In the pH range from 5.5 to similar to 2.2 the second-order rate constants are linearly dependent on the concentration of hydronium ion and (2) from pH similar to 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.