A kinetic study of hydrolysis of .BETA.-arylaminoacrolein derivatives.

Abstract

The reversible acid-catalyzed hydrolysis of β-arylaminoacrolein (I) has been studied kinetically. The kinetic runs were carried out in 1% aqueous ethanol in the presence of hydrochloric acid or acetic acid as well as in acetate buffer solutions at 25°C. The Hammett plot for the equilibrium constant K was linear. The value of log K was expressed by the equation log K=1.38σ-5.55. The loss of arylamine from the carbinolamine intermediate was rate-determining under strongly acidic conditions, while the rate of attack of water at the β-position of I was comparable to that of loss of arylamine from the intermediate under weakly acidic conditions. The reaction suffered general acid catalysis. The solvent-catalyzed term and catalytic constants for hydronium ion and for acetic acid were evaluated for both steps. General acid catalysis of acetic acid was of minor importance for the attack of water on I. The Hammett plot for the rate of reaction of water and conjugate acid of I was linear. The value of log kH1KBH+ was expressed by the equation log kH1KBH+=0.468σ-1.08. The reaction mechanism is discussed.