AM1 study of acid‐catalyzed hydrolysis of maleamic (4‐amino‐4‐oxo‐2‐butenoic) acids

The acid‐catalyzed hydrolysis mechanisms of maleamic (4‐amino‐4‐oxo‐2‐butenoic) acids were studied using AM1 method. The reaction proceeded mainly in two steps: (1) nucleophilic attack of the undissociated carboxyl group on the adjacent aminocarbonyl carbon via a zwitterionic intermediate; and (2) the rate‐determining proton transfer to form the zwitterionic tetrahedral intermediate. In each step, the hydration of water and hydronium ion molecules was important in stabilizing the polarized intermediates. The substituent effects at the amide moiety and the 2,3‐positions of the maleamic acids were qualitatively estimated for each step.