Insight into the Reaction Mechanism of α‐Amino Phosphonate Synthesis Using Succinic Acid as a Catalyst: Computational Kinetic Approach

The reaction mechanism in the synthesis of particular α‐amino phosphonates from 4‐methyl benzaldehyde, aniline, and trimethyl phosphite in the presence of succinic acid is theoretically investigated. The profile of the potential energy surface is constructed at both HF /6‐31 + G(d,p) and B3LYP /6‐31 + G(d,p) levels of theory for evaluating all the steps involved in the reaction mechanism. In order to investigate the effect of the structure on reactivity, some para ‐substituted benzaldehydes are subjected to kinetic examination. The overall reaction in the presence of electron‐withdrawing groups is thermodynamically much more favorable than in the presence of the electron‐donating groups; similarly, the reaction is kinetically more favorable and much easier in the presence of electron‐withdrawing groups. Moreover, step 2 (imine formation) is recognized as the rate‐determining step at both levels of theory. Also, step 1 is diffusion‐controlled with both electron‐withdrawing and electron‐donating groups, while the other steps are chemically controlled in the reaction mechanism.