An AM1 study of conformational preference for the herbicide atrazine

Abstract

The potential energy surface for atrazine, a commercially important herbicide, has been extensively investigated using the quantum mechanical semiempirical molecular orbital method AM1. Full symmetry unconstrained geometry optimisation was performed for each stationary point located on the energy surface. The relative stabilities and rotational barriers for the conformera were also calculated. Four minimum energy conformera were predicted to occur with respect to rotation about the triazine ring carbon atoms and the amino ethyl and amino isopropyl groups. A relatively low energy barrier to bond rotation of 30 kJ mol −1 was predicted. The conformation adopted by triazine molecules on protein binding suggests that this conformation is principally stabilised by intermolecular hydrogen bonding with the protein active site.