Conformational space analysis of neutral and deprotonated forms of benzoic acid, salicylic acid and phthalic acid using a genetic algorithm

In this paper we present a detailed conformational study of three aromatic systems constituting the basic units of humic acids namely benzoic acid, salicylic acid and phthalic acid. The genetic algorithm, based on the multi-niche crowding (MNC) method, coupled with the semi-empirical AM1 method is used to analyze the potential energy surface (PES) of these systems. This algorithm, implemented in the MOPAC program and piloted by scripts, provides better detection of global and local minima in a reasonable time. The results obtained are comparable with those of previous studies. Three factors can be cited to justify the stability of conformations i.e. effects of conjugation, steric interactions and intramolecular hydrogen bonds.