Metal interaction with organic acids: Semiempirical molecular modeling approach

Abstract

Metal interaction with organic acids is an important aspect in the environment. Both, acetic acid and benzoic acid were chosen as model molecules for aliphatic and aromatic structures, respectively. Monovalent alkalis were interacted with each acid through the hydrogen bonding of the COOH group. Divalent alkalis and heavy metals were interacted through hydrogen bonding with two acid units. PM5 semiempirical quantum mechanical calculations indicate that the interaction transform carboxyl band into metal carboxylate with a shift toward lower wavenumber. Monovalent metals showed reactive complexes which are further dedicated for interaction. Divalent metals showed stable complexes according to their lower dipole moment values, leaving no further interactions for these complexes. Increasing the hydrocarbon chain is not affecting either the vibrational characteristics or the reactivity of metal carboxylate in the environment. Higher level of theory indicates the suitability of PM5 method for this study.