INFLUENCE OF WATER MEDIUM ON THE STRUCTURE AND REACTION CHARACTERISTICS OF THE MOLECULE OF IMINODIACETIC ACID AND ITS IONS

Abstract

Object under examination: Iminodiacetic acid has amphoteric and complexing properties. Its molecules have a chelate structure, which explains its specifi c characteristics in reactions with different reagents. The use of iminodiacetic acid as a base material for chelate ion exchangers of type ANKB-50 opens the possibility of creating selective ion exchangers and separating reagents with similar chemical characteristics. Topic: The atomic and electronic structure of iminodiacetic acid molecules in vacuum and water mediums was calculated. The mechanisms of how the dielectric water medium infl uenced the structural parameters were noted. The origin of the zwitterionic structure of the molecule and the infl uence of the water medium on it were explained. The infl uence of the polarization effect of the water medium on the dissociation of acid molecules was described. Research method: Computer calculations of the molecular structure were carried out by B3LYP method, based on the density functional theory with the 6–31G++(d, p) basis. Results: The effect of a solvent as a continuous medium does not signifi cantly alter the structure of the molecule. However it leads to a few shifts in the energy levels of the single-particle orbitals. The infl uence of the water medium leads to an increase in the stabilization energy of the molecule of iminodiacetic acid, as well as its anion and dianion. It increases as ion charge increases. It was established that the water medium increases the effective charges of all atoms. For the fi rst time, attention was paid to the change in the energy of single-particle orbitals and their sequence as a result of water medium polarization. These effects were explained. Scope: Computer calculations of the structure of the molecule of iminodiacetic acid and its anions in vacuum and water mediums were made. It was proved that the molecule has a zwitter form. The charge distribution and atomic orbitals of the molecule were presented. A model based on the infl uence of the aqueous environment on the geometry and effective charges was proposed. The role of the water medium in the dissociation of the molecule of iminodiacetic acid was noted.

Keywords

• iminodiacetic acid
• anion
• water molecule
• molecular orbitals
• binding energy
• hydroxonium.