Studies on interfacial activity and metal-complexing ability of Kemp's triacid
Description
cis,cis-1,3,5-trimethylcyclohexane-1,3,5-tricarboxylic acid, more commonly known as Kemp's acid, was first synthesized by D. S. Kemp and K. S. Petrakis. Since then, the triacid molecule with its two carboxyl groups derivatized, has been extensively used in molecular recognition studies. Derivatives of Kemp's acid have been shown to selectively recognize nitrogenous aromatics through hydrogen bonding interactions. Surface active studies were also attempted with derivatives of the acid. The triacid molecule itself was not investigated for possible surface activity, before this work By virtue of one of its conformations, where the carboxyl groups are in a triaxial orientation, the triacid molecule has the potential for surface activity. Investigations of this potential surface activity of Kemp's triacid forms the main theme of this dissertation. The experiments undertaken to acquire the required information fall mainly under two categories: Interfacial/surface tension measurements and emulsion studies using Kemp's triacid as the surface-active agent The interesting feature of the acid molecule is the change in conformation accompanied by trianion formation at high solution pH. The existence of the two conformations of the acid molecule makes it attractive as a surface-active agent at low pH's, with gradual loss of surface activity with increase in solution pH. This feature of the acid has been utilized in preparing kinetically stable oil-in-water emulsions at lower pH's, and subsequently destabilize the same stable emulsions by simply increasing the emulsion pH The three carboxyl groups also provide an ideal site for metal ion binding. Hence, metal-complexation reactions with the triacid molecule have been investigated in this work with UV-Visible and infrared spectroscopy. Selectivity of these reactions have been also examined. From the stoichiometry results and the infrared spectral data, an attempt has been made to predict the structure of the metal-triacid complexes Finally, the surface/interfacial activity of the triacid-metal complexes has been determined, by interfacial tension and monolayer surface pressure-area isotherm measurements. These experimental results lead to the possibility of concentrating specific heavy metal ions at the oil-water interface, thus removing the toxic metals from the bulk aqueous phase