Thermodynamic and Theoretical Studies of average Ionization Constants of a Number of Phenolic Schiff Bases Derived from Salicylaldehyde by Conductivity Measurements

Abstract

In this work, three Schiff bases carrying acidic phenolic groups were synthesized derived from the reaction of salicylaldehyde with o,m, and p-amino phenols. A number of their physical and structural properties were determined by IR, UV spectra and melting points. The ionization constants of the synthesized Schiff bases were calculated at different temperatures by conductivity measurements. The effect of varying position of OH group with respect to the imine group on ionization constant was investigated. Depending on the results of varying temperatures, the thermodynamic functions of ionization were estimated. The study also concerned with the calculation of a number of theoretical parameters by employing the semiempirrcal Austin method 1 (AM1) including the atomic charges present on the hetro atoms in the molecules, in addition to some energetical and structural parameters. The determined parameters were correlated to the variation of ionization constants of the synthesized imines. Explanation and support for the experimental results were provides by these calculations. The overall results proved that, the ionization constant is affected by inductive, resonance, steric and by hydrogen bonding, and can be determined simply, precisely and accurately by conductivity measurements .

Keywords

• ionization constants
• phenolic schiff
• salicylaldehyde