AN ELECTROMETRIC METHOD FOR THE DETERMINATION OF IMPACT OF DMSO-WATER MIXTURES ON pKa VALUES OF SALICYLIC ACID DERIVATIVES

Abstract

Objective: The main objective of this present study is to conduct an experiment to analyze the variation of protonation-deprotonation equilibria with regards to the dielectric constants of an organic medium, influence of errors on protonation constants and effect of pH on the percentage of species. Methods: The present investigation was carried out by using pH meter at a temperature of 303 K and ionic strength of 0.16 mol dm-3 in Dimethyl sulfoxide (DMSO)-water mixtures. The processing of data was done by using Gran plot titration. The advanced principles of mathematics and fuzzy logic have been employed to correlate chemical problems, known as chemometrics. To obtain best-fit chemical models, a modelling strategy such as SCPHD is used and a computer program MINIQUAD 75 is also employed for the refinement of results. Results: In the present study, we found the influence of dielectric constants of a medium Dimethyl sulfoxide (DMSO)-water on protonation constants of 5-Sulfosalicylic acid and 5-Hydroxysalicylic acid has been studied. The species distribution diagrams were presented and understood the effect of pH on the percentage of species. The obtained skewness values are ranging from 0.11-0.36 and–0.56-0.38, for 5-Sulfosalicylic acid (5-SSA) and 5-Hydroxysalicylic acid (5-HSA), respectively, which describes the distribution curves are right skewed and left skewed. The kurtosis values are ranging from 2.12-3.56, which indicates the peak of the distribution curve exhibits both platykurtic and leptokurtic pattern. The changes in the concentrations of some influential parameters such as log F, acid, alkali, volume of titrands, ligand causes variation of stability constants and the order of the effect of influential parameters on stability constants are as alkali>acid>ligand>volume of titrand>log F. Conclusion: It is observed that the significant influence of co-solvent Dimethyl sulfoxide (DMSO)-Water mixtures on the protonation constants of ligands also studied how some factors such as changes in concentrations of ligand, acid, base log F and volume of the solution have influence on the protonation constants.