Solute-Solvent Interaction Effects on Protonation constants of Nicotinic Acid in Different Water-Methanol Mixtures

Nicotinic acid known as vitamin B۳ or niacin is one of the five vitamins associated with a pandemic deficiency disease in human diet. The deficiency of this compound in human diet causes serious central and peripheral nervous system. The biological function of this drug in human is believed to act through nicotinamide, which is contained in NAD and NADP coenzymes. Nicotinic acid penetrates into cells by means of active transport and passive diffusion, whose intensity is controlled by acid-base equilibria of the compound. Therefore, the acid-base equilibria of nicotinic acid should be known not only as a competing process in complexing reaction but also to explore its activity in cell-membrane transport.In this work, the protonation constants of nicotinic acid is determined in different aqueous solutions of methanol to show how solvent and solvent mixtures with different dielectric constants affect the formation of the protonated species of this drug, using potentiometric method.

کلیدواژه ها:

Protonation constants ، Nicotinek acid ، metanol -water mixtures ، Kamlet-Taft Solvatochromic parameters ، Solvent Effect