Solvent effects on protonation constants of picolinic acid in different aqueous solutions of ethanol

Knowledge of the physicochemical properties of the solvent, to understand the intermolecular interactions between solute-solvent and also solvent-solvent molecules, is required for proper bench work. These interactions generate new solvent properties that are absent in the pure solvent molecules which leading to phenomena such as preferential solvation that makes the nature of solute–solvents more complex. The pKa value is a key parameter to predict the dissociation state of a molecule with respect to pH. Many compounds are sparingly soluble in water and any experimental pKa determination requires the use of an organic or hydro-organic solvent. Mixtures of water and organic solvent, mainly methanol, ethanol, or ۱-propanol, are usually employed. In the present work, the protonation constants of picolinic acid is determined in different aqueous solutions of ethanol. It has been proposed that the tryptophan metabolite picolinic acid (pyridine-۲-carboxylic acid) has a physiological role in the absorption of zinc. Picolinic acid, in common with its organic derivative ethyl picolinate, is a bidentate chelating agent of divalent metals [۱-۶].

کلیدواژه ها:

Protonation constant ، Picolinic acid ، Ethanol-water mixtures ، Solvent effect