Protonation Constants of Procaine in Different Salts

Abstract

Acid−base equilibrium constants for the two amino groups of the procaine molecule have been determined at 25 °C in different saline media (NaCl, KCl, and CaCl2), by means of potentiometric titrations. The Pitzer model has been used to deal with the ionic strength dependence of activity coefficients, and the parameters proposed by this theory have been obtained, including the thermodymanic dissociation constants, pK T. Equations describing the dependence of stoichiometric acid−base equilibrium constants versus ionic strength are given.

Complexation Constants of Procaine with β-Cyclodextrin in NaCl Media

“…A 40 mL aqueous aliquot containing procaine hydrochloride, NoHCl (0.0100 mol • L -1 ) (Aldrich), and β-CD (0.0050 Acid-base equilibrium constants of procaine in NaCl at 25 °C were determined previously 8 in the absence of β-CD. When the latter species is present, it forms complexes with procaine (No and/or NoH + ) disturbing the acid-base equilibria.…”

“…A matter not addressed in the earlier works, , that is, the variation of complexation constants with ionic strength I , is studied here. Potentiometry has been extensively used in this laboratory to obtain acid−base equilibrium constants of different systems in various saline media. − In fact, we previously determined the acid−base equilibrium constants for the two amino groups of the procaine molecule at 25 °C in NaCl solutions . These data are necessary in order to obtain the complexation constants of No and NoH + with β-CD as a function of sodium chloride concentration, the aim of this work.…”

“…[5][6][7] In fact, we previously determined the acid-base equilibrium constants for the two amino groups of the procaine molecule at 25 °C in NaCl solutions. 8 These data are necessary in order to obtain the complexation constants of No and NoH + with β-CD as a function of sodium chloride concentration, the aim of this work. This salt was chosen as an inert electrolyte because no complexation of Clwith β-CD has been observed.…”

“…The activity coefficients can be expressed as a function of the concentration of the salt used to keep ionic strength constant by means of different approaches. The Pitzer model 10,[5][6][7][8] is often used to describe the experimental behavior, although a simpler model for activity coefficients, specifically, a model with a Debye-Hu ¨ckel term plus a linear parameter (DH + L), will suffice for the interpretation of the results found in this system, as explained in the discussion. Several models for activity coefficients can be found in refs 10 to 12.…”

Theoretical study of the interaction pattern and the binding affinity between procaine and DNA bases

“…Despite considerable advances in experiments [2][3][4][5] and theories [6][7][8], its molecular structure and pharmacological mechanism still remains to be clarified. Therefore, a number of experimental [9][10][11][12] and theoretical [13][14][15] studies of procaine have been performed on its structural and functional properties.…”