Partial molar volumes of some drugs in water and ethanol at 35 °C

Abstract

Partial molar volumes, vO, of six drugs, mostly anaesthetics, viz., cinchocaine HCl, lidocaine HC1, mepivacaine HC1, procaine HC1, propranolol HC1, tetracaine HCI, in water and ethanol, calculated from precision densities obtained at 35OC from a vibrating tube densitometer, are reported in this work. The data represent the smaller volumes of drug molecules in ethanol than in water. Volume contribution of hydrochloride part were calculated and excluded from V O to assess the volume of free base component of the solutes. Volumes of free bases were also found smaller in ethanol, although much closer to those in water. The differences in volumes are interpreted as due to hydrophobicity of solutes. Relative hydrophobicities were estimated from volumes of transfer from aqueous to organic media. Correlation of V O with van der Waal volumes are also reported. The hydrophobicity of these compounds is proposed to play a key role in the resulting drug action. Possible mechanism of drug binding with the membrane structure is also discussed.

Investigation of Volumetric and Optical Properties of Anti-Emetic Metoclopramide Hydrochloride Drug in Aqueous-Dimethylsulfoxide (DMSO) Solutions At 303.15 K

“…The   v is intrinsic volume plus volumetric effects due to solute-solvent interactions such as ion-solvent interactions, H-bonding etc. The partial molar volume of drug-HCl is due to individual ionic contributions of   v Drug and   v HCl (Marcus, 2006;Iqbal et al, 1994;Delgado et al, 2010) significant change in the φ 0 v of drug is observed from pure water to aqueous-DMSO mixtures and pure DMSO. The φ 0 v value of drug in all the systems is positive due to existence of strong drugsolvent interactions.…”

“…been studied. Apparent molar volume and adiabatic compressibility of aqueous solutions of some drugs and partial molar volumes of some drugs in water and ethanol were studied (Iqbal and Verrall, 1989;Iqbal et al, 1994). Physicochemical properties of some drugs in solution (Baluja et al, 2007) have been studied.…”

Universal Model Based on the Mobile Order and Disorder Theory for Predicting Lipophilicity and Partition Coefficients in All Mutually Immiscible Two-Phase Liquid Systems

“…Whereas the first quantity was obtained from the molecular structure according to the method of Van Krevelen, the molar volume was calculated from an additive-constitutive group contribution method. , Remember that, for substances which are solid at room temperature, the molar volume of the solute to consider in estimating their solubility or partition coefficient is not that of the crystalline substance, but the volume of the molecule in its hypothetical supercooled liquid state. However, to account for a certain amount of volume contraction − due to the strong H-bonded complexes that some molecular groups may form with water, the obtained volumes of the molecules containing these particular groups were systematically decreased by 15% in the aqueous phase as was previously done for the water solubility predictions. , …”

The Hydrophobic Effect. 3. A Key Ingredient in Predicting n-Octanol–Water Partition Coefficients

“…Actually, the presence of the solute molar volume in the log P thermodynamic predictive equation naturally arises from the volume dependence of both the mobile order and mixing entropy. PAH log P pred ) -1.152 + 0.0333V B (19) PCB log P pred ) -0.843 + 0.0333V B (20) aliphatic esters log P pred ) -2.431 + 0.0333V B (21) aliphatic ketones log P pred ) -2.487 + 0.0333V B (22) aliph primary alcohols log P pred ) -2.082 + 0.0333V B (23) aliph tertiary amines log P pred ) -2.468 + 0.0279V B (24) steroids (1 ester + 1 s OH) log P pred ) -4.462 + 0.0279V B (25) …”

“…21,22 However, as for the aqueous solubility predictions, the obtained volumes were, in the case of the steroids and of any molecule containing an aliphatic amine, systematically decreased by 15% in the water phase. Such reduction accounts for the volume contraction [23][24][25][26] of these molecules consecutively to the H-bonded complexes they form with the water molecules. Taking the aforementioned remarks into account, the n-octanol-water partition coefficient of selected substances, including compounds of environmental, medicinal, and pharmaceutical relevance, is estimated using the standard stability contants reported in Table 1.…”