The Effect of Dielectric Constant On The Kinetics of Reaction Between Plasma Albumin And Formaldehyde In Ethanol- Water Mixtures.

Abstract

This study determined the effect of increased concentration of ethanol solution on the rate of the reaction between plasma albumin and formaldehyde. It was design to investigate the kinetics of reaction between plasma albumin and low concentrations of formaldehyde  under  pseudo-first order conditions of formaldehyde. The reaction was studied at constant conditions at various dielectric constants and temperatures of   1%, 5%, 15%,20% and 20⁰C  25⁰C, 30⁰C  and 37⁰C respectively. The rate constant as a function of different permittivity in ethanol-water  mixtures  was  determined at constant  conditions.  The dielectric constant of the reaction medium was altered by the addition of the varying amounts of  ethanol  – water mixtures (1- 25% v/v) in a cuvette  and  the absorption  of  0.51 x10^-4 mol dm^-3 plasma albumin and 0.27 x10^-1 formaldehyde- plasma  mixtures  at 235 nm were measured. The values of dielectric constants for different aqueous ethanol- mixtures were taken from literature. The values of rate constants of the reaction of between plasma albumin and formaldehyde were found to decreased with the increase in the concentration of ethanol and the reaction was a second order or bimolecular . The Activation energy and  the  thermodynamic parameters (Gibbs free energy, enthalpy and entropy changes of the reaction)  decreased with  decrease  in dielectric constant of the  medium, that is with  increase in the proportion of the ethanol component  in the solvent mixtures.   The dependence of lnk₂ vs. reciprocal dielectric constant (1/D ) of this reaction was found  be linear  with  three  linear portions indicating three zones, that is  three mechanistic changes. Also the correlations between lnk₂ and the mole fractions of water and ethanol  ( ?_H2O and  ?_EtOH) have  shown  that there  was  an increase in rate of the studied reaction in  water but a  decrease  in rate in ethanol mole  fraction.  This leads us to suggest that the reaction rates were slowed by progressive addition of ethanol . A steady decrease in rate constant with decrease in dielectric constant values was observed with a statistically significant p-value =  0.0013 on a two tailed correlation analysis  at 95% confidence assurance.

Key Words; dielectric constant, kinetics ,  plasma albumin,   formaldehyde ,   ethanol- water mixtures.