Rajni Misra

Evaluation of the thermodynamic parameters for association process of hydrogen bond complexes from the dielectric relaxation measurements.

Abstract A relation between the free energy for dipole relaxation process and that for the association process has been proposed. Using this relation, an equation has been defined for evaluating the association equilibrium constant from the dielectric relaxation measurements. These equations have been applied to study the association of dimethyl sulphoxide and p-tolyl sulphoxide with proton donors (phenol and O-cresol) in an inert solvent carbon-tetra-chloride in the temperature range 298–322K. The calculation of the association equilibrium constant and hence the thermodynamic parameters have shown the wide scope, the proposed relations can be put to in the study of the association process of hydrogen bond complexes.

Dielectric studies in dilute solutions

Dielectric studies in dilute solutions of cyclohexane and benzene have been carried out in the temperature range 294–318°K. The observed data have been utilized to evaluate the relaxation times and thermodynamic parameters of these molecules. The high values ofα for 2-acetyl pyridine indicate the occurrence of more than one relaxation time. In the remaining systems, the observed lowα values indicate their rigid behaviour. The variation in the dielectric relaxation time is mostly correlated with the change in the heterocyclic configuration of the system.

On the Determination of Equilibrium Constant and Thermodynamic Parameters for the Association Process of Hydrogen Bond Complexes Using Relaxation Parameters

Abstract A dielectric study of H-bond complexes of three acetates namely ethyl acetate, butyl acetate, and benzyl acetate with the proton donor (O-Cresol) has been made. The equilibrium constant and the thermodynamic parameters for the association process as well as the dielectric relaxation process have been determined from the dielectric data using an equation, proposed in our earlier paper. The results obtained being in agreement with the literature values thus support the validity of the proposed equation.

Dielectric relaxation study from polarisability data

Abstract An analysis of the dielectric data using the polarisability plots have been carried out in our earlier paper [Current Sci. India 15 (1982) 695]. The polarisability equations proposed in our earlier paper have been modified by introducing a correction term. The equations of Higasi and Budo to evaluate relaxation time have been changed from using slope and dielectric data respectively to that using polarisability data. These proposed and modified equations have been applied to a number of systems for evaluating the relaxation parameters. The results obtained from the modified equations are in better agreement. It has also been confirmed from the present investigation that the angular frequency ‚ω‘ manifests as ‚ωC‘

Dielectric relaxation of some heterocyclic compounds in highly viscous media

Dielectric measurements on three heterocyclic compounds namely pyrrolidine, piperidine and 2-acetylpyridine in paraffin oil and paraffin oil + cyclohexane mixtures over the temperature range (294–318 K) at 9.8 GHz have been made. The data have been analysed using the method of Higasiet al and their dependence on macroscopic viscosity has been examined. The effect of solvent viscosity on the dipolar rotational process of the molecules in highly viscous media is also discussed.

Thermodynamics of H-Bond Through Dielectric Data Analysis

Abstract The dielectric measurements on the mixtures of benzaldehyde with phenol and cresols as well as of acetophenone with n-butylalcohol and phenol in carbontetrachloride have been made in the temperature range (290–318)K. The relaxation time of the complexed species have been calculated using Higasi et al., method. With the help of the equation proposed previously in one of our earlier papers, the equilibrium constants along with thermodynamical parameters for association process have been evaluated using different values of constants A and B. The fairly good agreement between the calculated values of equilibrium constant (K) and its literature values shows the applicability and reliability of the proposed equation and also the importance of the need for a detailed study in this direction.

Viscosity behaviour of binary mixtures of non-polar solvents

The viscous nature of binary liquid solutions of non-polar solvents,viz. n-heptane, benzene, carbon tetrachloride and paraffin oil has been studied in terms of the deviation from the ideal law. The ideal law is supposed to take the form of (weighted) geometric mean. The viscous behaviour has been observed over a range of temperatures (298–322°K). The relative excess volume and relative excess enthalpy of activation have been evaluated to study the increase in viscosity associated with the shrinkage in mixing of its components.