T. Thenappan

Dielectric and thermodynamic studies on a binary mixture of anisole with butyric or caprylic acid

The molecular interaction of anisole with fatty acids, such as butyric acid and caprylic acid, has been studied using standard dielectric methods. The permittivity at static and optical frequency (the sodium D-line) of a mixture of anisole + butyric acid and anisole + caprylic acid were measured at three different temperatures. Kirkwood correlation parameters, the excess permittivity, the Bruggeman parameter and excess free-energy were determined for each concentration of the mixture. A positive value of excess permittivity was obtained for the mixture of anisole + butyric acid, whereas for most concentrations of the anisole + caprylic acid mixture, the excess permittivity was negative at all studied temperatures. Negative and positive values of the Bruggeman parameters were obtained for the anisole + butyric acid and anisole + caprylic acid mixtures, respectively. Parallel and anti-parallel alignments of dipoles in the mixtures were identified.

Study of fluid structure and dielectric behaviour of alcohols in non-polar solvents

Abstract The determination of the structure and properties of associated liquids could provide deeper insight into the phenomena of the molecular interactions and is of great importance in biology and chemical physics. The IR and NMR spectroscopic methods were extensively used for determining the nature of association. However, these methods could give only circumlocutory information regarding the alignment of neighbouring molecules. This vital information could be obtained from dielectric measurements by virtue of the influence of local order and the overall dipole moment. In dilute solutions of alcohols with inert solvents, the interaction between the solute species among themselves may be given by a modified form of the correlation factor (g′) taking the solute-solvent and solvent-solvent interaction. Dielectric constant of the binary mixtures of 1-hexadecanol, 1-tetradecanol, 2-ethyl-1-hexanol and 2-ethoxyethanol in benzene were determined at 298K, 308K and 318K. The presence of α and β multimers in the above systems were identified and the results are interpreted accordingly.

Dielectric and spectrometric investigations of binary mixtures of tetrahydrofuran with propionic acid

The static permittivity (εm ) and the permittivity at the high-frequency limit (ε∞m ) of a binary mixture of propionic acid with tetrahydrofuran (THF) have been determined for different concentrations at temperatures of 303, 308, 313, and 318 K. The data have been used to compute the Kirkwood correlation factor, the excess permittivity, and the excess free-energy of the mixtures. The Kirkwood correlation factor is found to increase with increasing THF concentration. The mixture exhibited positive values of the excess permittivity and negative values of the excess free-energy of mixing, respectively. UV-Vis and FT-IR spectral measurements have also been carried out. The observed bathochromism and hypochromism in the UV-Vis spectra have been explained in terms of complex formation and ordering of dipoles of the complex. The FT-IR spectrum of the mixture shows considerable shifts in the positions of some of the absorption bands, indicating extensive hydrogen bonding between solute and solvent molecules.

Dielectric investigation of the tetrahydrofuran+caprylic acid system

Dielectric studies have been carried out for the binary mixture of tetrahydrofuran (THF) with caprylic acid at temperatures 303, 308, 313 and 318 K. The Kirkwood correlation factors, excess permittivity and excess free energy of the mixture were found through dielectric measurements for different concentrations of the system. Analysis of these parameters reveals the existence of H-bonded heterogeneous molecular aggregates in the mixture. Parallel alignment of dipoles of the complex in THF region has been identified.

Relaxation and thermodynamic studies of liquid mixtures of anisole with isopropanol in benzene

Dielectric relaxation behaviour in polar–polar mixtures of anisole and isopropyl alcohol in benzene has been observed using the measurements of dielectric permittivity and dielectric loss at microwave frequency at three different temperatures. Using the Higasi method, average relaxation time, relaxation time for intra-molecular rotation and inter-molecular rotation have been calculated for the mixtures at different compositions. Viscosity and density of the mixtures are obtained over the entire range of concentration and temperature studied. Thermodynamic parameters, such as enthalpy and entropy, have been calculated for all studied concentrations, i.e. pure liquids and their mixtures. Activation free energies due to dielectric relaxation and viscous mechanisms for the system are discussed.

Dielectric and thermodynamic behaviour of binary mixtures of anisole with o-chlorophenol and with o-cresol

The molecular interactions in binary mixtures of anisole with o-chlorophenol and o-cresol have been studied at three different temperatures using dielectric measurements. The static permittivity and the permittivity at optical frequency have also been determined and used to obtain the Kirkwood correlation factors, the Bruggeman parameter, the excess permittivity and the excess free energy for different concentrations of two binary mixtures, namely (1) anisole + o-chlorophenol and (2) anisole + o-cresol. Using the effective Kirkwood correlation factor, parallel and anti-parallel alignments among the dipoles are identified. The corrective Kirkwood correlation factor, the excess permittivity and the Bruggeman parameter are used to explain the interaction between unlike molecules. The temperature dependences of the above parameters are also reported. The investigation shows systematic changes in the dielectric behaviour with variations in concentration and temperature.

Dielectric relaxation in ternary systems of alcohols and nitriles in benzene at microwave frequency

The permittivity and the dielectric loss of ternary mixtures of equimolar concentrations of m-cresol, o-cresol with acetonitrile, acrylonitrile and benzonitrile in benzene have been measured at 8.33 GHz and 308 K. The distribution parameter α, the most probable relaxation time τ, the relaxation time for overall rotation of the molecule τ(1), the relaxation time for group rotation τ(2), and the excess dipole moment for various systems have been calculated by the Cole-Cole and Higasi methods. Data has been analyzed in terms of two-relaxation processes: overall rotation and group rotation.

Dielectric investigations of dilute solutions of anisole with H-bonded liquids

Measurements of static permittivity, refractive index and density have been carried out to study possible H-bonded complexes in solutions of anisole diluted by benzene together with high-static-permittivity alcohols, i.e. cyclohexanol, n-butanol, tert-butanol, isopropyl alcohol and 1-hexanol. The experiments were performed at 303 K. Dipole moments of the mixtures are calculated from the experimental data and these are used to obtain dipolar increments. The concentration ratio of proton donor to proton acceptor is plotted against a parameter, ΩB, which is determined from experimental data. From the plot, the dipole moment of the mixture and that of the component B are determined. The order of the complex can be obtained from the nature of the graph. The investigation shows that the interaction between the two components arises solely from a polarization effect.