The molecular interactions between the polar systems isopropyl alcohol (IPA) and aniline for various mole fractions at different temperatures were studied by determining the dielectric permittivity using an HP-LF impedance analyzer at radio frequencies, the plunger method in the microwave frequency range and Abbe’s refractometer in optical region. Kirkwood effective correlation factors, corrective Kirkwood correlation factors, excess permittivities, Bruggeman parameters, excess Helmholtz free energy, relaxation time, dipole moment and excessive dipole moment were calculated using the experimental data. Optimized geometries were calculated using Spartan Modeling software for both pure and equimolar systems of isopropyl alcohol and aniline for Hamiltonian quantum mechanical calculations. Conformational analysis of the formation of hydrogen bond between the two systems is supported by the FT-IR spectra.

Dielectric and Thermodynamic Studies on the Hydrogen Bonded Binary System of Isopropyl Alcohol and Aniline

The excess molar enthalpies, $$H^{\text{E}}$$
 , of piperidine (1) + cyclopentanone or cyclohexanone or cycloheptanone (2) at 308.15 K and densities, ρ, speeds of sound, u, and molar heat capacities, $$C_{\text{P}}^{{}}$$
 , of the same set of the mixtures have been measured as a function of composition at temperatures from 293.15 to 308.15 K. The measured ρ, u, and $$C_{\text{P}}^{{}}$$
 data have been employed to determine excess molar volumes, $$V^{\text{E}}$$
 , excess isentropic compressibilities, $$\kappa_{\text{S}}^{\text{E}}$$
 , and excess heat capacities, $$C_{\text{P}}^{\text{E}}$$
 . The thermodynamic properties have been fitted to Redlich–Kister equation to compute binary adjustable parameters and their standard deviations. The results have been analyzed in terms of Graph theory (which deals with the topology of the molecule) to correctly predict (1) state of the components in pure and mixed states, (2) to understand the nature and extent of molecular interactions existing in their mixtures, (3) $$V^{\text{E}}$$
 , $$\kappa_{\text{S}}^{\text{E}}$$
 , $$H^{\text{E}}$$
 , and $$C_{\text{P}}^{\text{E}}$$
 values. The analysis of $$V^{\text{E}}$$
 data in terms of Graph theory suggests that while piperidine is characterized by hydrogen bonding and exists as associated molecular entity, cyclopentanone, cyclohexanone, and cycloheptanone exist as mixture of open and cyclic dimers. The estimated inter-nuclear distances among the interacting atoms using quantum mechanical calculations also support the existence of proposed molecular entities in pure and mixed states. It has been found that $$V^{\text{E}}$$
 , $$\kappa_{\text{S}}^{\text{E}}$$
 , $$H^{\text{E}}$$
 and $$C_{\text{P}}^{\text{E}}$$
 data predicted by Graph theory compare well with the their experimental data. The IR studies also support this view point.

Thermodynamic properties of piperidine and cyclic alkanone mixtures

Dielectric relaxation studies of propan-1-ol with alkyl benzoates (methyl benzoate and ethyl benzoate) have been carried out, for various mole fractions, at different temperatures using a LF impedance analyzer, Plunger method, and an Abbe’s refractometer in the radio, microwave and optical frequency regions, respectively. Kirkwood’s effective correlation factor, the corrective Kirkwood correlation factor, Bruggeman parameter, relaxation time, excess inverse relaxation time and thermodynamic parameters were calculated using the experimental data. Conformational analysis of the formation of hydrogen bonds in the equi-molar binary mixtures of propan-1-ol with alkyl benzoates is supported by experimental and theoretical FT-IR values.

Thermodynamic, Dielectric and Conformational Studies on Hydrogen Bonded Binary Mixtures of Propan-1-ol with Methyl Benzoate and Ethyl Benzoate

The static permittivity (em ) and the permittivity at the high-frequency limit (e∞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 and spectrometric investigations of binary mixtures of tetrahydrofuran with propionic acid

Lead-free polycrystalline ceramics of Ba(Fe0.5Nb0.5)O3 and its solid solutions 0.91Ba(Fe0.5Nb0.5)O3-0.09BaTiO3 (BFN-BT) and 0.91Ba(Fe0.5Nb0.5)O3-0.09SrTiO3 (BFN-ST) were fabricated by a solid-state reaction process, and their electrical properties were characterized in a broad frequency range (100 Hz to 1 MHz) at a temperature range from 30 to 385°C. The prepared ceramics are single phased with monoclinic structure as confirmed by X-ray diffraction. The microstructure analysis was done by scanning electron microscope. Dielectric response show low temperature dielectric dispersion at low frequency showing space charge phenomena arising due to defects. Existence of sharp transition around (Tc~255°C) and broad transitions around (Tc~205°C) of dielectric constant (e´) versus temperature is demonstrated in the complex perovskite in BFN-BT and BFN-ST ceramics respectively at different frequencies (10.82, 20.2 and 32.2 kHz). The relaxor property was analyzed by the broadening of the maximum dielectric permittivity as well as its shifting to high temperatures with the variation of frequency measurements. In the pure BFN ceramic, dielectric studies confirmed that the compound do not have dielectric anomaly at different frequencies (10.82, 20.2 and 32.2 kHz) and temperature ranges (30 to 385°C). The frequency-dependent electrical data are also analyzed in the framework of conductivity and impedance formalisms.

	 

	Key words: Perovskite oxides, dielectric constant, electrical properties, scanning electron micrographs.

https://www.academicjournals.org/article/article1379429938_Singh et al.pdf

Dielectric relaxation, electrical conductivity and impedance response of Barium titanate (BT) and Strontium titanate (ST) doped Ba(Fe0.5Nb0.5)O3 ceramics

The dielectric absorption studies of acetophenone, pyridine and their binary mixtures, both consisting of rigid molecules, have been studied at 8.93 GHz in the dilute solutions of benzene at different temperatures. The relaxation times, dipole moments, thermodynamical parameters, viz. free energy, enthalpy and entropy of activation have been calculated from the dielectric data. The relaxation time (1: 11) of the single component agrees well with literature values. The experimental values of relaxation time (1: 11) of the dipolar mixture have been compared with the theoretical values obtained by employing different methods. The non-linear behaviour of ~ 2 versus mole fraction is explained on the basis of solute­ solute molecular association between these two-polar rigid molecules. The values of the molar entropy for the relaxation process indicate that , the cooperative orientation of the molecules in the single component system is retained in the mixture also.

/pdf/temperature-dependence-of-dielectric-relaxation-of-rigid-35nryal0i5.pdf

Temperature dependence of dielectric relaxation of rigid polar molecules acetophenone, pyridine and their mixtures in dilute solutions of benzene

Structural change analysis of pyridine and piperidine through dielectric relaxation studies

Static permittivity at 100 kHz, complex permittivity at 8.93 GHz and high frequency permittivity at frequency of the Dlines of sodium of cyclohexylamine (CHA), acetophenone (ACT), p-chloroacetophenone (PCLA) and for the binary mixtures of CHA+ACT and CHA+PCLA have been measured in dilute solutions of benzene at different temperatures. The measured values of permittivity and dielectric loss have been used to evaluate relaxation times [τ0, τ(1) and τ(2)], dipole moment (μ), distribution parameter (α) and thermodynamical parameters like molar free energy of activation (ΔF∈), molar enthalpy of activation (ΔH∈) and molar entropy of activation (ΔS∈). The relaxation times of binary mixture compositions are consistent with the computed values obtained from various theoretical methods. Present study suggests the existence of both the intramolecular and overall orientation in both the binary mixtures. Formation of complexes is noticed in 1:1 binary mixture of CHA+PCLA.

http://nopr.niscair.res.in/bitstream/123456789/9647/1/IJPAP%2042%2811%29%20849-853.pdf

Microwave dielectric relaxation study of binary mixtures of cyclohexylamine with acetophenone and p-chloroacetophenone in dilute solutions of benzene

Structural study of rapeseed-mustard variety PCR-7 oil-argemone-mexicana oil blend by dielectric relaxation studies

The study of the di electri c properties of binary mixture of cyclohexyl amine (C HA) in non-polar solvents such as benzene, 11 -heptane and I ,4-dioxane has been investigated. The low frequency molecular dynamics of CHA molecule have been studied by evalu ating the Kirkwood correlation factor (g), molar polarization (p2), excess correlation factor (8,1;') and excess free energy (t:.C 11 ). The observed val ues of g signifi cantly deviated fr om unity, which conlirm the inter-molecular association in C HA molecule in dilute solutions. The presence of a- and ~ -multimers in the above system was id enti tied . CHA establishes H-bonding with oxygen of I ,4-dioxane resultin g in reinforcement of inter-molecular association and causes hi gher values of g as compared to benzene and 11-heptane. The high fr equency molecular dynamics were examined using 8.93 GHz, which reveals th at a single relaxation process exists in C HA. These parameters have been used to thro w light o n the dynamic characteri st ics of molecular association in th ese binary mixtures of polar-non-polar liquids.

http://nopr.niscair.res.in/bitstream/123456789/25248/1/IJPAP%2041%2810%29%20801-805.pdf

K. S. Sharma

Papers

Temperature dependence of dielectric relaxation of rigid polar molecules acetophenone, pyridine and their mixtures in dilute solutions of benzene

Structural change analysis of pyridine and piperidine through dielectric relaxation studies

Microwave dielectric relaxation study of binary mixtures of cyclohexylamine with acetophenone and p-chloroacetophenone in dilute solutions of benzene

Structural study of rapeseed-mustard variety PCR-7 oil-argemone-mexicana oil blend by dielectric relaxation studies

Studies on dielectric properties of cyclohexylamine in non-polar solvents-Kirkwood correlation factor, molar polarization and excess free energy