Determination of the nature of the diperiodatocuprate(III) species in aqueous alkaline medium through a kinetic and mechanistic study on the oxidation of iodide ion

The nature of the diperiodatocuprate(III) (DPC) species present in aqueous alkaline medium has been investigated by a kinetic and mechanistic study on the oxidation of iodide by DPC. The reaction kinetics were studied over the 1.0 ´ 10)3±0.1 mol dm)3 alkali range. The reaction order with respect to DPC, as well as iodide, was found to be unity when [DPC] [I)]. In the 1.0 ´ 10)3±1.0 ´ 10)2 mol dm)3 alkali region, the rate decreased with increase in the alkali concentration and a plot of the pseudo-®rst order rate constant, k versus 1/[OH)] was linear. Above 5.0 ´ 10)2 mol dm)3, a plot of k versus [OH)] was also linear with a non-zero intercept. An increase in ionic strength of the reaction mixtures showed no e ect on k at low alkali concentrations, whereas at high concentrations an increase in ionic strength leads to an increase in k. A plot of 1/k versus [periodate] was linear with an intercept in both alkali ranges. Iodine was found to accelerate the reaction at the three di erent alkali concentrations employed. The observed results indicated the following equilibria for DPC.

INVESTIGATIONS ON THE SOLVENT EXTRACTION AND LUMINESCENCE OF LANTHANOIDS WITH MIXTURES OF HETEROCYCLIC β- DIKETONE S AND VARIOUS NEUTRAL OXO-DONORS

The thesis entitled “ Investigations on the solvent extraction and luminescence of lanthanoids with mixtures of heterocyclic β-diketone S and various neutral oxo-donors” embodies the results of investigations carried out on the solvent extraction of trivalent lanthanoids with various heterocyclic β-diketones in the presence and absence of neutral oxo-donors and also on the luminescent studies of Eu3+-heterocyclic β-diketonate complexes with Lewis bases. The primary objective of the present work is to generate the knowledge base, especially to understand the interactions of lanthanoid-heterocyclic β-diketonates with various macrocyclic ligands such as crown ethers and neutral organophosphorus extractants , with a view to achieve better selectivity. The secondary objective of this thesis is to develop novel lanthanoid luminescent materials based on 3-phenyl-4-aroyl-5-isoxazolones and organophosphorus ligands, for use in electroluminescent devices. In the beginning it describes the need for the development of new mixed-ligand systems for the separation of lanthanoids and the development and importance of novel luminescent lanthanoid- β-diketonate complexes for display devices. The syntheses of various para substituted derivatives of 4-aroyl-5-isoxazolones and their characterization by various spectroscopic techniques are described. It also investigate the solvent extraction behaviour of trivalent lanthanoids with 4-aroyl-5-isoxazolones in the presence and absence of various crown ethers such as 18C6, DC18C6, DB18C6 and B18C6. Elemental analysis, IR and H NMR spectral studies are used to understand the interactions of crown ethers with 4-aroyl-5-isoxazolonate complexes of lanthanoids. The synergistic extraction of trivalent lanthanoids with sterically hindered 1-phenyl-3-methyl-4-pivaloyl-5-pyrazolone in the presence of various structurally related crown ethers are studied. The syntheses, characterization and photyphysical properties of Eu3+-4-aroyl-5-isoxazolonate complexes in the presence of Lewis bases like trictylphosphine oxide or triphenylphosphine oxide were studied.

Photosensitivity of Laser Dye Mixtures in Polymer Matrix – A Photoacoustic Study

Laser induced photoacoustic (PA) technique is used in the study of photostability of polymethyl methacrylate (PMMA) films doped with Rhodamine 6G -Rhodamine B dye system. Energy transfer from a donor molecule to an acceptor molecule in a dye mixture affects the output of the dye system. Details of investigations on the role of laser power, modulation frequency and the irradiation wavelength on the photosensitivity of the dye mixture doped PMMA films are presented.

Photoacoustic studies on thermal parameters of liquid crystal mixtures

Complete thermal characterization of liquid crystal mixtures in the smectic phase consisting of various relative volume fractions of cholesterol and 1-hexadecanol have been carried out using the photoacoustic technique. Thermal diffusivity values of these liquid crystal mixtures are evaluated using the open cell photoacoustic technique whereas the thermal effusivity value is measured using the conventional photoacoustic technique. From the measured values of these transient thermophysical parameters, the thermal conductivity and heat capacity of the sample under investigation are calculated. Analyses of the results show that all the thermophysical parameters depend strongly on the volume fraction of the constituents. Results are interpreted in terms of enhanced hydrogen bonding and the consequent enhancement in cohesive thermal energy transport with increasing volume fraction of 1-hexadecanol

Photoacoustic studies on thermal parameters of liquid crystal mixtures

Complete thermal characterization of liquid crystal mixtures in the smectic phase consisting of various relative volume fractions of cholesterol and 1-hexadecanol have been carried out using the photoacoustic technique. Thermal diffusivity values of these liquid crystal mixtures are evaluated using the open cell photoacoustic technique whereas the thermal effusivity value is measured using the conventional photoacoustic technique. From the measured values of these transient thermophysical parameters, the thermal conductivity and heat capacity of the sample under investigation are calculated. Analyses of the results show that all the thermophysical parameters depend strongly on the volume fraction of the constituents. Results are interpreted in terms of enhanced hydrogen bonding and the consequent enhancement in cohesive thermal energy transport with increasing volume fraction of 1-hexadecanol

Photoacoustic studies on thermal parameters of liquid crystal mixtures

Complete thermal characterization of liquid crystal mixtures in the smectic phase consisting of various relative volume fractions of cholesterol and 1-hexadecanol have been carried out using the photoacoustic technique. Thermal diffusivity values of these liquid crystal mixtures are evaluated using the open cell photoacoustic technique whereas the thermal effusivity value is measured using the conventional photoacoustic technique. From the measured values of these transient thermophysical parameters, the thermal conductivity and heat capacity of the sample under investigation are calculated. Analyses of the results show that all the thermophysical parameters depend strongly on the volume fraction of the constituents. Results are interpreted in terms of enhanced hydrogen bonding and the consequent enhancement in cohesive thermal energy transport with increasing volume fraction of 1-hexadecanol

Use of photoacoustic effect for the detection of phase transitions in liquid crystal mixtures

We report on a laser induced photoacoustic study of the nematic-to-isotropic transition in certain commercial nematic liquid crystal mixtures, namely BL001, BL002, BL032 and BL035. A simple analysis of the experimental data using the Rosencwaig–Gersho theory shows that the heat capacities of all these compounds exhibit a sharp peak as the temperature of the sample is varied across the transition region. Also, substantial differences in the photoacoustic signal amplitudes in nematic and isotropic phases have been noticed for all the mixtures. The increased light scattering property of the nematic phase may be the reason for the enhanced photoacoustic signal amplitude in this phase.

Use of photoacoustic effect for the detection of phase transitions in liquid crystal mixtures

We report on a laser induced photoacoustic study of the nematic-to-isotropic transition in certain commercial nematic liquid crystal mixtures, namely BL001, BL002, BL032 and BL035. A simple analysis of the experimental data using the Rosencwaig–Gersho theory shows that the heat capacities of all these compounds exhibit a sharp peak as the temperature of the sample is varied across the transition region. Also, substantial differences in the photoacoustic signal amplitudes in nematic and isotropic phases have been noticed for all the mixtures. The increased light scattering property of the nematic phase may be the reason for the enhanced photoacoustic signal amplitude in this phase

Use of photoacoustic effect for the detection of phase transitions in liquid crystal mixtures

We report on a laser induced photoacoustic study of the nematic-to-isotropic transition in certain commercial nematic liquid crystal mixtures, namely BL001, BL002, BL032 and BL035. A simple analysis of the experimental data using the Rosencwaig–Gersho theory shows that the heat capacities of all these compounds exhibit a sharp peak as the temperature of the sample is varied across the transition region. Also, substantial differences in the photoacoustic signal amplitudes in nematic and isotropic phases have been noticed for all the mixtures. The increased light scattering property of the nematic phase may be the reason for the enhanced photoacoustic signal amplitude in this phase.

Thermodynamics of transfer of polar nonelectrolytes from water to aqueous salt solutions

The Setschenow parameter and thermodynamic parameters of transfer of a number of monosubstituted benzoic acids from water to different salt solutions have been reported. The data have been rationalized by considering the structure breaking effects of the ions of the salts, the localised hydrolysis model, the internal pressure theory and Symons' theory of water structure.

Second Order Fit for Mercuric Chloride Catalysed Solvolysis of Alkyl Chlorides in Aqueous DMSO Solvents

Kinetics of mercuric chloride catalysed solvolysis of l-butyl chloride, benzyl chloride. p-methylbenzyl chloride, l-phenylethyl chloride and triethylcarbinyl chloride have been studied in aq. DMSO, aq. acetonitrile and aq. ethanol. The kinetic data fit a second order rate equation in aq. DMSO. The calculated values of the second order rate coefficients increase in the case of aq. acetonitrile and aq. ethanol. The order in catalyst in 95%(v/v) aq. DMSO is less than unity.

Mercuric Chloride Catalysed Solvolysis of Benzyl Chloride in Water & Highly Aqueous Organic Solvent Systems

Kinetics of mercuric chloride catalysed solvolysis of benzyl chloride have been studied in water. 10% aq. ethanol, 10,20 and 30% aq. acetone and 20% aq. DMSO. The results confirm the operation of a mass law effect.

Thermodynamic Parameters of Transfer of 2-Nitrobenzoic Acid & 3-Nitrobenzoic Acid from Water to Aqueous Salt Solutions

The Setschenow parameters of solubility in salt solutions and the thermodynamic parameters (25·C) of transfer from aqueous solution to aqueous salt solutions for 2-nitrobenzoic acid and 3-nitrobenzoic acid have been reported. The data have been rationalized on the basis of the localized hydrolysis model and the structure breaking action of ions of the electrolytes.

Thermodynamics of Transfer of Aminobenzoic Acids from Water to Aqueous Salt Solutions

The Setschenow parameter and thermodynamic parameters of transfer of 2- and 4-aminobenzoic acids from water to salt solutions have been reported. The results are discussed in terms of the structure- breaking effects of the ions of the salts, the localized hydrolysis model, and the internal pressure theory.