Electrochemical Investigations of Sydnone Derivatives at Glassy Carbon Electrode

Electrochemical reduction of the –N=N– moiety of sydnone derivatives, like 3-phenyl sydnone, tolyl sydnone and anisyl sydnone, was studied using cyclic voltammetry at a glassy carbon electrode. In acid medium, the above compounds were found to show irreversible electrochemical charge transfer in the pH range studied. Electrochemical studies of these sydnones were carried out in partially aqueous media containing organic co-solvents such as acetonitrile, dimethylformamide, methanol and dimethylsulphoxide. Physical parameters such as the charge transfer coefficient and diffusion coefficient, as well as the effects of variation of the electroactive species concentration, sweep rate, organic solvents, and pH on peak parameters were studied. The reduced products were characterized by IR, NMR and mass spectral studies. The effect of surfactants on the electrochemical reduction of 3-phenyl sydnone was studied using cationic, anionic and non-ionic surfactants

Pseudo-single crystal electrochemistry on polycrystalline electrodes : visualizing activity at grains and grain boundaries on platinum for the Fe2+/Fe3+ redox reaction

The influence of electrode surface structure on electrochemical reaction rates and mechanisms is a major theme in electrochemical research, especially as electrodes with inherent structural heterogeneities are used ubiquitously. Yet, probing local electrochemistry and surface structure at complex surfaces is challenging. In this paper, high spatial resolution scanning electrochemical cell microscopy (SECCM) complemented with electron backscatter diffraction (EBSD) is demonstrated as a means of performing ‘pseudo-single-crystal’ electrochemical measurements at individual grains of a polycrystalline platinum electrode, while also allowing grain boundaries to be probed. Using the Fe2+/3+ couple as an illustrative case, a strong correlation is found between local surface structure and electrochemical activity. Variations in electrochemical activity for individual high index grains, visualized in a weakly adsorbing perchlorate medium, show that there is higher activity on grains with a significant (101) orientation contribution, compared to those with (001) and (111) contribution, consistent with findings on single-crystal electrodes. Interestingly, for Fe2+ oxidation in a sulfate medium a different pattern of activity emerges. Here, SECCM reveals only minor variations in activity between individual grains, again consistent with single-crystal studies, with a greatly enhanced activity at grain boundaries. This suggests that these sites may contribute significantly to the overall electrochemical behavior measured on the macroscale

Titanium(III)-haloamine titrations in aqueous sulphuric acid medium: Titrimetric and potentiometric methods

326-329Titanium(III) species, generated from cathodic reduction of titanium(IV) sulphate using a perforated cylindrical copper cathode under nitrogen cover, have been characterised by UV-visible spectra and by determination of redox potential of Ti(IV)-Ti(III) couple. Redox titrations of chloramine T, chloramine B, bromamine B, bromamine T, dichloramine T, dichloramine B, dibromamine B and dibromamine T with titanium(lll) sulphate by volumetry with both visible and potentiometric end points, have been carried out. The monohalo- and dihalo- sulphonamides undergo 2 and 4 electron reductions respectively. These halo-sulphonamides have been used as back titrants for establishing the. probable number of electrons involved in the titanium(III) sulphate reduction of certain typical compounds like hydroxylamine, cycIohexanoneoxime and p-nitrotoluene. Utility of titanium( III) as a reductant in the electro reduction processes and in analytical and kinetic studies have been-highlighted

Kinetics of Chlorination of Aniline by Dichloramine-T in Aqueous Acetic Acid Medium

120-123Chlorination of aniline by dichloramine-T in 1:1 aqueous acetic acid medium, in the presence and absence of acetate ions is first order in [oxidant], nearly first order in [aniline], inverse fractional order in [H+] and fractional order in added [acetate ion] at constant ionic strength. Effects of added reaction products and variations in ionic strength and solvent composition of the reaction medium have also been investigated. Mechanisms consistent with the observed results are discussed and the related rate laws deduced

Effect of Chloride Ion on Kinetics of Oxidation of Threonine by Chloramine- T in Acid Medium

960-96

Electrosynthesis of aminotelechelic poly(acrylamide): Initiated by Ti(III)- NH₂OH redox system

722-724Amino-terminated poly(acrylamide) of high molecular weight has been electrochemically synthesised, using titanium(III)-hydroxylamine redox system in aqueous sulphuric acid phase. Polymer is characterised by spectral analysis and molecular weight determination. Influence of various parameters like, concentration of titanium( lV) sulphate, hydroxylamine sulphate, sulphuric acid monomer, temperature and cathodic current on polymer yield has been studied. Suitable mechanism for Ti(III)-NH2OH initiated electro polymerisation of acrylamide is proposed

Mechanism of Redox Reactions in Partially Aqueous Medium: Kinetics of Oxidation of Amino Acids by Dichloramine-T

930-93

Aqueous polymerization of methyl methacrylate initiated by manganese (III) pyrophosphate - potassium thiocyanate redox system: A kinetic study

Aqueous free radical polymerization of methyl methacrylate monomer M], initiated by manganese (III) pyrophosphate - potassium thiocyanate redox system, has been studied in the pH range 2-3 and in the temperature range 25-40 degrees C at constant ionic strength. The rates of polymerization (R-p) and manganese (III) disappearance have been measured. The effects of certain salts, water miscible organic solvents, and surfactants on the rate of polymerization have been investigated, The temperature dependence of the rate has been studied and the activation parameters computed using the Arrhenius plot. A polymerization mechanism, involving chain initiation by radicals derived from decomposition of manganese (III)-thiocyanate complex formed irt situ and bimolecular chain termination, is suggested. The rate of polymerization is found to be proportional to M](1,2), Mn(III)](1/2), H+](1/2), NCS-] , Mn(II)](-1/2), P2O74-](-1/2). The overall energy of activation in the range studied (25-40 degreesC) is found to be 32.2 kJ mol(-1)