The oxidation of organic sulfides by quinolinium chlorochromate (QCC) resulted the formation of the corresponding organic sulfoxides. These reactions are first order ones with respect to QCC. A Michaelis-Menten type kinetics was observed with respect to the reactants. The reaction is catalyzed by p-toluene sulfonic acid (TsOH). The oxidation was studied in nineteen different organic solvents. An analysis of the solvent effect on Swain's equation showed that the both cation-and anion-solvating powers of the solvents play important roles. The correlation analyses of the rate of oxidation of thirty-four sulfides were done in terms of various single and multiparametric equations. In the reactions of aryl methyl sulfides, the best correlation could be obtained with Charton's LDR and LDRS equations. The oxidation reactions of alkyl phenyl sulfides exhibited an excellent correlation in terms of Pavelich-Taft equation. The negative values of polar reaction constants indicate an electron-deficient sulfur center in the rate-determining step. The proposed reaction mechanism involves the formation of a sulphenium cation intermediate in a slow step * Corresponding Authors Phone: +91 94144-10900 E-Mail: drpkvs27@yahoo.com [a]

In the past, solvents containing impregnation systems were in vogue, e.g. phenoloic‐alkyd, isophthalic polyester, silicone, etc. for electrical machines. The disadvantages of solvent borne impregnants are a higher dissipation factor (at elevated temperatures) and water absorption, etc., due to the presence of air voids formed during the curing process. The phenomenon has been controlled with the present day use of solvent/ess systems, e.g. polyester, polyesterimide, epoxy and silicone resins. Solvent/ess polyester resins are now indigenously available along with their additives such as: inhibitor, catalyst and reactive diluent, etc. Modern methods of impregnation for electrical machines in BHEL include: (a) Dip impregnation by rotational method (b) V P I process The methods include storing the catalysed resin in cool storage, warming for impregnation, and final impregnation under vacuum and pressure, and curing in an oven. A monitoring system has also been standardised for the impregnation resin to keep its viscosity and gelling time within the specified tolerances by the addition of an appropriate amount of inhibitor and reactive diluent. Proper monitoring keeps the tank life of the system indefinitely long and its properties within limits.

Oxidation of 36 monosubstituted benzaldehydes by pyridinium bromochromate (PBC) in dimethyl sulfoxide (DMSO), leads to the formation of corresponding benzoic acids. The reaction is first order with respect to both PBC and aldehydes. The reaction is promoted by hydrogen ions; the hydrogen–ion dependence has the form kobs = a + b[H+]. The oxidation of [2H]benzaldehyde (PhCDO) exhibited a substantial primary kinetic isotope effect. The reaction was studied in 19 different organic solvents and the effect of solvent was analysed using Taft's and Swain's multi-parametric equations. The rates of oxidation of para- and meta-substituted benzaldehydes showed excellent correlation in terms of Charton's triparametric LDR equation, whereas the oxidation of ortho-substituted benzaldehydes were correlated well with the tetraperametric LDRS equation. The oxidation of para-substituted benzaldehydes is more susceptible to the delocalized effect than is that of ortho- and meta-substituted compounds, which display a greater dependence on the field effect. The positive value of η suggests the presence of an electron-deficient reaction centre in the rate-determining step. The reaction is subjected to steric acceleration by the ortho-substituents. A suitable mechanism has been proposed.

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