Manish Srivastava

Liquid-Phase and Solventless Oxidation of Cyclohexane, Benzene, and Other Hydrocarbons by Cerium(IV) Catalyzed by Iridium(III) in Acidic Medium

Abstract Oxidation of some hydrocarbons dissolved in acetic acid by cerium(IV) sulphate at 100 °C in the presence of traces of iridium(III) chloride (catalyst-substrate 1:56818 to 151515) in the solution phase resulted in good to excellent yields of corresponding carbonyl compounds. In the cases of cyclohexane and benzene, 44% and 51.8% yields of corresponding carbonyl compounds were obtained, whereas in other cases, yield ranged from 34.9 to 99.8%. Yield decreased when reactions were performed in a microwave oven by adsorbing reactants (except acetic acid) on alumina. Decrease in the yield was probably due to the high temperature generated during the course of the reaction, resulting in the loss of organics from evaporation. Conditions were optimized for the highest yields under ambient conditions.

Liquid Phase and Microwave Assisted Oxidation of Some Hydrocarbons, Aromatic Aldehydes, and Phenols by Cerium(IV) Catalyzed by Iridium(III) in Acidic Medium

Abstract Addition of traces of iridium(III) chloride with cerium(IV) sulphate (catalyst–substrate ratio 1:75757 to 1:151515) in traditional water-bath heating resulted in the oxidation of propyl benzene, naphthalene, dimethoxy benzaldehyde, trimethoxy benzaldehydes, cresol, and quinol dissolved in acetic acid to give 70, 33, 96, 74, 49, and 66% yields respectively of the products, while phenol and resorcinol polymerized. Reactants adsorbed on alumina under solventless conditions in a microwave oven resulted in the decrease in yield. Oxidation of both hydroxyl groups takes place in quinol, whereas it was selective at the α-carbon in the side chain and at the methyl group in the case of propyl benzene and cresol, respectively. Conditions were tested for the highest yields under the experimental conditions.

Anodic Cyclization: A Protocol for the Green Synthesis of 2,5-Disubstituted 1,3,4-Oxadiazoles

An efficient and simple one-pot synthesis of chemically and pharmaceutically interesting 2,5-di-substituted 1,3,4-oxadiazoles is reported. The protocol involves anodic oxidation of N′-aroyl-hydrazones of aromatic aldehydes using LiClO4 as supporting electrolyte in MeCN solution under controlled potential at room temperature. The products were characterized by spectroscopic methods, and the mechanism was deduced from voltammetry studies. The mild reaction conditions, short reaction time, and excellent yields are notable advantages of the developed protocol.

A Novel Aspect of Hexacyanoferrate (III)- Iodide Ion Reaction in Acidic Medium

Iridium(III) chloride further catalyses the oxidation of iodide ions by K3Fe(CN)6, catalyzed by hydrogen ions obtained from perchloric acid. Rate when the reaction is catalyzed only by the hydrogen ions was separated from the rate when iridium(III) and H+ions both catalyze the reaction. Separate reactions, studied in the presence as well as in the absence of IrCl3 under similar conditions were found to follow second order kinetics in [I ̄] with direct proportionality in [Fe(CN)6] ̄ and [IrCl3]. Rate was found to follow first order kinetics with respect to [H+] at low concentrations, tending to become second order at higher concentrations of [H+]. Externally added [Fe(CN)6] ̄ ions in the beginning strongly retard the rate effect, but further addition affects the rate to a little extent. Change in ionic strength has no effect on the rate. Arrhenius parameters were calculated and probable mechanisms were proposed.