Sumanta K. Ghosh

Micellar catalysis on picolinic acid promoted hexavalent chromium oxidation of glycerol

Under pseudo-first-order conditions, monomeric Cr(VI) was found to be kinetically active in the absence of picolinic acid (PA), whereas in the PA-promoted path, the Cr(VI)–PA complex undergoes nucleophilic attack by the substrate to form a ternary complex which subsequently experiences redox decomposition, leading to glyceraldehydes and Cr(IV)–PA complex. The uncatalyzed path shows a second-order dependence on [H+], whereas the PA-catalyzed path shows zero-order dependence on [H+]. Both the uncatalyzed and PA-catalyzed path show a first-order dependence on [glycerol]T and [Cr(VI)]T. The PA-catalyzed path is first order in [PA]T. All these observations remain unaltered in the presence of externally added surfactants. The effect of the cationic surfactant cetyl pyridinium chloride (CPC) and anionic surfactant sodium dodecyl sulfate (SDS) on the PA-catalyzed path have been studied. CPC inhibits, whereas SDS accelerates the reaction. Here, SDS is a catalyst for glyceraldehydes production and at the same time reduction of carcinogenic hexavalent chromium to nontoxic trivalent chromium. The reaction proceeds simultaneously in both aqueous and micellar phase. Micellar effects have been explained by considering the preferential partitioning of reactants between the micellar and aqueous phase. The Menger–Portnoy model, Piszkiewicz cooperative model, and pseudo-phase ion exchange model have been tested to explain the observed micellar effect.

Efficient combination of promoter and catalyst for chromic acid oxidation of propan-2-ol to acetone in aqueous acid media at room temperature.

Oxidation of propan-2-ol to acetone was carried out in aqueous media at room temperature. The effect of promoter (PA, bpy, phen), micellar catalyst (SDS, CPC, TX-100) and their combination has been studied. The reactions were performed under the condition [Propan-2-ol]T≫[Cr(VI)]T at 30°C. Then kobs and half life of all the reaction were determined to identify which promoter and which combination are the most effective for this oxidation. Among the promoters phen accelerates the reaction most in aqueous media. In absence of promoters anionic surfactant SDS increases the rate more effectively than neutral surfactant TX-100. CPC retards the rate in comparison to aqueous media. The rate of the oxidation is highest in presence of the combination of bpy and SDS.

Toxicity of inorganic vanadium compounds

Vanadium causes a variety of toxic effects such as hematological and biochemical changes, e.g., hemolysis and decrease in erythrocyte count/hemoglobin level/hematocrit index, neurobehavioral injury, i.e. general activity and learning, and abnormalities in development and reproduction, e.g., ,embryotoxicity, teratogenicity, or morphological and functional lesions in liver, kidneys, bones, spleen and leukocytes. Inhalation of vanadium may cause rhinitis, pharyngitis, chronic productive cough, tracheobronchitis, and bronchopneumonia. Moreover, the most often observed side effects include loss of appetite and significant reduction of body weight, often leading to anorexia, weakness, and nose bleeding, vomiting, diarrhoea, dehydration, pulmonary hemorrhage, or death.

Micellar Catalysis on 1,10-Phenanthroline Promoted Chromic Acid Oxidation of Glycerol in Aqueous Media

Abstract On pseudo-first order conditions, the monomeric species of Cr(VI) was found to be kinetically active in the absence of phenanthroline (phen) whereas in the phen-promoted path, the Cr(VI)-phen complex undergoes a nucleophilic attack by glycerol to form a ternary complex which subsequently experience a redox decomposition leading to glyceraldehydes and Cr(III)-phen complex. The effect of the cationic surfactant, cetyl pyridinium chloride (CPC); anionic surfactant, sodium dodecyl sulphate (SDS) and nonionic surfactant, triton X-100 (TX-100) on the unpromoted and phen-promoted path have been studied. Micellar effects have been explained by considering the preferential partitioning of reactants between the micellar and aqueous phase.

Micelle catalyzed oxidation of propan-2-ol to acetone by penta-valent vanadium in aqueous acid media

Vanadium (V) oxidation of propan-2-ol shows a first-order dependency on the concentrations of propan-2-ol, vanadium (V), H+ and . These observations remain unaltered in the presence of externally added surfactant. The effects of the cationic surfactant (i.e. CPC), anionic surfactant (i.e. SDS) and neutral surfactant (i.e. TX-100) have been studied. CPC inhibits the reactions whereas SDS and TX-100 accelerate the reaction to different extents. Observed effects have been explained by considering the hydrophobic and electrostatic interactions between the surfactants and reactants. SDS and TX-100 can be used as catalysts in the production of acetone from propan-2-ol.

A review of biphasic hydroformylation for long chain substrates

The regioselective hydroformylation reactions of long chain olefins catalyzed by different unmodified and modified Co-based, Rh-based catalysts are summarized. The mechanism of homogeneous hydroformylation reactions using Co-based/Rh-based catalysts (unmodified) showed inhibition of reaction rate due to higher partial pressure of CO and also caused difficulty in separating catalysts from the product mixture. Hydroformylation reactions in biphasic medium using water soluble catalysts (Rh, Co, Ru/TPPTS) with an effective surfactant, cetyltrimethylammonium bromide (CTAB), are discussed. The homogeneous biphasic systems are not applicable for long chain olefins due to their low solubility in aqueous phase.

Effect of Some Non Functional Surfactants and Electrolytes on the Hexavalent Chromium Reduction by Glycerol: A Mechanistic Study: This paper is dedicated in the memory of Mr. Ajit Saha

Abstract Hexavalent chromium is a widespread environmental contaminant and a known human carcinogen. Kinetics of reduction of hexavalent chromium by bio-molecule glycerol in micellar media have been studied spectrophotometrically. The cytoplasmic reduction of hexavalent chromium to trivalent chromium occurs in micro-heterogeneous systems. In vitro, the micelles are considered to mimic the cellular membranes. The electron transfer processes occurring in the micellar systems is considered as model to obtain insight into the electron transport process prevailing in biological systems. Micellar media is also a probe to establish the mechanistic paths of reduction of hexavalent chromium to trivalent chromium. Effects of electrolytes common to biological system are studied to establish the proposed reaction mechanism strongly.

Surfactant-assisted bioremediation of hexavalent chromium by use of an aqueous extract of sugarcane bagasse

Agricultural products and by-products are now widely used for removal of hexavalent chromium from waste water. This option is more efficient and less expensive than conventional physicochemical treatments. The purpose of this study was reduction of carcinogenic hexavalent chromium to non-toxic trivalent chromium by use of aqueous extracts of sugar cane bagasse, which contains a variety of reducing components, for example sugar. The rate of this process is accelerated by use of surfactant as catalyst.

Micellar Catalysis on Pentavalent Vanadium Ion Oxidation of Ethanol in Aqueous Acid Media

Abstract Vanadium(V) oxidation of ethanol follows a first order dependency on the concentration of ethanol, vanadium(V), H+ and HSO4–. These observations remain unaltered in the presence of externally added surfactants. The effect of the cationic surfactant (i.e., N-cetylpyridinium chloride [CPC]), anionic surfactant (i.e., sodium dodecyl sulphate [SDS]) and neutral surfactant (i.e., Triton X-100 [TX-100]) has been studied. CPC inhibits the reactions, whereas SDS and TX-100 accelerate the reaction to different extents. Observed effects have been justified by considering the hydrophobic and electrostatic interaction between the surfactants and reactants. SDS and TX-100 can be used as catalysts in the production of acetaldehyde from ethanol.

Micellar catalysis of the 1,10-phenanthroline-promoted chromic acid oxidation of propan-2-ol in aqueous media

In aqueous media 1,10-phenanthroline (phen) promoted chromic acid oxidation of propan-2-ol produces propan-2-one (acetone). Acetone is separated from the mixture by fractional distillation. The effect of an anionic surfactant (SDS) and a neutral surfactant (TX-100) on the unpromoted and phen-promoted path have been studied. The catalytic effects of micelles have been explained by considering the preferential partitioning of reactants between the micellar and aqueous phases. The reaction becomes much faster when phen and TX-100 are combined together.