Mechanism of chloramine-T oxidation of methyl vinyl ketone and isopropyl methyl ketone in aqueous alkaline media

The oxidation kinetics of methyl vinyl ketone and isopropyl ketone by chloramine-T in aqueous alkaline solutions show first-order dependence on chloramine-T, both substrates and alkali. No effect of p-toluenesulphonamide was evident. Observed stoichiometry, negligible effect of ionic strength and a positive dielectric effect point to a mechanism involving interaction of enolate anions with chloramine-T in the rate determining step. Activation parameters and the isolation of the product formaldehyde are in agreement with the proposed mechanism.     

Kinetics and mechanism of oxidation of leucine by chloramine-T in alkaline media

Alkaline media oxidation of leucine by chloramine-T has been investigated. A first order dependence in chloramine-T and leucine and a near inverse first order dependence in hydroxide ion has been observed. Ionic strength had negligible effect while the effect of methanol addition was slightly negative. The oxidation process has been shown to proceed via two paths, one involving p-toluenesulfochloramide as the main oxidising species and the other involving hypochlorite ion, each interacting in a slow step with a leucine molecule leading to formation of monochloroleucine acid, which subsequently interacts with another molecule of p-toluenesulfochloramide or hypochlorite ion resp., yielding products.     

Kinetics of oxidation of ketoglutaric acids by alkaline chloramine-t solution

Kinetics of the oxidation of α-ketoglutaric and β-ketoglutaric acids by chloramine-T (CAT) have been investigated in highly alkaline media. The reactions show first order dependence in chloramine-T and fractional order in substrates. The order in hydroxide ions has been found to be second but shows a slight decrease at high concentration of alkali. No effect of p-toluene-sulphonamide was evident. Observed stoichiometry, positive effects of ionic strength and dielectric constant point to a mechanism involving formation of an intermediate in a termolecular rate determining slowest step among hypochlorite ion, hydroxide ion and enolic anion of keto acids followed by a fast step leading to products. Activation parameters have been computed and formaldehyde and formic acid were Identified as end-products.     

Micellar catalysed chlorination of acetophenone by chloramine-T

The chlorination of acetophenone by chloramine-T cat has been catalysed by anionic micelle, sodium lauryl sulphate (NaLS). Though the order in cat is one, the order in acetophenone is fractional at lower concentration and becomes zero at higher concentration in the presence and absence of NaLS. This is probably due to the change in rate-determining step. At lower acetophenone concentration, the decomposition of enol-chlorinating species complex is rate-determining whereas at higher concentration, the formation of chlorinating species is rate determining. The graph ofk ₂ versus detergent concentration is sigmoidal and the positive co-operativityversus log[D] graph is 1.11, indicating possible interaction between micelle and substrate.     

Oxidation of crotyl alcohol by N-chloro-4-methylbenzene sulphonamide in acidic medium and in alkaline media in the presence of os(VIII) catalyst-a kinetic pathway

The kinetic pathway of oxidation of crotyl alcohol by sodium salt of N -chloro-4-methylbenzene sulphonamide (chloramine-T) in acidic and alkaline medium has been studied. The speciation of chloramine-T has been made to suggest a proper and reasonable reaction mechanism. The thermodynamic quantities such as activation energy and activation entropy are evaluated in acidic as well as in catalysed alkaline medium. An anticipated reaction mechanism has been suggested.     

Estimation of xylenes with chloramine-T

The reaction between xylenes and chloramine-T has been found to proceed quantitatively over a wide range of experimental conditions. A back-titration procedure in which xylenes are reacted with excess of chloramine-T in 1M perchloric acid-0.03M sodium chloride medium has been developed. Inorganic ions other than chloride do not interfere. The method can be used for estimating xylenes in the presence of some other petrochemicals.     

Estimation of glutathione with chloramine-T and dichloramine-T

A simple but accurate method for the estimation of glutathione in aqueous solution has been developed, based on its oxidation with chloramine-T and dichloramine-T at room temperature. The direct titration with a visual or potentiometric end-point involves a one-electron change, corresponding to the oxidation of the thiol group to disulphide. Most amino-acids do not interfere, but cysteine, methionine and thiourea are oxidized under these conditions. A back-titration procedure in which glutathione is oxidized by excess of chloramine-T with a 10-electron change at pH 5 has also been developed.     

Beyond the corey reaction: one-step diolefination of cyclic ketones

The reactivities of the cyclic ketones cycloheptanone, cyclodecanone, and cycloundecanone with dimethylsulfoxonium methylide generated from trimethylsulfoxonium iodide and base (NaH) were studied in diglyme at 130 degrees C. Oxiranes, which primarily form via the Corey reaction, lead to ring expansions to give oxetanes and oxacyclopentanes when an excess of dimethylsulfoxonium methylide is used. The Corey reaction is suppressed in the presence of excess of base, and 1,3-terminal dienes form instead (we term this reaction the Yurchenko diolefination). Our mechanistic proposal involves the deprotonation of the betaine that forms after the attack of dimethylsulfoxonium methylide on the carbonyl group of the ketone. The key step of the diolefination reaction involves a [2,3]-sigmatropic rearrangement of the ylide to a gamma-unsaturated sulfoxide with a barrier of 9.9 kcal/mol (DeltaH298, MP2/cc-pVDZ, for the cycloheptane derivative). The elimination of sulfenic acid from the gamma-unsaturated sulfoxide in the terminal step of the diolefination is associated with a higher barrier (17.3 kcal/mol) but is strongly accelerated in the presence of base. The reactivity of cyclic ketones in the Yurchenko reaction depends on the ring size; medium-sized cyclodecanone is less reactive than either cycloheptanone or cyclododecanone.     

Kinetics and mechanism of metal ion catalysis: Part I. Kinetics of electron transfer from cycloheptanone in aqueous alkali

The kinetics of the electron transfer from cycloheptanone to OsO₄ in alkaline medium has been studied spectrophotometrically. The oxidation of cycloheptanone by Os^VIII, continuously regenerated by Fe(CN)^3– ₆ in alkaline medium in the 0.00123–0.01 M range, is zeroth order with respect to Fe(CN)^3– ₆ and first order with respect to Os^VIII. A suitable mechanism, based on rate data analysis, is proposed.     

Kinetics and mechanism of oxidation of acetone,ethyl methyl ketone and diethyl ketone with chloramine-T in hydrochloric acid medium

The kinetics of oxidation of aliphatic ketones (acetone, ethyl methyl ketone and diethyl ketone) by chloramine-T in presence of hydrochloric acid (0.1 to 0.3M) have been investigated at 30 °C. The rate of disappearance of chloramine-T has been found to be first order each with respect to oxidant, ketone and [H⁺], in the range of the acid concentrations studied. The thermodynamic and kinetic parameters have been evaluated by determining the rate constants at different temperatures. The products of the reaction have been identified as chloroketones by their NMR spectra. The solvent isotope effect has been studied in the case of the oxidation of acetone and ethyl methyl ketone. A mechanism has been proposed.     

An electron spin resonance study of radicals from chloramine-t-1 : Spin trapping of radicals produced in acid media

Under acid conditions aqueous solutions of chloramine-T form nitrogen-centred radicals via loss of the chlorine atom. The nitrogen radicals produced have been studied by ESR spectroscopy using the spintrapping method. Adducts of the spin trap phenyl-t-butyl nitrone are oxidized by chloramine-T in acid media to give a paramagnetic product in which the unpaired electron interacts with two inequivalent nitrogen atoms. The spin trap 5,5-dimethyl-2-pyrrolidine-1 -oxide is oxidized rapidly to 5,5-dimethyl-2-pyrrolidone-1-oxyl by chloramine-T under acid onditions. The water soluble trap α-4-pyridyl-1-oxide-N-t-butyl nitrone forms a stable nitroxide adduct with a nitrogen radical of chloramine-T in acid solution. Identical results were obtained with chloramine-B (sodium salt of N-chlorobenzene sulfonamide), indicating the involvement of the N-chloramine group in radical formation.     

Titrimetric determination of chloramine-T and some aldoses by amplification reactions

A titrimetric method with amplification has been worked out for the determination of chloramine-T and certain aldoses. It is based on Leipert determination of iodide produced in the case of chloramine-T by reduction of the determinand with excess of iodide, and extraction and subsequent reduction of the iodine liberated. In the other case, the aldoses are oxidized with iodine, the surplus oxidant is extracted, and the residual iodide is determined. The method is applicable to chloramine-T in the range 0.01-3 mg, with a relative error between -3.0 and -0.4% and a relative standard deviation of 0.6-0.8%, depending on the amount present, and to 0.05-1 mg of glucose, galactose or arabinose, or 0.1-2 mg of lactose or maltose, with a relative standard deviation of 1.4% for > 0.5 mg of aldose.     

Evaluation of the chloramine-T membrane electrode response in acidic solutions. The determination of the pKa of N-chloro-p-toluenesulfonamide (chloramine-T acid)

Measurements made with a combination of glass and chloramine-T ion-selective membrane electrodes in acidified chloramine-T solutions varying in ionic strength have been used to determine the dissociation constant of N-chloro-p-toluenesulfonamide (chloramine-T acid). Experimental data agree satisfactorily with reported values.     

Estimation of methionine and its metal complexes by oxidation with chloramine-T and dichloramine-T

A simple method for the estimation of methionine (HMt) in aqueous solution has been developed, based on its oxidation with chloramine-T and dichloramine-T at room temperature. The direct titration, with visual or potentiometric end-point involves a two-electron change, corresponding to the formation of methionine sulphoxide. Most amino-acids do not interfere, but cysteine, glutathione and thiourea are oxidized under these conditions. A back-titration procedure in which methionine is oxidized in 0.1M sodium hydroxide by excess of chloramine-T with a four-electron change corresponding to the formation of methionine sulphone has also been developed. Methionine is oxidized to the respective nitrile, however, with excess of dichloramine-T. The methods have also been employed in estimating methionine in two of its soluble complexes, [NiMt]ClO(4) and Na[AgMt(2)].     

Construction,analytical study and application of a new chloramine-t selective electrode

A chloramine-T (CAT) selective electrode with a liquid membrane of nickel batho-phenanthroline—chloramine-T dissolved in 2-nitro-p-cymene is described. The liquid membrane electrode exhibits rapid and near Nernstian response to chloramine-T activity from 10^-1 to 10^-4 M. The response is unaffected by pH in the range 5–9. Major interferences are penodate and perchlorate. In analytical applications, direct potentiometnc methods for the determination of chloramme-T, ascorbic acid, and arsenic(III), and a titnmetric method for ascorbic acid are described. Ascorbic acid and arsenic(IU) in the ranges 0.4–40 and 0.5–2 mg, respectively, can be determined with relative errors of 1–2%. The method has been applied to the determination of ascorbic acid in pharmaceutical preparations.     

Oxidative decolorization of indigo caramine dye with chloramine-T catalyzed by cobalt(II)

Decolorization of indigo caramine dye by oxidation process using chloramine-T as oxidant and Co(II) as catalyst in acidic buffer media, pH 5.8 has been kinetically studied at 300 K. Decolorization of indigo caramine dye was followed spectrophotometrically. Decolorization and oxidation led to a decrease in Chemical Oxygen Demand of the dye. The Co(II)-catalyzed reaction shows first-order dependence of the rate on chloramine-T and indigo caramine concentrations. It also shows fractional order dependence on [Co(II)] and [H⁺]. Addition of halide ions or reduction product of chloramine-T toluenesulfonamide, and variation of ionic strength and dielectric constant of the medium do not have any significant effect on the reaction rate. Activation parameters are evaluated from the Arrhenius plot, and a mechanism is proposed for the reaction.     

O-acyl derivatives of cyclopentanone and cycloheptanone oximes

By acylation of cyclopentanone and cycloheptanone oximes with carboxylic acids anhydrides or chlorides new esters were obtained of cyclopentanone and cycloheptanone oximes and their spectral characteristics were investigated.     

Total synthesis of ent-calystegine B4 via nitro-Michael/aldol reaction

Optically active ent-calystegine B4 was prepared in 13 steps from commercially available chiral L-dimethyl tartrate. The synthesis was achieved by the Michael addition and the aldol reaction of nitromethane to form cycloheptanone in a stereoselective manner. Reduction of the nitro group in the presence of Boc(2)O accomplished an efficient conversion to amino cycloheptanone, which readily afforded the desired ent-calystegine B4.     

Arylidene Polymers. IX. Synthesis,Characterization, and Morphology of New Polyesters of Diarylidenecycloalkanones Containing Thianthrene Units

New polyesters containing thianthrene tetraoxide were synthesized by the interaction of 2,7-dichloroformylthianthrene-5,5′,10, 10′-tetraoxide with 2,5-bis(p-hydroxybenzylidene)cyclopentanone, 2,5-divanillylidenecyclopentanone, 2,6-bis(p-hydroxybenzyiidene)-cyclohexanone, 2,6-divanillylidenecyclohexanone, and 2,7-bis(p-hydroxybenzylidene)cycloheptanone by using the interfacial polycondensation technique. The resulting polyesters were characterized by elemental and spectral analyses. All the synthesized polymers readily dissolved at room temperature in dimethylsulfoxide. The thermal properties of the polymers were evaluated and correlated to their structural units by TGA and DSC measurements. X-ray analysis of polymers showed that all the polyesters are amorphous. Moreover, the morphology of a new high performance polyester, poly[oxycarbonyl-2,7-thianthrene-5,5′,10,10′-tetraox-idecarbonzeoxyl(2-methoxy-p-phenylene)methylidyne(2-oxo-1,3-cyclohexanediylidenemethylidyne)methylidene(3-methoxy-p-phenylene)], has been investigated by scanning electron microscopy.     

Magnetic field dependence of the product yields of cycloheptanone photolysis in the dilute gas phase

The product yields of the gas-phase photolysis of cycloheptanone were measured in magnetic fields up to 10 kG. The magnetic-field effect is explained in terms of the radical pair model. A reaction mechanism is proposed that explains the magnetic field dependence, pressure dependence, and excitation enegy dependence of the gas-phase photochemistry of cycloheptanone.