Kinetics and mechanism of oxidation of erythro-series pentoses and hexoses by N-chloro-p-toluenesulfonamide.

The kinetics and mechanism of oxidation of D-glucose, D-mannose, D-fructose, D-arabinose, and D-ribose with chloramine-T in alkaline medium were studied. The rate law, rate = k [Chloramine-T] [Sugar] [HO-]2, was observed. The rate of the reaction was influenced by a change in ionic strength of the medium, and the dielectric effect was found to be negative. The latter enabled the computation of dAB, the size of the activated complex. The reaction rate was almost doubled in deuterium oxide. Activation energies were calculated from the Arrhenius plots. HPLC and GLC-MS analyses of the products indicated that the sugars were oxidized to a mixture of aldonic acids, consisting of arabinonic, ribonic, erythronic, and glyceric acids. Based on these data, a plausible mechanism involving the aldo-enolic anions of pentoses and keto-enolic anions of hexoses is suggested.

Oxidation of thiols by sodium N-haloarylsulphonamides.

The methods for direct titration of thiols with N-haloarylsulphonamides have been evaluated by studying the oxidation of 2-mercaptobenzoic acid, 2-mercaptopropionic acid, 3-mercaptopropionic acid, 2-naphthyl mercaptan, 2-mercaptoethanol, mercaptosuccinic acid, thiophenol, p-chlorothiophenol, butyl mercaptan and monothioglycerol, with chloramine-T (CAT), bromamine-T (BAT) and bromamine-B (BAB). The optimum conditions have been established. The precision was found to be poorer for titrations with CAT. BAB was found to give better precision and accuracy for the determination of all ten thiols studied, and is recommended for use.

Determination of thiocyanate with aromatic halosulphonamides in acid and alkaline media.

Ten organic aromatic halosulphonamides, both mono and dihalo compounds, ranging from chlorosulphonamides to iodosulphonamides, have been prepared and characterized by their infrared and NMR spectra and successfully used for determining thiocyanate in its metal salts and complexes. The proposed procedures are simple, rapid and reproducible, with an error of about +/-0.8%. These procedures are also useful for computing the number of thiocyanate ligands present in the complexes. Comparison of the present results with those from the argentometric method shows excellent agreement. The oxidation involves an 8-electron change per thiocyanate ion with the chloro and bromosulphonamides and a 6-electron change with iodosulphonamides.

Bromamine-B as a new oxidimetric titrant.

A new oxidimetric titrant, bromamine-B (sodium salt of N-bromobenzenesulphonamide) is introduced for use in aqueous medium. Direct potentiometric and visual end-point titrations and back-titration procedures have been developed for the determination of typical reductants.

Dichloramine-B as redox titrant in non-aqueous or partially aqueous media.

Dichloramine-B is proposed as a redox titrant in glacial acetic acid medium. The general conditions for its use and the procedures for estimating hydrazine, ascorbic acid, ferrocyanide, hydroquinone, oxine, antimony(III) and thallium(I) potentiometrically and allyl, crotyl and cinnamyl alcohols by a back-titration procedure are described.

Dibromamine-B as a new redox titrant in non-aqueous or partially aqueous media.

A new redox titrant, dibromamine-B (N,N'-dibromobenzene sulphonamide) is introduced for use in acetic acid medium. Direct potentiometric determinations of hydrazine, ascorbic acid, aniline, thiourea and its metal complexes and oxine and its metal complexes have been described.

A rapid method for the estimation of glutamic acid with chloramine-T.

Chloramine-T (added in excess) oxidizes glutamic acid in various solvent media and the reaction is rapid and stoichiometric with a 4-electron change in buffers of pH 1-6, in 0.01 M sulphuric and perchloric acids and in 0.1M hydrochloric acid. A back-titration procedure using a pH-4 buffer or 0.1M hydrochloric acid as reaction medium has been developed. rho-Toluenesulphonamide and a nitrile have been identified in the reaction products. The effect of other species on the oxidation has been investigated.

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)].

A direct method of estimating cyanide ion in metal salts and complexes by means of chloramine-T, dichloramine-T and lead tetra-acetate.

A simple and rapid method of determining cyanide in metal salts and complexes with chloramine-T, dichloramine-T and lead tetra-acetate, in presence of KBr and acetic acid, has been developed.

Estimation of cyanide ion in metal salts and complexes by means of chloramine-T and dichloramine-T.

A simple and accurate method for the estimation of cyanide in salts and complexes is based on oxidation with chloramine-T (in pH 4 buffer) or dichloramine-T (in presence of acetic anhydride). The oxidation involves a two-electron change. Halides interfere with the estimation of KCN, but the interference can be eliminated by precipitating and determining zinc cyanide. A method for estimating KCN and KCNS in mixtures is also described.

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.

Estimation of allyl alcohol by chloramine-T.

A simple but rapid and accurate method for the estimation of allyl in aqueous solution has been developed, based on its oxidation with chloramine-T at room temperature, in 0.5-1.0M hydrochloric acid medium. The reaction involves a two-electron change. The effect of such variables such as pH of the medium, presence of foreign ions and perchloric or sulphuric acid on the rate of oxidation is discussed.

Estimation of thiosemicarbazide with chloramine-T.

A rapid and accurate method for the estimation of thiosemicarbazide in aqueous solution has been developed based on its oxidation with chloramine-T at room temperature and pH 4. The effect of such variables as pH, mode of addition of reagents and concentration of chloride ion on the extent of oxidation has been studied.