Reactions of halogenated organic peroxyl radicals with some biologically important compounds in a quaternary microemulsion

Reactions of various halogenated peroxyl radicals with guanine, uric acid, xanthine, hypoxanthine and ascorbic acid in a quaternary microemulsion consisting of sodium lauryl sulfate/water/1-pentanol/cyclohexane have been studied using the technique of pulse radiolysis. For all purine derivatives and ascorbic acid, formation of the respective radical cations have been observed. Variation in biomolecular rate constant values for the reactions of peroxyl radicals with the above-mentioned compounds has been discussed in terms of diffusion of radicals.     

Titrimetric determination of some organic compounds with bromine chloride

Bromine chloride is used in hydrochloric acid medium as a standard reagent for the rapid and precise determination of organic compounds by direct or indirect titrimetric methods. Hydrazine and its aryl derivative undergo a 4-electron change. Carbonyl compounds are determined by reaction with excess of 2,4-dinitrophenylhydrazine and estimation of the surplus. Sulphanilamide undergoes a substitution reaction in 1:3 molar ratio to bromine chloride. Thiobarbituric acid and thiourea or its alkyl derivatives show an 8-electron change but aryl thioureas also undergo nuclear bromination. Thiosemicarbazide and semicarbazide give a 10- and a 2-electron change respectively. In the direct titration, methionine is oxidized to its sulphoxide whereas cystine and cysteine form cysteic acid. In presence of bromide, glutathione forms the sulphonic acid but in the presence of iodide the product is the disulphide. The analytical results obtained by bromine chloride method are compared favourably with those afforded by established procedures.     

Green synthetic approaches for biologically relevant organic compounds

The present review aims to present some framework of the effective and diverse green methodologies in conventional and unconventional media including water, solar energy, ionic liquids, ultrasonication and bio-based catalysts which constitute an important goal in organic synthesis and can be used to strengthen conventional laboratory techniques.     

Iodine trichloride as an analytical reagent for determination of some organic compounds

Procedures are described for the determination of organic compounds with iodine trichloride under Andrews's titration conditions. Samples are directly titrated with iodine trichloride or first reacted with an excess of iodine monochloride, with subsequent titration of the iodine formed. The direct titration is done initially in feebly acid medium, then the acidity is raised (biotin, methionine, cystine and thiomersal). Pre-oxidation with iodine monochloride is used if the organic compound reacts slowly [tryptophan and arsenic(III) compounds] or is determined in bicarbonate medium (hydroxylamine and thiosemicarbazide). The ferrocyanide formed by the reduction of ferricyanide (by thiourea and allylthiourea) can also be titrated. Arsenic(V) compounds are determined after reduction to arsenic(III), and iodine in organic compounds is converted into iodide by alkaline fusion into iodide and the iodide titrated.     

Electrocatalytic oxidation of some biologically important compounds at conducting polymer electrodes modified by metal complexes

Conducting poly(3-methylthiophene) electrodes were electrochemically prepared. The resulting polymer films were modified with an inorganic complex, ferrocene. The incorporation of the ferrocene/ferrocenium moiety into the polymer film resulted in enhanced charge transfer towards the oxidation of some organic molecules of biological interest. The electrochemical response of the complex-containing polymer electrode was compared to that of the unmodified polymer electrode and that of the substrate. Apparent diffusion coefficients of the redox species were estimated from the cyclic voltammetric data for different biological molecules at the ferrocene-containing polymer electrode. Infra-red spectroscopic measurements for the “as-grown” films revealed the presence of the inorganic complex within the polymer. The modified polymer electrode showed noticeable enhancement for the charge transfer across the film interface and can be used as an electrochemical sensor for biological compounds. Received: 3 June 1997 / Accepted: 7 July 1997     

Voltammetric determination of some organic compounds of arsenic reduced at the mercury electrode

Cyclic voltammetric scans for methylarsonic acid, dimethylarsinic acid and 3-acetamido-4-hydroxyphenylarsonic acid at a mercury electrode in an acidic medium show anodic adsorption waves when the starting potential is sufficiently negative; the related arsines are formed on the electrode. Detection limits are at the micromolar level for the absorption peak found at about ?0.1 V vs. SCE for all three compounds. Interferences are discussed.     

Spectrophotometric determination of ionization constants of some organic compounds in aqueous solution

Ionization constants of some phenols and anilines in aqueous solution with a ionic strength of 0.01 were measured at 25°C by spectrophotometric method. The set of substrates was selected on the basis of the results of preliminary calculations of ionization constants in terms of an elemental linear empirical approach with account taken of the lack of the corresponding consistent published data.     

Gas chromatographic retention indices of biologically and environmentally important organic compounds on capillary columns with low-polar stationary phases

This work presents linear temperature programmed retention indices on the columns with stationary phases of 5% phenylpolydimethyl silicone of 389 organic compounds, including extractive substances of plant tissues and environmentally important compounds. Certain factors which influence the values and reproducibility of retention indices during gas chromatographic analysis of multicomponent mixtures are discussed.     

Kinetic determination of some inorganic and organic compounds by oxidation with iodate

Sulphite (5.0 × 10^?1?5.0 × 10^?3 M), ascorbic acid and other compounds are oxidized by potassium iodate in dilute sulphuric acid; the production of iodide is monitored by an iodide-selective electrode. The time needed for a 40-mV potential change is inversely proportional to concentration. For sulphite (1.0 × 10^?5?1.0 × 10^?4 M), selectivity is improved by sweeping the sulphur dioxide formed in acidic EDTA-containing solution into the iodate solution.     

Catalysts for the determination of oxygen in organic compounds

Summary Thermal decomposition of metal-organic complexes of nickel, cobalt and iron has given catalysts which are very effective at about 900° for the conversion of carbon dioxide, water and other oxygencontaining sample decomposition products to carbon monoxide in the direct determination of oxygen in organic compounds when using a modified Unterzaucher type apparatus. A copper catalyst similarly prepared required a temperature of 1030° whereas a manganese complex decomposition product was ineffective.

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Katalysatoren zur Sauerstoffbestimmung in organischen Substanzen

Zusammenfassung Durch thermische Zersetzung metallorganischer Komplexe von Ni, Co und Fe erhält man Katalysatoren, die die Umwandlung von CO₂, H₂O und anderen sauerstoffhältigen Zerfallsprodukten zu CO bei etwa 900° C bei der direkten Sauerstoffbestimmung in einer modifizierten Unterzaucher-Apparatur sehr wirksam fördern. Ein ähnlich hergestellter Cu-Katalysator erfordert 1030° C und das Zersetzungsprodukt eines Mn-Komplexes ist unwirksam.