Kinetics of oxidative deamination of some amino acids by diperiodatoargentate(III) in alkaline medium

Kinetics of oxidation of some amino acids, viz. glycine, alanine, valine, leucine, phenylglycine and phenylalanine by diperiodatoargentate(III) have been investigated in alkaline medium. The order of the reaction is found to be one with respect to each reactant. The reaction rates are inversely dependent on both [OH^–] and [periodate]. The oxidation products are found to be ammonia and the corresponding keto acids. The presence of electron-withdrawing groups at the -carbon increases the rate of oxidation while the rate decreases with increasing alkyl chain length. A two-electron-transfer mechanism is proposed to explain the results.

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, , , , , , (III) . . OH^– . . - - ; . .

     

Electrochromic window based on polyaniline

A portable electrochromic display window (7 cm × 5 cm) has been constructed using a polyaniline-coated SnO₂ glass plate and an AlCl_3(aq) melt. The window colour can be switched from dark green to yellow or colourless by applying a small voltage of −0.5 to 2.5 V. It exhibits a fast response time (ms) and a long cycle life (1000). Received: 27 May 1997 / Accepted: 8 September 1997     

Kinetics and mechanisms of oxidations by metal ions. Part 17. Oxidation of formate ion by alkaline osmium tetroxide

Summary The oxidation of formate ion by alkaline osmium tetroxide, such that [HCO _inf2 ^p– ] [Os^VII], exhibits first-order dependence in [Os^VII], an order less than unity in [HCO _inf2 ^p– ], and zero-order in [OH^–]. HCO^2– reacts as an ion-pair formed with an alkali metal ion and [OsO₄(OH)₂]^2– is the reactive species of Os^VII. The formation of an intermediate Os^VII-HCO₂M complex is substantiated by the rapid-scan spectra of the reaction mixture. Anions (Cl^–, ClO _inf4 ^p– ) have no effect on the rate. The close agreement between the observed k _H/k _D = 7.1 and the theoretically calculated value (7.0), based on the stretching frequencies of C-H and C-D bonds in the free molecule, indicates an outer-sphere mechanism.Author to whom all correspondence should be directed.     

Identification of some 2[2-mercapto (or substituted mercapto)-4-thiazolyl] benzothiazoles by thin-layer chromatography

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Identification of some 2[2-mercapto (or substituted mercapto)-4-thiazolyl] benzothiazoles by thin-layer chromatography

     

New dioxouranium(VI) complexes with tridentate dibasic Schiff bases containing ONO donor sets

Summary Several new dioxouranium(VI) complexes with the tridentate dibasic Schiff bases derived from salicylaldehyde, 5-chloro-, 5-bromo-, 5-nitro-, 3,5-dichloro-, 4-methoxy-, 5-methoxy- and 3-ethoxysalicylaldehyde and 2-hydroxy-1-naphthaldehyde ando-aminobenzyl alcohol, have been synthesized from uranyl acetate dihydrate and the Schiff base in methanol. The complexes are of the type UO₂(AAA). MeOH (where AAAH₂ = a tridentate dibasic Schiff base). The complexes have been characterized by elemental analyses, i.r. and electronic spectra, conductance, magnetic susceptibility and molecular weight measurements. Thev (U=O) stretching frequency of the complexes occurs atca. 900 cm^–1 and the U-O distance is 1.74Å. The complexes are monomers, diamagnetic and octahedral.     

Thermoanalytical behaviour of carbaryl and its copper(II) and zinc(II) complexes

Non-isothermal techniques, i.e. thermogravimetry (TG) and differential scanning calorimetry (DSC), have been applied to investigate the thermal behaviour of carbaryl (1-naphthyl-N-methylcarbamate = 1-Naph-N-Mecbm) and its complexes, M(1-Naph-N-Mecbm)₄X₂, where M = Cu, X = Cl, NO₃ and CH₃COO and M = Zn, X = Cl. Carbaryl and Zn(1-Naph-N-Mecbm)₄Cl₂ complex exhibit two-stage thermal decomposition while the copper(II) complexes exhibit three and four-stage decomposition in their TG curves. The nature of the metal ion has been found to play highly influential role on the nature of thermal decomposition products as well as energy of activation ‘E*’. The presence of different anions does not seem to alter the thermal decomposition patterns. The complexes display weak to medium intensity exothermic and endothermic DSC curves, while the free ligand exhibits two endothermic peaks. The kinetic and thermodynamic parameters namely, the energy of activation ‘E*’, the frequency factor ‘A’ and the entropy of activation ‘S*’ etc. have been rationalized in relation to the bonding aspect of the carbaryl ligand. The nature and chemical composition of the residues of the decomposition steps have been studied by elemental analysis and FTIR data.