Kinetics Solvent Effect and Mechanism of Hydrolysis of Ethyl Caprylate Ester in Aqueous Organic Solvent Media

The specific rate constant of ethyl caprylate in alkali catalised hydrolysis in water-acetone mixture covering range of 30 to 70% (v/v) of acetone has been determined at temperature 20 to 400c. The rate of reaction decreases with increase in percentage of Acetone from 30 to 70% (v/v). The observed Activation energy decreases progressively with increase in acetone content of the medium. The effect of molar concentration of water and Dielectric constant on the reaction kinetic has also been studied. The thermodynamic parameters (DG*, DH* and DS*) has been determined which showed strong dependency on solvent composition.

Transport Reagents through the Pore Structure of a Membrane Catalyst under Isothermal and Non-Isothermal Conditions

The article presents the results of an experimental comparison of methane transport in the pore structure of a membrane catalyst under isothermal and non-isothermal Knudsen diffusion conditions. It is shown that under the conditions of non-isothermal Knudsen diffusion in the pore structure of the membrane catalyst, there is a coupling of dry reforming of the methane (DRM) and gas transport, which leads to the intensification of this process. The reasons for the intensification are changes in the mechanism of gas transport, an increase in the rate of mass transfer, and changes in the mechanism of some stages of the DRM. The specific rate constant of the methane dissociation reaction on a membrane catalyst turned out to be an order of magnitude (40 times) higher than this value on a traditional (powder) catalyst.

Degradation of trinitrotoluene by transgenic nitroreductase in Arabidopsis plants

The explosive 2,4,6-trinitrotoluene (TNT) is a highly toxic and persistent environmental pollutant. TNT is toxic to many organisms, it is known to be a potential human carcinogen, and is persistent in the environment. This study presents a system of phytoremediation by Arabidopsis plants developed on the basis of overexpression of NAD(P)H-flavin nitroreductase (NFSB) from the Sulfurimonas denitrificans DSM1251. The resulting transgenic Arabidopsis plants demonstrated significantly enhanced TNT tolerance and a strikingly higher capacity to remove TNT from their media. The highest specific rate constant of TNT disappearance rate was 1.219 and 2.297 mL/g fresh weight/h for wild type and transgenic plants, respectively. Meanwhile, the nitroreductase activity in transgenic plant was higher than wild type plant. All this indicates that transgenic plants show significantly enhanced tolerances to TNT; transgenic plants also exhibit strikingly higher capabilities of removing TNT from their media and high efficiencies of transformation.

Facet-dependent performance of BiOBr for photocatalytic reduction of Cr(vi)

BiOBr dominated with {110} facets giving a specific rate constant 3 times as high as BiOBr with {001} facets, and its much stronger internal electric field was believed to be the main reason.

Kinetics of zinc ion incorporation in base into a centrally aprotic beta-octabrominated cationic water-soluble porphyrin and its monolithium complex

The kinetics of zinc incorporation from pH 12 to 13 into the centrally aprotic BrP (4)2+ form of beta-octabromo-meso-tetrakis(N-methyl-4-pyridyl)porphyrin and its monolithium complex were studied at 25.0 °C, ionic strength (I) = 0.10. The reactions were first order in porphyrin and total zinc concentrations. For BrP (4)2+, the specific rate constant was 5.1 × 105 M -1 s -1 for Zn ( OH )2 aq , 9.9 × 104 M -1 s -1 for [Formula: see text] and [Formula: see text] was unreactive. The Li - BrP (4)3+ complex had a formation constant with BrP (4)2+ of 1.1 × 103 M -1 from both kinetic and equilibrium measurements. In solutions containing both BrP (4)2+ and Li - BrP (4)3+, zinc incorporation proceeded only through BrP (4)2+.

Enzyme-Catalyzed Decomposition of Dibenzoyl Peroxide in Organic Solvents

Catalytic activity of catalase (CAT, EC 1.11.1.6), immobilized on carbon black NORIT and soot PM-100, with respect to decomposition of dibenzoyl peroxide (BPO) in non-aque-ous media (acetonitrile and tetrachloromethane), was investigated with a quantitative UV-spectrophotometrical approach. Progress of the above reaction was controlled by selected kinetic parameters: the apparent Michaelis constant (Kmapp), the specific rate constant (Ksp), the activation energy (Ea), the maximum reaction rate (Vmax), and the Arrhenius’ pre-exponential factor (Z0). Conclusions on the tentative mechanism of the catalytic process observed were drawn from the calculated values of the Gibbs energy of activation (ΔG*), the enthalpy of activation (ΔH*), and entropy of activation (ΔS*)

Sulfate as a ligand in ruthenium(II) and (III) ammines

The trans-[RuSO4(NH3)4(L)]Cl complexes, (L = nicotinamide (nia), L-histidine (L-hist), 4-picoline (4-pic), 4-chloropyridine (4-Clpy), isonicotinamide (isn), pyrazine (pyz), 4-aminopyridine (4-NH2py), 4-cyanopyridine (4-CNpy), pyridine (py), imidazole (Him), and water (H2O)), were characterized by elemental analysis cyclic voltammetry, UV-vis, IR, and electron paramagnetic resonance spectroscopies. From the four ν (SO42–) observed only ν3 and ν4 split in two bands each for the sulfate unidentate coordination. The values of Δ/ξ parameters, extracted from g values, allow us to write the following order of increasing π-donation ability: pyz < (py, 4-CNpy, 4-Clpy. 4-pic, isn, nia) < Him < L-hist < 4-NH2py. The intense absorption in the 317-347 nm (ε ~ 2.3-5.6 × 103 M-1 cm-1) region was tentatively assigned to sulfate-to-metal charge transfer (LMCT) and the absorption in the range of 230-270 nm (ε ~ 2 - 6 × 103 M-1 cm-1) assigned to an internal (IL) π-π* transition in the heterocyclic ligands. The rate for the sulfate aquation in trans-[RuSO4(NH3)4L]0 complexes was evaluated through chronopotentiometric measurements and are in the 2.6 s-1 (chloropyridine) to 20 s-1 (pyrazine) range. The SO42– is aquated in trans-[RuIIISO4(NH3)4(4-pic)]Cl at the specific rate constant of (1.4 ± 0.4) × 10-5 s-1, which is very much slower than in trans-[RuIISO4(NH3)4(4-pic)] (5.4 s-1). The X-ray crystal structure data show that the Ru-Cl (2.3444(9) Å) and Ru-NH3 (2.100(2) Å) mean distances in trans-[RuCl(NH3)4(4-pic)]Cl2·H2O are similar to the ones observed in other tetraammineruthenium(III) complexes.Key words: ruthenium, sulfate, ammines.