The Kinetics of the Reaction of Carbon Dioxide with Propylene Oxide Catalyzed by a Chromium–Salen Complex

The kinetics of the reaction of CO₂ with propylene oxide utilizing a salenCrCl/PPNCl active catalytic system is studied with varying reaction conditions (temperature, pressure, and cocatalyst/catalyst ratio). The reaction proceeds selectively to form cyclic propylene carbonate (PC) at [PPNCl]/[salenCrCl] ratios above two. The value of the effective activation energy of PC formation is found.     

A comparison of the reduction of dinitrogen by a vanadium(ii)—catechol system with that by the active centre of nitrogenase

A comparison of the action of a nitrogenase active centre with that of the vanadium(II)—catechol system in water and alcohol as far as N₂ and C₂H₂ reduction, H₂ evolution and the inhibiting effect of CO are concerned demonstrates the existence of many similarities, thus enabling some tentative conclusions to be made regarding the mechanism governing the functioning of nitrogenase.     

Analysis of Amino Acids in a Single Human Red Blood Cell by Capillary Zone Electrophoresis with Intracellular NDA—derivatization and Electrochemical Detection

A novel method for determination of amino acids in individual red blood cells has been developed. In this method, the derivatization reagents (NDA and CN^-) are introduced into living cells by electroporation. After completion of derivatization,the amino acids in a single cell is determined by capillary zone electrophoresis with end-column amperometric detection.     

The Role of Catalyst Formation–Deactivation Processes and Evidence for a Nonlinear Mechanism in the Mizoroki–Heck Reaction with Aryl Chlorides

Kinetics and Catalysis - An operando kinetic study was made of the Mizoroki–Heck reaction with low-reactive aryl chlorides using the most practically attractive “ligand-free”...     

The mechanism of asymmetric reduction catalyzed by a C_2 symmetric bis-amino alcohol catalyst——In situ NMR study of the structure of new type of dual-centered catalyst

By means of 1H, 13C, 11B NMR, polar transfer DEPT135, DEPT90 and 2D NMR experiments, IR, etc, the structure of the diaminodihydroxyl ligand and its derivatives used in the asymmetric reduction of prochiral ketones were detected. The catalysts derived from the ligand and bo-rane formed in situ were also studied and the structure transformations in solution were monitored.The structure of the catalyst was proved to be a new type of dual-centered catalyst——bis-oxazaborolidine.     

The pyrolysis process of wood biomass samples under isothermal experimental conditions—energy density considerations: application of the distributed apparent activation energy model with a mixture of distribution functions

This work deals with the isothermal pyrolysis of Pine and Beech wood samples and kinetic studies, using the thermo-analytical technique, at five different operating temperatures. Pyrolysis processes were investigated by using the distributed apparent activation energy model, which involves the complex mixture of different continuous distribution functions. It was found that decomposition processes of wood pseudo-components take place in different conversion areas during entire pyrolyses, whereby these areas, as well as the changes in apparent activation energy (E _a) values, are not the same for softwood and hardwood samples. Bulk density (Bden) and energy density (ED) considerations have shown that both biomass samples suffer from low Bden and ED values. It was concluded that pyrolysis can be used as a means of decreasing transportation costs of wood biomass materials, thus increasing energy density. The “pseudo” kinetic compensation effect was identified, which arises from kinetic model variation and wood species variation. In the current extensive study, it was concluded that primary pyrolysis refers to decomposition reactions of any of three major constituents of the considered wood samples. Also, it was established that primary reactions may proceed in parallel with simultaneous decomposition of lignin, hemicelluloses and cellulose in the different regions of wood samples, depending on the operating temperature. It was established that endothermic effects dominate, which are characterized with devolatilization and formation of volatile products. It has been suggested that the endothermic behavior that arises from pyrolyses of considered samples may indicate the endothermic depolymerization sequence of cellulose structures.     

The difference between cholesterol-and glycyrrhizin-γ-cyclodextrin complexes— an analysis by MD simulations in vacuo and in aquo and the calculation of solvation free energies with AMSOL

Glycyrrhizin forms very stable, freely water-soluble inclusion complexes with cyclodextrin. In contrast, the [cholesterol//γ-cyclodextrin] complex is very sparingly soluble in aquo. The molecular dynamics simulations and AMSOL calculations reported in this paper support these experimental findings: cholesterol is much less soluble than glycyrrhizin, glycyrrhetinic acid, diglucuronic acid and γ-cyclodextrin. The [glycyrrhizin//γ-cyclodextrin] complex is the most stable one. The previously reported unusually large dipole moments of cyclodextrins were only found in the simulations; AMSOL calculations suggest a dipole moment of about 2 Debye for γ-cyclodextrin. The simulations illustrate how the guest molecules become included in the cyclodextrin cavity.     

Improvement in the physicochemical properties of titanium dioxide by surface modification with 1H-1-carboxylate of isopropyl-imidazole and 3-aminopropyltrimethoxysilane: case study—as a filler in polylactic acid composites

Journal of Thermal Analysis and Calorimetry - This work presents the surface functionalization of titanium dioxide nanoparticles with 1H-1-carboxylate of isopropyl-imidazole and...     

Convenient preparative method for synthesis of methyl (Z)-3-aryl-2-(carbobenzoxyamino)acrylates by Wittig—Horner reaction with the use of Et3N as a base

The Wittig—Horner reaction of CbzNHCH(CO₂Me)P(O)(OMe)₂ (1) with ArCHO (2) in the presence of Et₃N as a base affords methyl (Z)-3-aryl-2-(carbobenzoxyamino)acrylates (3) with high degrees of diastereoselectivity (Z)/(E) > 101. One recrystallization of the crude product is sufficient to obtain isomerically and chemically pure (Z)-3.Translated fromIzyestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2218-2220, November, 1995.The authors are grateful to the Dupont company (USA) for financing this study     

Deoxypyridinoline-bioinspired supramolecular antibacterial salts with a C—H⋯O hydrogen-bonded tetrameric host to construct the helical scaffold and sheet structures: The importance of rotational flexibility,anion shapes,and robust C—H⋯O hydrogen bonding

A new flexible hydrogen-bonded supramolecular host based on two deoxypyridinoline-bioinspired 6-hexanoic acid-substituted 3-hydroxypyridinium cations that adopt the twist and planar conformations and construct the orthogonal single helical scaffold and sheet structures with the triangular NO₃⁻ and spherical Br⁻ guest anions, respectively. The results demonstrated not only the importance of rotational flexibility, anion shapes, and robust C—H⋯O hydrogen bonding, but also the good antibacterial activity with the potential antibacterial application.