Substituent effects on the rate and selectivity of the hydrogenation of 2-nitroazobenzenes on raney nickel in alkaline and acid media

The scheme of chemical transformations of 2-nitroazobenzene derivatives during catalytic hydrogenation on Raney nickel was found to be common to compounds containing electron donor and electron acceptor substituents. A qualitative correlation between solvation interaction parameters and the solubility of substituted 2-nitroazobenzenes was observed. The selectivity of the reaction with respect to intermediate products was determined by the composition of the solvent and weakly depended on the nature of the substituent. The introduction of sodium hydroxide and acetic acid into solvents ensured high selectivity of the hydrogenation of substituted 2-nitroazobenzene derivatives with respect to the corresponding N-oxides and nitrohydrazo derivatives, respectively.     

Sulfonated and sulfoacylated poly(styrene-divinylbenzene) copolymers as packing materials for cation chromatography

Three different types of cation exchangers were produced from four basic poly(styrene-divinylbenzene) substrates with different properties. Porous PS-DVB resin beads were functionalized by sulfonation and sulfoacylation under various conditions to produce sulfonated resins with exchange capacities of 0.03-1.80 mM g(-1). The matrix with 50% of cross-linking is most suitable for updating by the proposed technique. Sulfuric and chlorosulfonic acids were used as the reagents for sulfonation. The sulfonating conditions, capacities, and the technique of the synthesis are given. The effects of parameters of the sulfonation reaction and the composition of the reactionary mixture on ion-exchange capacity of the sorbents were investigated. Selectivity and efficiency of the separation of some inorganic cations and derivatives of amines and hydrazines on the resins obtained are compared by ion chromatography with conductometric detection. As a result, the sulfoacylated resin was proved more efficient for the separation of these analytes. The resolution of the analytes strongly depends on the degree of functionalization. The best performance about 19,000 plates m(-1) was obtained using the sulfopropionylated beads with an ion-exchange capacity of 0.3 mM g(-1). The prepared sulfoacylated cation exchanger was compared with the commercially available Dionex CS-12 packing material. It was found that the separation of alkaline ions and 1,1-dimethylhydrazine (UDMH) were much better that those for the commercial material.     

Hydrogenation of Substituted Benzenes Containing Nitro and Azo Groups over Skeletal Nickel in Aqueous Solutions of 2-Propanol

Russian Journal of Physical Chemistry A - An analysis is made of the kinetic characteristics of the hydrogenation of 4-nitro- and 2-nitro-2'-hydroxy-5'-methylazobenzenes, 4-nitroaniline and...     

The influence of compression conditions on the peculiarities of self-propagating exothermal reaction in Al–Ni powder reactive materials

The paper deals with the effect of the compression conditions on the propagation front velocity of exothermal reaction and the specific heat release in Al–Ni powder reactive materials with mean particle sizes of 70–110 nm. It was shown that the velocity increases from 2.7 to 8 cm s^?1 and comes to saturation with the lowering of the porosity (η) from 0.91 to 0.34, while the dependence of the specific heat release has its maximum for η?=?0.5. The results of the X-ray diffraction analysis obtained in situ during the sample heating suggest that the sequence of phase transformations in the system does not depend on the porosity. In all cases, first in the temperature range of ~?500–540 °C the NiAl compound is formed. With the further heating up to ~?640 °C, the Ni₃Al, Ni₂Al₃ and NiAl₃ compounds are additionally formed. The calculation of kinetic parameters was performed using the obtained curves of the differential scanning calorimetry: activation energy, pre-exponential factor and reaction model. The comparison of the calculated results and the scanning electron microscopy data has shown that such behavior of the Al–Ni system with the porosity lowering occurs due to the growth of the transformation degree and is associated with the presence in the final powder mixture of mutually non-contacting Al and Ni agglomerates with the dimensions of over 10 μm.     

The influence of the nature of substituents on adsorbability and the rate of liquid-phase hydrogenation of nitrobenzenes

The influence of the nature of substituents on the rate of liquid-phase hydrogenation of nitrobenzenes on Raney nickel was studied in an aqueous solution of 2-propanol. Interrelation between the rate of the reaction on the equiaccessible surface of the catalyst and solvation parameters, reactivity indices, and adsorption values of hydrogenated compounds containing electron acceptor (4-nitrobenzoic acid) and electron donor (4-nitroaniline) substituents was considered.     

Concentration Effects in the Hydrogenation of 4-Nitro-2′-Hydroxy-5′-Methylazobenzene over Skeletal Nickel in an Aqueous 2-Propanol Solution

The kinetics of hydrogenation of 4-nitro-2′-hydroxy-5′-methylazobenzene in aqueous 2-propanol solution over the skeletal nickel is investigated at different initial concentrations. It is established that the hydrogenation of 4-nitro-2′-hydroxy-5′-methylazobenzene over a skeletal nickel in azeotropic aqueous 2-propanol solution proceeds via two parallel pathways at both low and high initial concentrations. It is shown that increasing the initial concentration of the hydrogenated compound above its level of solubility raises the rate of azo group transformation in 4-nitro-2′-hydroxy-5′-methylazobenzene, while the content of 4-amino-2′- hydroxy-5′-methylazobenzene does not change in the hydrogenate and is not accumulated in the bulk of solution.     

Gelatin and starch as stabilizers of the coupled enzyme system of luminous bacteria NADH:FMN–oxidoreductase–luciferase

We have studied the effects of a gel-like environment on the characteristics of enzyme preparations based on the coupled enzyme system of luminous bacteria, NADH:FMN–oxidoreductase–luciferase, to design a stable immobilizing reagent for bioluminescent analysis. Natural polymers, gelatin and starch, were used to create a viscous, structured microenvironment. The stability of the coupled enzyme system to such physical and chemical environmental factors as temperature, pH, and ionic strength in gelatin and starch-containing media was examined. It was shown that both gelatin and starch have a stabilizing effect on the enzymes of luminous bacteria under specific conditions. In particular, the enzymes’ activity is increased twofold in the presence of 1 and 5 % of gelatin at 20 °C and 25 °C, respectively (temperatures lower than the gel point). Also, the acceptable pH range of the coupled enzyme system expands into the alkaline region and becomes 6.8–8.1. Stabilization at low ionic strength (0.01–0.06 mol L^?1) is observed. At the same time, microenvironments based on either gelatin or starch do not change the enzymes’ thermal inactivation rate constants in the temperature range from 25 to 43 °C. Finally, gelatin and starch are suitable for development of a reagent for immobilization of enzymes which would be stable and resistant to physical and chemical environmental conditions.     

Thermodynamic and kinetic characteristics of liquid phase hydrogenation of substituted nitrobenzenes

Quantum-chemical calculations of the thermodynamic characteristics of hydrogenation of nitrobenzoic acid isomers and nitrophenol in the gas phase and also in aqueous and alcoholic media were performed. Correlation dependences between the calculated Δ_r G ₂₉₈^○ values and rate constants for the reaction in various media were obtained.     

Colloid and Nanosized Catalysts in Organic Synthesis: XXII. Hydrogenation of Cycloolefins Catalyzed by Immobilized Transition Metals Nanoparticles in a Three-Phase System

Russian Journal of General Chemistry - The processes of unsaturated cyclic hydrocarbons hydrogenation in a three-phase gas-liquid-solid catalyst system in the presence of nanostructured nickel,...