Suitable Reaction Conditions Research Articles

1202 Stimulus-dependent NMDA receptor activation in hippocampal CA1 neurons after ischemia

The partial catalytic dehydrogenation has been carried out with defined model components and model mixtures representing hydrocarbon groups and chemical composition of desulfurized Jet A-1 over 1.0 wt% Pt/Sn catalyst on γ-Al2O3 carrier. The hydrogen yield, cracking products and carbon deposit on the catalyst surface are studied in order to define suitable reaction conditions for a pressurized auxiliary power unit concept with gas conditioning for fuel cell systems. The results show that alkanes lead to high cracking rate and carbon deposit which can be suppressed with increased pressure up to 8 bar. The hydrocarbon group cycloalkanes represented by methylcyclohexane shows sufficient conversion of 32 wt% towards hydrogen evolution in model mixtures under pressurized conditions. The average hydrogen yield of the model mixture of 72 nlH2/kgfeed was achieved under defined reaction conditions of 425 °C catalyst bed temperature, 8 bar system pressure and 4 s of contact time on the catalyst.

On the relation between synthesis parameters and morphology of anionic polycaproamide obtained in organic media. I. Influence of the Na[O(CH2)2OCH3]2AlH2/ isophorone diisocyanate catalytic system

Polycaproamide granules were obtained by anionic polymerization of caprolactam in ethylbenzene, using the sodium bis(2-methoxyethoxy) aluminium hydride/isophorone diisocyanate catalytic system. Under these conditions, polymerization occurs heterogeneously and the nature of the particle growth seems to be essentially a microbulk one. The most suitable reaction conditions were established. The morphology of the granules was investigated by scanning electron microscopy. These granules result from the coalescence of a great number of small, spherical particles. the coalescence occurs during solidification of the separated polymer. Numerous globular formations were observed at the surface of the particles. The particles were individualized through mechanical dispersion and measured, and the average number of particles composing the aggregates was calculated. Using wide-angle X-ray scattering and differential scanning calormetry technics, the crystalline structure of the granular polycaproamide was studied. It contains almost entirely the α phase. The heat of fusion decreases slightly as compared with that corresponding to the anionic bulk polycaproamide. A schematic mechanism containing the stages involved in the obtaining of the granular polycaproamide is proposed. © 1996 John Wiley & Sons, Inc.

Synthesis of polymers in aqueous solutions: Esterification reaction of poly(methacrylic acid) with alkyl halides using DBU in aqueous solutions

A convenient esterification reaction of poly(methacrylic acid) (PMAA) with certain alkyl halides was performed using 1,8-diazabicyclo-[5.4.0]-7-undecene (DBU) as a base in aqueous solution or in water. The esterification reaction of PMAA with propargyl bromide (PB) proceeded very smoothly and quantitatively at 30°C to give corresponding poly(propargyl methacrylate), although the rate of the reaction decreased with increasing water. The reaction of PMAA with benzyl bromide, o-nitrobenzyl bromide, and p-nitrobenzyl bromide gave corresponding poly(methacrylic ester) using DBU under suitable reaction conditions in water. The esterification reactions of PMAA with PB were carried out using certain organic bases such as triethylamine, 4(N,N-dimethylamino)pyridine and pyridine. Inorganic bases such as sodium carbonate, sodium hydroxide, potassium carbonate, and potassium hydroxide were also tried under the same conditions as with DBU. However, the degrees of estrification with all these bases was much lower than that with DBU. © 1996 John Wiley & Sons, Inc.

Characterization of metal nitrates and clay supported metal nitrates by thermal analysis

Hydrated metal nitrates of Zn, Mn, Ni, Co, Cu, Fe, Cr and Bi, either pure or supported by an acid treated montmorillonite (K10 from Süd-Chemie), were studied using X-Ray diffraction, TG, DTG, DTA, together with MS analysis of gaseous products formed during thermal decomposition. The decomposition products were also analysed by thermoemanation analysis. The metal nitrates were present on the support in the form of crystalline hydrates and not as acetone solvates as supposed earlier. The thermal decomposition of supported metal nitrates started at lower temperatures than those observed for bulk metal nitrates. The supported reagents were tested in different organic oxidation and nitration model reactions. The activities in organic chemical reactions were controlled by the thermal stability of the supported metal nitrates, as expected for reactions involving nitrogen oxides as active intermediates. The suitable reaction conditions were obtained from thermal analysis.

Synthesis of HFC-134a over CrF3/AlF3 catalysts

The effect of the structure of AlF3 supports in CrF3/AlF3 catalysts and their activity were studied, and a selection of suitable reaction conditions for fluorination of trichloroethylene and HCFC-133a was made. We found that neither AlF3 (α- and γ-modifications) nor CrF3/α-AlF3 exhibits significant activity for the reaction of HF with CCl2=CHC1 or CF3CH2Cl. However, CrF3/γ-AlF3 exhibits high activity, which increases with increasing surface area and decreasing crystallite size of the γ-AlF3 support, and that dramatically affects the fiuorination of CF3CH2Cl. Investigation of a series of CrF3/γ-AlF3 catalysts shows that the turnover rates per unit of the total surface area and of the free CrF3 surface area significantly increase with increasing content of Cr3+ loading. Optimum temperature for the reaction of HF with CCl2=CHCl is 260°C, while with CF3CH2Cl it is 350°C, with flow ratios HF∶TCE = 6∶1 andHF∶HCFC-133a = 10∶1.

Carbon Dioxide as a Raw Material: The Synthesis of Formic Acid and Its Derivatives from CO2

AbstractThe use of carbon dioxide as a raw material for chemical syntheses is an ecologically and economically valuable extension to the carbon sources used at the present time. In order to convert the thermodynamically stable and comparatively unreactive CO2 molecule into the desired product in an efficient manner, suitable reaction conditions and activation mechanisms must be found. The catalytic reduction of CO2 to formic acid and its derivatives has been intensively studied in recent years. A number of new approaches to the synthesis of formic acid from CO2 have reached such a state of knowledge that continuing development may well lead to industrial‐scale operation in the near future. This can to a large extent be attributed to the fruitful interaction between investigative work into reaction mechanisms and the development of new catalytic systems.

Complexes with NSO and N2S2 Donor Ligands. Cobalt (II), Cobalt(III) and Nickel(II) Complexes Of 2,4-bis (2′-Mercapto-Phenylimino)Pentane, 2-(2-Mercaptophenyl)imino-4-pentanone and 2-(2-Mercaptophenyl)-salicylaldimine and Their Reactions

Abstract Reactions of acetylacetone and salicylaldehyde with 2-aminobenzenethiol yielded the benzothiazolines Hopatz and Hopbtz, respectively, rather than the corresponding Schiff bases. The reactions of benzothiazolines with Co(OAc)2.4H2O,Co(NO3)2.6H2O, Co(acac)2.2H2O and Ni(acac)2.H2O afforded the corresponding metal Schiff base chelates. Under suitable metal template reaction conditions two moles of 2-aminobenzenethiol have been found to condense with one mole of acetylacetone (in the diketo form) leading to the synthesis of Co(II) and Co(III) complexes of a quadridentate N2S2 donor ligand. The reaction of [CoII (pdmpi)]H2O {H2pdmpi = 2,4-bis (2′-tnercaptophenylimino) pentane} synthesized in this study, with Cd(NO3)2.4H2O and Mn(CO)5Br afforded [{coII(pdmpi)}2 Cd](NO3)2and [CoII (pdmpi) Mn(CO) 3Br] where CoII (pdmpi) functions as a bldentate S,S-donor metallo-ligand. The cobalt(II) complex CoII (pdmpi)H2O smoothly reacts with bifunctional alkylating agents like 1,2-dibromoethane to form the inacrocycli...

Polymerisation of methyl methacrylate with tert‐butyllithium and triisobutylaluminium in toluene: mechanism of initiation and termination by matrix‐assisted laser desorption ionisation time‐of‐flight mass spectrometry (MALDI TOF MS)

AbstractThe polymerisation of methyl methacrylate (MMA) using triisobutylaluminium/tert‐butyllithium in hydrocarbon at 0°C and −78°C has been investigated by matrixassisted laser desorption ionisation time‐of‐flight mass spectrometry (MALDI TOF MS). Although the system gives extremely good control over molecular weight and narrow molecular weight distribution, initiation of polymerization can be complicated by formation of small amounts of tert‐butyl isoprenyl ketone (1), and termination of polymerization can occur by end cyclisation of the end unit of 3. Both complications in initiation and termination can be avoided by suitable reaction conditions. Incorporation of 1 is suppressed by increasing the alkylaluminium content and by higher temperature. Termination by cyclisation has been found to occur over much longer time scales than propagation and can therefore be avoided by controlled termination after the appropriate reaction time.

Light alkenes from syngas via dimethyl ether

A new route, named the SDTO method, for the synthesis of light alkenes from syngas is proposed. The method consists of the conversion of syngas to dimethyl ether, followed by the conversion of dimethyl ether to light alkenes. Catalysts for the two reactions have been developed. For the first reaction, the catalyst was synthesized by combining a methanol synthesis catalyst with λ-Al 2O 3 or zeolites, which possess both metallic and acidic functions. The conversion of the reaction is much higher than that of the methanol synthesis reaction. Suitable reaction conditions are: 210–280°C; P>.0MPa and gas hourly space velocity (GHSV) < 1500 h −1. The catalyst for the second reaction was a modified SAPO-34 molecular sieve. The effects of the modification on the catalyst and the factors influencing the reaction have been investigated. A fluid bed reactor is considered to be a suitable reactor type for these catalysts. Under the reaction conditions of 550°C and weight hourly space velocity (WHSV MeOH) > 6 h −1 or line velocity of MeOH> 15, the selectivity for ethylene and total light alkenes are ca. 60 and ca. 90, respectively (conversion= 100%). The stability of the modified SAPO-34 catalyst has been tested under severe conditions. The results from the serial connection of the two conversion steps without any separation show that the yield of C 2 =–C 4 = alkenes could be > 100 g/(m 3 syngas).

Correlation between the reactivity and the structural and thermal properties of supported metal nitrates

Montmorillonite-supported iron(III) nitrate and copper(II) nitrate reagents, and other supported metal nitrates prepared in the same way, were investigated by thermal and X-ray powder diffraction methods. The metal nitrates are present on the support in the form of crystalline hydrate and not as acetone solvate as supposed earlier. Thermal decomposition of metal nitrates that are active in model reactions proceeds in a different way from that of the practically inactive nitrates. In the former case, water release and nitrate decomposition itself are simultaneous process. These and other results contributed to determination of suitable reaction conditions for the montmorillonite-supported reagents.

Hydrorefining of Shale Oil (Part 4) Pretreatment for Arsenic Removal.

With the objective of selecting suitable reaction conditions and catalysts for a guard reactor used in shale oil hydrorefining for arsenic removal, two kinds of Mo-Ni-Al2O3 catalysts and γ-alumina have been evaluated. It was confirmed that most of the arsenic present in shale oil is removed under such relatively mild reaction conditions as 300°C and 2.0 LHSV, using conventional Mo-Ni catalysts for petroleum hydrorefining.All arsenic removed from the shale oil deposited on the catalyst, and no arsenic was detected in the effluent gas from the reactor. The arsenic deposition profiles in the catalyst pellets vary depending on the reactivity and diffusibility of arsenic compounds. Suitable catalysts for the upper layer in the guard reactor should be provided with medium initial activity for arsenic removal, with larger pore diameter, and with the shape of pellets with a greater ratio of external surface area to volume. The metal contents of the catalyst should be increased commensurate with the expected amount of arsenic deposition.

The reductive decomposition of calcium sulphate—I. Kinetics of the apparent solid—solid reaction

The reductive decomposition of calcium sulphate by hydrogen is used for the regeneration of calcium-based atmospheric fluidized bed combustion (AFBC) SO 2 sorbents. The apparent solid—solid reaction between CaS and CaSO 4, one of the steps involved in the reaction mechanism of the reductive decomposition of CaSO 4, has been investigated in a thermobalance construction provided with a coupled system for the analysis of product gases. By creating suitable reaction conditions in the experimental set-up, it is possible to study this step separately. The apparent solid—solid reaction between CaS and CaSO 4 takes place when a mixture of these compounds is heated in an inert atmosphere to temperatures above 1100 K: ▪ The fractional production rate of CaO (or SO 2) appears to depend on the ratio in which CaSO 4 and CaS are present initially. A simple model is formulated to calculate the fractional production rate as a function of the fractional degree of production and the initial composition of the reactants. One of the principal assumptions of the model is the presence of a liquid phase formed by mixtures of CaS and CaSO 4. Fractional production rates calculated after determining the required model parameters (kinetic constants and volume plus composition of the liquid phase) show close agreement with experimentally obtained values.

Comparative study of barium salts of 2,5-dihalo-3,6-dihydroxy- p-benzoquinone as reagents for the spectrophotometric determination of sulphate

The spectrophotometric determination of sulphate employing barium salts of fluoranilic, bromanilic or iodanilic acid was studied. The synthesis of fluoranilic and iodanilic acids and the preparation of the barium salts of the haloanilic acids as reagents are described. Suitable reaction conditions for linear calibration were established. The molar absorptivities for the reaction products of the Ba haloanilates with sulphate were between 1.87 × 10 4 and 2.78 × 10 4 1 mol −1 cm −1 at their absorption maxima. The relative standard deviation at 5 μg of sulphate was <2%.

新規紙力増強剤 新ホフマンＰＡＭ

Hofmann degraded PAM has high qualities as dry-strength resins, but it loses the cationicity in the aqueous solution.Many attempts have been done to commercialize the high qualities of Hofmann degraded PAM without the denaturation of the properties.We have now reached the results that Hofmann reaction at the high temperture for the short time can also be suitable reaction conditions to produce Hofmann degraded PAM for the drystrength resins.The results of search have made possible to supply Hofmann degraded PAM with the best quality by setting the reaction apparatus near the paper machine. (We call the apparatus “Hofmanizer system” and the product “New Hofmann PAM”.) “New Hofmann PAM” is characterized by the very high ability of adsorption on the surface of pulp fibers which brings the following three major advantages;(1) high drainnage…to increase the operation speed(2) high effect of dry-strength…to cut down on the amount(3) high retention…to reduce the load of waste water treatmentThe consumer trials were conducted several times and good results have been obtained.

Radiolabeling of the biologically active peptide 163–171 of human interleukin-1β

N-succinimidyl[2,3- 3H]propionate was used for the radiolabeling of the biologically active peptide fragment 163–171 of human interleukin-1β (VQGEESNDK). Suitable reaction conditions were studied to obtain useful labeling of the molecule. A mixture of mono- (70%) and bi- (30%) propionyl derivatives was obtained with a total 3H specific activity of 87 Ci/mmol of peptide. The conditions for an efficient chromatographic separation of labeled peptide from unreacted reagents and by-products were established. The labeled peptide maintained the same biological activity as that of the corresponding unlabeled molecule, indicating that the labeling procedure did not alter the biological characteristics of the peptide. This thus allows the use of the radiolabeled peptide for receptor binding studies.

Ozone-oxidation products of triterpenoid hydrocarbons belonging to the hopane and migrated hopane series.

The ozone oxidation reaction of eleven triterpenoid monoenes belonging to the hopane and migrated hopane series was investigated. Under suitable reaction conditions, various reaction products including three ozonides, seven epoxides and one ketone were obtained from the eight starting materials. The reaction of glutin-5-ene was also examined for comparison

Homogene, abschreckbare Hochdruckphasen mit NaCl-Struktur in den systemen CdTe-SnTe und CdTe-PbTe

The formation of solid solutions in the systems CdTe-SnTe and CdTe-PbTe has been investigated at high pressures and temperatures. At suitable reaction conditions homogeneous, quenchable high-pressure phases Cd x M 1 − x IV Te with NaCl-type structure can be recovered in the region 0 ⩽ x ⩽ 0.75 which are metastable at ambient pressure. For higher values of x the high-pressure phases are not quenchable; CdTe with zincblende-type structure is formed after release of pressure. There is a linear relationship between the lattice constant a of the NaCl-type phases and the composition x. Extrapolation of a for x → 1 gives for each system a lattice constant for the NaCl-type modification of CdTe at normal pressure. The mean value is a = 6.045 A ̊ . Data for the electrical conductivity of the NaCl-type solid solutions are presented.

Modification of the transport properties of ion exchange membranes. IX. Layer formation on a cation exchange membrane by acid-amide bonding, and transport properties of the resulting membrane

In order to modify the transport properties of sulfonic acid-type cation exchange membranes, chlorosulfonyl groups were introduced as reactive groups into the membrane composed of a styrene-divinylbenzene copolymer and poly (vinyl chloride) fabric. The chlorosulfonated membrane was then reacted with various amino compounds. Suitable reaction conditions of the copolymer membrane with chlorosulfonic acid were examined in detail. After the chlorosulfonated membrane had been immersed in an aqueous solution of amino compounds to form a different kind of layer by acid amide bonding, mainly on the membrane surface, the membrane was immersed in aqueous sodium hydroxide solution to hydrolyze unreacted chlorosulfonyl groups to sodium sulfonate groups. The amino compounds used were p-aminosalicylic acid, L-tyrosine and polyamino compounds such as triethylenetetramine, polyethyleneimines etc. Formation of the polyamino compound layer on the surface of the cation exchange membrane by acid amide bonding conferred stable monovalent cation permselectivity on the membrane in electrodialysis. All reactions were confirmed by measurements of attenuated total reflectance infrared spectra.

Nickela-Heterocyclen als Intermediate der präparativen Isocyanatchemie

When isocyanates act on a Ni 0 system, the direction of the coupling to form either head-to-tail or head-to-head products is dependent upon the ligands coordinated about the nickel atom. These homo-coupling reactions are suppressed in the presence of hetero π-systems such as aldehydes or imines in favour of the formation of cyclic cross products. Some reactions utilizing these new compounds are indicated. Treatment of isocyanates with unsaturated hydrocarbons on (Lig)Ni 0 complexes leads to a 1 1 CC coupling reactioni yielding novel products. It is shown in detail how these reactions to azanickelacyclopentanes can be developed into catalyses. When suitable ligands and reaction conditions are chosen, unsaturated carboxylic amides are formed. With mono-enes and 1,3-dienes the products of the catalysis are open chain carboxylic amides, while α,ω-dienes afford functionalized cyclopentyl carboxylic amides.

ChemInform Abstract: Highly Selective Acyclic Stereocontrol Based on 1,2‐Rearrangement

Contrary to the firm and long-standing credence on the involvement of racemization, the “cationic” 1, 2-rearrangement reactions may proceed stereospecifically under suitable reaction conditions to allow the complete 1, 2-chirality transfer. This fact provides a solid basis for the development of a novel and useful synthetic reactions to achieve the highly selective acyclic steoeocontrol. This paper deals with a survey of the new synthetic methodology based on the novel 1, 2-rearrangements under Lewis acidic conditions as well as the newly exploited silicon-directed relative streocontrol, which would find a broad applicability in the highly stereoselective synthesis of a wide variety of useful compounds including chiral pheromones, macrolides, and so on.