Ion pair catalysis of the autooxidative cleavage of benzoin in emulsion systems

A study was made of the autooxidation of benzoin in organic-aqueous sodium hydroxide emulsions in the presence of several quaternary ammonium salts. The rate of the reaction was found to be accelerated by these salts, probably by ion pair extraction. In pyridine and acetonitrile systems the reaction was almost exclusively the formation of benzoate. Neither benzil nor benzaldehyde were intermediates in the oxidation process. The rate law for the reaction was found to be which led to the conclusion that the rate-determining step in the catalyzed pathway was the reaction of oxygen with the ion pair:      

An exploratory investigation of the use of alkali metals in nitrous oxide control

Using chemical kinetic modeling, we have investigated the feasibility of using sodium hydroxide (a representative alkali-metal compound) to control nitrous oxide emissions from combustion sources. The key reaction is where the sodium atom is produced by the reaction when small amounts of fuel are added to lean combustion products. Because sodium hydroxide is regenerated by one sodium atom is potentially capable of destroying several N₂O molecules. The mechanism is discussed in detail. Moreover, we have studied the possibility of using NaOH in conjunction with RAPRENOX (cyanuric acid injection) to control NO _x emissions without producing N₂O as a by-product. The results are discussed at length. © 1996 John Wiley & Sons, Inc.     

Autooxidation of diethyl hydroxylamine

The autooxidation of diethyl hydroxylamine (DEHA) has been studied both in solution and in the gas phase between 0° and 60°C. The results obtained are interpreted in terms of a nonchain free radical mechanism in which reaction (1) is the rate-determining step. This reaction is followed by the reaction of HO₂ radicals with DEHA to give hydrogen peroxide. The initial stoichiometry is given by which implies that the hydrogen peroxide reacts with DEHA to give water and diethyl nitroxide radicals. The activation energy of reaction (1) is 16.5 ± 2 kcal/mol, leading to a dissociation energy of 69.5 ± 2 kcal for the O?H bond in DEHA. The oxidation of DEHA in the gas phase is nearly ten times slower than that observed in chlorobenzene solution under similar experimental conditions. This result is related to the stabilization of the free radicals produced by the solvent.     

Über Chalkogenolate. 154. Reaktion von N-Methylformamid mit Kohlenstoffdisulfid 1. Darstellung und Eigenschaften von N-Methyl-N-formyl-dithiocarbamaten

On Chalcogenolates. 154. Reaction of N-Methyl Formamide with Carbon Disulfide. 1. Synthesis and Properties of N-Methyl N-Formyl Dithiocarbamates N-Methyl formamide reacts with carbon disulfide in the presence of sodium hydride, potassium hydroxide, and barium hydroxide to form the corresponding N-methyl N-formyl dithiocarbamate. The prepared compounds have been characterized with chemical and thermal methods as well as by means of electron absorption, infrared, nuclear magnetic resonance (¹H and ¹³C), and mass spectra.     

Potentiometric titration of polyelectrolyte gels equilibrated with a solution of a strong polyelectrolyte: Influence of gel swelling

A weak acid gel (carboxylmethyldextran) was titrated with sodium hydroxide while equilibrated with a solution sodium poly(vinyl sulfate), a salt of a strong acid polyelectrolyte. It was found that the quantity in which V/V₀ is the volume of gel relative to its volume in acid form in pure water, is independent of the concentration C_p of the polyelectrolyte solution and of the relative volume of gel. The relation where α is the degree of ionization, pK′ is the apparent pK of the gel, γ is the activity coefficient of the counterion in the gel phase, and v is the number of ionizable groups, is found to be constant for all values of C_p and for 0.1 < α < 0.9. These results can be extended to highly crosslinked ionexchange resins.     

An unusual picoline derivative from the trifluoroacetolysis of thiostrepton

Trifluoroacetolysis of thiostrepton followed by treatment with methanol and aqueous sodium hydroxide led to the formation of N‐(2‐picolinoyl)serine methyl ester, the first pyridine‐containing compound isolated from the chemical degradation of thiostrepton.     

Kinetics and mechanism of base-catalyzed hydrolysis of Cu(II)-malonamide complex

A kinetic study of base-catalyzed hydrolysis of Cu(II)-malonamide complex has been performed in sodium hydroxide solution (0.2–1.25M). The reaction follows an irreversible first-order consecutive path: The variation of k_1obs and k_2obs with alkali concentration was found to be in good agreement with the equations: where B₁, B₂, C₁, and C₂ are empirical constants. The mechanism of hydrolysis of Cu(II)-malonamide complex has been discussed and rate equations have been derived. Retardation of rate of hydrolysis due to coordination of Cu(II) with malonamide, in alkaline medium, has been explained in terms of comparatively slow breakdown of the C? N bond of the tetrahedral intermediate (TI). Thermodynamic parameters have also been evaluated.     

H2S-promoted thermal isomerization of butene-2 CIS to butene-1 or butene-2 trans around 500°C

H₂S increases the thermal isomerization of butene-2 cis (B_c) to butene-1 (B₁) and butene-2 trans (B_t) around 500°C. This effect is interpreted on the basis of a free radical mechanism in which buten-2-yl and thiyl free radicals are the main chain carriers. B₁ formation is essentially explainedby the metathetical steps: whereas the free radical part of B_t formation results from the addition–elimination processes: . It is shown that the initiation step of pure B_c thermal reaction is essentially unimolecular: and that a new initiation step occurs in the presence of H₂S: . The rate constant ratio has been evaluated: and the best values of k₁ and k_1', consistent with this work and with thermochemical data, are . From thermochemical data of the literature and an “intrinsic value” of E_?3 ? 2 kcal/mol given by Benson, further values of rate constants may be proposed: is shown to be E₄ ? 3.5 ± 2 kcal/mol, of the same order as the activation energy of the corresponding metathetical step.     

Study of the kinetics of the Chichibabin reaction

The rate of hydrogen and ammonia evolution during the amination of N-heteroaromatic systems with sodium amide was studied. The ease of the Chichibabin reaction of heterocycles decreases in the following order: 1-methylbenzimidazole > isoquinoline > 1-methylperimidine > benzo[f]quinoline > pyridine acridine. The decrease in the rate of amination in the presence of free-radical inhibitors constitutes evidence for a free-radical step in the Chichibabin reaction. It is shown that the Chichibabin reaction has autocatalytic character and is accelerated in the presence of sodium salts of heterylamines. Opinions regarding the mechanism of this autocatalysis are expressed.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 244–252, February, 1976.     

Emulsion polymerization of vinyl acetate

Emulsion polymerization of vinyl acetate with sodium laryl sulfate as emulsifier and potassium persulfate as initiator was studied and found to follow the rate equation suggested by Harriot:      

Enhanced Electrogenerated Chemiluminescence of Tris(2,2′‐bipyridyl) Ruthenium(II)/tripropylamine in the Presence of Pyridine and Its Analogues

In the present work, we conducted an investigation on the electrochemical and ECL behavior of Ru(bpy) /TPrA system in the presence of pyridine and its analogues on platinum and gold electrode. Results showed that pyridine and its analogues enhanced Ru(bpy) /TPrA ECL signal and exhibited different enhancement effects on different electrodes. On platinum electrode, the maximum enhancement factor of about 5 was obtained. On gold electrode, a low‐oxidation‐potential (LOP) ECL signal occurred and increased.     

On the reaction between ethylene and cyclopentene,a radical mechanism

The bimolecular reaction is shown to proceed via a simple, nonchain, radical mechanism: with the net reaction the same as (1). Rate constants are estimated for each step and for each possible competing reaction and shown to yield minor or negligible side reactions in agreement with the observations of Lalonde and Back. Estimated and observed rate constants (1) and (1′) are in excellent agreement with the assumption that k'_-1 is a typical radical disproportionation with zero activation energy. From the reported data a best value for k′₁ is where θ = 2.303RT kcal/mol.     

联苯甲酰桥联β-环糊精吸附U(VI)的动力学和热力学

β-环糊精与对甲苯磺酰氯在低温碱性溶液中反应合成6-对甲苯磺酰酯-β-环糊精,并利用红外光谱和核磁共振氢谱对其进行表征;联苯甲酰与6-对甲苯磺酰酯-β-环糊精以摩尔比为1: 2反应合成一种新型的联苯甲酰桥联β-环糊精(BB β-CD)材料,并采用紫外可见分光光度法对其合成机理以及BB β-CD和联苯甲酰对U(VI)的吸附行为进行研究;同时采用扫描电镜对材料吸附U(VI)前后的外貌形态进行表征。通过间歇吸附法考察pH、反应时间、温度以及干扰离子等因素对吸附过程的影响。结果表明,相比联苯甲酰,BB β-CD能更有效地吸附U(VI),在pH=4.5,反应时间为60 min条件下,最大吸附量为12.16 mg·g^-1,吸附率高达91.2%。动力学和热力学拟合结果表明,吸附过程更符合准二级动力学速率方程,Langmuir等温吸附模型比Freundlich等温吸附模型更适合模拟吸附过程,且吸附是自发吸热的过程。     

The thermal decomposition of biacetyl

The thermal decomposition of biacetyl has been studied at small percentage conversion over the temperature range 375-417°C. For these conditions, an almost quantitative mass balance was obtained by gas-chromatographic analysis. The following equation was obtained for the overall reaction Between 240° and 277°C, the decomposition of biacetyl initiated by methyl radicals has also been studied. As source of radicals, the thermolysis of azomethane was used. Moreover, the Arrhenius parameters of the following reactions were determined: where A is in sec^?1 for reaction (1) and in cm³mole^?1 sec^?1 for reactions (3) and (4); E is in kcal/mole. Evidence is provided that the displacement reaction (4) proceeds by a two step mechanism.     

Kinetics of the gas-phase reaction of allyl alcohol with iodine. The heat of formation and stabilization energy of the hydroxyallyl radical

The reaction of iodine with allyl alcohol has been studied in a static system, following the absorption of visible light by iodine, in the temperature range 150-190°C and in the pressure range 10-200 torr. The rate-determining step has been found to be and k₃ is consistent with the equation From the activation energy and the assumption E_-3 = 1 ± 1 kcal mol^?1, it has been calculated that kcal mol^?1. The stabilization energy of the hydroxyallyl radical has been found to be 11.4 ± 2.2 kcal mol^?1.     

Effects of Olefins on the Thermal Decomposition of Propane Part IV. Influence of Propylene

On the basis of the thermal decomposition of mixtures of propylene and propane with molar ratios of 0.0–0.33 in the temperature range 779–812K, the influencing functions describing the inhibition by propylene of the decomposition of propane were determined. The rate-reducing effect is explained mainly by the reactions (in which ^.R = ^.H, ^.CH₃ and 2-?₃H₇) and also by the addition reactions It was established that the bulk of the allyl radicals formed participate in the chain step, but, due to their lower reactivity, they restore the decomposition chain more slowly than the original radicals do. From the characteristic change in the ratio υ/υ, the rate ratios of hydrogenabstraction reaction by radicals from propylene and propane could be determined. In these reactions there was no significant difference between the selectivities of the radicals. For an interpretation of the changes, the decomposition mechanism must be completed with the reaction Evaluation of the influencing curves revealed that the initiation reactions must be taken into account. By parameter estimation we have determined the rate ratios characterizing the above initiation reactions, the unimolecular decomposition of propane, hydrogen abstraction by radicals from propane and propylene, intermolecular isomerization of the 2-propyl radical via propane and propylene, and abstraction of propane hydrogens by the ethyl and methyl radicals; these are given in Tables II.     

Synthesis and characterization of sulfone-containing polyesters derived from 4,4′-dicarboxydiphenyl sulfone by direct polycondensation

Several sulfone-containing polyesters having inherent viscosities 0.43-0.19 dL g^?1 were prepared by direct polycondensation of 4,4′-dicarboxydiphenyl sulfone (DCDPS) with various aromatic and aliphatic diols, by p-toluenesulfonyl chloride and N,N′-dimethylformamide in pyridine solution. The polyesters were examined by elementary analysis, IR spectra, inherent viscosity, x-ray diffraction, solubility, DSC, and TGA. The diffraction diagram showed that all polyesters were crystalline except that obtained from bisphenol-A. All polymers were soluble in sulfonic acid (18M), phenol and p-chlorophenol, but not in acetone and toluene. These polymers obtained from aromatic bisphenols lost no mass below 325°C, but 10% loss of mass was recorded above 396°C in nitrogen. DCDPS copolymerized with isophthalic acid (IPA) and bisphenol-A had inherent viscosity up to 0.49 dL g^?1, with relatively narrow distribution of molar mass . © 1995 John Wiley & Sons, Inc.     

Role of ɣ-Al<Subscript>2</Subscript>O<Subscript>3</Subscript> on the mechanical and microstructural properties of metakaolin-based geopolymer cements

The main target of this work is to investigate the influence of ?-Al₂O₃ on the properties of metakaolin-based geopolymer cements. The kaolin used as starting material for producing geopolymer cements contains approximately 28 and 64% of gibbsite and kaolinite, respectively. This kaolin was transformed to metakaolins by calcination at 500, 550, 600, 650, and 700?°C for 1?h. Gibbsite contained in kaolin was transformed to γ-Al₂O₃ during the calcination process. The hardener was obtained by mixing commercial sodium silicate and sodium hydroxide solution (10?M) with a mass ratio sodium silicate/sodium hydroxide equal to 1.6:1. Geopolymer cements, GMK-500, GMK-550, GMK-600, GMK-650, and GMK-700, were obtained using the prepared hardener with a mass ratio hardener/metakaolin equal to 0.87:1. It could be seen that the specific surface area of metakaolins decreases with increasing the calcination temperature of kaolin owing to the formation of the particles of γ-Al₂O₃. The compressive strengths 18.21/29.14/36.61/36.51 increase in the course GMK-550/GMK-600/GMK-650/GMK-700. The X-ray patterns and micrograph images of geopolymer cements, GMK-600, GMK-650, and GMK-700, indicate the presence of γ-Al₂O₃ in their structure. It was typically found that γ-Al₂O₃ remains largely unaffected during the geopolymerisation, and therefore could act as an inert filler and reinforce the structure of geopolymer cements.

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Über Chalkogenolate. Reaktion von Formamid mit Kohlenstoffdisulfid 1. Darstellung und Eigenschaften von N-Formyl-dithiocarbamaten

On Chalcogenolates. 147. Reaction of Formamide with Carbon Disulfide. 1. Synthesis and Properties of N-Formyl Dithiocarbamates Formamide reacts with carbon disulfide in the presence of sodium hydride to yield crude sodium N-formyl dithiocarbamate. Pure compounds have been produced via N-formyl dithiocarbamic acid. The N-formyl dithiocarbamates were characterized by means of diverse methods.     

Effects of alkenes on the thermal decomposition of propane part II. Influence of ethylene

Experiments with propane-ethylene mixtures in the temperature range 760–830 K resulted in refinement of the role of ethylene inhibition in the decomposition of propane. The source of the rate-reducing effect of ethylene is the reaction This replaces the decomposition chains more slowly by means of the reactions than H-atoms do by direct H-abstraction from propane. Analysis of the ratios of the product formation rates showed that the selectivity of the ethyl radical for the abstraction of hydrogen of different bond strengths from propane was practically the same as that of the H-atom. The ratio of the rate constants of hydrogen addition to ethylene and methyl-hydrogen abstraction from propane by the H-atom (3) was determined as was that of the decomposition and the similar H-abstraction of the ethyl radical Interpretation of the influence of ethylene required the completion of the mechanism with further initiation of the reaction besides termination via ethyl radicals.