Diels-Alder reaction volumes in the solid state and solution

The densities of anthracene, tetracyanoethylene, maleic anhydride, N-phenylmaleineimide, trans, trans-1,4-diphenylbuta-1,3-diene, and their Diels-Alder adducts were measured in the solid state and in solution at 25 °C. The reaction volumes in the solid state were calculated from the difference in molar volumes. They turned out to be low, close to each other (–4 to –11 cm³ mol^–1), and slightly different from the reaction volumes (–8±1 cm³ mol^–1) calculated from the van der Waals radii. The reaction volumes in solutions (–15 to –32 cm³ mol^–1) were found from the difference in partial molar volumes of the reactants in dioxane, acetonitrile, and 1,2-dichloroethane, The experimental Diels-Alder reaction volumes in solution are determined not only by the formation of new bonds in an adduct: a considerably higher contribution (to 75%) is made by a change in the volume of intermolecular empty spaces in solution on going from reactants to adducts.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2386–2390, November, 2004.     

Hysteresis effect and autooscillation phenomena in the oxidation of 1-hexene on palladium

The gas-phase oxidation of 1-hexene on a palladium film has been investigated in a gradient-free reactor at atmospheric pressure and temperatures of 293–693 K, at flow rates of 0.3–0.15 liter/min and an initial concentration of hexene in air of 15.5·10^–4 M. Autooscillation phenomena have been observed and a hysteresis effect in the reaction rate as function of temperature, caused by the branched-chain heterogeneous-homogeneous reaction mechanism.Translated from Teoreticheskaya i éksperimental'naya Khimiya, Vol. 24, No. 1, pp. 107–110, January–February, 1988.     

Nature of the intermediate product of the reaction of the pentacyanocobaltate(II) ion with nitric oxide

The reaction of the pentacyanocobaltate(II) ion with nitric oxide in aqueous solution was studied. Infrared spectroscopy and mass spectrometry with bombardment by fast atoms showed that the intermediate product formed in this reaction is a binuclear complex of cobalt containing bridge NO^– groups.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 28, No. 2, pp. 176–180, March–April, 1992.     

Nonempirical calculations of potential-energy surfaces for nucleophilic addition of H− and F− to an acetylene molecule

The minimal energy paths for the nucleophilic addition of a hydride ion (H^–) and a fluoride ion (F^–) to a molecule of acetylene (A) have been calculated with the use of 3–21++G and 3–21+G double basis sets in the framework of the Hartree-Fock-Roothaan method. The values of the total energies of the reactants, transition states, and products have been refined by means of calculations with more complete basis sets [6–31++G// 3–21++G and 6–31++G*//3–21++G for reaction (1); 6–31+G*//3–21+G and 6–31++G**//3–21+G for reaction (2)] and by taking into account the correlation energy for reaction (1) in the framework of the SCEP/6–31++*//3–21++G method. It has been established that the activation energy of reaction (2) is 15.94 kJ/mole lower than that for reaction (1), that reaction (1) is exothermic, and that the enthalpy change accompanying reaction (2) is close to zero. The character of the distribution of the electron density along the minimal energy paths of both reactions has been analyzed, and the differences appearing as a result of the replacement of the soft nucleophile H^– by the harder nucleophile F^– have been ascertained. The results of the calculations have been compared with the results available in the literature for reaction (1).Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 25, No. 2, pp. 149–155, March–April, 1989.     

The Solvent Effect on the Rate of Reaction between Propanethiol and Chlorine Dioxide

The products and kinetics of the liquid-phase oxidation of propanethiol by chlorine dioxide in organic media (n-heptane, 1,4-dioxane, carbon tetrachloride, benzene, diethyl ether, ethyl acetate, acetone, and acetonitrile) at temperatures from –10 to 70°C were examined. The reaction rate constants and activation parameters were measured in the above solvents. A strong solvent effect on the reaction kinetics was found (k= 1.67 × 10^–3or 52.7 l mol^–1s^–1(25°C) in heptane or acetonitrile, respectively). The data were analyzed in terms of the Leydler–Eyring and Koppel–Palm equations. The formation of high-polarity intermediates in the test reaction was suggested.     

Use of the plastein reaction for the modification of cotton-plant proteins

Pronase hydrolysates have been obtained from cottonseed meal which were then used as a substrate for the performance of the plastein reaction. The possibility has been shown of introducing deficient amino acids — lysine methionine, threonine, and tryptophan — by means of this reaction.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 92–96, January–February, 1986.     

Mechanism of the condensation of acetone on the surface of aluminum oxide

The condensation of acetone on the surface of aluminum oxide was studied by the methods of the temperature-program surface reaction, mass spectrometry, and infrared spectroscopy, and a reaction mechanism is proposed.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 21, No. 3, pp. 333–338, May–June, 1985.     

Dehydrogenation of cyclohexane over Pt/Al2O3 in the presence of ZrNi as a hydrogen acceptor

Conclusions The use of the ZrNi-H system as a hydrogen acceptor in a dehydrogenation reaction permits a significant increase in the conversion of cyclohexane to benzene due to a shift in the thermodynamic equilibrium upon the removal of hydrogen from the reaction stream. This permits us to carry out the reaction at a temperature 100–200°C below those commonly used and accumulate hydrogen.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 10, pp. 2405–2407, October, 1988.     

Interaction of the natural antioxidant echinochrome with hydroperoxides under anaerobic conditions

The action of cumene hydroperoxide and oxidized ethyl esters of the fatty acids of linseed oil on echinochrome (2,3,5,7,8-pentahydroxy-6-ethylnaphthalene-1,4-dione), an active scavenger of peroxide radicals, was investigated under anaerobic conditions (argon). The dependence of the rate of consumption of echinochrome on the initial concentrations of the components indicates the occurrence of two competitive reactions: a) with hydroperoxides and b) with the radicals formed in the thermolysis of hydroperoxides. The upper limit of the values of the rate constants of the reaction of echinochrome with cumene hydroperoxide (5·10^–7 M^–1·sec^–1) and with the total hydroperoxides of linseed oil (3·10^–6 M^–1·sec^–1) was determined.The numeration of the reaction used corresponds to the scheme of free-radical oxidation from [5].Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 2, pp. 329–333, February, 1991.The authors would like to express sincere gratitude to V. A. Roginskii for participating in the discussion of the results.     

Study of the products of the reaction of succinic anhydride derivatives with urea

Conclusions The product of the reaction of isododecenylsuccinic anhydride with urea at 120–160°C is isododecenylsuccinimide.Deceased.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 8, pp. 1900–1902, August, 1988.     

Bifurcation of irregular oscillatory regimes in the Belousov-Zhabotinskii reaction in a closed reactor

We describe the bifurcation diagram for irregular oscillatory regimes in the Belousov-Zhabotinskii reaction in a closed reactor upon variation of the initial concentrations of ferroin and potassium bromate. We formulate rules for transition from one regime to another.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol, 28, No. 5–6, pp. 474–478, September–December, 1993.     

Kinetic-Spectrophotometric Determination of Trace Quantities of Thiocyanate Based on Its Landolt Effect on the Reaction of Bromate with Hydrochloric Acid1

A new method for the rapid and sensitive determination of trace quantities of thiocyanate based on its Landolt effect on the bromate-hydrochloric acid reaction was developed. The induction period of the reaction is proportional to the SCN^– concentration. The decolorization of methyl orange by the reaction products was used to monitor the reaction spectrophotometrically at 525 nm. We were able to determine thiocyanate in the range 2 × 10^–7–4 × 10^–5 M by this method. The relative standard deviation for 10 determinations of 1.5 × 10^–6 M thiocyanate ion is 0.19% and the detection limit of the method was 7.00 × 10^–8 M. The method was applied to the determination of thiocyanate in human blood serum and of saliva samples with satisfactory results.     

Pulsed Corona Discharge-Induced Reactions of Acetophenone in Water

The reactions of acetophenone in water by pulsed corona discharges have been investigated to provide fundamental information concerning the reactions of acetophenone in water. Experimental results indicated that photolysis of acetophenone did not involve a hydroxyl radical mechanism and the majority flux of hydroxyl radicals originated from the dissociation of gas-phase oxygen in the plasma channels. The rate constants for photolysis and pyrolysis were determined to be 1.5×10^–7 M-s^–1, 2.2×10^–4 s^–1, respectively. The rate constant for the oxidative reactions was measured as 1.2×10^–7 M-s^–1. Results from this study support the proposal that acetophenone degradation reaction proceed through the oxidative reaction pathway, where molecular oxygen accelerates acetophenone degradation, photolysis, and pyrolysis pathways.     

Contribution of singlet oxygen to the accelerated decolorizing of dye mixtures

Binary mixtures of dispersed dyes, which during irradiation with polychromatic light give an effect of accelerated decolorization, were studied. Quantum yields of the formation of singlet oxygen by individual dyes were estimated during irradiation of solutions in ethyl acetate with light of 435 and 546 nm as well as quantum yields of the reaction of dyes with singlet oxygen. It was found that the contribution of the reaction of dyes with singlet oxygen to the effects of accelerated decolorization were vanishingly small. The quantum yield of the photodestruction of dyes in a mixture was 10^–3-10^–5 and the quantum yield of reaction with singlet oxygen was less than 10^–6. It was concluded that accelerated decolorization of the systems studied is not determined by reaction with singlet oxygen.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 9, pp. 2014–2017, September, 1991.     

Reaction of the Intermetallic Compound SmFe11Ti with Gaseous Ammonia

The reaction of the intermetallic compound SmFe₁₁Ti with ammonia at the initial NH₃ pressure of 0.6 – 0.8 MPa in the temperature range 150 – 450 °C in the presence of 10 wt % NH₄Cl as activator was studied. Depending on the reaction temperature, SmFe₁₁Ti undergoes both hydrogenation to form a hydride phase of the starting intermetallic compound and disproportionation to form a hydride phase of a new intermetallic compound. The reaction products are finely dispersed powders. The magnetic properties of the products were studied.__________Translated from Zhurnal Obshchei Khimii, Vol. 75, No. 6, 2005, pp. 881–885.Original Russian Text Copyright © 2005 by Fokin, Shul’ga, Tarasov, Fokina, Korobov, Burlakova, Shilkin.     

On the characteristics and mechanism of the radiation-induced chain reaction between sulfur dioxide and molecular oxygen in acid solutions

Characteristics of the -induced chain reaction between sulfur dioxide and molecular oxygen in perchloric and sulfuric acid media in the presence of Ce(III) ions have been studied. The concentration effects of dissolved oxygen (0.2·10^–3–9.4·10^–3 mol/dm³, sulfur dioxide (0.3·10^–1–2.0·10^–1 mol/dm³ and Ce(III) (0.2·10^–3–4.8·10^–3 mol/dm³) and dose rate (0.26·10¹⁹–1.0·10¹⁹ eV/dm³·s) on the radiation — chemical yield of oxygen consumption G(–O₂) and accumulation of sulfate G(HSO ₄ ^– ), have been investigated. The reaction proceeds with G(–O₂) reaching 10²–10³ molecule/100eV in a catalytic regime. The reaction rate in perchloric acid medium is 3–4 times lower than that in the sulfuric acid medium and depends on the SO₂, O₂ and Ce(III) concentrations, the reaction order varying from 1.0 to 0 and/or in the reverse direction. The mechanism of the process involves chain propagation with 3 stages and 3 intermediates: SO₃H, HSO₅ and Ce(IV). The catalytic effect is caused by the interaction of HSO₄ with Ce(IV) ions followed by their reduction when interacting with SO₂, yielding SO₃H radicals. Chain termination may be due to one or two of the three intermediates or due to all three particles, the kinetics depending on this. Kinetic equations describing the experimental data have been obtained.     

Reactivity of the carbocation generated in the photolysis of 1,2,2,4,6-pentamethyl-1,2-dihydroquinoline toward azide ion

The reaction of the azide ion with the carbocation generated in the photolysis of 1,2,2,4,6-pentamethyl-1,2-dihydroquinoline in methanol was studied by pulse (conventional and laser) and steady-state photolysis techniques. The adduct of the azide ion was characterized by ¹H NMR spectrum. Experimental results were interpreted taking into account a competition between the addition of methanol and azide ion to the carbocation. The rate constants for the reaction of the azide ion with the carbocation (k _Az) were measured at 2—48 °C in a wide range of [N₃ ^–]₀ concentrations from 2·10^–7 to 0.1 mol L^–1 at different ionic strengths () of the solution. The resulting k _Az values are more than an order of magnitude lower than those for diffusional-controlled reactions and vary from 3.2·10⁸ ( = 0) to 4.5·10⁶ L mol^–1 s^–1 ( = 0.8 mol L^–1) in the presence of NaClO₄ (18 °C). The activation energy of addition of the azide ion to the carbocation is 21 kJ mol^–1, which is by 12 kJ mol^–1 lower than the activation energy of the reaction of the carbocation with methanol. The features of the reaction under study are discussed from the viewpoint of the structures of carbocations generated in the photolysis of dihydroquinolines.     

Use of a kinetic model for selecting the optimal conditions for the reaction of unsaturated aldehydes with peracids

The selectivity of the formation of unsaturated acid on the concentration, reagent ratio, temperature, conversion, and solvent was determined using a kinetic model for the reaction of unsaturated aldehydes with organic peracids and the kinetic parameters of this reaction were calculated.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 31, No. 5, pp. 298–302, September–October, 1995.     

Investigation of the primary products of impulse pyrolysis of ammonium perchlorate using a time-of-flight mass spectrometer

Conclusions The primary products of the decomposition reaction of ammonium perchlorate in the temperature interval 250–500° are ammonia and perchloric acid.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 6, pp. 1372–1373, June, 1968.     

Kinetic Aspects of Dimethylamine Hydroxyethylation in the Presence of Water

The kinetics of dimethylamine hydroxyethylation at an ethylene oxide : dimethylamine : water molar ratio of 1 : 3 : (0.1–0.5) was studied in the temperature range 20–50°C. A kinetic model of the reaction, which adequately describes the experimental data, was suggested.__________Translated from Zhurnal Prikladnoi Khimii, Vol. 78, No. 4, 2005, pp. 687–689.Original Russian Text Copyright © 2005 by Danov, Kolesnikov, Efremov, Mezhenin.