Oxidative transformations of cembrane diterpenoids III. Epoxycembrenes

Summary 1. It has been established that the epoxidation of cembrene with perbenzoic and peracetic acids takes place stereospecifically at each of the trisubstituted double bonds with the formation of 4S,5R-, 7S,8S-, and 11S,12S-monoepoxycembrenes, the structures and absolute configurations of which have been established by spectral methods.2. Epoxidation of cembrene at the C₁₁–C₁₂ double bonds under the conditions used takes place preferentially as compared with epoxidation at the C₇–C₈ double bond.Novosibirsk Institute of Organic Chemistry, Siberian Branch of the Academy of Sciences of the USSR. Novosibirsk State University. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 525–531, July–August, 1977.     

Recyclization reactions of small rings. 8. Synthesis of 5-substituted 2-oxazolidones from thiazolidine-2,4-dione and oxiranes

Treatment of oxiranes with thiazolidine-2,4-dione gives N-(2-hydroxypropyl)-thiazolidine-2,4-diones which can recyclize to 5-substituted 2-oxazolidones in basic medium.For Communication 7 see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1137–1140, August, 1991.     

New Method for Studying the Ignition Characteristics of Condensed Systems by Laser Radiation

Russian Physics Journal - A method for determining the characteristics of laser ignition of the condensed systems is presented, which ensures uniform distribution of the heat flux density over the...     

Surface Tension in Aqueous Dodecylethylaminocarbonyldimethylbenzylammonium Chloride

The surface tension of aqueous solutions of the cationic surfactant dodecylethylaminocarbonyldimethylbenzylammonium chloride is measured for the first time over a wide concentration range from 7.9×10^{- 7} to 3.9×10^{- 2} M at 20-35°C. The critical micelle concentration of DAEDMBAC as influenced by temperature is determined.     

Micelle formation in aqueous dodecylpyridinium chloride

Micelle formation in aqueous dodecylpyridinium chloride is studied at 20, 25, 30, 35, and 40°C using the surface tension and conductivity methods.     

Kinetics of coal char gasification in a carbon dioxide medium

Solid fuel samples with different carbon contents are gasified by successively subjecting to pyrolysis in argon and oxidation in carbon dioxide at various temperatures to determine the rate of the chemical reactions and the activation energy required for simulating and optimizing the operation of gas generators. The samples were prepared from bituminous coal, lignite, and anthracite of the Kuznetsk and Kansk-Achinsk coal basins. The gasification of coal char samples in a carbon dioxide medium at 900–1200°C is analyzed by thermogravimetry. The temperature dependences of the weight change rate and gasification time of coal char samples are measured and used to calculate the preexponential factor and activation energy of the carbon oxidation reaction. It is found that, with increasing oxidizing medium temperature from 900 to 1200°C, the gasification time of the coal char samples obtained from anthracite and bituminous coal decrease 8- and 22-fold, respectively. A physicomathematical model of coal char gasification in a fixed bed, with the oxidizing gas diffusing through the ash layer formed, is proposed.     

Development and testing of granular catalysts for combustors of regenerative gas turbine plants

Two types of granular catalysts for effective methane combustion in combustors of gas turbine plants (GTPs) were developed: (1) catalysts based on noble metals with a low Pd content (1–2 wt %), characterized by a low methane ignition temperature, and (2) catalysts based on manganese oxides and hexaaluminates, which have an increased thermal stability. The methane oxidation kinetics was investigated, and combustion in the catalyst chamber of the GTP was simulated. For optimizing the combustion technology, the following two-step process using a combined catalytic package is suggested. The inlet zone of the combustor is filled with a highly active Pd catalyst, which initiates methane oxidation and ensures that the temperature at the exit of this zone is the initial temperature of methane combustion. This takes place in the next zone, which is filled with an oxide catalyst tolerant to high temperatures. The pilot testing of the catalysts was carried out in a model catalytic combustor. The results are in satisfactory agreement with calculated data. Long-term tests indicate the high stability of the catalysts. The Pd catalyst was demonstrated to retain its high activity and to provide an ignition temperature of 240°C. The initial activity of the hexaaluminate-based catalysts remains unchanged after tests at 930°C. The use of a combined charge of the palladium (7–15%) and manganese (85–93%) catalysts in the model GTP combustor allows a high natural gas combustion efficiency to be achieved at a low level of hazardous emissions (NO _x , 0–1 ppm; CO, 1–3 ppm; hydrocarbons, 3–10 ppm).     

Recyclization of benzimidazo[2,1-<Emphasis Type="Italic">b</Emphasis>]thiazanium salts into 1-(2,3-epithiopropyl)benzimidazol-2-ones under the action of epichlorhydrin

It has been shown that the reaction of epichlorhydrin with 3-hydroxybenzimidazo[2,1-b]thiazanium salts leads to recyclization of the thiazanium ring with the formation of substituted 1-(2,3-epithiopropyl)benzimidazol-2-ones in high yield. The proposed method enables the introduction of functional groups unstable in alkaline medium into the structure of thiirane derivatives.     

Synthesis of 1,3,4-oxadiazole and xanthen-2-one luminophoric epoxide monomers

Epoxide derivatives of 2,5-bis-oxyphenul-1,3,4-oxadiazoles and fluorescein, which are luminescent epoxide monomers, are synthesized. Their luminescence properties are studied.L. M. Litvinenko Institute of Physical Organic Chemistry, National Academy of Sciences of Ukraine, Donetsk 340114Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 407–412, March, 1999.