Synthesis of 20-deoxoluteone

20-Deoxoluteone has been synthesized from sclareol. Sclareol was brominated with phosphorus tribromide to form a mixture of primary allyl bromides, from which, by the malonic synthesis, a mixture of bicyclogeranylgeranylacetic acids was obtained which was cyclized with fluorosulfonic acid to form a mixture of two diastereomeric -lactones. The predominating lactone was converted by successive reduction with lithium tetrahydroaluminate, oxidation with oxalyl chloride in dimethyl sulfoxide, reaction with methylmagnesium iodide, and oxidation by the chromium trioxide/pyridine complex into 20-deoxyluteone.Institute of Chemistry, Moldavian SSR Academy of Science, Kishinev. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 346–353, May–June, 1990.     

Catalytic and Physicochemical Properties of Oxidative Condensation Products in the Oxidative Dehydrogenation of Propane by Sulfur Dioxide on SiO2

The effect of the deposition of oxidative condensation products in the reaction of oxidative propane dehydrogenation in the presence of SO₂ on the catalytic, acid–base, and texture characteristics of silica was studied. It was found that the oxidative condensation products exhibited high catalytic activity in this reaction. The carbonization of silica from 0 to 40 wt % was accompanied by an increase in the yield of propylene from 3.4 to 46 mol % (640°C; a C₃H₈/SO₂/He + N₂ mixture, 10 : 10 : 80 vol %). Further accumulation of condensation products resulted in a considerable decrease in the pore volume and radius; this imposed diffusion limitations on both propane conversion and selectivity to propane conversion products. The nature of active and deactivated condensation products was studied by DRIFT spectroscopy, diffuse-reflectance UV–VIS spectroscopy, EPR spectroscopy, XPS, thermal analysis, and electron microscopy.     

Uronic (hexenuronic) acid profile of ethanol–alkali delignification of giant reed Arundo donax L.

The effect of process variables on uronic acids (UAs) and hexenuronic acids (HexAs) in the annual crop Arundo donax L. during ethanol–alkali pulping has been examined. A substantial loss of UA moieties (up to 90%) was observed by the end of pulping (target kappa number 18) performed with 25% NaOH and 40% EtOH (by volume) within the temperature range of 130–150 °C. At the same time, the progressive formation of HexA in pulp was detected from the early phases of delignification. The proportion of HexA in the residual UA of the final pulp was found to be 84%, indicating almost complete conversion of 4-O-methylglucuronic acid side groups (MeGlcA) of heteroxylan into HexA. The kinetics of UA degradation and HexA formation has been described in terms of three consecutive first-order reaction stages. The overall rate of UA degradation was one order higher than the rate of UA conversion into HexA. The values of apparent activation energy were estimated as 68.6 and 94.7 kJ mol^–1, respectively. The reaction medium alkalinity was shown to be the controlling factor for UA and HexA stability during ethanol–alkali pulping. An increase in alkali charge from 5% to 35% (as NaOH) led to UA loss of 40%, but promoted HexA formation from 11.8 to 20.1 mol g^–1. The addition of organic solvent to the alkaline pulping solution had a similar effect, and about 10% of UA was lost and the content of HexA increased from 6.9 to 10.9 mol g^–1 with an increase in ethanol proportion in the liquor from 20% to 60%.     

Vapor phase oxidation of methylpyridine aldehydes

A study is made of the contact oxidation of -, ß- and -methylpyridines by air, over the temperature range 390°–490° C, contact time 0.17–1.0 sec, mole ratio oxygenmethylpyridine 0.5 to 401, with dilution of the air-vapor mixture with water in the ratio 15–103 mole water per mole methylpyridine, using two vanadium oxide catalysts differing in respect of sizes of specific surface areas.Use of the low specific surface area catalyst increases the selectivity of the process, by diminishing the proportion of secondary reaction products of the aldehydes and decreasing the complete oxidation of the methylpyridines.     

Determination of trace amounts of morpholine and its thermal degradation products in boiler water by HPLC

Summary Morpholine and its amine-type thermal degradation products present in boiler feed water and steam condensate were derivatised with N-succinimidyl-p-nitrophenylacetate. These pre-column derivatives were determined by high-performance liquid chromatography with UV detection at 280 nm. The analytical column was Supelco-sil-ODS with an isocratic mobile phase. Morpholine and its breakdown products were monitored in the range 0.01–10 g ml^–1 with a relative standard deviation of 0.4–3.0%. Chromatographic analysis of boiler feed water and steam condensate samples collected from a boiler servicing a petroleum refinery is described.     

Oxidation of mesitylene by hydrogen peroxide in AcOH-Ac2O-H2SO4

By the oxidation of raesitylene by hydrogen peroxide in AcOH-Ac₂O-H₂SO₄ one can obtain mesitol (2,4,6-trimethylphenol) (with a selectivity of 57–69% at a mesitylene conversion of 22–16% and the acetate of mesitol with a selectivity of 72–85% at 25–22% conversion. The peroxide responsible for the oxidation of mesitylene in this system is in the form of peracetic acid, formedin situ. Over the concentration range studied, the reaction is first order in AcOOH, mesitylene, and H₂SO₄. Hydroxylation of mesitylene by AcOOH proceeds by an electrophilic substitution mechanism, the limiting step being the formation of the -complex.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 12, pp. 2716–2721, December, 1990.The authors express their thanks to L. V. Efremova, G. M. Maksimov, and V. D. Chinakov for their assistance in this work.     

Kinetic Factors Determining Specific Features of Solid Phase Formation in Dichlorosilane Oxidation

Experimental data on the kinetic regularities of aerosol SiO₂ formation in the course of dichlorosilane oxidation by oxygen at different initial pressures, compositions of the reaction mixture, and temperatures ranging from 380 to 578 K are presented. It is shown that the regularities of the process, including the specific feature of the transition from the regime of solid phase formation in the form of a film to the regime of aerosol formation can be explained on the basis of the Volmer–Weber–Frenkel–Zeldovich nucleation theory taking into account the branched chain nature of the reaction. The conditions for the transition of chain combustion into the regime of chain–thermal explosion almost coincide with the conditions of intensive formation of aerosol. The SF₆ additives inhibit the process and thereby increase the dispersity of aerosol and the minimal pressure of its formation.     

The CO2 Reforming of Natural Gas in a Pulsed Corona Discharge Reactor

The conversion of CO ₂ and (CH ₄+CO ₂ ) mixtures to CO, at room temperature and atmospheric pressure conditions, in pulsed corona discharges, was investigated. Conversion of pure CO ₂ was 16.8% at 10 cm ³ -min ^–1 flow rate, which corresponds to 75 mol-min ^–1 rate of conversion. The CO ₂ conversion was improved to 38% (85 mol-min ^–1 by feeding the reactor with CH ₄+CO ₂ gas mixture (1:1 ratio), simultaneously with CH ₄ conversion of 46% (102.7 mol-min ^–1 ) at 10 cm ³ -min ^–1 flow rate of feed gases and 9 W power conditions. Rate of CO production is increased from 110 to 180 mol-min ^–1 with the variation of feed gas (CH ₄+CO ₂ mixture, 1:1 ratio) flow rate from 10 to 40 cm ³ -min ^–1 at 9W, which corresponds to energy efficiency of 2.5 to 4.1%. Highest energy yield of 25 g/kWh for CH ₄ conversion, 29 g/kWh for CO ₂ conversion, and 33 g/kWh for CO production were achieved.     

Investigation of a cylindrical chemosorptive denuder for sampling and phase separation of toluene diisocyanate aerosols

A cylindrical chemosorptive denuder in series with a glass fibre filter has been evaluated for sampling toluene diisocyanate (TDI) aerosols. The sampler is designed for measuring personal exposure to diisocyanates. Several denuder coatings and derivatising reagents were investigated. Dimethylpolysiloxane (SE-30) and 5% phenyl dimethylpolysiloxane (SE-54) with either dibutylamine (DBA) or dipentylamine (DPeA) as derivatising reagents yielded the lowest vapour breakthrough (the amount (%) of the vapour that passes through the denuder), close to values predicted by theory. Immobilisation of the SE-30 denuder coating by in-situ cross-linking yielded comparable results. With an SE-30/DBA-coated denuder operating within an airflow range of 100–500 mL min^–1, the phase separation was shown to be consistent with theoretical predictions derived by use of the Gormley–Kennedy equation. This provides a means of calculating the vapour breakthrough and correcting experimentally obtained values with regard to vapour–particulate phase distribution, suggesting that the denuder can provide accurate phase-distribution measurements. The SE-30/DBA denuder can be used over a concentration range spanning nearly six orders of magnitude. Its capacity is sufficient to perform 15-min exposure measurements of a TDI aerosol with air concentrations as high as 1,700 g m^–3, 40 times higher than the Swedish occupational exposure limit (OEL). At the other end of the range, the estimated limit of detection (LOD) was less than 2 ng m^–3 for both the vapour and the aerosol phases when LC–ESI–MS–MS was used for chemical analysis.Electronic Supplementary Material Supplementary material for this article is available at     

Effect of the chemical nature of the support on the properties of platinum catalysts for the combined oxidation of CO and H2

The steady-state rate of hydrogen oxidation catalyzed by platinum on an inert support (corundum) is greater than the rate of oxidation of carbon monoxide, while the rate of hydrogen oxidation on a platinum-vanadium catalyst is less than the rate of oxidation of carbon monoxide. The conditions for the complete selective oxidation of the reaction mixture components were determined. Hydrogen is oxidized on the Pt/corundum cataljst at 273K in a non-steady-state mode, while CO is oxidized on the same catalyst at 273 K and on Pt/BaSO₄-V₂O₅ at 383–393K in a steady-state mode.Deceased.Translated from Teoreticheskaya i éksperimental'naya Khimiya, Vol. 31, No. 2, pp. 81–85, March–April, 1995.     

Simultaneous determination of plutonium and americium in biological and environmental samples

A radiochemical method is given to determine the specific activity of²³⁸Pu, and²⁴¹Am from the global fallout in environmental and biological samples. The radiochemical recovery was for human livers Pu: 60–70%, Am: 40–60%; Bran: Pu: 50–70%, Am: 30–40%; Soil: Pu: 50–80%, Am: 30–50%. The resolution of the alpha-spectrum was for soils 30–40 keV and for livers and brans 40–60 KeV. To facilitate the wet ashing of large amounts of bran (15 kg), which are necessary to determine the presently very small activity concentrations of the transuranic elements in these types of samples, a fermentation process was employed. The procedure was tested by using NBS standard reference material and subsequently applied for the determination of Pu and Am from the global fallout in livers, plant tissues (bran), and soils.     

Simple and quick rotational temperature determination in N2-containing discharge plasma

A quick spectroscopic method of rotational temperature determination based on the low-resolution emission spectrum of the N₂ (v=2v=()) vibronic band profile of the second positive system iras developed. The new method of molecular gas temperature determination was used in an rf glow discharge excited in N₂ and N₂ + Ar + B₂ H₆ gas mixture at u pressure range 500–13011 Pa. This method of molecular gas temperature measurement is applicable to nonisothermic plasmas used in plasma-chemical reactors.     

Asparagus polysaccharides. I. Isolation and characterization of polysaccharides ofA. neglectus: Glucomannans of the roots

Water-soluble polysaccharides and pectin substances have been isolated from various organs ofA. neglectus and their quantitative amounts and monosacchardie compositions have been determined. Native acetylated glucomannans (A, B, and C) containing 13, 15, and 20% of acetyl groups and being homogeneous according to the results of gel chromatography have been isolated from the roots. On the basis of the results of periodate oxidation, methylation, and IR spectroscopy it has been established that the neutral polysaccharides of the roots ofA. neglectus is a mixture of three glucomannans consisting of -14 linear-bound D-gluco- and D-mannopyranose residues.Deceased.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 702–706, November–December, 1981.     

Preparation of 16-substituted 3-hydroxyestra-1,3,5(10)-triene-17-ones starting with the bromination of estrone acetate

The bromination of estrone acetate (Ia) leads to a mixture of acetates of 16-bromo-16-bromo-, and 16,16-dibromoestrone (IIa, IIIa, and IVa) in a ratio of 63:28:9. On treatment with an aqueous methanolic solution of potash, depending on the conditions, a mixture of (IIa) and (IIIa) gives 3,16-dihydroxyestra-1,3,5(10)-trien-17-one (V) or 3,17-dihydroxyestra-1,3,5(10)-trien-16-one (VI). When 5 g of (Ia) was brominated with 2.8 g of Br₂ in chloroform and the products were chromatographed on silica gel, 0.36 g of (IVa), C₂₀H₂₂Br₂O₃, mp 165–166°C (from ether) 0.37 g of (IIIa), mp 169–170.5°C, 4.6 g of a mixture of (IIa) and (IIIa), 30 mg of (Ia) and 0.2 g of a mixture of 16- and 16-bromoestrones was obtained. The action of potash on a mixture of (IIa) and (IIIa) in aqueous MeOH at 20°C led to the epimerization of the (IIa) into (IIIa) and then the conversion of the latter into (V) with mp 203.5–206°C; diacetate with mp 172–173°C (acetone-ethanol). Similarly, but with heating (98°C, 3 h), a mixture of (IIa) and (IIIa) was converted into (VI), with mp 234–236°C. Characteristics of the IR and PMR spectra of the compounds obtained are given.S. Ordzhonikidze All-Union Scientific-Research Institute of Pharmaceutical Chemistry, Moscow. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 465–469, July–August, 1983.     

Kinetics and Mechanism of 4-Nitrotoluene Oxidation with Ozone in an Acetic Acid Solution in the Presence of a Metal–Bromide Catalyst

The kinetics and mechanism of a reaction between ozone and 4-nitrotoluene in an acetic acid solution in the presence of a cobalt–bromide catalyst were studied at 100°. Under these conditions, 4-nitrobenzoic acid was the main reaction product (96.6%). The rate of oxidation exhibited a first order with respect to the substrate, ozone, and the catalyst and a zero order with respect to oxygen. The main stages of the catalytic cycle were considered. It is believed that the selective oxidation of 4-nitrotoluene at the methyl group in the presence of a catalyst occurs as a nonchain ion–radical process, in which the role of ozone is reduced to the generation of an active catalyst species (Co³⁺Br^– Co²⁺Br^·). This species involves 4-nitrotoluene in the oxidation process at a high rate.     

Spectrophotometric determination of gallium(III) with carminic acid and hexadecylpyridinium chloride

A Spectrophotometric method is proposed for determining dipyridamole in pure form and in pharmaceutical preparations. Chromotrope 2B was used as a charge-transfer complex forming agent with absorption maximum 40 nm red shifted relative to the chromotrope 2B itself. The variables affecting the formation of the C.T. complex were studied and optimized. Linear calibration graphs were obtained up to 60 g ml^–1 at room temperature. The method was found to be accurate, precise and can be successfully used for authentic and pharmaceutical preparations in the working range up to 600 g.A conductimetric method using phosphotungstic acid as ion-associate forming agent is proposed. The relative average error is 1–2%. Water-ethanol (12) mixture was used as solvent. Excellent recoveries and low standard deviations were obtained. Working ranges are 40–260 mg and 35–110 mg for pure dipyridamole and tablets, respectively.On leave from Department of Chemistry, Faculty of Science, Allepo University, Allepo, Syria     

Determination of the composition of a high-boiling condensate from natural gas by capillary gas chromatography and mass spectrometry

Summary A condensate from natural gas containing nearly 50% of the fraction boiling in the range from 180–320 C was analysed by capillary gas chromatography and by mass spectrometry with the aim to determine its composition and to evaluate suitability as a gasoline component.

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Bestimmung der Zusammensetzung eines hochsiedenden Kondensats aus Erdgas mit Hilfe der Capillar-Gas-Chromatographie und der Massenspektrometrie

Zusammenfassung Ein Kondensat aus Erdgas, das fast 50% der im Bereich 180–320 C siedenden Fraktion erhielt, wurde mit Hilfe der Capillar-GC und der MS analysiert. Die Zusammensetzung des Kondensats sollte im Hinblick auf seine Eignung als Benzinzusatz aufgeklÄrt werden.

     

Mechanism of the formation of carbon dioxide in the oxidation of formaldehyde

Summary The ways in which carbon dioxide is formed in the oxidation of formaldehyde at 451 were Investigated. It was shown that not more than 3–5% of the CO₂ formed can arise by the oxidation of CO. The bulk (95–91%) of the CO₂ is formed directly from formaldehyde.     

Selective stoichiometric and catalytic oxidation of lower alkanes in the system Co(III)-CF3COOH

It has been found that cobalt(III) trifluoroacetate is capable of oxidizing with a high selectivity (90%) methane to methyltrifluoroacetate at 130–180°C and 10–40 atm. In the presence of oxygen the selective oxidation of methane proceeds catalytically with respect to the cobalt salt. Ethane and propane are oxidized with the formation of ethanol and isopropanol trifluoroacetates, respectively (yield 80%). The further oxidation of triethanol trifluoroacetate leads to the formation of the ethyleneglycol ester, together with products of the splitting of the C-C bond in the alkyl group of the initial ester. The data obtained lead to the assumption that the reactions of the alkanes and alkyl esters with Co(III) include an electron transfer stage from the RH molecule to the Co(III) ion, with the intermediate formation of the cation radical RH⁺.N. S. Kurnakov Institute of General and Inorganic Chemistry, Academy of Sciences of the USSR, Moscow. Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 27, No. 3, pp. 301–307, May–June, 1991. Original article submitted February 19, 1991.     

Oxidation of hydrocarbons with dioxygen via peroxide intermediates

Cyclohexane, cyclohexene, and -pinene react with dioxygen in the liquid phase in the presence of catalysts based on platinum, heteropoly compounds (HPCs), metal-containing HPCs, and combinations of these components. In cyclohexane and -pinene oxidations occurring by an autooxidation mechanism at 160–170 and 80– 90°C, respectively, the catalysts serve to control free-radical processes. The simultaneous action of a Ru-containing phosphotungstate as a hydroperoxide decomposition catalyst and of a V-containing phosphotungstate as a scavenger of hydroxyl and alkoxyl radicals increases the cyclohexanol + cyclohexanone selectivity of cyclohexane oxidation without yielding a hydroperoxide. A Pt/C catalyst affords an increase in -pinene conversion in a fixed time. In combination with ammonia or tetrahexylammonium chloride admixtures, it retards side reactions and raises the yield of verbenol and verbenone, which are the most valuable products. During cyclohexane, cyclohexene, and -pinene oxidation with an O₂-H₂ mixture at room temperature, no free-radical chain reaction develops in the Pt-HPC system and reactive intermediates form and interact, involving the HPC, with hydrocarbons on the surface of the platinum catalyst. Analysis of reactivity and of the composition of substrate oxidation products suggests a mechanism for the conjugate oxidation of hydrocarbons in systems with various HPCs. In this mechanism, HPC composition determines, to a large extent, the nature of reactive intermediates, which may be peroxides or radicals bound to platinum or HPC. The properties of catalytic systems in oxidation with O₂-H₂ mixtures can be controlled by selecting an appropriate HPC as the modifying component.__________Translated from Kinetika i Kataliz, Vol. 46, No. 2, 2005, pp. 219–232.Original Russian Text Copyright © 2005 by N. Kuznetsova, L. Kuznetsova, Kirillova, Detusheva, Likholobov, Khramov, Ansel.