A quantum-chemical study of alternative chlorotropic isomerization mechanisms for bis(diethylamino)-chlorophosphonium methylide

The MNDO-PM3 method has been used in the supermolecular approximation to examine alternative mechanisms for the chlorotropic isomerization of unsolvated bis(diethylamino)chlorophosphonium methylide and solvated forms of it containing chloroform of 1∶1 and 1∶2 compositions. It is shown that the most favorable channel for the chlorotropic rearrangement of unsolvated P-chloroylide corresponds to the sigmatropic mechanism. There are effects from specific interactions with the chloroform that make themselves felt in the preferential chlorotropic transformation of the isomers by the dissociation-recombination mechanism, whose activation energy E_1∶2 ^≠=kcal/mol is comparable with the observed activation barrier for the 1,2-shift of the chlorine atom in the related P-chloroylide. Institute for Bioorganic Chemistry and Petroleum Chemistry, National Academy of Sciences of Ukraine, 1 Murmanskaya ul., Kiev 253094, Ukraine. Translated from Teoreticheskaya i éksperimental'naya Khimiya, Vol. 35, No. 4, pp. 215–221, July–August, 1999.     

Lipids from leaves ofEphedra equizetina

The content and composition by class and fatty acid of neutral (NL), glyco- (GL), and phospholipids (PL) in leaves ofEphedra equizetina Bunge (Ephedraceae) are determined. The acid composition of NL, GL, and PL includes saturated 12∶0–32∶0 acids and unsaturated 15∶1, 16∶1, 18∶1, 18∶2, and 18∶3 acids. Unsaponified components of the total lipids also contained biologically active substances such as α-tocopherol, carotenoids, high-molecular-weight fatty alcohols, triterpenes, and sterols. Academician S. Yu. Yunusov Institute of the Chemistry of Plant Substances. Academy of Sciences of the Republic of Uzbekistan, Tashkent, fax (371) 120 64 75. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 718–721, November–December, 1999.     

Optimization of enzymatic production of biodiesel from castor oil in organic solvent medium

We studied the production of fatty acid ethyl esters from castor oil using n-hexane as solvent and two commercial lipases, Novozym 435 and Lipozyme IM, as catalysts. For this purpose, a Taguchi experimental design was adopted considering the following variables: temperature (35–65°C), water (0–10 wt/wt%), and enzyme (5–20 wt/wt%) concentrations and oil-to-ethanol molar ratio (1∶3 to 1∶10). An empirical model was then built so as to assess the main and cross-variable effects on the reaction conversion and also to maximize biodiesel production for each enzyme. For the system containing Novozym 435 as tatalyst the maximum conversion obtained was 81.4% at 65°C, enzyme concentration of 20 wt/wt%, water concentration of 0 wt/wt%, and oil-to-ethanol molar ratio of 1∶10. When the catalyst was Lipozyme IM, a conversion as high as 98% was obtained at 65°C, enzyme concentration of 20 wt/wt%, water concentration of 0 wt/wt%, and oil-to-ethanol molar ratio of 1∶3.     

HPLC separations of meropenem and selected pharmaceuticals using a polar endcapped octadecylsilane narrow bore column

Summary Stability indicating high performance liquid chromatography methods have been developed for the assay of meropenem in combination with either dopamine (A), aminophylline (B), metoclopramide (C) or ranitidine (D) in intravenous fluid mixtures. Separations B, C and D were performed on a polar endcapped ODS column (150×2 mm) with aqueous, pH 3.0—acetonitrile (89∶11, 88∶12, and 92∶8) eluent and detection at 270, 290, 317 nm respectively. Meropenem was linear over the concentration ranges 126.88–507.50, 131.25–525, and 131.25–525 gmg mL⁻¹. Aminophylline, metoclopramide and ranitidine were linear over the concentration ranges 13–52, 37.5–150, and 25–100 μg mL⁻¹. Separation A was performed on a conventional ODS column (150×2.1 mm) with aqueous, pH 3.0—acetonitrile (85∶15) eluent and detection at 280 nm. Meropenem and dopamine were linear in the 61.25–245 and 10–40 μg mL⁻¹ ranges, respectively. Accuracy and precision for all methods were 0.20–3.30% and 0.10–1.58%, respectively. Accelerated stability studies have been carried out on each drug by exposure to acid, base, H₂O₂, and heat for different time periods.     

Separation of amino acids. Possibilities offered by optimized associations of low-voltage electrophoresis and chromatography on finely textured paper and on cellulose thin-layers

Summary Three optimized small-scale methods for amino acid separation are described and compared. Two dimensional separations are based on paper or cellulose thin-layer ionophoresis and chromatography with simple and inexpensive apparatus. The influence of experimental conditions on resolution and amount required for amino acids possessing almost identical mobilities, is studied. The quickest procedure based on the coupling of 200×200×0.25 mm thin-layer, low-voltage electrophoresis (20 V/cm) with chromatography, and the system: cellulose −1.04 mol dm⁻³ formic acid — tertbutanol/methanol/pyridine/formic acid/water (33∶43∶9.6∶0.4∶20), provides very reproducible results with high separating power for small samples (2–10 nmoles).     

Fatty acids from the Okhotsk sea sponge <Emphasis Type="Italic">Forcepia uschakowi</Emphasis>

The fatty-acid (FA) composition of total lipids from the Okhotsk sea marine sponge Forcepia uschakowi was studied. A total of 56 acids were identified by GC and GC—MS. The principal saturated acids were 16∶0 and 18∶0. The main monoene acid was 15-Me-24∶1(14), which was observed for the first time in sponge lipids. Polyunsaturated acids represented of 64.1% of the total FA of F. uschakowi. Of these, the principal ones were non-methylene-separated acids 26∶2(5,9) and 26∶3(5,9,19), which are typical of sponges, and bromo-acid 6-Br-26∶2(5,9). __________ Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 422–424, September–October, 2007.     

Chemisorption and oxidative decomposition of pyridine on hydrated manganese dioxide

An experimental study using IR spectroscopy and TPSR techniques showed that the extensive oxidation of pyridine on the surface of hydrated manganese dioxide in a two-step adsorption-catalytic mode proceeds through the formation of complexes of the heterocycle with Lewis acid sites. L. V. Pisarzhevskii Institute of Physical Chemistry, National Academy of Sciences of Ukraine, 31 Prospekt Nauki, Kiev 03039, Ukraine. Translated from Teoreticheskaya i éksperimental'anaya Khimiya, Vol. 36, No. 2, pp. 101–104, March–April, 2000.     

Formation of fluorosulfatodimerization products in reactions of perfluoroaliphatic α,β-unsaturated carbonyl compounds and conjugated dienes with electrochemically generated peroxydisulfuryldifluoride

Reactions of fluoroaliphatic α,β-unsaturated carbonyl compounds and perfluoro-2,7-dimethylocta-3,5-diene with electrochemically generated peroxydisulfuryldifluoride proceed to give both 1∶1 adducts and fluorosulfatodimerization products, whose formation is explained by generation of heteroallyl and allyl radicals due to the addition of a fluorosulfonyloxy radical to the sterically hindered vinyl carbon atom. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2207–2209, November, 1999.     

Single-stage polyepoxyacrylate analog formation in thin films in contact with a substrate

IR spectroscopy has been applied to the photo-initiated polymerization of a model system containing an ED-20 epoxide resin and methacrylic acid, which has been used in thin layers between windows of KRb or teflon. The KRb substrates inhibit cationic polymerization and alter the ratio of the rates of the cationic and radical processes, which affects the structure of the final product. Institute for Macromolecular Compound Chemistry, National Academy of Sciences of Ukraine, 48 Kharkov Shosse, Kiev, Ukraine 253160. Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 34, No. 1, pp. 58–61, January–February, 1998.     

Mechanism of reactions of photocatalytic synthesis of chlorohydrins

A mechanism of photocatalytic synthesis of chlorohydrins from olefins and peroxo complexes of titanium (IV) is proposed. It consists of formation of radical-containing complexes, their reactions with olefins, and decomposition of the α-oxides obtained by hydrogen chlorides. L. V. Pisarzhevskii Institute of Physical Chemistry, National Academy of Sciences of Ukraine, 31 Prosp. Nauki, 252039 Kiev, Ukraine. Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 33, No. 1, pp. 17–21, January–February, 1997.     

The reaction of sulfamic acid derivatives with epoxides

Reactions of diglycidyl and allylglycidyl ethers with salts of sulfamic acid followed by acidic hydrolysis of the products afforded the corresponding aminoethers. The alcoholysis of sulfamic acids with ethanol was suggested as a method for mild elimination of the sulfo group. For Part 4, see Ref. 1. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 508–511, March, 1997.     

The C−C bond chain termination mechanism in Fischer-Tropsch synthesis on a Co/SiO2·Zr(IV) catalyst

Two forms of chain termination are considered: on account of hydrogenation of metal-carbon bonds in surface intermediates and because of the elimination of hydrogen, which leads to the formation of α-olefins as primary products. L. V. Pisarzhevskii Institute of Physical Chemistry, National Academy of Sciences of Ukraine, 31 Prospekt Nauki, Kiev 252039, Ukraine. Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 35, No. 1, pp. 44–49, January–February, 1999.     

Kinetics and mechanism of the reaction of 1-benzoyloxy-4-[4-(dimethylamino)styryl]pyridinium tetrafluoborate with trimethyl-benzylammonium chloride in acetonitrile

The reaction of 1-benzoyloxy-4-[4-(dimethylamino)styryl]pyridinium tetrafluoborate with trimethylbenzylammonium chloride in acetonitrile takes place with the formation of an ion pair of 1-benzoyloxy-4-[4-(dimethylamino)styryl]pyridinium chloride, the slow decomposition of which to the σ adduct is rate-determining. The equilibrium constants of the individual steps of formation of ions from the ionogens PhCOCl and DASPO are determined. L. M. Litvinenko Institute of Physical Organic Chemistry and Carbon Chemistry, National Academy of Sciences of Ukraine, 70 Lyuksemburg ul., Donetsk 341114, Ukraine. Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 34, No. 3, pp. 148–152, May–June, 1998.     

Determination of potential degradation products of piroxicam by HPTLC densiometry and HPLC

Summary HPTLC densitometry and HPLC are considered for the simultaneous determination of the degradation products of piroxicam (2-aminopyridine, DP-I and DP-II). The substances were separated on silica gel with fluorescence indicator in ethylacetate — toluene — diethylamine (10∶10∶5) and toluene — absolute ethanol — glacial acetic acid (8∶1.2∶0.5) systems. The measuring absorbance (detection of reflectance) of the separated substances was carried out “in situ” at 296 nm using 4-level calibration (external standard, nonlinear regresson function) in the concentration range 600–1200 ng 2-aminopyridine/spot and 300–600 ng DP-I and DP-II/spot. The HPLC method was carried out using RP-8 stationary phase and methanol + phosphate-citrate buffer, pH 3 mobile phase with addition of sodium pentanesulfonate (40+60, v/v). 2-aminopyridine wass detected at 300 nm, DP-I at 280 nm and DP-II at 248 nm. The concentration range for 2-aminopyridine is 2–40 μg/ml, for DP-I and DP-II 2–20 μg/ml (for an injection volume of 10 μl). The results were evaluated by linear regression analysis.     

Effect of the extent of oxidation of activated carbons by O2 and HNO3 on the acidity and composition of surface functional groups and their ion-exchange properties

We have studied the effect of the extent of oxidation of carbon sorbents KAU and SKN by different oxidizing agents on the acidity of the surface functional groups and their qualitative composition, and also the selectivity of sorption of copper and lead ions from drinking water under static and dynamic conditions. We propose a mechanism for the formation of different types of acid groups on the carbon surface during its progressive oxidation. Institute for Sorption and Problems of Endoecology, National Academy of Sciences of Ukraine, 32/34 Akademika Palladina Prosp., Kiev-142, Ukraine 252680. Loughborough University, Loughborough, Great Britain. Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 34, No. 1, pp. 27–31, January–February, 1998.     

Theoretical study of the pathway for diazine ring formation in a series of 4-dimethylaminonaphthalic acid derivatives under Vilsmeier-Haack reaction conditions

Using the semiempirical quantum-chemical PM3 method, we have studied the formation of a quaternized diazine ring in a series of 4-dimethylaminonaphthalic acid derivatives under Vilsmeier-Haack reaction conditions. We have established that the reaction may occur via a two-step cycloisomerization of the intermediate Vilsmeier adduct, through six-center cyclic transition states. Institute of Single Crystals, National Academy of Sciences of Ukraine, 60 Prospekt Lenina, Khar'kov 310001, Ukraine. Translated from Teoreticheskaya i éksperimental'naya Khimiya, Vol. 36, No. 4, pp. 201–205, July–August, 2000.     

Kinetics of nonstationary condensation of methane on a perovskite catalyst

The interaction of methane with the oxidized surface of the KNaSrCoO_3−x is first order in methane with respect to formation of higher hydrocarbons and zero order with respect to formation of CO₂. At the initial stage the rate of formation of the reaction products is independent of the amount of oxygen from the catalyst consumed (up to 5–7 monolayers of oxygen), after which the rate of the reaction falls linearly. The overall amount of oxygen consumed in the reaction reaches 30 monolayers. L. V. Pisarzhevskii Institute of Physical Chemistry, National Academy of Sciences of Ukraine, 31 Prospekt Nauki, Kiev 03039, Ukraine. Translated from Teoreticheskaya i éksperimental'naya Khimiya, Vol. 36, No. 3, pp. 182–187, May–June, 2000.     

Acid-base interactions in the methanesulfonic acid-propylene carbonate system

The methanesulfonic acid (MSA)—propylene carbonate (PC) system with component concentrations of 0–100% was studied at 30°C using the Multiple Attenuated Total Reflection (MATR) IR spectroscopy. The formation of a strong 1∶1 molecular complex of MSA with PC was established. In the presence of an excess of the acid, a second MSA molecule adds to this complex to give the molecular complex (2MSA)·PC. When excess propylene carbonate is used, the MSA·PC complex is solvated by a propylene carbonate molecule. No protonation of the base or formation of complexes with a strong symmetrical H bond was observed. Continuous absorption was not detected in IR spectra of the solutions. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 313–318 February, 1999.     

Interaction of immobilized 2,8,14,20-tetramethyl-4,6,10,12,16,18,22,24-octahydroxycalix[4]arene with Na+, Cs+, and NH4 + ions and organic cations

The equilibrium in the system water—electrolyte—cross-linked polymer containing immobilized 2,8,14,20-tetramethyl-4,6,10,12,16,18,22,24-octahydroxycalix[4]arene was studied. Immobilized calixarene 1 was shown to form 1∶1, 1∶2, 1∶3, and 1∶4 compounds with inorganic cations (Na⁺, Cs⁺, and NH₄ ⁺), and with organic cations (hexamethylen-tetramine and β-diethylaminoethylp-aminobenzoate) 1∶1 compounds are formed. The affinity of immobilized calixarene1 increases in the series of cations: hexamethylenetetramine <Na⁺, Cs⁺, NH₄ ⁺<β-diethylaminoethylp-aminobenzoate. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2214–2216, November, 1998.     

Unusual formation of 7-vinylcycloheptatriene derivatives in the catalytic cyclopropanation of cyclooctatetraene with diazocarbonyl compounds in the presence of rhodium catalysts

The reaction of cyclooctatetraene with methyl diazoacetate or diazoacetone in the presence of rhodium binuclear complexes gives, besides 9-substituted bicyclo[6.1.0]nona-2,4,6-trienes (mixture ofanti- andsyn-isomers, total yields 60–75%), isomeric β-(cyclohepta-2,4,6-trien-1-yl)acrylates or 4-(cyclohepta-2,4,6-trien-1-yl)but-3-en-2-one in 20–34% yields. In the case of methyl diazoacetate, a mixture ofE- andZ-isomers in a ratio of −3.5∶1 was obtained, while diazoacetone gave onlyE-isomer. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2204–2206, November, 1999.