Partial Molar Volumes of Uracil,Thymine, Adenine in Water and of Adenine in Aqueous Solutions of Uracil and Thymine

The partial molar volumes of uracil, thymine and adenine in water and adenine in aqueous solutions of uracil and thymine, at fixed composition, were determined over a range of temperatures. The partial molar volumes of adenine in aqueous uracil and thymine are less than in pure water.     

Decomposition of benzenediazonium fluoborate in esters of α,β-unsaturated acids

Summary It was shown that In contrast to the Meerwein-Koelsch reaction, the decomposition of benzenediazonlum fluoborate In esters of ,-unsaturated acids proceeds by a heterolytlc mechanism with the phenyl attacking the -carbon and the carbalkoxyl group of these esters. The reaction with ethyl crotonate gave -methylatropic acid (after hydrolysis) and a small amount of a dibasic acid, C₁₄H₁₆O₄ (or C₁₄H₁₄O₄). With methyl acrylate it gave atropic acid, phenyl acrylate, and a smaller amount of -methyl--phenylglutaric acid. With methyl methacrylate It formed benzylacrylic acid and the product of further conversions of phenyl methacrylate, namely the keto phenol 2-methyl-5-hydroxyindan-1-one.     

Breaking of Symmetry of Solitons in the Ion-Radicals of α,ω-Disubstituted Polyenes

Quantum-chemical calculations in the AM1 approximation were made for the optimized geometry and also the electron and spin density distributions in the ion-radicals of ,-substituted polyenes [R—(CH=CH) _n —R]^±·. It was found that a soliton (of hole or electron type) with half-integral spin forms waves for the and components of the electron density, in contrast to the wave for the charges in the ions of polymethine dyes with a closed electron shell, containing a zero-spin soliton. The introduction of terminal groups of medium electron-donating power [—NH₂,—C(CN)₂] leads to the breaking of symmetry of the soliton at n2, whereas in unsubstituted polyenes the symmetrical geometry and symmetrical distribution of the electron and spin density are retained irrespective of the length of the conjugation chain.     

Congresses,Conferences, Symposia,Meetings, and Seminars in the Field of Chemical Sciences Held in 1995–1996

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Congresses, Conferences, Symposia, Meetings, and Seminars in the Field of Chemical Sciences Held in 1995–1996     

Congresses,Conferences, Symposia,Meetings, and Seminars in the Field of Chemical Sciences Held in 1995–1996

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Congresses, Conferences, Symposia, Meetings, and Seminars in the Field of Chemical Sciences Held in 1995–1996     

Quantitative analysis of geraniol,nerol, linalool,and α-terpineol in wine

A mixture of [(2)H(7)]-geraniol, [(2)H(7)]-nerol, [(2)H(7)]-linalool and [(2)H(7)]-alpha-terpineol was prepared for use as internal standards in a rapid and accurate analytical method, employing gas chromatography-mass spectrometry (GC/MS), to determine the concentration of geraniol, nerol, linalool and alpha-terpineol in wine. The method avoids the possible formation, degradation and interconversion of these compounds during their analysis.     

Congresses,Conferences, Symposia,Meetings, and Seminars in the field of chemical sciences held in 1995–1996

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Congresses, Conferences, Symposia, Meetings, and Seminars in the field of chemical sciences held in 1995–1996     

Congresses,conferences, symposia,meetings, and seminars in the field of chemical sciences held in 1995–1996

Information Congresses, Conferences, Symposia, Workshops, and Seminars in the Field of Chemical Sciences Held with Participation of the Russian Academy of Sciences

II International Symposium Chromatography and spectroscopy in analysis of environmental objects and toxicology     

Congresses,conferences, symposia,meetings, and seminars in the field of chemical sciences held in 1995–1996

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Congresses, conferences, symposia, meetings, and seminars in the field of chemical sciences held in 1995–1996     

Congresses,Conferences, Symposia,Meetings, and Seminars in the Field of Chemical Sciences held in 1995–1996

Information

Congresses, Conferences, Symposia, Meetings, and Seminars in the Field of Chemical Sciences held in 1995–1996     

Efficient Stereoselective Synthesis of C,O,S,N-Glycosides in High Yield

The Koenig-Knorr method is still the most useful method for the synthesis of glycosides thoughpartly inherent disadvantages of this method could not be overcome. Recently Schmidt et al. reportedthat glycosyl trichloroacetimidates can be used to synthesize C, O and S-glycosides stereoselectively inhigh yield under mild reaction conditions.     

Lignin-type, α,β-unsaturated aldehydes of lignin-type in organic solvents

A 1:1 reaction of [HO(CH₂)₃]₃P with 4-hydroxy-3-methoxy-cinnamaldehyde (coniferaldehyde) or 3,5-dimethoxy-4-hydroxycinnamaldehyde (sinapaldehyde) in acetone at room temperature affords phosphonium zwitterions of the type R₃P⁺CH(4-O^?-Ar)CH₂CHO; other phosphines [R = Et, n-Bu, (CH₂)₂CN, and p-Tol] do not react under the same conditions. In alcohols R??OH(D) [R?? = CD₃, Et, (CD₃)₂CD, s-Bu, HOCH₂CH₂], the above phosphines (except the cyano-derivative) and those where R = i-Pr, Cy, Me₂Ph, MePh₂ do react within an equilibrium established between the reactants and the zwitterion-hemiacetal products R₃P⁺CH(4-O^?-Ar)CH₂CH(OH)(OR??) that are formed as a mixture of two diastereomers. The nature of the phosphine and the alcohol affects the equilibrium and the diastereomeric ratio.     

Cleavage of hindered α-methylbenzylamides,intermediates in the resolution of carboxylic acids

α-Methylbenzylamides, useful intermediates in the resolution of carboxylic acids, are cleaved with a two step procedure; enolizable amides are not racemized.     

Selective reduction of α,β-unsaturated esters in the presence of olefins

Several α,β-unsaturated esters containing also isolated olefins or other functionalities subject to saturation were selectively reduced to the corresponding saturated esters by magnesium in methanol.     

The rate of intramolecular end-to-end photodimerisation of α,ω-dianthrylpolystyrene in solution

To study the effect of molecular weight on the rate of the intramacromolecular end-to-end reaction of a flexible polymer, the intramolecular photodimerisation of α,ω-dianthrylpolystyrene has been carried out by successive illumination with a 337 nm pulsed nitrogen laser of a dilute solution of butanone at 30°C. The extent of dimerisation against the number of pulses (measured fluorometrically) was converted, based on several assumptions, to the apparent diffusion-controlled rate constants for polymer cyclisation. The rate constants for polymer cyclisation decrease in proportion to DP^−0·3 for the range of DP = 110–2600. The implications of this result in the chain dynamics of polymers are briefly discussed.     

Application of Short Sequential Extraction Procedure（SSEP） for the Determination of Zn, Cu, and Cd Contents in Riverbed Sludge in Hejiagou, Harbin, China

IntroductionThe environment is contaminated by high concen-trations of metals from different sources such as conta-minated soils[1—10], sediments[11—15], and sewage orindustrial sludge[16—20]. However, there has been noreport on the determination of he…     

A peroxidase-based method for the determination of dopamine, adrenaline, and α-methyldopa in the presence of thyroid hormones in pharmaceutical forms

The analytical properties of two commercial plant peroxidases isolated from horseradish roots and soybean hulls in the catalysis of the transformation of some catecholamines were demonstrated in the absence and presence of thyroid hormones (l-thyroxine and 3,3′,5′-iodothyronine). For the first time the reactions of dopamine, adrenaline, and α-methyldopa oxidation with H₂O₂ catalysed by horseradish peroxidase with the addition of l-thyroxine as the amplification agent were studied and proposed as the indicator reactions for the simple and rapid enzymatic determination of the indicated catecholamines in their concentration ranges 0.5-300, 4-300, and 100-400 μM, respectively. The catalytic activity of the enzyme (characterized by the reaction rate) was controlled spectrophotometrically. The optimum conditions for the indicator reactions were thoroughly characterized. The mechanism of the stimulatory effect of l-thyroxine on the oxidation of the catecholamines was discussed. The developed enzymatic procedures were successfully applied for the determination of dopamine, adrenaline, and α-methyldopa in some pharmaceutical forms.     

Reaction of Lewisite-1 with Alcohols,Diols, and Thiols in Water—A Simple Method of Derivatization of Thiodiglycol

Reaction of 2-chlorovinyldichloroarsine (Lewisite-1) with alcohols, thiols, diols, and hydroxy thiols in water at 40°C has been examined. The expected derivatization products, dialkyl 2-chlorovinylarsonites or corresponding arsonodithiolites, were obtained with alcohols and thiols, whereas reactions with bifunctional diols and hydroxythiols produced analogous cyclic esters. All derivatives may be easily detected using gas chromatography. This reaction was found useful to easily transform bis(2-hydroxyethyl) sulfide (thiodiglycol), a sulfur mustard decomposition product, to a stable eight-membered cyclic arsonite derivative. After extraction with dichloromethane, the derivative may be easily and selectively detected using GC/MS at a 100 ppb level thiodiglycol content in water matrices, eliminating tedious evaporation of water and then silylation. This method may be applied to analyze Chemical Weapons Convention related environmental water samples.     

Ferrocenyl-substituted α,β-unsaturated ketones in synthesis of tetrahydropyrimidinones

Ferrocenyltetrahydropyrimidin-2-ones were prepared by reactions of linear and cyclic ,-unsaturated ketones of the ferrocene series with urea in i-PrOH in the presence of t-BuOK. The structures of the compounds prepared were studied by ¹H and ¹³C NMR and IR spectroscopy, and also by single crystal X-ray diffraction.Translated from Zhurnal Obshchei Khimii, Vol. 74, No. 11, 2004, pp. 1887–1893.Original Russian Text Copyright © 2004 by E. Klimova, Lorez, T. Klimova, Garcia, Hernandez, Ramirez.This revised version was published online in April 2005 with a corrected cover date.