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1.
A. F. Fucaloro K. Dewey G. Fan K. Imuta D. Jensen M. Muranaka 《Journal of solution chemistry》2008,37(9):1289-1304
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. 相似文献
2.
Kachkovskii A. D. Yushchenko D. A. Kachkovskii G. A. 《Theoretical and Experimental Chemistry》2002,38(6):351-356
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. 相似文献
3.
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. 相似文献
4.
《有机化学》1993,(2)
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. 相似文献
5.
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 相似文献6.
Information
Congresses, Conferences, Symposia, Meetings, and Seminars in the field of chemical sciences held in 1995–1996 相似文献7.
Information
Congresses, Conferences, Symposia, Meetings, and Seminars in the Field of Chemical Sciences Held in 1995–1996 相似文献8.
Information
Congresses, Conferences, Symposia, Meetings, and Seminars in the Field of Chemical Sciences Held in 1995–1996 相似文献9.
10.
Pedersen DS Capone DL Skouroumounis GK Pollnitz AP Sefton MA 《Analytical and bioanalytical chemistry》2003,375(4):517-522
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. 相似文献
11.
Information
Congresses, Conferences, Symposia, Meetings, and Seminars in the Field of Chemical Sciences held in 1995–1996 相似文献12.
Information
Congresses, conferences, symposia, meetings, and seminars in the field of chemical sciences held in 1995–1996 相似文献13.
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. 相似文献
14.
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. 相似文献
15.
The phthalate esters such as MDP,DEP,BDP and DEHP in air,soil and plant smples in plastic film greenhouse were clean up with fine silica gel column and determined with HPLC.It was found that the concentrations of PEs in ari and soil samples in plastic film greenhouse are much higher than those of contrast samples. But concentration of PEs in plants in plastic film greenhouse are not remarkably affected by the pollution of air and soil. 相似文献
16.
LI Yu WANG Zhe ZHAO Wen-Jin 《高等学校化学研究》2006,22(6):696-702
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… 相似文献
17.
Nikulin S. S. Poyarkova T. N. Misin V. M. Karmanova O. V. 《Russian Journal of Applied Chemistry》2010,83(1):127-133
The effect of additions of an organic cationic electrolyte, N,N-dimethyl-N,N-diallylammonium chloride, on the threshold of rapid coagulation, duration of the first coagulation step, and values of the
1-min and maximal turbidity was examined. The coagulating performance of additives in recovery of rubber from SKS-30 ARK butadiene—styrene
latex was studied in relation to the concentrations of the dispersed phase and sulfuric acid and to temperature. 相似文献
18.
R. O. Molina-Vázquez M. Jimenéz-Reyes Y. Lira-López D. Tenorio 《Journal of Radioanalytical and Nuclear Chemistry》2013,295(2):915-922
Five archaeological sites have been selected for a study of the precedence of obsidian from the Valley of Maltrata, Veracruz, Mexico: Teteles de la Ermita and Barriales de las Besanas (pre-Classic, 1,500 B.P. 100 A.P.), Rincón de Aquila (pre-Classic and Classic, 1,500 B.P.–650 A.P.), Tepeyacatitla (Classic, 100–650 A.P. and Rincón Brujo (post-Classic 900/1,000–1,521 A.P.). For this investigation, 51 artifacts were analyzed by neutron activation analysis. The statistic analysis of the chemical compositions allowed us to identify the places of origin of the obsidian sources: Sierra de Pachuca, Pico de Orizaba, Zaragoza-Oyameles, Otumba and Paredón. Based on these results it can be affirmed that the settlements of the valley of Maltrata actively participated in the interregional trade routes of obsidian from the pre-Classic period to the post-Classic period, and maintained relations with the Olmec, Teotihuacan, Cantona and Mexica cultures, among others. 相似文献
19.
E. I. Klimova E. A. Vazquez Lopez T. Klimova M. Martinez Garcia Ortega S. Hernandez L. Ruiz Ramirez 《Russian Journal of General Chemistry》2004,74(11):1757-1762
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. 相似文献
20.
Mieczysław S. Sokołowski Leszek Konopski 《Phosphorus, sulfur, and silicon and the related elements》2013,188(10):2311-2327
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. 相似文献