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981.
The kinetics of spontaneous hydrolysis of monoalkylsubstituted ketenes has been studied. The influence of inductive and steric effects of substituents upon the rate has been quantitatively estimated in terms of -analysis. Increasing length and branching of alkyl substiuents decrease the rate of ketene hydrolysis. 相似文献
982.
Isobutane and methane chemical ionization (CI) mass spectra of C-17a-epimeric, 17a-substituted 3-methoxyestra-1,3,5(10),8-tetraen-17a-ols and at C-17-epimeric 17-substituted 3-methoxyestra-1,3,5(10)-trien-17-ols, as well as of some their derivatives, have been studied. In each epimeric pair, the peak intensity ratio [MH-H(2)O](+) / [MH](+) is greater for stereoisomers having an axial (or quasi-axial) hydroxyl group. The same regularity in the peak intensity ratio [MH-CH(3)COOH](+) / [MH](+) is valid for acetates in the D-homo series. The observed quantitative differences in CI mass spectra of epimers are explained by steric hindrance of the attack of the proton-donating cation caused by the angular 18-methyl group. No differences in the ease of elimination of the silanol molecule were observed in CI mass spectra of epimeric silyl ethers. 相似文献
983.
Horváth-Szabó G Czarnecki J Masliyah JH 《Journal of colloid and interface science》2002,253(2):427-434
Equilibrium liquid crystal (LC) layer on an interface between crude oils and water was observed at high pH. This layer is composed mainly of sodium naphthenates produced in situ at the water/oil interface. Transient LC layer was also evolved at the interface of aqueous phase of sodium hydroxide solutions and oleic phase of naphthenic acid (NA) solutions as result of a chemical reaction between NaOH and NA. This chemical reaction causes transport process resulting in a disturbance of the interface. Optical observation of this interface disturbance reviled that the interface covered with LC shows considerably lower flexibility as compared to LC free interface. The LC layer eventually dissolves in the water phase at low oil-to-water ratio, while at high oil-to-water ratio it can form an equilibrium phase, which spreads spontaneously at the oil-water interface. 相似文献
984.
Socher G Nussbaum R Rissler K Lankmayr E 《Fresenius' Journal of Analytical Chemistry》2001,371(3):369-375
Unknown fatty acid ethoxylate samples have been transesterified in supercritical methanol, using a loop made of a stainless-steel tubing as the reactor vessel. The initiator acids, now present as the corresponding methyl esters, were determined by gas chromatography-mass spectrometry (GC-MS). Quantitative transesterification is achieved by heating a solution of the ethoxylate sample in methanol at 280 degrees C for 10 min under pressure. The influence of reaction time, temperature, and presence of a Lewis acid catalyst has been investigated. The method of transesterification was optimized in respect of low cost, short reaction time, and availability to laboratories with standard analytical equipment. 相似文献
985.
S. V. Larionov L. I. Myachina L. A. Sheludyakova E. G. Boguslasvskii A. V. Tkachev S. N. Bizyaev 《Russian Journal of Coordination Chemistry》2004,30(12):846-849
Copper(II) compounds with the optically active diaminodioxime (H2L) derived from the monoterpenoid (+)-3-carene, Cu(H2L)(NO3)2 H2O (I), Cu(H2L)(ClO4)2 H2O (II), Cu(H2L)Br2 H2O (III), and Cu(H2L)SO40.5H2O (IV) with µeff equal to 1.81, 1.79, 1.71, and 1.8 µB, respectively, were prepared. Studies of the complexes by IR and EPR spectroscopy showed that I and II are mononuclear ionic complexes. Compound III apparently has polymeric structure (the CuN4Br2 coordination unit). According to EPR data, the Cu2+ ions in polycrystalline compounds III and IV undergo exchange interactions.Translated from Koordinatsionnaya Khimiya, Vol. 30, No. 12, 2004, pp. 897–900.Original Russian Text Copyright © 2004 by Larionov, Myachina, Sheludyakova, Boguslavskii, Tkachev, Bizyaev. 相似文献
986.
The inclusion of dulcin in alpha- and beta-cyclodextrin has been studied by fluorescence spectroscopy. To quantitatively describe complex formation between the beta-cyclodextrin and dulcin, an association constant of 290 M(-1) at 21 degrees was obtained. The thermodynamics associated with the complex formation between dulcin and beta-cyclodextrin in aqueous solution has been studied. The obtained value of DeltaG(0) = -13.7 kJ/mole at 21 degrees , together with DeltaH(0) = -33.6 +/- 2.3 kJ/mole and DeltaS(0) = -67.2 +/-8.3 Jmole(-1) K(-1) indicate that dulcin has a very marked tendency to associate with beta-cyclodextrin in water. The inclusion complex of dulcin in beta-cyclodextrin has been used to determine dulein in the range 0.13-5 mug/ml the method has been applied to determine dulcin in soft drinks. 相似文献
987.
Investigations on Lithiation and Substitution of HP[Si(t-Bu)2]2PH HP[Si(t-Bu)2]2PH 1 is monolithiated by reaction with LiPH2 · DME or LiBu in toluene. The crystalline compound HP[Si(t-Bu)2]2PLi · 2 DME 2 can be isolated in DME. Reaction of 2 with Me2SiCl2 leads to HP[Si(t-Bu)2]2P? SiMe2Cl 4 , ClMe2Si? P[Si(t-Bu)2]2P? SiMe2Cl 5 , HP[Si(t-Bu)2]2P? SiMe2? P[Si(t-Bu)2] 2PH 6 . Isomerization by Li/H migration between 4 and 2 leads to the formation of 5 . Reaction of Li(t-Bu) with 1 or 2 yields LiP[Si(t-Bu)2]2PLi 3 by further lithiation. 3 could not be obtained purely, only in a mixture with 2 . These compounds favourably generate with t-BuPCl2 in hexane Cl(t-Bu)P? P[Si(t-Bu)2]2P? P(t-Bu)Cl 9 , in THF HP[Si(t-Bu)2]2P? P(t-Bu)? P[Si(t-Bu)2]2 PH 12 (main product), 9 , H(t-Bu)P? P[Si(t-Bu)2]2P? P(t-Bu)Cl 10 , H(t-Bu)P? P[Si(t-Bu)2]2P? P(t-Bu)H 11 as well as HP[Si(t-Bu)2]2P? P(t-Bu)H 13 and HP[Si(t-Bu)2]2P? P(t-Bu)2 14 . 相似文献
988.
G. D. Krapivin P. A. Pavlov V. G. Kul'nevich 《Chemistry of Heterocyclic Compounds》1987,23(3):340-345
Compounds were synthesized by reaction of 5-R-2-cyanofurans with thioglycolic acid, which, according to IR, PMR, and mass spectrometric data, exist in the form of two tautomers, 4-hydroxythiazole and thiazolin-4-one.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 404–409, March, 1987. 相似文献
989.
M. O. Manukyan A. V. Babakhanyan G. A. Panosyan A. Kh. Gyul’nazaryan S. T. Kocharyan 《Russian Journal of General Chemistry》2007,77(8):1370-1372
Ammonium salts containing phenacyl group in combination with 4-allyloxy(phehoxy)-2-butynyl group, when treated with a suspension of potassium hydroxide in benzene, undergo the 3,2-Stevens rearrangement with the formation of allenic amino ketones which under the reaction conditions give the furan derivatives. 相似文献
990.
G. I. Sarapulova G. K. Balakhchi L. L. Dmitrieva N. A. Nedolya 《Russian Journal of Organic Chemistry》2001,37(12):1714-1718
A prototropic rearrangement of N-prop-2-enylbenzocarbothioamide afforded two stereoisomeric N-prop-1-enylbenzocarbothioamides (IIa, b) isolated as individual compounds. The stereoisomerism is due to hindered rotation around thioamide bond C(S)-N and also to -diastereoisomerism. The configuration of the isolated isomers was investigated by IR spectroscopy, AM1 and PM3 methods. In the molecules occurs the p,-conjugation with participation of nitrogen atom and multiple bonds resulting in formation of a united delocalized MO in the planar fragment C(S)-NC = C. 相似文献