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981.
U. D. N. Bajpai 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(3):629-636
A combined system of potassium permanganate and pyruvic acid was found to initiate radical polymerization of vinyl monomers, especially acrylamides. From kinetic investigations of the polymerization of methacrylamide, it was found that this initiator induced a radical polymerization which proceeded with an overall activation energy of 15.7 kcal/mol. The rate is given by Rp=K[methacrylamide] 1 [pyruvic acid]° [KMnO4]1 in aqueous and water-DMF mediums. In the presence of DMF the initial rate was found to decrease but the kinetic equation remained the same. The investigations were done at 35 ± 0.2°C in nitrogen. Besides the clinical importance of pyruvic acid found in blood, urine, muscles, etc., it is a good initiator in conjunction with KMnO4 for vinyl polymerization. It is therefore interesting to study the polymerization of methacrylamide using the KMnO4-pyruvic acid redox couple in aqueous systems in order to find whether this system follows the same kinetic features of vinyl polymerization by a radical mechanism. 相似文献
982.
A short and efficient enantioselective synthesis of natural product (S)-3-hydroxypiperidine has been achieved starting from commercially available raw materials employing two catalytic routes: (i) cocatalyzed hydrolytic kinetic resolution (HKR) of racemic methyl-3-(oxiran-2-yl)propanoate; (ii) proline-catalyzed α-aminooxylation followed by Horner–Wardsworth–Emmons olefination in high enantiomeric purity (97% ee) and high overall yield (38%). 相似文献
983.
A probable biogenetic type synthesis of coumestans by coupling in-situ generated o-quinones by mushroom tyrosinase oxidation of catechol and 4-hydroxy coumarins is reported. 相似文献
984.
A simple reversed-phase high-performance liquid chromatographic method employing C-18 column has been developed for simultaneous analysis of three intermediates in the synthesis of S-duloxetine, the antidepressant drug, viz., 2-acetyl thiophene (AT), N,N-dimethyl-3-keto-(2-thienyl)-propanamine (DKTP) and (S)-N,N-dimethyl-3-hydroxy-(2-thienyl)-propanamine (DHTP). Good separations were achieved by employing an isocratic system using acetonitrile and 0.05 M phosphate buffer (pH 7.0) containing 0.02% diethylamine. The detection was carried out at 241 nm. The method was validated for linearity, range, accuracy and precision. The developed method was applied for monitoring the progress of chemical synthesis of DKTP from AT followed by the biocatalytic reduction of DKTP to DHTP as the disappearance of the substrate and formation of the product can be monitored simultaneously by the present method. 相似文献
985.
986.
Static and dynamic scattering properties of polymer blends and block copolymers are examined within the random phase approximation (RPA). A self-consistent theoretical scheme for a simultaneous analysis of elastic and quasielastic scattering data is presented. The case of a triblock copolymer made of an ordinary central block and two deuterated lateral blocks in a matrix of deuterated homopolymers is considered in detail. The theoretical predictions of the RPA are compared with the experimental data obtained by elastic neutron scattering experiments using mixtures of deuterated poly(dimethylsiloxane) homopolymers and copolymers made of three blocks of approximately equal sizes. The lateral blocks are deuterated poly(dimethylsiloxane) and the central one is an ordinary poly(dimethylsiloxane). A good agreement is found in the whole range of wavevectors covered by the experiments. An extension of the RPA to the analysis of the dynamical scattering data for the same systems is put forward. It is shown how the time relaxations of the bare response functions obtained from the single chain dynamics are used to extract the intermediate scattering function characterizing the system of interacting chains. © 1996 John Wiley & Sons, Inc. 相似文献
987.
Preparation and Molecular Structures of Oligofunctional Dirhenium Carbonyl Derivatives from Dirhenium Nonacarbonylphosphane Starting with dirheniumdecacarbonyl, one CO-Ligand was eliminated oxidatively and substituted by the labile acetonitrile ligand. As an intermediate eq-Re2(CO)9NCCH3 was received. The reaction of this labilised carbonyl with tris(trimethylsilyl)phosphine and subsequent methanolysis gave ax-Re2(CO)9PH3, which was isolated and characterized for the first time. Photochemical and thermal reaction of ax-Re2(CO)9PH3 led to the new bi- and trinuclear complexes Re2(μ-H)(μ3-PHRe(CO)5)(CO)8, Re2(μ-PH2)2(CO)8 and Re2(μ-H) · (μ-PH2)(CO)8, which were characterized by IR-, 1H- and 31P-NMR spectroscopy. The structures of ax-Re2(CO)9PH3, Re2(μ-H)(μ3-PHRe(CO)5)(CO)8 and Re2(μ-PH2)2(CO)8 were confirmed by single-crystal X-ray analysis. ax-Re2(CO)9PH3 has a very short Re? P bond length of 228(2) pm. 相似文献
988.
The title compound ist the first example of an adduct between telluric acid and the twenty four membered ring anion of a cyclododecaphosphate. [C(NH2)3]12P12O36 · 12 Te(OH)6 · 24 H2O crystallizes trigonal (rhomboedral: R3) with Z = 3 and the unit-cell dimensions a = 15.854(9), c = 51.26(2) Å in the hexagonal setting. The crystal structure was solved by direct methods and refined to a final R value of 0.031. It is characterized by a succession of three different typs of alternating layers perpendicular to the c direction. This layers are connected only by hydrogen bonds. The individual layers are built up of A: P12O36 anions, guanidinium cations and water of crystallisation, B: hexagonal arranged Te(OH)6 groups and guanidinium cations and C: water of crystallization. 相似文献
989.
990.
U. M. Dzhemilev V. A. D’yakonov L. O. Khafizova A. G. Ibragimov 《Russian Journal of Organic Chemistry》2005,41(3):352-357
Cyclomagnesation of terminal and cyclic olefins and 1,2-dienes with RMgHlg and R2Mg in the presence of dichloro(dicyclopentadienyl)titanium(IV) gives non-Grignard cyclic and acyclic organomagnesium compounds. The reaction direction depends on the structure of unsaturated initial compound. The most probable reaction mechanism is discussed.__________Translated from Zhurnal Organicheskoi Khimii, Vol. 41, No. 3, 2005, pp. 363–368.Original Russian Text Copyright © 2005 by Dzhemilev, D’yakonov, Khafizova, Ibragimov. 相似文献