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991.
Bismuth (0–110 μg) is determined spectrophotometrically at 495 nm after its adsorptive extraction from dilute sulphuric acid as hexadecyltributylphosphonium tetraiodobismuthate(III) on microcystalline benzophenone and dissolution of the solid phase in carbon tetrachloride. The effects of acidity, diverse ions and masking studies are reported. The system is applied to the determination of bismuth in pharmaceutical samples. 相似文献
992.
The CNDO/2 method was used to investigate the conformation and structure of alkylsubstituted allophanates. The possibility of the existence of isomers both with coplanar and with noncoplanar main chains NCNC was studied. It was shown that the formation of conformers with a cis-structure of the ester group is more probable. On the basis of an analysis of the dependence of the reactivity on the structure of the main chain, hypotheses were advanced on the role of the more stable conformers in various channels of polyaddition of isocyanates.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 22, No. 3, pp. 360–363, May–June, 1986. 相似文献
993.
T. V. Moskovkina V. I. Vysotskii M. N. Tilichenko 《Chemistry of Heterocyclic Compounds》1985,21(2):142-147
2-(2-Oxo-3-hydroxy-1,3-diphenylpropyl)cyclohexanone, 2-(2,3-dioxo-1,3-diphenylpropyl)cyclohexanone, and 2-benzyl-7a-hydroxy-3-phenylperhydrobenzofuran are formed by the action of monoperphthalic acid on 8a-methoxy-2,4-diphenyl-4a,5,6,7,8,8a-hexahydrochromene. Under analogous conditions, 4a-methoxy-10-phenyl-1,2,3,4, 4a,6,7,8,9,10a-decahydroxanthene forms 7a-hydroxy-3-phenyloctahydrobenzo[b]furan-2-spiro-1-cyclohexan-2-one and its dehydration product. The behavior of the compounds obtained toward acetic anhydride and a methanolic solution of HCl was studied. The configurations of the reaction products and the reaction path are considered.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 177–181, February, 1985. 相似文献
994.
N. N. Papadopoulos N. M. Spyrou N. F. Tsagas G. E. Hatzakis 《Journal of Radioanalytical and Nuclear Chemistry》1995,192(1):55-64
A novel technique has been developed to increase the sensitivity, precision and accuracy of short-lived nuclide activation analysis and especially of delayed fission neutron counting, by improving the counting statistics. This has been achieved by approaching the irradiated sample to the detector during the counting period in order to compensate for the rapid radioactive decay by variation of the counting efficiency, permitting prolongation of the counting period with constant count rate. The sample holder movement with approximately exponentially decreasing velocity is implemented by a variable DC motor with a rotary to linear movement converter, which is being replaced by a more reliable stepping motor. 相似文献
995.
A. S. Mengliev U. N. Zainutdinov N. N. Stepanichenko S. A. Auelbekov Kh. A. Aslanov 《Chemistry of Natural Compounds》1995,31(1):68-69
The tetrahydric alcohol Lgochilin belongs to the 9,13-epoxylabdane series of diterpenoids. It is produced by many species of plants of the Lagochilus genus and can be used as the starting material for the synthesis of new compounds with a broad spectrum of physiological action [1, 2]. Many lagochilin derivatives possess hemostatic (3, 4) and antiviral properties. Lagochilin derivatives with aromatic hydroxaldehydes and naphthaldehydes have been synthesized, and the cytotoxic effects of the compounds synthesized in cell cultures have been studied.Tashkent State University, (fax (3712) 46 24. 42. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 86–88, January–February, 1995. Original article submitted October 17, 1994. 相似文献
996.
N. A. Turovskii S. Yu. Tselinskii I. A. Opeida Yu. E. Shapiro 《Theoretical and Experimental Chemistry》1993,28(4):254-257
A kinetic study has been made of the interaction of benzoyl peroxide with a number of chloride salts of amines. It is shown that a change of the cation in quaternary ammonium salts does not have any significant effect on the kinetic parameters of the reaction. By means of NMR spectroscopy it has been determined that the structure of the NR4
+ cation does not change during the course of the reaction. The role of the cation in the process of activation of a diacyl peroxide by chloride salts of amines has been investigated by means of MNDO calculations.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 28, No. 4, pp. 324–328, July–August, 1992. 相似文献
997.
Summary The enzyme L-asparaginase fromE. coli has been included in polyacrylamide gel, and some of its properties have been investigated: stability, pH dependence, heat stability, Km. It has been shown that the enzymegel obtained has a better stability then the native enzyme.Institute of Organic Synthesis, Academy of Sciences of the Latvian SSR, Riga. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 382–384, May–June, 1976. 相似文献
998.
A.B. Antonova N.E. Kolobova P.V. Petrovsky B.V. Lokshin N.S. Obezyuk 《Journal of organometallic chemistry》1977,137(1):55-67
A rearrangement of transition metal acetylenic π-complexes into compounds with vinylidene n-ligands has been established. Compounds CpMn(CCHPh)-(CO)2 and Cp2Mn2(μ-CCHPh)(CO)4 with terminal and bridging phenylvinylidene (benzylidenecarbene) ligands respectively were obtained from the π-complexes CpMn(CO)2(PhCCR) where R H, Ph3Ge or Ph3Sn. Reactions leading to conversion of the terminal CCHPh group into a bridging ligand and vice versa were studied. Under the action of L Ph3P, (EtO)3P or (PhO)3P, substitution of CO groups in vinylidene complexes takes place and compounds CpMn(CCHPh)-(CO)L are formed. IR, 1H and 13C NMR spectra of the novel complexes are discussed. The data obtained indicate an electron-withdrawing property of the CCHPh ligand and stronger bonding of this ligand to the metal as compared with a CO group. 相似文献
999.
B. N. Achar G. M. Fohlen J. A. Parker 《Journal of polymer science. Part A, Polymer chemistry》1983,21(2):589-597
The thermal reactions of pure metal(11) 4,4′,4″,4′″-phthalocyanine-tetracarboxylic acids of copper, cobalt, and nickel at 350–400°C in vacuum have been studied using Fourier transform infrared spectrometry, gas chromatography, and mass spectrometry. Based on these observations, novel in situ reactions for the synthesis of heat-resistant phthalocyanine “sheet” polymers are described. The poly(metal phthalocyanine) polymers of copper, cobalt, and nickel so synthesized have been characterized by elemental analysis, infrared spectroscopy, and dynamic thermogravimetric analysis. The most noteworthy property of these polymers is their extreme resistance to heat in an anaerobic atmosphere and their high char yields (89–93%) at 800°C in a nitrogen atmosphere. 相似文献
1000.
Summary 1. Paper chromatography has shown that the fruit ofC. dubium contains not less than eight substances of coumarinic nature; six of these (A, B, C, D, E, and H) have been isolated in the crystalline state.2. Substances B, D, and E are identical with isoimperatorin, imperatorin, and oxypeucedanin, respectively. Some properties of substance H have been determined. Prangenin [F] has been detected in the fruit ofC. dubium by paper chromatography.3. The structure of two new compounds has been established: substance A (cnidicin) (I) is 5, 8-di-(, -dimethylallyloxy) psoralen, and substance C (cnidilin) (II) is 5-(, -dimethylallyloxy)-8-methoxypsoralen.Khimiya Prirodnykh Soedinenii, Vol. 2, No. 6, pp. 375–380, 1966 相似文献