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921.
Ludovica Verzegnassi Catherine Riffé-Chalard Werner Kloeti F. O. Gülaçar 《Analytical and bioanalytical chemistry》1999,364(3):249-253
A new application is described of the on-line high-performance liquid chromatography/positive and negative ion atmospheric
pressure chemical ionization mass spectrometry (APCI(+/–)-MS) to the identification of tetrapyrrolic compounds in sediment
samples containing complex mixtures of natural pigments and their diagenetic products. The method relies on the production
of radical anions in order to determine the molecular masses of the molecules which yield abundant fragment ions when analyzed
in the positive mode. This approach allows to verify the occurrence of coeluting components by examining their negative ion
spectra and to complete their identification on the basis of their fragment ions produced in the positive ion spectra.
Received: 24 September 1998 / Revised: 23 December 1998 / Accepted: 29 December 1998 相似文献
922.
Ya. L. Garazd M. M. Garazd A. Aitmambetov V. P. Khilya 《Chemistry of Natural Compounds》1999,35(3):301-304
A number of 7-O-aminoacyl derivatives of isoflavones have been obtained by the interaction of 2-R-7-hydroxy-3,4-ethylenedioxyisoflavones with the symmetrical anhydrides of N-protected amino acids.Kiev Tara Shevshenko University, Ukraine, 252033, Kiev, Ul. Vladimirskaya, 64, tel./fax 225-12-73. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 334–338, May–June, 1999. 相似文献
923.
924.
A. I. Kryukov S. Ya. Kuchmii A. V. Korzhak 《Theoretical and Experimental Chemistry》1996,32(5):258-261
A study was made of reactions forming chlorohydrins from cyclohexane and other olefins acted upon by H2O2 and HCl or H2O2 and TiCl4 in alcoholic solutions. The catalyzing action of titanium (1V) was established, and possible reaction mechanisms are discussed.L. V. Pisarzhevskii Institute of Physical Chemistry, National Academy of Sciences of Ukraine, 31 Prosp. Nauki, 252039, Kiev, Ukraine. Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 32, No. 5, pp. 295—299, September–October, 1996. Original article submitted February 9, 1996. 相似文献
925.
A. I. Yanovsky N. Ya. Turova A. V. Korolev D. E. Chebukov A. P. Pisarevsky Yu. T. Struchkova 《Russian Chemical Bulletin》1996,45(1):115-121
Anodic oxidation of tantalum in isopropyl alcohol or prolonged reflux of an alcohol solution of Ta(OPri)5 afford crystalline oxoisopropoxide Ta2O(OPri)8 · PriOH (1). In its molecule, two octahedra about Ta atoms are linkedvia the shared edge [(OPri)O]. Compound1 is the first example of oxoalkoxide containing such a small number of metal atoms. Unlike the known polynuclear molecules M
n
O
m
(OR)
p
, oxoalkoxide1 is stable in solutions; on transition to the gas phase, this compound is desolvated to form a very stable molecule Ta2O(OPri)8 (apparently, consisting of two octahedra with a shared edge). According to the data of mass spectrometry, analogous molecules exist in the gas phase over Ta(OAlk)5 (Alk = Me, Et, Pri, or Bu11). When compound1 is heated invacuo (10–2–10–3 Torr), Ta(OPri)5 is sublimated. Crystals of Ta7O9(OPri)17 (2) were formed upon prolonged storage of solutions of1 in PriOH. Heptanuclear molecule2 consists of two [Ta4] tetrahedra with a shared vertex. These tetrahedra are additionally linked togethervia one 3-oxo and two 2-OPri groups. Complex2 is a representative of heptameric oxoalkoxides of a new structural type.Deceased in I995.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 125–131, January, 1996. 相似文献
926.
Ya. L. Kogan L. S. Fokeeva L. G. Shunina E. I. Knerel'man 《Russian Chemical Bulletin》1996,45(6):1380-1382
It has been found that thin polyaniline films doped with several zinc salts in solutions at pH 5.5 become electroconductive and electroactive in neutral aqueous electrolytes. The shape of the voltammetric characteristics depends on the initial state of the film. The effect of secondary doping withm-cresol is observed for polyaniline complexes with zinc salt of camphorsulfonic acid.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1450–1452, June, 1996. 相似文献
927.
V. P. Perevalov M. A. Andreeva L. I. Baryshnenkova V. Ya. Gurvich B. I. Stepanov 《Chemistry of Heterocyclic Compounds》1990,26(2):204-208
2-Methyl-2,4,12,13H-pyrazolo[3,4-5,6]pyrimido[1,2-b]benzo[d,e]isoquinoline-4,12-dione and its 8-nitro- and 8-amino-substituted derivatives were obtained starting from 4-amino-3-carbamoyl-1-methylpyrazole and naphthalic and 4-nitronaphthalic anhydrides. The spectral properties of the synthesized compounds were studied.See [1] for Communication 8.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 237–241, February, 1990. 相似文献
928.
G. Ya. Popova T. V. Andrushkevich G. A. Zenkovets L. M. Plyasova N. V. Grebenyuk 《Reaction Kinetics and Catalysis Letters》1990,41(1):21-25
Catalytic properties of V-Sb-O systems in acrolein oxidation have been studied. It has been established that the changes in the activity and selectivity of the catalysts are due to the phase and chemical properties of the system.
-- . , .相似文献
929.
G. G. Verba M. Asanova N. Ya. Plugar' A. A. Abduvakhabov B. Sh. Khakimdzhanov U. N. Musaev 《Chemistry of Natural Compounds》1990,26(2):205-207
A method is proposed for the oxidation of hexadec-11Z-en-1-ol to hexadec-11Z-enal by Cr(VI) reagents on polymeric supports.A. S. Sadykov Institute of Bioorganic Chemistry, Uzbek Academy of Sciences, Tashkent. V. I. Lenin Tashkent State University. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 252–255, March–April, 1990. 相似文献
930.
A. G. Seleznev V. M. Radchenko V. D. Shushakov M. A. Ryabinin R. R. Droznik L. S. Lebedeva V. Ya. Vasilyev 《Journal of Radioanalytical and Nuclear Chemistry》1990,143(1):253-259
248Cm and249Bk metals were prepared by thermal reduction of their oxides with thorium and metallic249Cf with metallic lanthanum. These rare actinide samples of 1.0 mg in mass were thin layers on a flat substrate and were investigated by X-ray technique. Dhcp lattice parameters of -Cm, -Bk and -Cf as main phases in X-ray diagrams are presented. The effect of impurities on the -Cm lattice parameters is shown. Fcc lattices for the high temperature form of Cm metal (-Cm) with a=0.4933 nm, and of Cm and Bk monoxides (a=0.502–0.504 nm and a=0.5002 nm, respectively) have been observed. Thermal expansion coefficients for -Cm and -Bk at 80–300 K were calculated. Identification problems of fcc lattices and oxidation features of metals prepared are discussed. 相似文献