Luminescence Quenching between Ce and Eu in LAB3O6

The Ce³⁺ and Eu³⁺ ions in LaB₃O₆ quench each other's luminescence. However, Ce³⁺ quenches Eu³⁺ more effectively than Eu³⁺ quenches Ce³⁺. The critical distances for this quenching are about 15 and 6 Å respectively.     

Common and Specific Features of the Michael Condensation in the Series of 3-R-3H-Furan-2-ones

The Michael condensation in the series of 5-aryl-3H-furan-2-ones with chalcones containing electron-donating substituents was studied. In the case of ,-unsaturated ketones containing an electrondonating substituent, the reaction does not stop at the stage of formation of 1,5-dicarbonyl compounds but is accompanied by intramolecular cyclodehydration yielding a new series of furo[2,3-b]-4H-pyrans. A mechanism of formation of these products was suggested. The structure of reaction products was proved by IR and ¹H NMR spectroscopy.     

Synthesis ofO-methyloximes and nitrones of a series of substituted 4-[2-hydroxy-2-(1H-1,2,4-triazol-1-ylmethyl)cyclohexylidenemethyl]-benzaldehydes and their fungicidal activity

O-Methyloximes and nitrones of a series of substituted 4-[2-hydroxy-2-(1H-1,2,4-triazol-1-ylmethyl)cyclohexylidenemethyl]benzaldehydes have been synthesized, and their fungicidal activity has been assayed. All of them exhibit low fungicidal activity in thein vitro assays and high activity in thein vivo assays; theO-methyl oximes are more active than the corresponding nitrones.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2082–2087, December, 1993.     

Esters of 4,5-dihydro-1H-imidazole-1-oxyl-3-oxide-carboximidic acid

Esters of 4,5-dihydro-1H-imidazole-1-oxyl-3-oxide-carboximidic acid were synthesized. Their structures and magnetic properties were investigated.     

Lipophilic extracts in phytotherapy and phytocosmetics: Production and biological properties

This review considers methods of obtaining lipophilic extracts from plant raw material, and their composition, biological properties, and use in phytotherapy and phytocosmetics.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Republic of Uzbekistan, Tashkent, fax (371) 240 64 75. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 437–448, July–August, 1998.     

Reaction of 2,5-diphenyl-1,2,3-diazaarsole with 2-diazopropane

Conclusions The reaction of 2-diazopropane with 2,5-diphenyl-1,2,3-diazaarsole (I) gave 2,4-di-phenyl-6,6-dimethyl-1-arsa-2,3-diazabicyclo[3.1.0]hex-3-ene (III).Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 1, pp. 230–231, January, 1986.The authors thank R. M. Mukhamadeeva and P. N. Sobolev for taking the spectra.     

Chemiluminescence flow system for the determination of ammonium ion

A novel chemiluminescence (CL) system for ammonium ion combined with flow-injection analysis is presented in this paper. It is based on the CL reaction between luminol, immobilized electrostatically on an anion-exchange column, and chlorine electrochemically generated on-line via a platinum electrode from hydrochloric acid in a coulometric cell. Ammonium ion reacts with chlorine and decreases the observed CL intensity. The system responds linearly to ammonium ion concentration in the range 1.0-100 muM, and the detection limit is 0.4 muM. A complete analysis, including sampling and washing, could be performed in 1 min with a relative standard deviation of <6.0%. The system is stable for over 500 determinations and has been applied successfully to the determination of ammonium ion in rainwater samples.     

ESR.-Spektrum von Diphenylpicrylhydrazyl (DPPH)

The ESR. sprectra of DPPH in mixed organic solvents have been measured with a K-band superheterodyne spectrometer and self-locking magnetometer with high precision. Approximately 150 lines have been resolved in the spectra. Both the zero and first order derivative spectra were analyzed by a line shape analysis program for determination of the coupling constants. The smallest coupling constant was found to be 377 ± 5 mG, all other coupling parameter are multiples of this constant. A set of most probable coupling constants is given. The two nitrogen coupling constants are found to be equal within experimental error, and there exist several rotational relations and several possible assignments.