Photophysical properties of poly-2-phenyl-5-(p-vinyl)-phenyloxazole

2-Phenyl-5-(p-vinyl)phenyloxazole (POS) has been synthesized. Copolymers of POS with styrene and the homopolymer poly–POS have been prepared. The polymers have been characterized through measurements of fluorescence decay times (using synchrotron radiation for excitation) and examination of excimer formation in the homopolymer. Fluorescence decay times of 0.6(±0.4) nsec and 9 (±0.2) nsec have been recorded at 298°K in toluene solution for monomer and excimer, respectively. Poly-POS exhibits excimer formation characterized by an activation energy of 5.9(±0.5) kJ/mole and a binding energy of 17.0(±1.0) kJ/mole.     

Phosphorylthioacetamides in the synthesis of annulated quinoxalines

Diethoxyphosphorylthioacetamide in the reaction with 2,3-dichloroquinoxaline acted as a thionating reagent, giving diethoxyphosphorylacetonitrile and 2-chloro-3-[(3-chloro-2-quinoxalinyl)thio]quinoxaline. Reactions of phosphorylthioacetamides with N-methylquinoxalinium iodide in alcohol media in the presence of a base proceeded stereoselectively to afford cis-3-phosphoryl-1,3,3a,4,9,9a-hexahydro-2H-pyrrolo[2,3-b]quinoxaline-2-thiones. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 1010–1013, May, 2007.     

Potentiometric Determination of Ascorbic Acid: Estimation of Its Contribution to the Total Antioxidant Capacity of Plant Materials

It was found that an iodine-modified platinum electrode gives a linear potentiometric response to 1.0 × 10^–5 to 1.0 × 10^–3 M ascorbic acid in model solutions. Ascorbic acid in some preparations was determined by potentiometry. The contribution of ascorbic acid to the total antioxidant capacity of aqueous extracts of hips, hop cones, and lemon juice was estimated.     

Delocalization model of regioselectivity and reactivity of free radicals in reactions of addition to olefins

On the basis of the concept of polarity (philicity) of free radicals as proposed by the authors, within the framework of methods of qualitative surfaces of potential energy (linear combinations of configurations of fragments) and stabilization energy, an effective model has been developed for the regioselectivity and reactivity of radicals in processes of addition. A critical examination is made of certain key aspects of the change in regiochemistry and reactivity with changes in the electronic structure of the free radical and substrate. The dominant trends in regioselectivity and reactivity in processes of free-radical addition to olefins are controlled by electronic effects and can be predicted by analyzing interactions of diabatic potential energy surfaces or orbital interactions for a system consisting of a free radical and an unsaturated substrate.Presented at 3rd All-Union Symposium Dynamics of Elementary Atomic-Molecular Processes (Chernogolovka, June 1985) and at the 9th All-Union Conference on Quantum Chemistry (Ivanovo, June 1985).Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 23, No. 2, pp. 135–148, March–April, 1987.The authors are grateful to M. V. Bazilevskii for his constructive discussion of the results obtained in this work.     

C-substituted diethyleneimides of acids of phosphorus

Conclusions We have obtained the hitherto undescribed 2,2-dimethyl- and 2-ethylethyleneimides of alkylphosphorous acids and, by addition of sulfur and selenium to these compounds, the corresponding ethyleneimldes of alkylthio-and selenophosphoric acids.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 5, pp. 1143–1144, May, 1968.     

The synthesis of some new derivatives of 1, 7-dimethylxanthine

We have synthesized a group of new 8-substituted 1, 7-dimethylxanthines which are of interest for biological investigation as very close structural analogs of some 8-substituted theobromine derivatives obtained previously. In particular, we have carried out the conversion of 8-hydroxymethyl-1, 7-dimethlxanthine (I) [1] into 8-chloromethyl-1, 7-dimethylxanthine (II) and from this, by heating it for 6 hours with an excess of diethylamine or by condensing it with sodioacetylaminomalonic ester in ethanol we have obtained 8-diethylaminomethyl-1, 7-dimethylxanthine (III) and its hydrochloride (compare [2]) or 8-(-acetylamino-, -diethoxycarbonylethyl)-1, 7-dimethylxanthine (IV). The hydrolytic cleavage of the latter, accompanied by partial decarboxylation, led to 1, 7-dimethyl-8-xanthinylalanine (V) (cf. [3]).     

Structure and electrical conductivity of the ferrocuprate solid solutions Sm1/2Gd1/2BaCuFeO5.05, Gd1/2Yb1/2BaCuFeO5.02 and Ho1/3Yb2/3BaCuFeO5.05

The unit cell parameters of the crystal structures of the ferrocuprate solid solutions Sm_1/2Gd_1/2BaCuFeO_5.05, Gd_1/2Yb_1/2BaCuFeO_5.02, and Ho_1/3Yb_2/3BaCuFeO_5.05 in air in the temperature range 293–1093 K have been determined by X-ray powder diffraction, and their electrical conductivity has been studied. The structural characteristics of layered ferrocuprates are determined by the size of rare-earth cations in their structures, whereas the conductivity of ferrocuprates depends on the electronic configuration of these cations. Original Russian Text ? A.I. Klyndyuk, 2007, published in Zhurnal Neorganicheskoi Khimii, 2007, Vol. 52, No. 3, pp. 370–374.     

Analogs of carbohydrate-metabolism coenzymes

Conclusions We synthesized two analogs of the natural coenzyme adenosine diphosphate glucose: N₆-methyl-ADPG and N₆, N₆-dimethyl-ADPG.For communication 11, see [1].The following abbreviations are used in this article: ADPG) adenosine-5'-diphosphate-a-D-glucopyranose; N₆-methyl-ADPG) N₆-methylamino-9--D-ribofuranosylpurine-5-diphosphate--D-glucopyranose; N₆, N₆-dimethyl-ADPG) N₆, Ng-dimethylamino-9--D-ribofuranosylpurine-5-diphosphate--D-glucopyranose.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2514–2521, November, 1969.     

Uptake of thorium ions from aqueous solutions by a molecular sieve (13X type) powder

The adsorption of thorium(IV) ions on molecular sieve (13X type) powder from aqueous solutions has been studied as a function of shaking time pH, thorium ion concentration and temperature. The conditions of maximum adsorption of thorium ions obeys Langmuir and D-R isotherms over the entire concentration range studied. Thermodynamic quantities such as H, G and S have been calculated fromK _D values determined at various temperatures. The results show endothermic heat of adsorption, but negative free energy value indicates that the process of thorium adsorption on molecular sieve powder is favored at high temperature. The influence of various cations and anions on thorium(IV) ion adsorption was examined. A wavelength dispersive X-ray fluorescence spectrometer was used for measuring the thorium ion concentration in solutions.