Effect of maltodextrins on the surface activity of small-molecule surfactants

We report on the effect of commercially important polysaccharides (maltodextrins with variable dextrose equivalent (Paselli SA-2, MD-6 and MD-10) on the surface activity at the air–water interface of small-molecule surfactants (sms), possessing different hydrophobic–lipophilic balance ((SSL (Na⁺), the main component is a sodium salt of stearol–lactoyl lactic acid, and PGE (080), polyglycerol ester of C18 fatty acid), and widely used in food products. A marked change of the surface activity of sms was found in the presence of maltodextrins by tensiometry. The combined data of laser multiangle light scattering and mixing calorimetry have suggested that this result is governed by specific complex formation between maltodextrins and sms in aqueous medium. Measurements have been made of the molar mass, the second virial coefficient and the enthalpy of intermolecular interactions in aqueous solutions. The implication of a degree of polymerization of maltodextrins in this phenomenon was shown. The interrelation between the molecular parameters of the formed complexes and their surface activity at the air–water interface has been revealed and discussed.     

π-Electronic structure of the nitrofuran system

Anion radicals of 2-vinylene derivatives of 5-nitrofuran were obtained by electrochemical generation. The hyperfine structure (hfs) of the ESR spectra of these anion radicals indicates delocalization of the unpaired electron over their entire π-electron system. The effect of the vinylene grouping on the distribution of the unpaired electron in the anion radicals and on the distribution of the unpaired electron in the vinylene grouping itself was examined on the basis of the hfs constants. It was found that the vinylene grouping by localizing more than 10% of the density of the unpaired electron on itself reduces, by a factor of 1.4, the effect of substituents in the 2 position of 5-nitrofuran on the distribution of the spin of the unpaired electron in the nitrofuran framework.     

Esr and polarography of nitroazoles. 4. Polarographic study of nitrobenzimidazoles

The electrochemical reduction of 2-substituted 5(6)-benzimidazoles has been studied with the aid of classical polarography and cyclic voltammetry in acetonitrile. The influence of the substituents in position 2 on the magnitudes of the half-wave potentials of the first stage is exerted by induction and resonance mechanisms with approximately the same contributions, and that on the magnitudes of the half-wave potentials of the second stage predominantly by the resonance mechanism. The possibilities of taking the radical-stabilizing factor into account in the correlations are discussed. In order to study the 2-substituted 5(6)-nitrobenzimidazole series, their pK _a values in acetonitrile have been determined by potentiometric titration.For communication 3, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1246–1251, September, 1984.     

Nitroazines. 4. Polarographic behavior of 5-nitropyrazolo[3,4-b]pyridines and the esr spectra of their electrochemically generated free radicals

1-Methyl- and 1-phenyl-substituted derivatives of 5-nitropyrazolo[3,4-b]pyridines are reduced at a dropping mercury electrode in a single one-electron wave with the formation of radical anions in interval of potentials from –0.94 to –1.06 V. Compounds unsubstituted at the N(₁) nitrogen atom give an additional polarographic wave at E_1/2 = –1.4 V due to the reduction of the deprotonated form (anion). The potentials and HFS constants of the ESR spectra of the corresponding electrochemically generated free radicals are given.For Communication 3, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 689–693, May, 1985.     

Oxygen activation on metallic centers and oxidizing abilities of such oxygen

It was shown that metallcontaining peroxides such as XOOOBu-t [X = (t-BuO)₂Al, (t-BuO)₃Ti] generate molecular oxygen in the electron-excited singlet state (¹O₂). These ozonides and η²-peroxocomplex Ph₃Bi(η²O₂) demonstrate high oxidative activity towards some classes of organic substances under mild conditions (20 °C).     

Mass spectrometric identification of cyclic polysulfides in sediment of the Eastern Gulf of Finland. I

Structures of six cyclic polysulfides, previously unknown as organic environmental pollutants, were analyzed from a sediment sample from the Eastern Gulf of Finland. The determinations were done by gas chromatography connected to mass spectrometry. High resolution (HRMS) measurements of the isotopic composition of four compounds could be done to confirm their molecular formulae. Total low resolution (LRMS) spectra were used to elucidate structures of all six compounds by thermochemical approach, application of fragmentation rules and by ICLU simulation of the spectra. The compounds were deduced to be (in the order of GC- retention) 1,2,4-trithiacycloheptane, tetrathiacyclopentane, 1,2,4,5-tetrathia-cyclohexane, 1,2,3,4- tetrathiacycloheptane, 1,2,3,4-tetrathiacyclohexane and 1,2,4,6-tetrathiacyclooctane.     

Free radicals in electrochemical reduction of 3,5-dicarbethoxy-1,4-dihydropyridines with nitrophenyl groups in positions 2, 4, and 6

In the electrochemical reduction of 2,6-bis- and 2,4,6-tris(nitrophenyl) derivatives of 3,5-dicarbethoxy-1,4-dihydropyridine, in the first stage, one of the para-nitrophenyl groups in position 2 or 6 of the heterocycle is reduced. Free radicals have been obtained and identified, the primary species being ion radicals of the nitrophenyl type. The presence of the heterocycle in the molecule of the 1,4-dihydropyridine derivative stabilizes secondary free radicals of the nitrosophenyl type. In the process of electrochemical reduction, no evidence has been found of any intramolecular transfer of electrons or protons from the dihydropyridine part of the molecule to the nitrophenyl groups. Derivatives of 2,6-bis(p-nitrophenyl)-3,5-dicarbethoxy-1,4-dihydropyridine have been synthesized, and the oxidation and methylation of these derivatives have been studied.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 481–487, April, 1991.     

Free radicals in the electrochemical reduction of derivatives of 3,5-dinitro-1,2-dihydropyridine

The characteristics (potentials, limiting currents, reversibility) of the electrochemical reduction of 3,5-dinitro-1,2-dihydropyridines were determined by cyclic voltammetry and polarography. It was established by ESR that the free radicals formed in these processes have a radical-dianion structure in the case of both the N-unsubstituted and the N-substituted dihydropyridines. The hyperfine coupling constants of the interaction between the unpaired electron and the nuclei of the atoms at various positions of the heterocycle were determined.Latvian Institute of Organic Synthesis, Riga LV-1006. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 212–218, February, 1997.     

Synthesis,Structures, and Properties of Layered Quaternary Chalcogenides of the General Formula ALnEQ4 (A = K,Rb; Ln = Ce,Pr, Eu; E = Si,Ge; Q = S,Se)

Four related quaternary compounds containing rare‐earth metals have been synthesized employing the molten flux method and metathesis. The reactions of Eu and Rb₂S₅ with Si and Ge in evacuated fused silica ampoules at 725 °C for 150 h yielded RbEuSiS₄ ( I ) and RbEuGeS₄ ( II ), respectively. On the other hand, a reaction between CeCl₃ and K₄Ge₄Se₁₀ at 650 °C for 148 h has yielded KCeGeSe₄ ( III ) and KPrSiSe₄( IV ) was obtained by the reaction of elemental Pr, Si and Se in KCl flux at 850 °C for 168 h. Crystal data for these compounds are as follows: I , orthorhombic, space group P2₁2₁2₁ (#19), a = 6.392(1), b = 6.634(2), c = 17.001(3) Å, α = β = γ = 90°, Z = 4; II , monoclinic, space group P2₁/m (#11), a = 6.498(2), b = 6.689(3), c = 8.964(3) Å, β = 108.647(6)°, Z = 2; III , monoclinic, space group P2₁ (#4), a = 6.852(2), b = 7.025(2), c = 9.017(3) Å, β = 108.116(2)°, Z = 2; IV , monoclinic, space group P2₁ (#4), a = 6.736(2), b = 6.943(2), c = 8.990(1) Å, β = 108.262(2)°, Z = 2. The crystal structures of I ‐ IV contain two‐dimensional corrugated anionic layers of the general formula, [LnEQ₄]^? (Ln = Ce, Pr, Eu; E = Si, Ge and Q = S, Se) alternately piled upon layers of alkali cations. In addition to structural elucidation, Raman and UV‐visible spectroscopy, and magnetic measurements for compound III (KCeGeSe₄) are also discussed.