The Study of <Emphasis Type="Italic">cis-trans</Emphasis> Equilibrium and Complexation with DNA of <Emphasis Type="Italic">meso</Emphasis>-Substituted Carbocyanine Dyes

The effect of DNA was studied on cis-trans equilibrium and spectral and fluorescent properties of a number of meso-substituted carbocyanine dyes: 3,3′-diethyl-9-thiomethylthiacarbocyanine iodide (K1), 3,3′-diethyl-9-methoxythiacarbocyanine iodide (K2), 3,3′-9-triethylthiacarbocyanine iodide (K3), 3,3′-dimethyl-9-ethyloxacarbocyanine iodide (K4), 3,3′-9-triethyl-5,5′-dimethyloxacarbocyanine iodide (K5), and 3,3′,9-triethyl-6,6′-dimethoxyoxacarbocyanine iodide (K6). Equilibrium between the cis and trans isomeric forms was detected for the thiacarbocyanine dyes in a number of organic solvents, with a shift of the equilibrium toward the cis-isomer caused by an increase in the solvent polarity. The oxacarbocyanines are present only in the form of trans-isomers in both polar and nonpolar solvents. Interaction of the dyes with DNA leads to the formation of stable noncovalent complexes. The complexation of the thiacarbocyanine dyes results in a shift of the isomeric equilibrium and occurs predominantly via the cis-form of the dye. The oxacarbocyanine dyes produce complexes with DNA in the initial trans-form.__________Translated from Khimiya Vysokikh Energii, Vol. 39, No. 4, 2005, pp. 280–286.Original Russian Text Copyright © 2005 by Pronkin, Tatikolov, Anikovskii, Kuz’min.     

Coordination of Pyridine <Emphasis Type="Italic">N</Emphasis>-Oxides with Alkali and Alkaline-Earth Metal Cations in Aqueous Solution

Complexation of pyrdine N-oxides with lithium, sodium, potassium, magnesium, and calcium halides in aqueous solution was studied. The complexes are unstable (K < 0.6 l mol⁻¹) and exist in solution in an equilibrium with their components. The stability of the complexes was studied in relation to the kind of the cation and anion and to the properties of substituents in the N-oxides.__________Translated from Zhurnal Obshchei Khimii, Vol. 75, No. 1, 2005, pp. 133–136.Original Russian Text Copyright © 2005 by Ryzhakov, Andreev.     

Specific features of the thermodynamics of activation in the LaNi<Subscript>5</Subscript>-H<Subscript>2</Subscript> and CeNi<Subscript>5</Subscript>-H<Subscript>2</Subscript> systems

Using heat conducting Tian—Calvet calorimetry and volumetric measurements, the first hydrogen absorption—desorption cycles in the LaNi₅-H₂ and CeNi₅-H₂ systems were studied. The pressure—composition isotherms were plotted, the equilibrium pressures of hydrogen along the absorption and desorption branches and in the region of hysteresis for different activation steps were determined, and the enthalpies of phase transitions α → β and β → α were calculated. The profiles of the heat evolution curves were analyzed. It was concluded that the mechanism of the reactions studied changes upon activation.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 134–139, January, 2005.     

Salting-Out of <Emphasis Type="Italic">n</Emphasis>-Propyl Alcohol with Potassium Nitrate from Aqueous Solutions

The solubility of components and critical phenomena in the ternary system constituted by potassium nitrate, water, and n-propyl alcohol were studied by the visual polythermal method in the temperature range 25–80°C. The temperature of formaiton of the critical node of the monotectic equilibrium (critical solution-solid phase) and the solution compositions corresponding to the critical solution points at different temperatures were determined. The isothermal solubility diagrams of the system were constructed and the distribution coefficients of n-propyl alcohol at different temperatures were calculated. A comparative analysis of the salting-out effect exerted by potassium nitrate on aqueous solutions of n-propyl alcohol and isopropyl alcohol was done.__________Translated from Zhurnal Prikladnoi Khimii, Vol. 78, No. 3, 2005, pp. 398–402.Original Russian Text Copyright © 2005 by Sinegubova, Cherkasov, Il’in.     

Thermodynamics and Kinetics of Reaction of (Oxo)(hydroxo)molybdenumtetraphenylporphyrin with Pyridine

The reaction of meso-tetraphenylporphyrin with Mo(VI) oxide in boiling phenol resulted in a stable complex O=Mo(OH)TPP. Thermodynamics and kinetics of the reaction between (oxo)(hydroxo)molybdenumtetraphenyporphyrin with pyridine in toluene were studied by spectrophotometric method. This reaction was found to occur in three equilibrium elementary stages: replacement of OH^– by Py (K ₁=9.1 × 10³ l/mol, k ₁=5.25 s^–1 mol^–1 l), the formation of dication (dipyridine)(hydroxo)molybdenumtetraphenylporphyrin as a result of cleavage of a double bond Mo=O (K ²=39.3 l/mol, k ₂=1.83 × 10^–2 s^-1 mol^–1 l), and the formation of cationic complex[Mo(Py)₃TPP]³⁺ · 3OH^– (K ₃=1.0 l/mol, k ₃=1.19 × 10^–3 s^–1 mol^–1 l).__________Translated from Koordinatsionnaya Khimiya, Vol. 31, No. 5, 2005, pp. 380–386.Original Russian Text Copyright © 2005 by Tipugina, Lomova, Motorina.     

Thermodynamic Parameters of Interconversions of Isopolyanions in Solutions of Tungsten(VI)

Interactions in the WO ₂ ²⁻ -H⁺-H₂O system was studied by pH-potentiometric titration at 25 ± 0.1°C for c _w ⁰ = 8 × 10⁻³ to 2 × 10⁻² mol/l. An accurate mathematical model for polycondensation of tungsten(VI) anions in aqueous solution was proposed. The concentration constants of formation were calculated and the diagrams of distribution of isopolyanions of tungsten(VI) were plotted for pH from 1 to 8 with nitrate ions as a supporting electrolyte at different ionic strengths of the solution (I = 0.10 to 0.50). The dependences of the concentration equilibrium constants in solutions on the ionic strength were approximated by Pitzer’s method. The thermodynamic constants of formation and standard Gibbs energies of formation of isopolytungstates from WO ₄ ²⁻ were calculated. The most probable scheme of interconversions of isopolyanions in solution at different pH values was proposed.__________Translated from Koordinatsionnaya Khimiya, Vol. 31, No. 8, 2005, pp. 583–589.Original Russian Text Copyright © 2005 by Rozantsev, Sazonova.     

Reaction of N,N-Dimethyl-N′-(2-hydroxybenzyl)ethylenediamine with Copper(II) in the Presence of Surfactants

The protolytic properties of N,N-dimethyl-N′-(2-hydroxybenzyl) ethylenediamine (HL) and its complexation with copper(II) in the presence of cationic (cetyltrimethylammonium bromide) and nonionic (Triton X-100) surfactants were studied by pH-metry, spectrophotometry, and mathematical simulation of the equilibria. Cetyltrimethylammonium bromide affects the H₂L₂ ⇄ 2HL equilibrium. Along with the protonated monomeric and dimeric species, triprotonated tetrameric species were revealed in surfactant solutions, as in aqueous solutions of isopropyl alcohol. The surfactants affect the complexation of HL with Cu(II). The 1 : 2 complex with the phenolate form in solutions of cetyltrimethylammonium bromide is formed in a more acidic medium (pH ∼5.5) compared to an aqueous solution of isopropyl alcohol (pH ∼11). The apparent stability constants of the complexes increase in the presence of surfactants, especially of cetyltrimethylammonium bromide.__________Translated from Zhurnal Obshchei Khimii, Vol. 75, No. 3, 2005, pp. 379–382.Original Russian Text Copyright © 2005 by Sal’nikov, Boos, Ryzhkina, Ganieva.     

Determination of the Inductive Constant of the Succinimide Group from the Reaction Series of Thermolysis of Nitro Esters

The inductive constant σ* of the succinimide group was determined using the previously obtained equation correlating the rate constant k _l ofliquid-phase homolysis of the O-NO₂ bond in nitro esters with the σ* constants of electronegative substituents. The kinetics of thermolysis of N-nitroxymethyl- and N-(2-nitroxyethyl)succinimide in the melt and solutions was studied manometrically. Adequate data for k _l were obtained. The σ* constant of the succinimide group was determined to be 4.5. The σ* constants for the phthalimide group and some other imide substituents were determined by a similar procedure.__________Translated from Zhurnal Obshchei Khimii, Vol. 75, No. 6, 2005, pp. 954–957.Original Russian Text Copyright © 2005 by Goncharov, Dubikhin, Nazin, Fedorov, Shastin.     

The experimental detection of a retro-Prince reaction exemplified by a homogeneous acid-catalyzed decomposition of isopentenols

The occurrence of the retro-Prince reaction in the transformations of an equilibrium mixture of 2-methyl-3-buten-2-ol and 3-methyl-2-buten-1-ol in 24.9–49 % aqueous sulfuric acid at 25 °C has been experimentally proved.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 332–334, February, 1994.The work was carried out with the financial support of the Russian Foundation for Basic Research (Grant No. 93-03-18356).     

Inclusion Complexes of β-Cyclodextrin with Keto/Enol Tautomers of 2-Acetyl-1-tetralone. A Comparative Study

The keto–enol interconversion of 2-acetyl-1-tetralone (ATLO) and of 2-acetyl-cyclohexanone (ACHE) occurs at measurable rates in aqueous acid or neutral medium. This finding allowed us to determine the keto–enol equilibrium constants, K _E, by following two distinct methods. Both methodologies afford results in complete agreement. The first one is a test of the Beer-Lambert law under two different experimental conditions that contain the substrate only in the enol form or in a mixture of both tautomers in equilibrium. The second method analyses the UV-absorption spectrum of each substrate under keto–enol equilibrium in aqueous β-cyclodextrin (β-CD) solutions of variable concentration: the presence of β-CD increases the percentage of the enol due to the formation of 1:1 inclusion complexes between this tautomer and β-CD. Rates of keto–enol tautomerization, in neutral and acid medium, and of nitrosation in acid medium under non equilibrium conditions have also been measured. Throughout the study, the presentation of the results is done by comparing the different behaviour observed between ATLO and ACHE. While the enol of ACHE included into the β-CD cavity shows to be unreactive either in tautomerization or in nitrosation, in the case of ATLO it is observed tautomerization through the complexed enol. In addition, with ACHE only the enol tautomer forms inclusion complexes with β-CD, whereas with ATLO the keto tautomer entries also to the β-CD cavity, however the stability constant with the enol is near 3-fold that of the keto isomer. These main differences can be rationalized on the basis of the molecular structure of these diketones.This revised version was published online in July 2005 with a corrected issue number.     

Mutual Solubility of Components and Critical Solution Points in the System Water-Isopropyl Alcohol-<Emphasis Type="Italic">n</Emphasis>-Dodecane in the Temperature Range 5–120°C

The mutual solubility of components and critical solution points in the ternary system water-isopropyl alcohol-n-dodecane were studied by a visual-polythermal technique at saturated vapor pressure in the temperature range 5–120 °C. The mixture composition in the critical solution point was studied in relation to temperature.__________Translated from Zhurnal Prikladnoi Khimii, Vol. 78, No. 3, 2005, pp. 394–397Original Russian Text Copyright © 2005 by Sinegubova, Il’in, Cherkasov.     

Polyfunctional Derivatives of Isocytosine. Effect of Hydration on Prototropic Tautomerism of 2-(2-Hydroxyethyl)amino-6-methylpyrimidin-4(3<Emphasis Type="Italic">H</Emphasis>)-one

Hydration of 2-(2-hydroxyethyl)amino-6-methylpyrimidin-4(3H)-one forms an equilibrium mixture of 4-oxo-3,4-dihydro and 4-hydroxy tautomers. The intermediate in mutual transitions of these tautomers has a zwitter ionic structure. The equilibrium shifts to the 4-oxo-3,4-dihydro form as the polarity of the medium decreases.__________Translated from Zhurnal Obshchei Khimii, Vol. 75, No. 4, 2005, pp. 677–682.Original Russian Text Copyright © 2005 by Erkin, Krutikov.     

A New Procedure for Preparing Perfluoroalkoxypropanoic Acid Fluorides

Condensation of perfluoro carboxylic acid fluorides with hexafluoropropene epoxide in the presence of N,N, N′,N′-tetraalkyldiaminomethanes was studied.__________Translated from Zhurnal Prikladnoi Khimii, Vol. 78, No. 3, 2005, pp. 438–440.Original Russian Text Copyright © 2005 by Igumnov, Lekontseva, Shipigusev, Mukhametshin.     

Influence of the Structure of the Organic Moiety of Copper(II) Porphyrins on Their Reactivity toward Acids

The acid-induced dissociation of copper(II) porphyrin complexes with a high degree of meso- and β-substitution in the ligand was studied. The copper(II) complexes with octaethylporphyrins containing 0, 1, 2, 3, and 4 meso-phenyl substituents were ranked with respect to the stability. Octaβ-alkyl and unsymmetrical meso-phenyl substitution affects not only the quantitative characteristics of dissociation of the complexes but also the kinetic relationships of the process.__________Translated from Zhurnal Obshchei Khimii, Vol. 75, No. 3, 2005, pp. 497–503.Original Russian Text Copyright © 2005 by Kosareva, Klyueva, Lomova, Suslova.     

Structure of Solutions of Polyamido Acid Salts in a Mixed Solvent

The changes in the structural organization of solutions of N,N-dimethylhexadecylammonium salt of the polyamido acid based on 3,3’,4,4’-diphenyltetracarboxylic dianhydride and o-tolidine in a dimethylacetamide-dioxane mixed solvent during 24-h keeping at room temperature were studied by polarized light scattering. The stability of the salt solutions was studied as influenced by the composition of the mixed solvent, chemical nature of its components, and molecular weight of the polymer.__________Translated from Zhurnal Prikladnoi Khimii, Vol. 78, No. 3, 2005, pp. 474–478.Original Russian Text Copyright © 2005 by Kalinina, Silinskaya, Sklizkova, Kozhurnikova, Filippov, Kudryavtsev.     

Potentiometric investigations of some catechol derivatives of scandium

The equilibrium reactions of scandium(III) with some triprotic catechol derivatives (H₃L) were studied. The selected ligands that are 2,3-dihydroxybenzoic acid (2,3-DHBA), 3,4-dihydroxybenzoic acid (3,4-DHBA), 3.4-dihydroxyhydrocinnamic acid (3,4-DHHCA), and 3,4-dihydroxyphenylacetic acid (3,4-DHPA) were investigated in aqueous solution by means of potentiometry in 0.1 M ionic medium at 25°C. The stability constants are reported for the ScL and ScL(H₂L)^– mononuclear complexes. 2,3-DHBA can bind to Sc³⁺ ion strongly and the salicylate mode (COO^–, O^–) is effective over the acidic pH range. But in higher pH range, 3,4-DHBA, 3,4-DHHCA, and 3,4-DHPA act more efficiently through catecholate groups (O^–, O^–).Translated from Koordinatsionnaya Khimiya, Vol. 31, No. 3, 2005, pp. 229–233.Original Russian Text Copyright © 2005 by Türkel, Özer.This revised version was published online in April 2005 with a corrected cover date.This revised version was published online in April 2005 with a corrected cover date.     

Kinetics of Formation of Peroxyacetic Acid

The kinetics of the reaction of acetic acid with hydrogen peroxide, leading to peroxyacetic acid, were studied at various molar reactant ratios (AcOH-H₂O₂ from 6 : 1 to 1 : 6) at 20, 40, and 60°C and sulfuric acid (catalyst) concentrations of 0 to 9 wt %. The reaction is reversible, and the equilibrium constant decreases as the temperature rises: K = 2.10 (20°C), 1.46 (40°C), 1.07 (60°C); Δ_r H ⁰ = − 13.7±0.1 kJ mol⁻¹, Δ_r S = −40.5±0.4 J mol⁻¹ K⁻¹. The maximal equilibrium concentration of peroxyacetic acid (2.3 M) is attained at 20°C and a molar AcOH-to-H₂O₂ ratio of 2.5 : 1. The rate constants of both forward and reverse reactions increase with increase in sulfuric acid concentration from 0 to 5 wt %. Further raising the catalyst concentration does not affect the reaction rate. The reaction mechanism is discussed.__________Translated from Zhurnal Obshchei Khimii, Vol. 75, No. 7, 2005, pp. 1187–1193.Original Russian Text Copyright © 2005 by Dul’neva, Moskvin.     

Synthesis and Investigation of Indium Dodecatungstosilicate

Indium dodecatungstosilicate of the composition [In(OH)⋅5H₂O]₂ [SiW₁₂O₄₀]⋅H₂O is synthesized and studied by means of IR spectroscopy, thermogravimetry, and X-ray phase analysis. The crystals of this compound are triclinic, space group P1, a 13.079(3), b 13.795(3), c 13.967(3) Å, α 90.08(3)°, β 103.76(3)°, ψ107.76(3)°, Z 2, and π_calc 4.900 g cm⁻³.__________Translated from Zhurnal Obshchei Khimii, Vol. 75, No. 1, 2005, pp. 21–23.Original Russian Text Copyright © 2005 by Kaziev, Dutov, Quinones, Ita, Sychkin.     

N,N′-Bis(trimethylsilylmethyl)thiocarbamide and N,N′-Bis(trimethylsilylmethyl)-λ6-thiocarbamide S,S-Dioxide

N,N′-Bis(trimethylsilylmethyl)-λ⁶-thiocarbamide S,S-dioxide was synthesized by oxidation of N,N′-bis(trimethylsilylmethyl)thiocarbamide with hydrogen peroxide. The synthesized dioxide is a less active reducing agent than previously studied S,S-dioxides of organosilicon thiocarbamides in which the silicon atom is separated from the thiocarbamide fragment by a -CH₂CH₂CH₂- bridge.__________Translated from Zhurnal Obshchei Khimii, Vol. 75, No. 6, 2005, pp. 912–914.Original Russian Text Copyright © 2005 by Vlasova, Grigor’eva, Voronkov.     

Mechanism of Replacement of the Nitro Group and Fluorine Atom in <Emphasis Type="Italic">meta</Emphasis>-Substituted Nitrobenzenes by Phenols in the Presence of Potassium Carbonate

The relative mobilities of the nitro group and fluorine atom in 1,3-dinitrobenzene and 1-fluoro-3-nitrobenzene by the action of phenols in the presence of potassium carbonate in dimethylformamide at 95–125°C were studied by the competing reaction method. The rate constant ratios k(NO₂)/k(F) were correlated with the differences between the corresponding activation parameters (ΔΔH ^≠ and ΔΔ S ^≠). The greater mobility of the nitro group was found to be determined by the entropy control of the reactivity of arenes. The activation parameters (ΔH ^≠ and ΔS ^≠) were calculated, and the enthalpy-entropy compensation effect was revealed. The reaction mechanism is discussed.__________Translated from Zhurnal Organicheskoi Khimii, Vol. 41, No. 7, 2005, pp. 999–1005.Original Russian Text Copyright © 2005 by Khalfina, Vlasov.