Complexation of citric and tartaric acids with Na and K ions in aqueous solution

The formation of MTar^–, MCit^2– and M₂Cit^– complexes (M is Na⁺ or K⁺) was established in reactions of aqueous solutions of citric and tartaric acids with sodium or potassium chloride solutions; their stability constants were determined by potentiometric titration in aqueous solution at 298.15 K and ionic strength 0.1 and 0.3 mol/l with tetraethylammonium chloride (TEACl) as a supporting electrolyte. Heat effects of reactions between citric acid solutions and sodium or potassium chlorides were measured by calorimetric method at 288.15, 298.15, and 308.15 K and at the ionic strength 0.1, 0.2, and 0.3 M TEACl. The increasing ionic strength was found to decrease exothermic effect of complex formation processes, while the temperature produced the opposite effect. Extrapolation to zero ionic strength was used to find thermodynamic stability constants and standard heat effects of complex formation reactions in solutions of oxyacids. The changes in entropy and heat capacity were calculated as well as standard enthalpies of formation of Na and K complexes of the indicated oxyacids in aqueous solution at 298.15 K.__________Translated from Koordinatsionnaya Khimiya, Vol. 31, No. 4, 2005, pp. 253–261.Original Russian Text Copyright © 2005 by Zelenina, Zelenin.     

Synthesis and characterization of cationic astatine compounds with sulphur-containing ligands stable in aqueous solutions

The formation of cationic astatine compounds with thiourea, thiourea derivatives and some N-acylthioureas was investigated in aqueous solutions. The ion mobilities in free electrolytes were determined for the detection of carrier-free astatine compounds and their characterization. Informations about the stability of this group of compounds could be given after investigations in the presence of halogenide and pseudo halogenide ions /Cl^–, Br^–, I^–, SCN^–/. First results on the reaction of At//⁺ with thiourea derivatives and N-acylthioureas in acid and neutral solutions are reported. The cationic astatine compound formation with representatives of this group is shown.     

Spectrophotometric study of thiocyanato complexation of cobalt(II) and nickel(II) ions in micellar solutions of a nonionic surfactant triton X-100

Complexation of cobalt(II) and nickel(II) with thiocyanate ions has been studied by precise spectrophotometry in aqueous and micellar solutions of a nonionic surfactant Triton X-100 of varying concentrations (20–100 mmol-dm^–3). With regard to cobalt(II), the formation of [Co(NCS)]⁺, [Co(NCS)₂], and [Co(NCS)₄]^2– was established. The formation constant of [Co(NCS)₄]^2–, is increased with increasing concentration of the surfactant, suggesting that the [Co(NCS)₄]^2– complex is formed in micelles. In contrast, the formation constants of [Co(NCS)]⁺ and [Co(NCS)₂] are remained practically unchanged. On the other hand, with nickel(II), the formation of sole [Ni(NCS)]⁺ and [Ni(NCS)₂] was established in both aqueous and micellar solutions examined, their formation constants being also remained unchanged. Interestingly, no higher complex was confirmed in the nickel(II) system, unlike cobalt(II). The unusual affinity of the [Co(NCS)₄]^2– complex with micelles will be discussed from thermodynamic and structural points of view.     

Capillary Flow of Cationic Polyelectrolyte Solutions

The flow rates and the dynamic contact angles of aqueous solutions of cationic polyelectrolyte (CPE) in quartz capillaries with radius of 3–4 m are measured. It is shown that the surface tension and viscosity of CPE solutions with concentrations from 10^–1 to 10^–5 g/l are the same as for water. Surface inactivity of CPE leads to the substantial difference between the capillary properties of their solutions and those of surfactant solutions. It is established that, as the solution concentration increases, the advancing contact angles are reduced from 83° to 75°; the receding contact angles lie between 10° and 20°. Large hysteresis of contact angle can probably be related to the formation of metastable wetting film behind the receding meniscus. Surface hydrophobization occurs as a result of the adsorption of CPE molecules on the negatively charged quartz surface. The specific features of the application of CPE solutions in the deposition technology of hydrophobic coatings, the capillary imbibition and displacement of oils from hydrophobic pores are discussed.     

Photochemical reduction of organic electron acceptors in aqueous solutions

Conclusions The formation of OH radicals in the photoreduction of aqueous solutions of anthraquinonesulfonic acid as the result of electron transfer from water (OH^–) to a triplet molecule has been demonstrated.Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 11, pp. 2615–2617, November, 1969.     

Pulsed Electrodeposition of Zinc–Manganese Alloys

High-quality Zn–Mn coatings with an Mn content reaching 50% are obtained from citrate–sulfate solutions in pulsed electrolysis at a pulse length of 0.1 ms to 1 s. Due to the formation of a blocking film of citrate–hydroxide zinc compounds, cathodic potential increases with time, which helps reach a codeposition potential of Mn ions. An electrolysis with a pulsed current superposed on a dc increases the Mn content and makes no impact on the coating quality.     

Formation of oxoperoxo complexes of vanadium(V) with aminopolycarboxylates in acidic aqueous solutions

Summary The electronic spectra of KVO₃–H₂O₂–L–HClO₄(KOH) aqueous solutions, where L is ethylenediaminetetraacetate (edta), 1,2-cyclohexanediaminetetraacetate (cdta),N-(carbamoylethyl)-iminodiacetate (keida) or iminodiacetate (ida) ion were measured and, based on their pH dependence changes (ca. 0.5–7.0) and time, the formation of carboxylato-oxoperoxo complexes of vanadium(V) and their stabilities at room temperature were studied. The monoperoxo complexes with edta, keida and ida are formed immediately after mixing stock solutions, whereas the monoperoxo complex with cdta is formed only by slow decomposition of the stable diperoxo complex. The stabilities of the monoperoxo complexes decrease in following order: cdta>edta>keida>ida.     

The Role of Iron–Carbon Galvanic Contact in the Formation of Dispersed Iron Hydr(oxides) in Water and Electrolyte Solutions

The comparative analysis of phase formation on the iron surface in aqueous medium in the presence and absence of iron–carbon (coke) galvanic contact was carried out. The role of galvanic contact in phase formation processes was determined. It was shown that, in the presence of galvanic contact almost complete oxidation of iron ions on the surface of an iron half-element and a rather efficient stationary formation of dispersed phases serving as sorbents of heavy metals from solutions take place. The effect of anionic composition of solution on the parameters of phase formation was studied. It was established that maximal amount of iron–oxygen-containing phases is formed in zinc chloride solution. The presence of sulfate and nitrate ions in solution decreased significantly the rate of phase formation in iron–carbon galvanic contact.     

Quenching of excited states of pyrene sulfonate solutions and their metal complexes by molecular oxygen

The results of study of fluorescence quenching, by molecular oxygen, of unsubstituted pyrene solutions within the framework of exchange complex are generalized. The oxygen quenching rate constants of the fluorescence and triplet state of pyrene monosulfonate and pyrene tetrasulfonate solutions and their aggregates and complexes (second and first coordination spheres) with REE ions in H₂O, DMSO, and DMFA are measured. The effect of the number of substituting sulfo groups, aggregates, complex formation, and the nature of the solvent on the efficiency of this quenching is investigated. It is shown that, in contrast to metalloporphyrins with the paramagnetic Cu(II) ion, the formation of pyrenesulfonates complexes with REE paramagnetic ions does not lead to an increase in oxygen quenching efficiency of the triplet state of organic ligands.Translated from Teoreticheskaya i Eksperimental'naya Khimiya, Vol. 23, No. 3, pp. 302–311, May–June, 1987.The authors express their deep gratitude to Prof. V. L. Ermmolaev for a fruitful discussion of the results.     

Lignin-Silica-Titania Hybrids as Precursors for Si–Ti–C–O Fibers

Lignin-silica-titania and lignin-titania hybrid fibers have been prepared by sol-gel processing from lignin, tetraethoxysilane, and titanium tetrakis(2,4-pentanedionate) using a mixture of 2,4-pentanedione and tetrahydrofuran as solvent and H2SO4 as catalyst. Amounts of H2O and H2SO4, to add to the solutions with the Si-to-Ti atomic ratios of 0–1.0, were determined for achieving favorable spinnability of fibers from the solutions. The FT-IR spectrum of the fibers indicated the formation of hybrid fibers. The hybrid fibers, cured in air to avoid coalescense, could be converted into Si–Ti–C and TiC fibers upon pyrolysis at 1500°C in Ar.     

Adsorption of Ethoxylated Alkyl Phenols on Silica Gel from Aqueous Micellar Solutions

Adsorption of ethoxylated nonylphenols (Neonols) from their micellar solutions on coarse-pore KSK silica gel was studied under static conditions. The energy of adsorption interaction between micelles and silica gel surface was determined using the Hill–de Boer isotherm. For the initial parts of the isotherms (from 1 to 6 CMC₁), it was equal to –15.8kT. The study of coadsorption of Neonols with dye methylene blue showed that the micellar adsorption layer is fragmentary and that the amount of the adsorbed surfactant is dependent on the conditions of the adsorption layer formation.     

Self- and heteroassociates of cumyl hydroperoxide: FTIR-spectroscopy, chemometrics (factor analysis) and quantum chemical calculations

Self- and heteroassociation of cumyl hydroperoxide and acetophenone in n-decane solutions were studied by FTIR spectroscopy (3100–3700 cm⁻¹, 298–358 K). To interpret spectroscopic data, the new approach of factor analysis was offered. Equilibrium constants and thermodynamic parameters of associate formation were determined. The DFT calculations of cumyl hydroperoxide conformations, their self- and heteroassociates were carried out.     

Quantitative Correlations for the Estimation of Thermodynamic and Molecular Properties of Pyridines and 2,2′-Bipyridyines

Standard heats of formation, entropies, ionization potentials, and molecular dipole moments of a series of pyridines have been calculated by MNDO, AM1 and PM3 methods. Linear relationship have been established which permit a priori estimation of thermodynamic and molecular characteristics of pyridines. Correlation have been found between the values of pK_a for 2,2′-bipyridines for aqueous solutions and their gas phase proton affinities.__________Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, 391–402, March, 2005.     

Electrical Conductivity and Complexation of Sodium Borate in Trehalose and Sucrose Aqueous Solutions

The formation equilibrium constants for the esterification reaction between sucrose or trehalose and borate ion have been determined by measuring the pH changes produced when the corresponding sugar is added to sodium borate solutions. The speciation of the ternary sugar–borate–water system was calculated from this equilibrium information and used to separate the contribution of each ionic species to the electrical conductivity of the system. From the analysis of the results it is concluded that, in the viscosity region studied, the complex borate–trehalose and borate–sucrose ions obey Walden's rule, while the behavior of the smaller borate ion is not clear. The dramatic difference of the infinite dilution molar conductivity, and consequently of the hydrodynamic radius, of the trehalose– and sucrose–borate ester ions is ascribed to the formation of an intramolecular diester in aqueous trehalose.     

Photodynamic effects in the components of cotton seeds

The formation of a stable radical cation and of an unstable peroxide form of gossypol in the light under aerobic conditions has been established on the basis of an analysis of the ESR spectra obtained. The formation of mono- and dianions of gossypol in its alkaline solutions has been shown.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenni, No. 3, pp. 354–360, May–June, 1987.     

Determination of number and composition of platinum(IV) aqua complexes in solutions using mathematical statistics methods

Conclusions The formation of monoaqua compounds in acidified solutions of Pt(IV) hydroxy complexes was confirmed, and their composition was determined by comparing the curves that express the degree of forming the complexes as a function of the solution pH with the results of a statistical processing of the titration curves.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 8, pp. 1859–1861, August, 1976.     

Diels-Alder reaction volumes in the solid state and solution

The densities of anthracene, tetracyanoethylene, maleic anhydride, N-phenylmaleineimide, trans, trans-1,4-diphenylbuta-1,3-diene, and their Diels-Alder adducts were measured in the solid state and in solution at 25 °C. The reaction volumes in the solid state were calculated from the difference in molar volumes. They turned out to be low, close to each other (–4 to –11 cm³ mol^–1), and slightly different from the reaction volumes (–8±1 cm³ mol^–1) calculated from the van der Waals radii. The reaction volumes in solutions (–15 to –32 cm³ mol^–1) were found from the difference in partial molar volumes of the reactants in dioxane, acetonitrile, and 1,2-dichloroethane, The experimental Diels-Alder reaction volumes in solution are determined not only by the formation of new bonds in an adduct: a considerably higher contribution (to 75%) is made by a change in the volume of intermolecular empty spaces in solution on going from reactants to adducts.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2386–2390, November, 2004.     

Genesis of phase composition of supported Al?Fe?O catalysts

XPS, ESR and ESDR methods have been used for studying Al–Fe–O catalysts calcined at 620–1270 K. -Al₂O₃ interaction with impregnating solutions of iron oxalate complexes was shown to lead to the formation of isolated Fe³⁺ ions, and supported phases of solid solutions and associates at 620–820 K.     

Specifics of Interaction of Acetone Molecules with Quasi-free Electrons: Analysis of Positron Annihilation Characteristics in Aqueous and Alcoholic Acetone Solutions

The yields of formation of radiolytic hydrogen (H₂) and orthopositronium (o-Ps) in aqueous and alcoholic acetone solutions were experimentally determined. A decrease in the o-Ps yield with an increase in the acetone concentration is much weaker than the decline in the yield of solvated electrons (e^– _s) under picosecond pulse radiolysis conditions. In contrast, the decrease in the o-Ps yield is minimal in higher alcohols where the inhibiting action of acetone e^– _s is most pronounced. These findings seem to contradict the conventional concepts of Ps formation via the intratrack reaction of positron recombination with a track electron (e^–), which competes with the reaction of e^– scavenging by dissolved acetone molecules. This contradiction can be eliminated, assuming that the scavenging of e^– by acetone begins from the formation of the weakly bound transient state (CH₃)₂CO···e^– capable of donating e^– to a positron. This opens up an additional pathway for the formation of the Ps atom.     

On the mechanism of formation of intratrack yields of water radiolysis products upon irradiation with fast electrons and positrons: 1. Model formulation

A mathematical model is constructed for the formation of main transient (e _aq ^– , H, OH) and final (H₂, H₃O⁺, OH^–, Ps) radiolytic products formed in tracks of fast electrons and positrons in water and aqueous solutions. The model takes into account the occurrence of reactions of epithermal electrons, along with thermal and hydrated electrons, with a solute; the ambipolar character of diffusion of charged intratrack particles; and new pathways of the formation of hydrogen and positronium due to the appearance of weakly bound adducts of electrons with their scavengers, in addition to the traditional routes.__________Translated from Khimiya Vysokikh Energii, Vol. 39, No. 3, 2005, pp. 165–170.Original Russian Text Copyright © 2005 by Stepanov, Byakov.