Effect of substituent in the heterocyclic ring on the course of the nuclear-chemical synthesis

Ion-molecule reactions of free phenyl cations generated by β-decay of tritium incorporated in labeled benzene with various pyridine derivatives were studied. The effect of electron-donor (methyl groups) and electron-acceptor (bromine) substituents in the heterocyclic ring on the course of electrophilic addition and electrophilic substitution was studied. The one-step nuclear-chemical synthesis yielded N-phenyl quaternary salts of methyl and bromo derivatives of pyridine and quinoline, labeled with tritium.     

Investigation of Nanometer- and Submicron-Size Dispersed Phases in Titanium Pseudo- β -Alloys using Scattering and Diffraction of Neutrons,Electrons, and X-Ray Radiation

Metal Science and Heat Treatment - The size and volume fraction of fine particles of secondary β -phase formed during hardening heat treatment of pseudo-β-titanium alloy VT22 are...     

Kinetics of the reaction of Np(VI) with iminodiacetic acid

The stability of Np(VI) in 5–200 mM iminodiacetic acid (H₂IDA) solutions at 23.5–55°С was studied by spectrophotometry. In a solution with pH 2 and excess Np(VI), 1 mol of H₂IDA reduces 2 mol of Np(VI) to Np(V). In 1 and 0.5 M HClO₄ solutions containing 200 mM H₂IDA and 1 mM Np(VI), no more than 36 and 65% of Np(VI), respectively, is reduced at 44.5°С. Complete reduction of Np(VI) is observed in solutions containing 0.2 M HClO₄ and less. In the examined ranges of H2IDA concentrations and temperatures, Np(VI) is consumed in accordance with the first-order rate law. The reduction mechanism involves formation of a Np(VI) iminodiacetate complex, which is followed by intramolecular charge transfer. The generated radical reduces Np(VI). The activation energy is 107 ± 3 kJ mol^–1.     

Uranium(III) in aqueous solutions: Preparation,properties, synthesis of solid compounds

Published data on the preparation procedures, stability, and complexation of U(III) in aqueous solutions are summarized and correlated. Reactions with inorganic and organic free radicals studied by the flash radiolysis method, the spectroscopic properties, the extraction and ion-exchange behavior of U(III), and methods for isolation of solid U(III) compounds from aqueous solutions are discussed.     

Radiation-Chemical Behavior of Plutonium in the Heterogeneous System PuO2-Ground Water

Radiation-chemical behavior of plutonium in the heterogeneous system PuO₂-ground water from the Red forest in the vicinity of Chernobyl NPP was studied. It was found that, in nonirradiated and irradiated ground water, Pu(IV) passes into the aqueous phase with subsequent transformation into Pu(V) and Pu(III). The degree of plutonium leaching is governed by the amount of organic substances, particularly fulvic and mellitic acids, in the ground water, and the degree of conversion of Pu(IV) to Pu(III) and Pu(V), by the ionizing radiation dose. The physicochemical and radiation-chemical behavior of plutonium in the systems was judged from the spectral characteristics of the irradiated and nonirradiated solutions.     

Synthesis and properties of actinide dimolybdate complexes M<Subscript>2</Subscript>[AnO<Subscript>2</Subscript>(MoO<Subscript>4</Subscript>)<Subscript>2</Subscript>]·H<Subscript>2</Subscript>O (M = Rb,Cs; An = Np,Pu)

New Np(VI) and Pu(VI) dimolybdates Rb₂NpO₂(MoO₄)₂·H₂O (I), Cs₂NpO₂(MoO₄)₂·H₂O (II), Cs₂PuO₂(MoO₄)₂·H₂O (III), and Rb₂PuO₂(MoO₄)₂·H₂O (IV) were synthesized under hydrothermal conditions. The crystal structures of the compounds were determined, and their absorption spectra in the UV, visible, and IR ranges were measured. The compounds crystallize in the monoclinic system. Their crystal structure is based on [AnO₂(MoO₄)₂]_n^2n– anionic layers (An = Np, Pu) formed by (AnO₂)O₅ pentagonal bipyramids and MoO₄ tetrahedra, sharing common vertices. Each An atom in the layer is bonded to other five An atoms via MoO₄ tetrahedra with the formation of a 4343² network. The effect of the ionic radius of the outer-sphere cation on the parameters of the crystal structure and features of the absorption spectra is discussed.     

Mechanism of Np(VI) oxidation with ozone in alkaline solutions

Bubbling of an ozone-oxygen mixture containing 0.1?C0.5 vol % O₃ at a rate of 15?C20 l h^?1 through 13 ml of a 2 × 10^?5?1 × 10^?4 M solution of Np(VI) in 0.1 and 1 M LiOH leads to the formation of Np(VII). The initial rate increases approximately in proportion to [Np(VI)] and [O ₃ ^gas ]^0.5. Up to 80% of Np(VI) is oxidized at maximum. At the O₃ concentration in the gas phase increased to 1?C4 vol %, Np(VI) is oxidized completely. Under the same conditions, Np(VI) in a concentration of (1?C5) × 10^?3 M is oxidized to almost 100%. Analysis of published data and additional experiments on the reaction of O₃ with Np(VI) ions in LiOH solutions allow a conclusion that the ozonation involves the reactions O₃ + OH^? = HO ₂ ^? + O₂, O₃ + HO ₂ ^? + OH^? = O ₃ ^? + O ₂ ^? + H₂O, and O₃ + O ₂ ^? = O ₃ ^? + O₂, followed by O ₃ ^? + NpO₂(OH) ₄ ^2? = O₂ + NpO₄(OH) ₂ ^3? + H₂O. In addition, HO ₂ ^? reduces Np(VII) and Np(VI) and reacts with O ₃ ^? . Certain contribution is made by the reaction Np(VI) + O₃ = Np(VII) + O ₃ ^? . The dependence of the Np(VII) accumulation rate on [O ₃ ^gas ]^0.5 was interpreted in terms of the concept of a heterogeneous-catalytic process.     

Interaction of tetravalent actinides and Np(V) with some hydroxy carboxylic acids

Interaction of actinides(IV) with hydroxyisobutyric acid (HHIB) in aqueous solutions and in the course of crystallization of solid compounds was studied. The complexes ML _n ^(4-n)+ (M = U, Np, Pu; L^? is hydroxyisobutyrate anion; n = 1, 2, 3) exist in solution. Their apparent stepwise stability constants K?? _i were measured, and the overall concentration stability constants ??₃ of the complexes ML ₃ ⁺ were calculated. For U(IV) and Np(IV), log??₃ is close to 13.3?C13.4, and for Pu(IV), log??₃ = 14.5 ± 0.9 (ionic strength I = 0.1?C0.3). In the course of crystallization in air, complexes of U(IV) with hydroxyisobutyric acid, as well as those with citric acid, undergo oxidative degradation, which can be accompanied by complete oxidation of U(IV). The crystalline compounds formed in the process are oxalates of U(IV) or U(VI). The complexation of Np(V) with HHIB was studied. NpO ₂ ⁺ forms with HHIB the complexes NpO₂L and NpO₂L ₂ ^? . Their concentration stability constants are logK ₁ = 2.04 ± 0.15 and logK ₂ = 0.71 ± 0.10 (I = 0.4), i.e., log??₂ = 2.75 ± 0.25.     

Oxidation of Np(V) with Xenon Trioxide in an HClO<Subscript>4</Subscript> Solution

Oxidation of Np(V) to Np(VI) with xenon trioxide in a 0.5–1.4 M HClO₄ solution was studied by spectrophotometry. The reaction rate is described by the equation–d[Np(V)]/dt = k[Np(V)][XeO₃], where k = 4.6 × 10^–3 L mol^–1 s^–1 in 1 M HClO₄ at 92°С. The activation energy is close to 92 kJ mol^–1. The activated complex is formed in contact of NpO ₂ ⁺ and ХеО₃ without participation of Н⁺ ions. The activated complex transforms into NpO ₂ ²⁺ and the products: ОН, Хе, and О₂. The ОН radical oxidizes Np(V). Admixtures of Со²⁺ and especially Fe³⁺ accelerate the Np(V) oxidation.