The ratio Pu(V)/Pu(IV) in natural water

The behavior of the ratio Pu(V)/Pu(IV) depends on whether the symbols represent absolute concentrations of soluble species, or fractions of the total soluble plutonium, or insoluble, colloidal substances.Mound is operated by EG&G Mound Applied Technologies for the U.S. Department of Energy under Contract No. DE-AC04-88DP43495.     

Bi(OTf)3 catalyzed disproportionation reaction of cinnamyl alcohols

Bi(OTf)₃ catalyzed disproportionation reaction of cinnamyl alcohols provides chalcones and benzyl styrenes. The use of various metal triflates is investigated herein for facile and efficient redox transformation. A plausible mechanism has been proposed.     

New polynuclear U(IV)-U(V) complexes from U(IV) mediated uranyl(V) disproportionation

U(IV) promotes the disproportionation of otherwise stable uranyl(V) Schiff base complexes affording U(IV)-U(V) oxo clusters with new geometries and the first example of a U(IV)···UO(2)(+) cation-cation interaction.     

A DSC study on the kinetics of disproportionation reaction of (hfac)Cu(COD)

The kinetics of disproportionation reaction of hexafluoroacetylacetonate-copper(I)-cycloocta-1,5-diene [(hfac)Cu^I(COD)] was investigated by the use of differential scanning calorimetry (DSC) with different heating rates in dynamic nitrogen atmosphere. First, the activation energies (E_as) of the disproportionation reaction were estimated with model-free isoconversional methods, respectively. The E_as were found to fall within the range between 17.6 and 18.7 kJ mol⁻¹, with no temperature and heating rate effects observed. Then, when the E_a was ascertained, the model-fitting methods with least square fitting procedure were adopted to determine the kinetic model for the disproportionation reaction. As a result, the disproportionation reaction follows second-order reaction kinetics.     

The photochemical disproportionation reaction in the system CuCl(s)-H2O(l)

The photochemical production of Cu⁰ in the system CuCl(s)—H₂O(l) was investigated using reflectance spectoscopy. For u.v. light activation the spectral sensitivity follows the excitonic absorption band of CuCl. The system may also be activated with visible light (after an induction period) through a sensitized process with the photoproduct Cu⁰ as the sensitizer. The experimental data, including the time-course of the reaction, are consistant with the following mechanism: Cu⁰ aggregates are formed close to the phase boundary. Continued exposure increases the depth of the Cu⁰ containing layer but the local concentration of Cu⁰ stays essentially constant. With u.v. light there is a continued increase in the number of Cu⁰ aggregates but visible light activation has in addition the effect of enlarging the aggregates. As the depth of the layer increases the reaction is slowed down due to an inner filter effect from Cu⁰; the Hurter equation, usually employed to characterize the photographic process in silver halide systems, is obeyed.     

The Existence of Hexafluoroarsenic(V) Acid

The homogeneous mixture of anhydrous hydrogen fluoride aHF and antimony pentafluoride AsF₅ is known as a superacidic system. The high acidity is derived from the formation of [H₂F]⁺ [AsF₆]^?. No experimental evidence exists for the existence of the free acid molecule HAsF₆. The reaction of trimethylsilyl N,N‐dimethylcarbamate in the binary system aHF/AsF₅ led to decomposition of trimethylsilyl N,N‐dimethylcarbamate at ?50 °C to dimethylammonium hexafluoridoarsenate and cocrystallization of HAsF₆. The single‐crystal X‐ray structure displays an HAsF₆ molecule involved in an asymmetric hydrogen bridge to the hexafluoridoarsenate anion. As a result of the incalculable situation in the crystal lattice, the molecular structure of HAsF₆ is calculated by quantum chemical structure optimization of the extreme cases of [FHF‐AsF₅]^? (strong hydrogen bond) and HAsF₆ (no hydrogen bond) at the PBE1PBE/6‐311G(3df,3pd) level of theory.     

First Evidence for the Existence of Hexafluoroantimonic(V) Acid

By reacting IPr ? InBr₃ with AgSbF₆ in dichloroethane at room temperature, we could obtain single crystals comprising [{(IPr ? InBr₃)(Ag ? (CH₂Cl)₂)}₂][SbF₆]₂ ( 1 ) and two identical HSbF₆ units. It is presumed that the reaction gave rise to [IPr ? InBr_3?x][SbF₆]_x (x=1, 2, or 3) which reacted with adventitious water to give HSbF₆ and [IPr ? InBr_3?x(OH)][SbF₆]_x?1. The experiment was reproduced at 60 °C, eventually leading to the indium hydroxide [{IPr ? In(OH)_0.5(H₂O)_4.5}₂][SbF₆]₅ ( 2 ).     

The reaction of alkoxides with dicobalt octacarbonyl: Trapping of the Co(I) intermediate in the disproportionation (“base reaction”) with a hardLewis base

Dicobalt octacarbonyl reacts with alcoholates (RO^–) yielding alkoxycarbonylcobalt tetracarbonyls,ROC(O)Co(CO)₄.

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Reaktion von Alkoxiden mit Dicobaltoctacarbonyl: Abfangen des Co(I) Zwischenproduktes in der Disproportionierung (Basen-Reaktion) mit einer hartenLewis Base (Kurze Mitteilung)

Zusammenfassung Dicobaltoctacarbonyl reagiert mit Alkoxiden (RO^–) zu Alkoxycarbonylcobalt tetracarbonylen,ROC(O)Co(CO)₄.

     

The Chemistry of (U,Pu)O2 Dissolution in Nitric Acid

The focus of this paper is the chemistry of mixed uranium plutonium oxide (MOx,) in nitric acid. An overview of dissolution chemistry is discussed by comparing the differences in the dissolution characteristics of uranium and plutonium oxides. An overview of batch dissolution experiments, studying the dissolution chemistry of high surface area MOx powders and low surface area MOx pellets with reference to the effects of nitrous acid, nitric acid and temperature are described. The results are discussed in terms of the autocatalytic mechanism and mass transfer limited dissolution.     

Vanadium(V) Complexes in Hydrochloric Acid Solutions

^51V NMR, electronic, and vibrational spectroscopies were applied to study the ionic state of vanadium(V) in hydrochloric acid solutions at cHCl = 1.0-11.3 M and vanadium(V) concentration of 1 M.     

Kinetic study of the reaction betweentrans-tetracyanodioxorhenate(V) and thiocyanate ions

Transition Metal Chemistry - The kinetics of the reaction between NCS− and the diprotonated forms of [ReO2(CN)4]3− have been studied in theca. 1 to 3 pH range. This study showed that...     

DFT study of the structure and stability of Pu(III) and Pu(IV) chloro complexes

The structural characteristics and energies of PuCl _n ^{(3 − n)+} and PuCl _n ^{(4 − n)+} complexes (n = 2–8) have been studied by the density functional theory (DFT) method in the SVWN5 local functional approximation.     

Direct spectrophotometric analysis of low level Pu(III) in Pu(IV) nitrate of Pu precipitation process feed solution

To achieve end user’s specified PuO₂, controlling and monitoring of Pu in its fourth valency state is essential prior to the conversion of Pu-nitrate to its oxide through oxalate precipitation process. Conventional radiometric procedure for the analysis of Pu oxidation state in Pu-nitrate solution containing trace level of Pu(III) has limitation due to oxidation of Pu(III) during the sample preparation with respect to acidity. A simple direct spectrophotometry using an optic fiber spectrophotometer was attempted for the estimation of trace level of Pu(III), after separating the bulk amount of Pu(IV) by maintaining the sample acidity. By using a synergistic mixture of 30 % TBP and 1 M theonyl trifluoro acetone in benzene, the Pu(IV) could be removed to a level which doesn’t interfere in the Pu(III) absorption.     

Catalytic disproportionation of alkyl(and alkenyl)dichlorosilanes

Russian Chemical Bulletin -     

Quantum chemical calculations of the redox potential of the Pu(VII)/Pu(VIII) couple

The redox potential of the Pu(VII)/Pu(VIII) couple was studied by density functional theory calculations. The spin-orbit effect was corrected at the CASSCF level. The redox potential (relative to the standard hydrogen potential) of the Pu(VII)/Pu(VIII) couple in alkaline solution was found to vary from 4.36 to 1.06 V depending on the number of Pu-O oxo bonds, coordination numbers, and coordination modes. The redox potential drops substantially as the number of Pu-O oxo bonds increases. Pu(VIII) may be synthesized in strong alkaline solution assuming that both Pu(VII) and Pu(VIII) exist in penta-oxo form, Pu (VII)O 5OH (4-) and Pu (VIII)O 5OH (3-), respectively. The Mulliken population of Pu in Pu(VII) and Pu(VIII) complexes are very similar, suggesting that the spin-orbit effect is rather small in Pu(VII) complexes and that when Pu(VII) is oxidized to Pu(VIII) the electron is stripped mainly from the ligand. Consequently, Pu(VIII) is in an unstable oxidation state and easily reduced back to Pu(VII) by the solvent water molecules. In acidic medium, the Pu(VII)/Pu(VIII) redox potential is too high to get the Pu(VIII) valence state.     

Electrochemistry and Spectroelectrochemistry of the Pu (III/IV) and (IV/VI) Couples in Nitric Acid Systems

The solution chemistry of Pu in nitric acid is explored via electrochemistry and spectroelectrochemistry. By utilizing and comparing these techniques, an improved understanding of Pu behavior and its dependence on nitric acid concentration can be achieved. Here the Pu (III/IV) couple is characterized using cyclic voltammetry, square wave voltammetry, and a spectroelectrochemical Nernst step. Results indicate the formal reduction potential of the couple shifts negative with increasing acid concentration and reversible electrochemistry is no longer attainable above 6 M HNO₃. Spectroelectrochemistry is also used to explore the irreversible oxidation of Pu(IV) to Pu(VI) and shine light on the mechanism and acid dependence of the redox reaction.