共查询到20条相似文献,搜索用时 31 毫秒
1.
Gary L. Silver 《Journal of Radioanalytical and Nuclear Chemistry》2014,301(3):905-908
Equations representing disproportionation reactions should be numerically verifiable. Comprehensive, balanced equations for plutonium disproportionation reactions can be verified in several ways. Overall equations for Pu disproportionation reactions do not meet all the requirements. 相似文献
2.
G. L. Silver 《Journal of Radioanalytical and Nuclear Chemistry》2013,298(3):1933-1935
Maxima in the fractions of the trivalent and hexavalent oxidation states of plutonium are inherent in the algebra of its disproportionation reactions. The maxima do not support overall disproportionation equations as satisfactory representations of aqueous plutonium. 相似文献
3.
G. L. Silver 《Journal of Radioanalytical and Nuclear Chemistry》2005,267(1):53-57
Summary This paper illustrates a generalized form of the method of proportional equations. It permits equilibrium calculations for
Pu disproportionation reactions at any oxidation number and any pH by means of combining arbitrary proportions of tri- and
hexavalent plutonium. Two methods for estimating the work of Pu polymer formation are illustrated. One method uses the work
of disproportionation of tetravalent plutonium. The other method suggests the transition between hydrous Pu(IV) oxide and
polymer is accompanied by a small change in free energy. 相似文献
4.
J. M. Navarrete V. M. Urbina T. Martínez L. Cabrera 《Journal of Radioanalytical and Nuclear Chemistry》2005,263(3):779-781
The disproportionation of pentavalent plutonium is traditionally represented by two inconsistent equations. The inconsistency puts the widely-accepted, fourth-power hydrogen-ion dependence of the reaction into question. The balanced reaction equation suggests that both the stoichiometry and the acid-dependence of Pu(V) disproportionation depend on the pH of the plutonium solution.Los Alamos National Laboratory is operated for the U.S. Department of Energy by the University of California under Contract No. W-7405-ENG-36. 相似文献
5.
G. L. Silver 《Journal of Radioanalytical and Nuclear Chemistry》2004,262(3):779-781
The disproportionation of pentavalent plutonium is traditionally represented by two inconsistent equations. The inconsistency puts the widely-accepted, fourth-power hydrogen-ion dependence of the reaction into question. The balanced reaction equation suggests that both the stoichiometry and the acid-dependence of Pu(V) disproportionation depend on the pH of the plutonium solution.Los Alamos National Laboratory is operated for the U.S. Department of Energy by the University of California under Contract No. W-7405-ENG-36. 相似文献
6.
7.
G. L. Silver 《Journal of Radioanalytical and Nuclear Chemistry》2008,277(2):471-473
Disproportionation equations are illustrated for two oxidation numbers (N) and for the general case of any N. The new method illustrates the effect of N on the coefficients in disproportionation equations. An estimate of the equilibrium constant for the first hydrolysis reaction
of tetravalent plutonium is obtained by a new approach. The estimated value agrees with many previous results. 相似文献
8.
G. L. Silver 《Journal of Radioanalytical and Nuclear Chemistry》2003,258(1):157-158
Balanced disproportionation equations indicate phenomena not predicted by the traditional, two-reaction-product equations. This communication illustrates unanticipated maxima in oxidation state distributions and suggests that they might be useful for characterizing alpha coefficients in aqueous solutions.(Los Alamos National Laboratory is operated for the U.S. Department of Energy by the University of California under Contract No. W-7405-ENG-5) 相似文献
9.
Summary Equilibrium prevails at all points in plutonium predominance region diagrams. Triple points combine equilibrium with equal
fractions of three Pu oxidation states. A rearrangement equation can be used to describe plutonium at a triple point. Two-reaction-product
disproportionation equations are not satisfactory for that purpose. 相似文献
10.
针对自由基共聚合反应歧化终止和偶合终止两类机理生成的线型共聚物,应用统计物理的基本原理,对处于最可几分布状态下的线型共聚物分子量分布函数进行了理论推导,并以此分布函数,结合自由基共聚合机理动力学处理和概率计算,从另一种途径得到Mayo-Lowis和Alfrey-Goldfinger简单共聚物组成方程,研究结果有助于进一步理解简单共聚模型组成方程的物理学基础,同时也将为线型自由基共聚合反应机理的研究提供一个新方法. 相似文献
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12.
采用氨吸附-差热技术、红外光谱对氢型丝光沸石(HM)在不同温度氨吸附性质进行了研究,得到氨的可逆吸附与不可逆吸附的相对量及其随温度的变化。在接近甲苯岐化反应实际进行的条件下,测定了HM上吸附氨的红外光谱和催化活性。实验结果表明氨在L酸中心上的吸附是可逆的,在B酸上的吸附是不可逆的,从而证实了B酸是甲苯岐化反应的催化活性中心。在我们实验条件下,L酸中心似乎对岐化反应没有直接的作用。 相似文献
13.
Gury Zvilichovsky 《Tetrahedron》1977,33(17):2259-2266
8-Alkyl-7-hydroxyxanthines undergo in aqueous solution, near pH 5, an unusual spontaneous autocatalytic disproportionation. They yield the corresponding 8-alkylxanthines as the reduction product and 6-amino-5-nitrosouracil as the oxidation product. The disproportionation can also be induced by anhydrides at pH 4–12. The alkyl group at position 8 is essential for these reactions. Possible mechanisms are discussed. 相似文献
14.
Carp DJ Bartholomai GB Relkin P Pilosof AM 《Colloids and surfaces. B, Biointerfaces》2001,21(1-3):163-171
The effect of xanthan on foam formation and on physical mechanisms of destabilization involved in the breakdown of foams made from native and denatured soy protein at neutral pH was studied by a bubbling and a whipping-rheological method. Parameters describing foam formation and destabilization by liquid drainage and disproportionation obtained by the two methods showed that the addition of xanthan was accompanied by delayed rates of drainage and disproportionation and reduced foam height decay (collapse). Drainage showed the largest reduction, mainly because of the increased bulk viscosity. In the absence of xanthan, protein denaturation enhanced foam formation and stability against drainage and disproportionation, but increased the collapse of foams. In the presence of xanthan, differences in foam formation and drainage/disproportionation stability between native and denatured soy protein were greatly reduced. However, differences in foam collapse were greatly enhanced. The increased stability of foams in the presence of xanthan could not be explained purely in terms of increased aqueous phase viscosity. More specific interactions of xanthan and soy proteins at the air-water interface influencing the surface rheology, and the protein composition and aggregation, are involved. 相似文献
15.
针对自由基聚合歧化终止和偶合终止两类机理生成的线型高聚物,应用统计物理的基本原理,对其分子量分布重新进行了理论推导,其方法简洁清晰,无须任何附加假定,导出FlorySchulz分布.结果有助于从另一方面理解FlorySchulz分布的物理学基础. 相似文献
16.
A. Yu. Zuev A. N. Petrov A. I. Vylkov D. S. Tsvetkov 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2007,81(1):73-77
The paper presents the results obtained in studying the oxygen nonstoichiometry of undoped lanthanum cobaltite LaCoO3?δ as a function of temperature and oxygen pressure. A model analysis of the defect structure of the compound was performed. Two models were considered. For the first model, it was assumed that electrons and electron holes were quasi-free, whereas, in the second model, they were considered localized on cobalt ions. The internal electronic disordering and thermally excited disproportionation of cobalt were also taken into consideration in the first and second models, respectively. For both models, systems of nonlinear equations comprising the corresponding mass action law, mass balance, and electroneutrality equations were constructed. Verification equations were obtained for both models by solving these systems. The correspondence of the suggested models to experimental data was checked by the nonlinear regression method. Both models almost equally correctly described the data on the oxygen nonstoichiometry of LaCoO3?δ. The conclusion was drawn that these data were insufficient for selecting the most realistic model of the defect structure of this compound. 相似文献
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18.
A theoretical study of the inner-sphere disproportionation reaction mechanism of the pentavalent actinyl ions 总被引:1,自引:0,他引:1
The inner-sphere mechanisms of the disproportionation reactions of U(V), Np(V), and Pu(V) ions have been studied using a quantum mechanical approach. The U(V) disproportionation proceeds via the formation of a dimer (a cation-cation complex) followed by two successive protonations at the axial oxygens of the donor uranyl ion. Bond lengths and spin multiplicities indicate that electron transfer occurs after the first protonation. A solvent water molecule then breaks the complex into solvated U(OH)2(2+) and UO2(2+) ions. Pu(V) behaves similarly, but Np(V) appears not to follow this path. The observations from quantum modeling are consistent with existing experimental data on actinyl(V) disproportionation reactions. 相似文献
19.
Barakat KA Cundari TR Rabaâ H Omary MA 《The journal of physical chemistry. B》2006,110(30):14645-14651
A computational study of gold(II) disproportionation is presented for the atomic ion as well as complexes with chloride and neutral ligands. The Au2+ atomic ion is stable to disproportionation, but the barrier is more than halved to 119 kcal/mol in an aqueous environment vs 283 kcal/mol in the gas phase. For dissociative disproportionation of chloride complexes, the loss of chlorine, either as an atom (Delta G(aq) = +20 kcal/mol) or as an anion (Delta G(aq) = +15 kcal/mol) represents the largest calculated barrier. The calculated transition state for associative disproportionation is only 9 kcal/mol above separated Au(II)Cl3(-) anions. For the disproportionation of Au(II)L3 complexes with neutral ligands, disproportionation is highly endergonic in the gas phase. Calculations imply that for synthesis of a monometallic Au(II) complex, a nonpolar solvent is preferred. With the exception of [Au(CO)3]2+, disproportionation of Au(II)L3 complexes to Au(I)L and Au(III)L3 is exergonic in solution phase for the ligands investigated. The driving force is provided by the very favorable solvation free energy of the trivalent gold complex. The solvation free energy contribution to the reaction (Delta G(solv)) is very large for small and polar ligands such as ammonia and water. Furthermore, calculations imply that choosing ligands that would yield neutral species upon disproportionation may provide an effective route to thwart this decomposition pathway for Au(II) complexes. Likewise, bulkier ligands that yield larger, more weakly solvated complex ions would appear to be desirable. 相似文献
20.
Brad M. Rosen Xuan Jiang Christopher J. Wilson Nga H. Nguyen Michael J. Monteiro Virgil Percec 《Journal of polymer science. Part A, Polymer chemistry》2009,47(21):5606-5628
Disproportionation of Cu(I)X is the major step in Single‐Electron Transfer Living Radical Polymerization (SET‐LRP). The disproportionation of Cu(I)X mediated by Me6‐TREN in various solvents was studied through UV–vis spectroscopy and Dynamic Light Scattering (DLS). UV–vis experiments reveal that disproportionation is dependent on both solvent composition and concentration of Me6‐TREN, consistent with a revised equilibrium expression and corroborated by mathematical models. Electrochemistry data do not accurately predict the extent of disproportionation in the presence of Me6‐TREN. Exemplified by DMSO, a favored solvent for SET‐LRP, UV–vis spectroscopy shows that under certain conditions disproportionation is four‐orders of magnitude greater than the value reported from electrochemistry experiments. Through UV–vis and DLS analysis, it was demonstrated that DMSO, DMF, DMAC, and NMP, stabilize colloidal Cu(0), while acetone, EtOH, EC, MeOH, PC, and H2O facilitate agglomeration of Cu(0) particles. Additionally, for colloidal Cu(0) stabilizing solvents, the amount of ligand and solvent composition decide the particle size distribution. Therefore, the kinetics of SET‐LRP are cooperatively and synergistically determined by the complex interplay of solvent polarity, the extent of disproportionation in the solvent/ligand mixture, and the ability of that mixture to stabilize colloidal Cu(0) or control particle size distribution. The implications of these results for SET‐LRP are discussed. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5606–5628, 2009 相似文献