Molecular structure and vibrational characteristics of thorium tetrafluoride

The molecular structure of ThF₄ is studied by synchrotron electron diffractometry and mass spectrometry. The thermally mean values of internuclear distances are found at a temperature of 1370±20 K: r_g(Th-F) = 2.124(5) å, r_g(F-F) = 3.418(31) å, δ(F-F) = 0.049(32) å, and LF-Th-F = 107.2(1.7)?. These distances agree with the tetrahedral structure of the molecule. The missing vibration frequencies of the ThF₄ molecule are calculated in a combined analysis of electron diffraction and spectroscopic data: v₁ = 620(30) cm^-1 and v₂ = 115(15) cm^-1.     

Stabilities and thermodynamics of uranyl(II) and thorium(IV) complexes of 2-mercaptoethanol

The complexation of UO₂ ⁺² and Th⁺⁴ ions with 2-mercaptoethanol has been studied by potentiometric and conductometric titration techniques. Uranyl ion forms 11 and 12 complexes in the pH-range 3.3–6.5 and thorium ion forms 12, 13, and 14 complexes in the pH-range 3.2–4.8 with considerable overlapping. Their logk _stab. values are determined at 10, 20, and 30°C at ionic strength =0.1M (NaClO₄) by applyingCalvin-Melchior's extension of theBjerrum method. The overall changes in thermodynamic functions G, H, and S accompanying complexation determined at 20°C are –19.48 kcal/mole, –22.77 kcal/mole, –11.23 cal/deg·mole for uranyl complexes and –33.94 kcal/mole, –4.93 kcal/mole, 99.00 kcal/deg·mole for thorium complexes, resp.     

A combined anion exchange-solvent extraction procedure for separating trace amounts of Eu,Gd, Dy,Sm and Er from thorium tetrafluoride

A combined anion exchange-solvent extraction procedure has been developed to facilitate the spectrographic determination of trace quantities of Eu, Gd, Dy, Sm and Er in thorium tetrafluoride.     

The ESR spectrum of arsenic tetrafluoride

The ESR spectrum of AsF₄, generated by γ-radiolysis of a solid solution of AsF₃ in SF₆, is reported. The ⁷⁵As hyperfine interaction is 1576 G, and the two kinds of ¹⁹F nuclei have interactions of 49 G (equatorial) and 238 G (apical). These data are compared with those from the well-known PF₄ radical.     

Kinetics and thermodynamics of the sorption of uranium and thorium ions from nitric acid solutions onto a TBP-impregnated sorbent

Summary Kinetics and equilibrium studies on the sorption of uranium and thorium ions were carried out from nitric acid solutions by tri-n-butyl phosphate (TBP) loaded supported sorbent, commercially known as Egy-Sorb, using batch technique. Analysis of the rate data in accordance with three kinetic models revealed that the particle diffusion process was the rate determining mechanism and the sorption process of the metal ions onto impregnated sorbent follows first order reversible kinetics. The values of the first order rate constants, the rate constants of intraparticle transport, and the particle diffusion coefficients for the uranium and thorium ions were determined from the graphical representation of the proposed models. Experimental isotherms of both ions were successfully fit to Langmuir and Freundlich isotherm models over the entire concentration range studied. The effect of temperature on the equilibrium distribution values has been utilized to evaluate the changes in standard thermodynamic quantities.     

Chemistry of thorium : Volumetric determination of thorium

Thorium has been determined volumetrically. It has been precipitated with m-nitrobenzoic acid according to the method of Neish. Thorium m-nitrobenzoate has been then dissolved in sulphuric acid and titrated with titanous chloride to determine the NO₂-group which gives the amount of thorium directly.     

Conductometric estimation of thorium in dilute thorium chloride

Summary Conductometric titrations of thorium chloride against oxalic acid, ammonium oxalate and silver nitrate have been carried out at high dilutions (0.001, 0.0005 and 0.00033 M) of the chloride. Oxalic acid is found to be a suitable titrant for rapid estimation of thorium, the minimum error being +0.5%. The other titrants do not give good results. The titrations with ammonium oxalate indicate the step-wise ionisation of ThCl₄ into ThCl₂ ²⁺, ThCl³⁺ and Th⁴⁺. For mixtures of thorium chloride and cerous chloride, only the equivalence point corresponding to complete precipitation of both thorium and cerium is indicated.The authors express their sincere thanks to Prof. S. S.Joshi for his keen interest in this work and to Dr. G. S.Deshmukh for his advice and help in so many ways during the progress of these studies.     

How to purify commercial sulfur tetrafluoride

Commercial SF₄ was purified by conditioning at 300 °C followed by distillation.     

Pentafluorophenylbromine(V) tetrafluoride

Pentafluorophenylbromine(V) tetrafluoride has been prepared by the oxidation of pentafluorophenyl bromide at 128°C with elemental fluorine.     

汽化热量热计的建立及物质汽化潜热的测定

在J.H.Mathews仪器的基础上进行适当改进,本文建立了一种等温绝热型汽化热量热计,经对甲醇、乙醇、苯、甲苯和水等物质的测定,精度可达0.1-0.2%,与文献值对比,准确度在0.3%以内,在纯物质测定的基础上,对水+乙醇、苯+甲醇两个二元物系进行了等压积分汽化潜热的测定,文中对采用“差分-积分图”方法反映汽化过程中体系的焓变作了一些探讨,另外,本文还就我国石油轻馏分汽化热的测定进行了初步的探索和研究。     

Radiochemical separation of thorium acetylacetonate from other thorium species

A solvent extraction technique to separate different chemical species of thorium is presented. The products formed by the chemical effects of the /n,/ reaction on the Th/acac/₄ were separated by this method and the retention value was measured.     

Quasi-relativistic study of electronic structure of uranium tetrafluoride

Conclusions A comparison of the results obtained in a calculation of the electronic structure of UF₄, performed in the NR and QR approximations of the X-SW method, leads to a number of conclusions as to the role of relativistic effects in the electronic structure of molecules. a) An accounting for relativistic effects leads to changes in the spatial distribution of charge in the molecules and to a consequent change in the interpretation of the bond in terms of the ratio of ionic and covalent components. b) Relativistic compression of the wave functions of the s and p electrons (primary relativistic effects) and delocalization of the d and f functions (secondary relativistic effects) lead to substantial changes in the orbital energies and the corresponding ionization potentials in heavy molecules. c) Primary and secondary relativistic effects are responsible for considerable changes in the electronic excitation energies and the EA, changes that may account to as much as 200%. d) An accounting for spin-orbit interaction effects is extremely important in interpreting photoelectron and optical spectra. In the example of UF₄, it has been shown that NR wave functions are inadequate for use in calculating spin—orbit splittings in heavy molecules. Just as inadequate may be an accounting for spin—orbit interaction in first-order perturbation theory for systems of closelying MOs, the charge density of which is determined to a considerable degree by AOs of a single type (for example, 5f AOs of uranium in UF₄).Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 20, No. 4, pp. 406–415, July–August, 1984.The authors wish to express their appreciation to M. I. Timokhin for assistance in performing the calculations.     

The first examples of germanium tetrafluoride and tin tetrafluoride complexes with soft thioether coordination--synthesis, properties and crystal structures

The first thioether complexes of the hard Lewis acidic GeF(4) and SnF(4) have been prepared by reaction of [GeF(4)(MeCN)(2)] or [SnF(4)(MeCN)(2)] respectively with the thioether ligand in rigorously anhydrous CH(2)Cl(2) solution. The isolated compounds were characterised spectroscopically (IR, (1)H and (19)F{(1)H} NMR) and by microanalyses. Crystal structures of four representative examples, [GeF(4){MeS(CH(2))(2)SMe}], [GeF(4){EtS(CH(2))(2)SEt}], [SnF(4){EtS(CH(2))(2)SEt}] and [SnF(4){(i)PrS(CH(2))(2)S(i)Pr}], reveal distorted octahedral adducts with chelating thioethers, and weak, secondary Ge-S and Sn-S bonds. These compounds are the first reported examples of thioether complexes with any main group metal/metalloid fluoride acceptor.     

Treatment of dimethyl (+)-L-tartrate with sulfur tetrafluoride

Treatment of dimethyl (+)-L-tartrate (I) with sulfur tetrafluoride results in the formation of an intermediate, 2-fluoro-1,2-bis(methoxycarbonyl)ethyl fluorosulfite (II), which under the action of hydrogen fluoride, present in the reaction mixture, is converted into dimethyl (?)(2S:3S)-2-fluoro-3-hydroxysuccinate (III). The reaction of the latter with SF₄ leads to dimethyl meso-2,3-difluorosuccinate (IV). The structure and configurations of the compounds obtained were established by ¹H and ¹⁹F NMR. Treatment of dimethyl (+)-L-tartrate (I) with sulfur tetrafluoride in the presence of excessive hydrogen fluoride gave dimethyl meso-2,3-difluorosuccinate in 96% yield.