13775-07-0Relevant articles and documents
Reactions of methyl and ethyl radicals with uraniun hexafluoride
Lyman, John L.,Laguna, Glenn
, p. 183 - 187 (1985)
We have measured the rates of reaction of both methyl and ethyl radicals with uranium hexafluoride (UF6) in the gas phase.The method we used was to photolyze samples of UF6 in the presence of either methane or ethane.The radicals produced by reaction of f
LOW-TEMPERATURE PHASE TRANSITIONS AND MAGNETIC SUSCEPTIBILITIES OF LOW-DIMENSIONAL URANIUM FLUORIDES
Ikorskii, V. N.,Goncharuk, V. K.,Nikitin, P. S.,Polishchuk, S. A.,Gabuda, S. P.
, p. 898 - 901 (1986)
Measurements have been made on the magnetic susceptibilities of the quasi-one-dimensional magnetic α-UF5 and the cluster magnetic U2F9 (a four-nuclear type) over the range 4.2-300 K.The Curie-Weiss law applies for α-UF5 above 200 K, with μef = 2.37μB, θ = -148 K; that law also applies to U2F9 above 150 K, with μef = 2.9μB and θ = 118 K.The antiferromagnetic ordering is discussed for the one-dimensional chains in α-UF5 together with the phase transition observed in U2F9 at 6 K.It is assumed that the U4+ and U5+ valency states are stabilized below the phase-transition point, and only then can U2F9 be cosidered as the compound UF4.UF5.
Thermochemistry of uranium compounds. XII. Standard enthalpies of formation of the α and β modifications of uranium pentafluoride. The enthalpy of the β-to-α transition at 298.15 K
O'Hare, P. A. G.,Malm, John G.,Eller, P. Gary
, p. 323 - 330 (1982)
A solution-calorimetric determination of the enthalpies of reaction of the α and β modifications of UF5 with Ce(SO4)2 + H2SO4 is described.Auxiliary measurements were made of the enthalpies of reaction of UO2, γ-UO3, and HF(aq).From these results are calculated the standard enthalpies of formation ΔH0f(298.15 K) of β-UF5, -(2083.0 +/- 6.3) kJ/mol and of α-UF5, -(2075.5 +/- 6.7) kJ/mol.The enthalpy of the (β-to-α) transition is (7.5 +/- 2.1) kJ/mol at 298.15 K.Suggested ΔH0f values are also given for U4F17 and U2F9.
OPTICAL STUDY OF alpha -UF5 AND beta -UF5.
Hecht,Malm,Carnall
, p. 79 - 89 (1986)
The optical absorption spectra of polycrystalline samples of both alpha - and beta -UF//5 have been measured in the range 2700-500 nm at 4, 77 and about 293 K using a recording spectrophotometer. It was assumed that the crystal field in both cases was dominated by weak covalent interactions; consequently crystal-field analyses were developed based on the angular overlap model. Crystal-field parameters consistent with the experimental data were derived.
Orientational Ordering and Site-Selective Photochemistry of UF6 Isolated in Argon Matrices
Jones, Llewellyn H.,Swanson, Basil I.,Ekberg, Scott A.
, p. 1285 - 1286 (1984)
High-resolution studies of the ν3 mode of UF6 in argon matrices show two dominant sites with a high degree (80percent) of orientational ordering.Upon photolysis UF5 is formed but recombines in part to form UF6 on metastable sites.One site is considerably more amenable to photolysis than the other.On high-temperature annealing (40 K) all the UF5 is converted back to UF6 and the original dominant sites are re-formed to a considerable extent.Through all this photoexcitation, dissociation, recombination, and annealing the original ordering is preserved.
Reactions of uranium hexafluoride photolysis products
Lyman, John L.,Laguna, Glenn,Greiner, N. R.
, p. 175 - 182 (1985)
This paper confirms that the ultraviolet photolysis reactions of UF6 in the B band spectral region is simple bond cleavage to UF5 and F.The photolysis products may either recombine to UF6 or the UF5 may dimerize, and ultimately polymerize, to solid UF5 pa
Chemical kinetics of the gas-phase reaction between uranium hexafluoride and hydrogen
Myerson,Chludzinski Jr.
, p. 3905 - 3911 (1981)
A study was made of the chemical kinetics of the homogeneous gas-phase reaction between uranium hexafluoride and hydrogen by measuring the rate of disappearance of UF6. It has been concluded that the rate-limiting step for which the kinetics have been measured is UF6 + H2 = UF5 + HF + H (2). The reaction has been studied in a steady-state flow system over a temperature range of ～625-825 K. Various surface-to-volume ratios were employed to aid in distinguishing gas-phase reactions from surface reactions. The steady-state concentration of the UF6 after reaction with H2 was monitored in a special multipass infrared spectrophotometer at the 626-cm-1 absorption band of UF6. The principal problems were corrosion, plugging, surface intrusion, and the deleterious effects of minute traces of water; these problems have greatly slowed progress in this field. Several series of measurements involving different initial species concentrations and residence times, with each series at constant temperature, show that the rate is first order in UF6. Our measurements yield a dependable Arrhenius curve in terms of a second-order expression for k, the bimolecular specific reaction rate constant for the disappearance of UF6. It is believed that this overall rate of the disappearance of UF6 is somewhat less than twice that of the critical reaction step 2, indicated above, so that the specific reaction rate constant k2 is ～8.7 × 1014 exp(-34550 kcal/RT) cm3 mol-1 s-1. Conclusions have been reached concerning the relative importance of the various elementary reaction steps involved in the chemical mechanism.
Formation and characterization of HUF and DUF in solid argon
Vent-Schmidt, Thomas,Hunt, Rodney Dale,Andrews, Lester,Riedel, Sebastian
, p. 3863 - 3865 (2013/07/25)
Reactions of laser-ablated U atoms with HF and DF in condensing and solid rare gas produce HUF and DUF as the major new products based on close agreement between observed and calculated vibrational frequencies and deuterium shifts for U-H and U-F stretchi
Matrix IR spectra of the products from F2, ClF, and Cl2 reactions with pulsed-laser evaporated uranium atoms
Hunt, Rodney D.,Thompson, Craig,Hassanzadeh, Parviz,Andrews, Lester
, p. 388 - 391 (2008/10/08)
Pulsed Nd:YAG laser ablated uranium atoms were codeposited with F2 and excess Ar onto a CsI window at 12 K. Infrared spectra revealed the presence of several uranium fluorides including the previously characterized UF4, UF5, and UF6. Lower laser energy favored new absorptions at 400, 446, 496, and 561 cm-1. These product absorptions increased stepwise during annealings which permitted diffusion and reaction of the fluorine. Similar studies with ClF produced the above absorptions plus a new band at 554 cm-1 which is tentatively assigned to ClF2-. The first bands appearing at 400 and 446 cm-1 are assigned to UF and UF2, respectively. The 496- and 561-cm-1 bands are tentatively assigned to UF3 and F3-, respectively. Finally, uranium atoms were reacted with Cl2. In addition to several absorptions due to UCl4, a new doublet at 312 and 308 cm-1 is assigned to UCl2.
High Oxidation State Binary Transition Metal Fluorides as Selective Fluorinating Agents
Dukat, Wolfgang W.,Holloway, John H.,Hope, Eric G.,Rieland, Matthias R.,Townson, Paul J.,Powell, Richard L.
, p. 1429 - 1430 (2007/10/02)
High oxidation state transition metal fluorides are selective fluorinating agents for dichloromethane, those with d0 electronic configurations undergo hydrogen-fluorine exchange and metal reduction, while dn species undergo chlorine-
