Dissociative equilibria of vapor-phase (UO/sub 2/(hfacac)/sub 2/)/sub 2/ and UO/sub 2/(hfacac)/sub 2/THF

Journal Article · Thu Oct 01 04:00:00 EDT 1981 · J. Phys. Chem.; (United States)

DOI:https://doi.org/10.1021/j150620a010· OSTI ID:6044369

Woodin, R L; Cox, D M; Hall, R B; Kaldor, A

Dissociative thermal equilibria of dimeric uranyl bis(hexafluoroacetylacetonate) ((UO/sub 2/(hfacac)/sub 2/)/sub 2/) and uranyl bis(hexafluoroacetylacetonate) tetrahydrofuran (UO/sub 2/(hfacac)/sub 2/THF) have been studied in the vapor phase at temperatures from 80 to 200/sup 0/C by using molecular-beam mass spectrometry. Equilibria observed in this temperature range are (1) (UO/sub 2/(hfacac)/sub 2/)/sub 2/ in equilibrium 2UO/sub 2/(hfacac)/sub 2/ and (2) UO/sub 2/(hfacac)/sub 2/THF in equilibrium UO/sub 2/(hfacac)/sub 2/ + THF. Thermochemical data derived from these experiments (at 400 K) are ..delta..H/sup 0//sub 1/ = 23 +- 3 kcal/mol, ..delta..S/sup 0//sub 1/ = 36 +- 3 eu, ..delta..H/sup 0//sub 2/ = 33 +- 3 kcal/mol, and ..delta..S/sup 0//sub 2/ = 55 +- 5 eu. Data for reaction 1 are in good agreement with published values. Comparison of measured reaction entropies and statistical mechanical entropy calculations indicates that (UO/sub 2/(hfacac)/sub 2/)/sub 2/ has a loose structure, most probably involving an oxygen from one uranyl group completing the coordination sphere of the second uranyl. The entropy change for reaction 2 may be considered an upper bound on the entropy of activation assuming a Gorin model for dissociation. An upper bound of 10/sup 25/ /sup 4/ s/sup -1/ is then derived for the reaction preexponential factor, consistent with a value of 10/sup 18/ s/sup -1/ used to model the infrared-laser-induced dissociation of UO/sub 2/(hfacac)/sub 2/THF.

• Research Organization: Exxon Research and Engineering Co., Linden, NJ
• OSTI ID: 6044369
• Journal Information: J. Phys. Chem.; (United States), Journal Name: J. Phys. Chem.; (United States) Vol. 85:20; ISSN JPCHA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEAR CHEMISTRY
400500* -- Photochemistry
400702 -- Radiochemistry & Nuclear Chemistry-- Properties of Radioactive Materials
ACTINIDE COMPLEXES
BEAMS
CHEMICAL REACTIONS
COMPLEXES
DATA
DIMERS
DISSOCIATION
ENTHALPY
ENTROPY
ESTERS
EXPERIMENTAL DATA
FURANS
HETEROCYCLIC COMPOUNDS
INFORMATION
LASERS
MASS SPECTROSCOPY
MEDIUM TEMPERATURE
MOLECULAR BEAMS
NUMERICAL DATA
ORGANIC COMPOUNDS
ORGANIC FLUORINE COMPOUNDS
ORGANIC HALOGEN COMPOUNDS
ORGANIC OXYGEN COMPOUNDS
PHOTOCHEMICAL REACTIONS
PHYSICAL PROPERTIES
SPECTROSCOPY
TETRAHYDROFURAN
THERMODYNAMIC PROPERTIES
URANIUM COMPLEXES
URANYL COMPLEXES