Uranyl chloride

Uranyl chloride is a chemical compound with the chemical formula UO₂Cl₂. It consists of uranyl cations UO2+2 and chloride anions Cl⁻. It is fluorescent.^[1] Uranyl chloride also refers to inorganic compounds with the formula UO₂Cl₂(H₂O)_n where n = 0, 1, 2, or 3. These are yellow salts.

Uranyl chloride

[O=U=O]Cl2
Names
IUPAC name Dichlorodioxouranium
Other names Uranium(VI), dichlorodioxy Uranium(VI) dichloride dioxide
Identifiers
CAS Number	7791-26-6 Y
3D model (JSmol)	Interactive image hydrate: Interactive image dihydrate: Interactive image trihydrate: Interactive image
ChemSpider	21172763
ECHA InfoCard	100.029.315
EC Number	232-246-1
PubChem CID	hydrate: 129671572 dihydrate: 129693634 trihydrate: 20376300
UNII	W2V47QQ17S Y
CompTox Dashboard (EPA)	DTXSID0064882
InChI hydrate: InChI=1S/2ClH.H2O.2O.U/h2*1H;1H2;;;/q;;;;;+2/p-2 Key: DPJRXHIPGVVIJZ-UHFFFAOYSA-L dihydrate: InChI=1S/2ClH.2H2O.2O.U/h2*1H;2*1H2;;;/q;;;;;;+2/p-2 Key: FGKUZTMTIQYKJZ-UHFFFAOYSA-L trihydrate: InChI=1S/2ClH.3H2O.2O.U/h2*1H;3*1H2;;;/q;;;;;;;+2/p-2 Key: BYLGCROXFJTSJF-UHFFFAOYSA-L
SMILES [Cl-].O=[U+2]=O.[Cl-] hydrate: O.O=[U+2]=O.[Cl-].[Cl-] dihydrate: O.O.O=[U+2]=O.[Cl-].[Cl-] trihydrate: O.O.O.O=[U+2]=O.[Cl-].[Cl-]
Properties
Chemical formula	UO2Cl2
Molar mass	340.93 g·mol−1
Appearance	bright yellow large crystals[1]
Melting point	Decomposes
Boiling point	Decomposes
Solubility in water	soluble[1]
Solubility	Soluble in alcohols, acetone and ethers,[1] insoluble in benzene
Hazards
Safety data sheet (SDS)	External MSDS
Related compounds
Related compounds	Uranyl fluoride Chromyl chloride Molybdenum dichloride dioxide Tungsten dichloride dioxide Sulfuryl chloride Uranium hexachloride
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Y verify (what is YN ?) Infobox references

Synthesis and structures

Structure of the molecular complex uranyl chloride trihydrate (UO₂Cl₂(H₂O)₃). Color scheme: red = O, green = U, darker green = Cl, white = H.^[2]

The hydrates are obtained by dissolving uranyl sulfate or uranyl acetate in hydrochloric acid followed by crystallization from concentrated solutions. Depending on the method of drying, one obtains the mono- or the trihydrate. The monohydrate is described as a yellow, sulfur-like powder. It is very hygroscopic.^[3] The trihydrate is greenish-yellow. Both hydrates are fluorescent solids that are highly soluble in water.^[4]

The anhydrous material can be obtained by the reaction of oxygen with uranium tetrachloride:

UCl₄ + O₂ → UO₂Cl₂ + Cl₂

In terms of structures, all three of these compounds feature the uranyl center (trans-UO2+2) bound to five additional ligands, which can include (bridging) chloride, water, or another uranyl oxygen.^[5][6]

Reactions

The aquo ligands can be replaced by a variety of donors, e.g. THF.^[7] Uranyl chloride, and its two hydrates, (UO₂Cl₂·H₂O and UO₂Cl₂·3H₂O) decompose in the presence of light. This photosensitivity over the years, from time to time, has attracted scientific interest and there have been various unsuccessful attempts to develop applications in photography using these compounds.^[1]

Industrial importance

The company Indian Rare Earths Limited (IREL) has developed a process to extract uranium from the Western and Eastern coastal dune sands of India. After pre-processing with high-intensity magnetic separators and fine grinding, the mineral sands (known as monazite), are digested with caustic soda at about 120 °C (248 °F) and water. The hydroxide concentrate is further digested with concentrated hydrochloric acid to solubilise all hydroxides to form a feed solution composed of chlorides of uranium, rare earth elements and thorium. The solution is subjected to liquid–liquid extraction with dual solvent systems to produce uranyl chloride and thorium oxalate. The crude uranyl chloride solution is subsequently refined to nuclear grade ammonium diuranate by a purification process involving precipitation and solvent extraction in a nitrate media.^{[citation needed]}

Safety

Uranyl chloride is highly toxic by ingestion and inhalation. Cumulative toxic effects are also probable, with the target organs being the liver and the kidneys. It is toxic to aquatic organisms, and may cause long-term catastrophic effects in the aquatic environment. As all uranium compounds, this salt is radioactive.^[1]