Selenium oxydichloride

Selenium oxydichloride is the inorganic compound with the formula SeOCl₂. It is a colorless liquid. With a high dielectric constant (55) and high specific conductance, it is an attractive solvent. Structurally, it is a close chemical relative of thionyl chloride SOCl₂, being a pyramidal molecule.

Selenium oxydichloride

Structure of the selenium oxydichloride molecule 3D model of the selenium oxydichloride molecule
Names
IUPAC name Selenium oxychloride
Other names Seleninyl chloride
Identifiers
CAS Number	7791-23-3 Y
3D model (JSmol)	Interactive image
ChemSpider	23049 Y
ECHA InfoCard	100.029.313
EC Number	232-244-0
PubChem CID	24647
RTECS number	VS7000000
UNII	1G57T5401W Y
CompTox Dashboard (EPA)	DTXSID50884438
InChI InChI=1S/Cl2OSe/c1-4(2)3 N Key: LIRMPIXWGWLNND-UHFFFAOYSA-N N InChI=1/Cl2OSe/c1-4(2)3 Key: LIRMPIXWGWLNND-UHFFFAOYAX
SMILES O=[Se](Cl)Cl
Properties
Chemical formula	SeOCl2
Molar mass	165.87 g/mol
Appearance	colorless liquid
Density	2.43 g/cm3, liquid
Melting point	10.9 °C (51.6 °F; 284.0 K)
Boiling point	177.2 °C (351.0 °F; 450.3 K)
Refractive index (nD)	1.651 (20 °C)
Structure
Molecular shape	trigonal pyramidal
Hazards
GHS labelling:[1]
Pictograms
Signal word	Warning
Hazard statements	H301, H314, H331, H373, H410
Precautionary statements	P260, P261, P264, P270, P271, P273, P280, P301+P310, P301+P330+P331, P303+P361+P353, P304+P340, P305+P351+P338, P310, P311, P314, P321, P330, P363, P391, P403+P233, P405, P501
NFPA 704 (fire diamond)	3 0 1
Lethal dose or concentration (LD, LC):
LDLo (lowest published)	2 mg/kg (rabbit, dermal)[2]
Related compounds
Related compounds	SOCl2, POCl3
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). N verify (what is YN ?) Infobox references

Preparation and reactions

Selenium oxydichloride can be prepared by several methods, and a common one involves the conversion of selenium dioxide to dichloroselenious acid followed by dehydration:^[3]

SeO₂ + 2 HCl → Se(OH)₂Cl₂

Se(OH)₂Cl₂ → SeOCl₂ + H₂O

The original synthesis involved the redistribution reaction of selenium dioxide and selenium tetrachloride.

Pure selenium oxydichloride autoionizes to a dimer:^[4]

SeOCl₂ ↔ (SeO)₂Cl⁺
₃ + Cl⁻

The SeOCl₂ is generally a labile Lewis acid and solutions of sulfur trioxide in SeOCl₂ likely form [SeOCl]⁺[SO₃Cl]⁻ the same way.^[5]

The compound hydrolyzes readily to form hydrogen chloride and selenium dioxide,^{[citation needed]} and very few organic compounds dissolve in it without reaction. At elevated temperatures, it is a strong oxidizer, yielding a chloride, selenium dioxide, and diselenium dichloride.^[6]

See also

• Selenium oxybromide SeOBr₂
• Selenous acid H₂SeO₃