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Thionyl chloride

Thionyl chloride
Thionyl-chloride-2D-dimensions.png
Ball-and-stick model of thionyl chloride
Thionyl chloride 25ml.jpg
Names
IUPAC name
Sulfurous dichloride
Other names
  • Thionyl dichloride
  • Sulfurous oxychloride
  • Sulfinyl chloride
  • sulfinyl dichloride
  • Dichlorosulfoxide
  • Sulfur oxide dichloride
  • Sulfur monoxide dichloride
  • Sulfuryl(IV) chloride
Identifiers
3D model (Jmol)
ChEBI
ChemSpider
ECHA InfoCard 100.028.863
EC Number 231-748-8
PubChem CID
RTECS number XM5150000
UNII
UN number 1836
Properties
SOCl2
Molar mass 118.97 g/mol
Appearance clear, colourless liquid (yellows on ageing)
Odor pungent and unpleasant
Density 1.638 g/cm3, liquid
Melting point −104.5 °C (−156.1 °F; 168.7 K)
Boiling point 74.6 °C (166.3 °F; 347.8 K)
reacts
Solubility soluble in most aprotic solvents: toluene, chloroform, diethyl ether. Reacts with protic solvents: MeOH etc
Vapor pressure
  • 384 Pa (-40 °C)
  • 4.7 kPa (0 °C)
  • 15.7 kPa (25 °C)
1.517 (20 °C)
Viscosity 0.6 cP
Structure
pyramidal
1.44 D
Thermochemistry
121.0 kJ/mol (liquid)
309.8 kJ/mol (gas)
-245.6 kJ/mol (liquid)
Hazards
Main hazards
  • Toxic
  • Reacts violently with water to release toxic gas
GHS pictograms The corrosion pictogram in the Globally Harmonized System of Classification and Labelling of Chemicals (GHS)The exclamation-mark pictogram in the Globally Harmonized System of Classification and Labelling of Chemicals (GHS)The skull-and-crossbones pictogram in the Globally Harmonized System of Classification and Labelling of Chemicals (GHS)
GHS signal word Danger
H302, H314, H331
P261, P280, P305+351+338, P310
R-phrases R14, R20/22, R29, R35
S-phrases (S1/2), S26, S30, S36/37/39, S45
NFPA 704
Flammability code 0: Will not burn. E.g., water Health code 4: Very short exposure could cause death or major residual injury. E.g., VX gas Reactivity code 2: Undergoes violent chemical change at elevated temperatures and pressures, reacts violently with water, or may form explosive mixtures with water. E.g., phosphorus Special hazard W: Reacts with water in an unusual or dangerous manner. E.g., cesium, sodiumNFPA 704 four-colored diamond
Flash point Non-flammable
US health exposure limits (NIOSH):
PEL (Permissible)
 none
REL (Recommended)
 C 1 ppm (5 mg/m3)
IDLH (Immediate danger)
 N.D.
Related compounds
Related thionyl halides
Related compounds
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Thionyl chloride is an inorganic compound with the chemical formula SOCl2. It is a moderately volatile colourless liquid with an unpleasant acrid odour. Thionyl chloride is primarily used as a chlorinating reagent, with approximately 45,000 tons per year being produced during the early 1990s. It is toxic and will react violently with water to produce toxic gases, it is also listed as a Schedule 3 compound as it may be used for the production of chemical weapons.

Thionyl chloride is sometimes confused with sulfuryl chloride, SO2Cl2, but the properties of these compounds differ significantly. Sulfuryl chloride is a source of chlorine whereas thionyl chloride is a source of chloride ions.

The major industrial synthesis involves the reaction of sulfur trioxide and sulfur dichloride:

Other methods include syntheses from phosphorus pentachloride, chlorine and sulfur dichloride, or phosgene:

The first of the above four reactions also affords phosphorus oxychloride (phosphoryl chloride), which resembles thionyl chloride in many of its reactions.

SOCl2 adopts a pyramidal molecular geometry with Csmolecular symmetry. This geometry is attributed to the effects of the lone pairs on the sulfur(IV) centre.

In the solid state SOCl2 forms monoclinic crystals with the space group P21/c.


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