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Thionyl chloride
General
Systematic name	Thionyl dichloride
Other names	Sulfurous oxychloride Sulfurous dichloride Sulfinyl chloride Sulfinyl dichloride Dichlorosulfoxide
Molecular formula	SOCl2
Molar mass	118.97 g/mol
Appearance	clear to yellow odorous liquid
CAS number	7719-09-7
Properties
Density	1.638 g/ml, liquid
Solubility in water	Reactive
Melting point	−104.5 °C
Boiling point	76 °C
Viscosity	? cP at ? °C
Structure
Molecular shape	pyramidal
Dipole moment	? D
Hazards
MSDS	External MSDS
EU classification	Corrosive (C)
NFPA 704

R-phrases , , , S-phrases , , , Flash point non flammable Supplementary data page Structure and
properties n, ε_r, etc. Thermodynamic
data Phase behaviour
Solid, liquid, gas Spectral data UV, IR, NMR, MS Related compounds Other anions Thionyl bromide
Thionyl iodide Related compounds Sulfuryl chloride
Selenium oxydichloride Except where noted otherwise, data are given for
materials in their standard state (at 25 °C, 100 kPa)
Chemical infobox

Thionyl chloride (or thionyl dichloride) is an inorganic compound with the formula SOCl₂. SOCl₂ is a reactive chemical reagent used in chlorination reactions. It is a colorless, distillable liquid at room temperature and pressure that decomposes above 140 °C. SOCl₂ is sometimes confused with sulfuryl chloride, SO₂Cl₂, but the chemical properties of these S(IV) and S(VI) compounds differ significantly.

Properties and structure

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The molecule SOCl₂ is pyramidal, indicating the presence of a lone pair of electrons on the S(IV) center. In contrast, COCl₂ is planar.

SOCl₂ reacts with water to release hydrogen chloride (HCl) and sulfur dioxide (SO₂).

H₂O + O=SCl₂ → SO₂ + 2 HCl

Because of its high reactivity toward water, SOCl₂ would not be expected to occur in nature.

Industrial usage

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Thionyl chloride is used inside lithium-thionyl chloride batteries as the positive active material with lithium as the negative active material. It is also used as a reagent for the production of other chemical compounds or materials.

In military usage, thionyl chloride is used in the "di-di" method of producing G-series nerve agents.

Organic chemistry usage

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Preparation of acid chlorides

Thionyl chloride is widely used both in the laboratory and on an industrial scale. It reacts with carboxylic acids to produce acyl chlorides.

RC(O)OH + O=SCl₂ → RC(O)Cl + SO₂ + HCl

Sulfonic acids react with thionyl chloride to produce sulfonyl chlorides. Likewise, thionyl chloride will transform sulfinic acids into sulfinyl chlorides and phosphonic acids into phosphoryl chlorides.

Chlorination of alcohols

Thionyl chloride also reacts with alcohols to produce alkyl chlorides.

R-OH + O=SCl₂ → R-Cl + SO₂ + HCl

A milder alternative is the Appel reaction.

Miscellanous reactions

Thionyl chloride will react with primary formamides to form isocyanides.

Amides will react with thionyl chloride to form imidoyl chlorides. However, primary amides under heating with thionyl chloride will continue on to form nitriles.

Synthesis of thionyl chloride

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

SO₃ + SCl₂ → SOCl₂ + SO₂

Other methods include:

SO₂ + PCl₅ → SOCl₂ + POCl₃

SO₂ + Cl₂ + SCl₂ → 2 SOCl₂

SO₃ + Cl₂ + 2 SCl₂ → 3 SOCl₂

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

Safety and toxity considerations

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SOCl₂ is toxic, corrosive, and lachrymatory. It is a skin and inhalation hazard, as well as being odorous,

Industrial production of thionyl chloride is controlled under the Chemical Weapons Convention, where it is listed in schedule 3.

References

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1. Allen, C. F. H.; Byers, Jr., J. R.; Humphlett, W. J. Org. Syn., Coll. Vol. 4, p.739 (1963); Vol. 37, p.66 (1957). (Article)
2. Rutenberg, M. W.; Horning, E. C. Org. Syn., Coll. Vol. 4, p.620 (1963); Vol. 30, p.62 (1950). (Article)
3. Weinreb, S. M.; Chase, C. E.; Wipf, P.; Venkatraman, S. Org. Syn., Coll. Vol. 10, p.707 (2004); Vol. 75, p.161 (1998). (Article)
4. Hazen, G. G.; Bollinger, F. W.; Roberts, F. E.; Russ, W. K.; Seman, J. J.; Staskiewicz, S. Org. Syn., Coll. Vol. 9, p.400 (1998); Vol. 73, p.144 (1996). (Article)
5. Hulce, M.; Mallomo, J. P.; Frye, L. L.; Kogan, T. P.; Posner, G. H. Org. Syn., Coll. Vol. 7, p.495 (1990); Vol. 64, p.196 (1986). (Article)
6. Kurzer, F. Org. Syn., Coll. Vol. 4, p.937 (1963); Vol. 34, p.93 (1954). (Article)
7. Mondanaro, K. R.; Dailey, W. P. Org. Syn., Coll. Vol. 10, p.212 (2004); Vol. 75, p.89 (1998). (Article)
8. Krakowiak, K. E.; Bradshaw, J. S. Org. Syn., Coll. Vol. 9, p.34 (1998); Vol. 70, p.129 (1992). (Article)
9. Niznik, G. E.; Morrison, III, W. H.; Walborsky, H. M. Org. Syn., Coll. Vol. 6, p.751 (1988); Vol. 51, p.31 (1971). (Article)
10. Krynitsky, J. A.; Carhart, H. W. Org. Syn., Coll. Vol. 4, p.436 (1963); Vol. 32, p.65 (1952). (Article)
11. N. N. Greenwood, A. Earnshaw, Chemistry of the Elements, Pergamon Press, 1984.

External links

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• Usage of thionyl chloride in Organic Syntheses
• NIOSH Pocket Guide to Chemical Hazards

Chlorides | Thionyl compounds | Acyl chlorides | Nonmetal halides | Reagents for organic chemistry | Inorganic sulfur compounds | lachrymatory agents

Chlorid thionylu | Thionylchlorid | Chlorure de thionyle | Cloruro di tionile | 塩化チオニル | Chlorek tionylu | Тионилхлорид