|Jmol-3D images||Image 1|
|Molar mass||118.97 g/mol|
|Appearance||clear, colorless to yellow liquid with unpleasant odor|
|Density||1.638 g/cm3, liquid|
|Melting point||−104.5 °C|
|Boiling point||74.6 °C|
|Solubility in water||exothermic reaction|
|Solubility||soluble in benzene, chloroform, CCl4|
|Refractive index (nD)||1.517 (20 °C) |
|Dipole moment||1.4 D|
|EU classification||Corrosive (C)|
|R-phrases||R14, R20/22, R29, R35|
|S-phrases||(S1/2), S26, S30, S36/37/39, S45|
|Main hazards||Water- and moisture- sensitive, reactive.
Never add water to this product as the hydrolysis reaction with water is violent.
|Related thionyl halides||Thionyl fluoride
|Related compounds||Sulfuryl chloride
|Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)|
|(what is: / ?)|
Thionyl chloride is an inorganic compound with the formula SOCl2. It is a reactive chemical used as a reagent in chlorination reactions. It is a colorless, distillable liquid at room temperature and pressure with a nauseating pungent odor that decomposes above 140 °C.
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.
Approximately 45,000 tons per year of SOCl2 were produced in the early 1990s.
Properties and structure
The molecule SOCl2 is pyramidal, indicating the presence of a lone pair of electrons on the sulfur(IV) center. In contrast, the stoichiometrically related COCl2 is planar. SOCl2 reacts with water to release hydrogen chloride and sulfur dioxide.
- SOCl2 + H2O → 2 HCl + SO2
- SO3 + SCl2 → SOCl2 + SO2
- SO2 + PCl5 → SOCl2 + POCl3
- SO2 + Cl2 + SCl2 → 2 SOCl2
- SO3 + Cl2 + 2 SCl2 → 3 SOCl2
- SO2 + COCl2 → SOCl2 + CO2
The first of the above four reactions also affords phosphorus oxychloride (phosphoryl chloride), which resembles thionyl chloride in many of its reactions.
Thionyl chloride is mainly used in the industrial production of organochlorine compounds, which are often intermediates in pharmaceuticals and agrichemicals. In some cases it requires purification prior to use.
Thionyl chloride is widely used in organic synthesis for the synthesis of organochlorides. It usually is preferred over other reagents, such as phosphorus pentachloride, as its by-products (HCl and SO2) are gaseous, which simplifies purification of the product. Classically, it converts carboxylic acids to acyl chlorides
- RCO2H + SOCl2 → RC(O)Cl + HCl + SO2
- RCH2OH + SOCl2 → RCH2Cl + HCl + SO2
Many of the products of thionyl chloride are themselves highly reactive, which in combination with its easily removed by-products makes thionyl chloride well suited to one pot synthesis. Examples include the synthesis of oxazoline rings and the Darzens reaction (shown below) which proceeds via an internal nucleophilic substitution.
Thionyl chloride can facilitate numerous chemical transformations, some of which are shown below. Going clockwise from the top: Thionyl chloride will transform sulfinic acids into sulfinyl chlorides and phosphonic acids into phosphoryl chlorides. 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. and can also produce nitriles from amides via E2 elimination. Thionyl chloride can be used in variations of the Pummerer rearrangement. Sulfonic acids react with thionyl chloride to produce sulfonyl chlorides. Sulfonyl chlorides have also been prepared from the direct reaction of the corresponding diazonium salt with thionyl chloride.
- MCln·xH2O + x SOCl2 → MCln + x SO2 + 2x HCl
SOCl2 is a reactive compound that can violently and/or explosively release dangerous gases upon contact with water and other reagents. Industrial production of thionyl chloride is controlled under the Chemical Weapons Convention, where it is listed in Schedule 3. Thionyl chloride is used in the "di-di" method of producing G-series nerve agents.
- Oxalyl chloride
- Phosphorus pentachloride
- Sulfur dichloride
- Thionyl bromide
- Arndt-Eistert reaction
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