Хлорид тионила: свойства и применение

Inorganic compound (SOCl2)
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|Name = Thionyl chloride
|ImageFile = Thionyl chloride 2D dimensions. png
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|ImageFile1 = Thionyl chloride from xtal 3D balls B. png
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|ImageName1 = Ball and stick model of thionyl chloride
|ImageFile2 = Freshly distilled thionyl chloride in a bomb. jpg
|IUPACName = Thionyl chloride
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|Section4 = Chembox Thermochemistry
|DeltaHf = −245.6kJ/mol (liquid)
|Entropy = 309.8kJ/mol (gas)
|REL = C 1ppm (5mg/m3) but is occasionally also used as a solvent. It is toxic, reacts with water, and is also listed under the Chemical Weapons Convention 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.

SOCl2 adopts a trigonal pyramidal molecular geometry with Cs molecular symmetry. This geometry is attributed to the effects of the lone pair on the central sulfur(IV) center. In the solid state SOCl2 forms monoclinic crystals with the space group P21/c.

Thionyl chloride has a long shelf life, however "aged" samples develop a yellow hue, possibly due to the formation of disulfur dichloride. It slowly decomposes to S2Cl2, SO2 and Cl2 at just above the boiling point. Thionyl chloride is susceptible to photolysis, which primarily proceeds via a radical mechanism. Samples showing signs of ageing can be purified by distillation under reduced pressure, to give a colourless liquid.

Thionyl chloride is mainly used in the industrial production of organochlorine compounds, which are often intermediates in pharmaceuticals and agrichemicals. 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. Many of the products of thionyl chloride are themselves highly reactive and as such it is involved in a wide range of reactions.

With primary amines, thionyl chloride gives sulfinylamine derivatives (RNSO), one example being N sulfinylaniline. Thionyl chloride reacts with primary formamides to form isocyanides and with secondary formamides to give chloroiminium ions; as such a reaction with dimethylformamide will form the Vilsmeier reagent. By an analogous process primary amides will react with thionyl chloride to form imidoyl chlorides, with secondary amides also giving chloroiminium ions. These species are highly reactive and can be used to catalyse the conversion of carboxylic acids to acyl chlorides, they are also exploited in the Bischler–Napieralski reaction as a means of forming isoquinolines. Primary amides will continue on to form nitriles if heated (Von Braun amide degradation). Thionyl chloride has also been used to promote the Beckmann rearrangement of oximes.

Thionyl chloride converts phosphonic acids and phosphonates into phosphoryl chlorides. It is for this type of reaction that thionyl chloride is listed as a Schedule 3 compound, as it can be used in the "di di" method of producing G series nerve agents. For example, thionyl chloride converts dimethyl methylphosphonate into methylphosphonic acid dichloride, which can be used in the production of sarin and soman.

As |SOCl2 reacts with water it can be used to dehydrate various metal chloride hydrates, such magnesium chloride (|MgCl2*6H2O), aluminium chloride (|AlCl3*6H2O), and iron(III) chloride (|FeCl3*6H2O). MCl \mathit{n}\! .\! \mathit{x}\ H2O{} + \mathit{x}\ SOCl2 > MCl \mathit{n}{} + \mathit{x}\ SO2{} + 2\! \mathit{x}\ HCl

SOCl2 is highly reactive and can violently release hydrochloric acid upon contact with water and alcohols. It is also a controlled substance under the Chemical Weapons Convention, where it is listed as a Schedule 3 substance, since it is used in the manufacture of G series nerve agents and the Meyer and Meyer–Clarke methods of producing sulfur based mustard gases.

In 1849, the French chemists Jean François Persoz and Bloch, and the German chemist Peter Kremers (1827 ? ), independently first synthesized thionyl chloride by reacting phosphorus pentachloride with sulfur dioxide. However, their products were impure: both Persoz and Kremers claimed that thionyl chloride contained phosphorus, and Kremers recorded its boiling point as 100 °C (instead of 74.6 °C). In 1857, the German Italian chemist Hugo Schiff subjected crude thionyl chloride to repeated fractional distillations and obtained a liquid which boiled at 82 °C and which he called Thionylchlorid. In 1859, the German chemist Georg Ludwig Carius noted that thionyl chloride could be used to make acid anhydrides and acyl chlorides from carboxylic acids and to make alkyl chlorides from alcohols.