| Thionyl chloride | |
|---|---|
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| Other names | thionyl dichloride, sulfurous oxychloride, sulfurous dichloride, sulfinyl chloride, sulfinyl dichloride, dichlorosulfoxide |
| Identifiers | |
| CAS number | 7719-09-7 |
| EC number | 231-748-8 |
| UN number | 1836 |
| RTECS number | XM5150000 |
| Properties | |
| Molecular formula | SOCl2 |
| Molar mass | 118.97 g/mol |
| Appearance | clear to yellow odorous liquid |
| Density | 1.638 g/cm3, liquid |
| Melting point |
−104.5 °C |
| Boiling point |
74.6 °C |
| Solubility in water | reacts |
| Solubility | soluble in benzene, chloroform, CCl4 |
| Refractive index (nD) | 1.517 (20 °C) [1] |
| Viscosity | 0.6 cP |
| Structure | |
| Molecular shape | pyramidal |
| Dipole moment | 1.4 D |
| Hazards | |
| MSDS | External MSDS |
| EU Index | 016-015-00-0 |
| EU classification | Corrosive (C) |
| R-phrases | R14, R20/22, R29, R35 |
| S-phrases | (S1/2), S26, S36/37/39, S45 |
| NFPA 704 |
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| Flash point | Non-flammable |
| Related compounds | |
| Related thionyl halides | Thionyl
fluoride Thionyl bromide |
| Related compounds | Sulfuryl
chloride Selenium oxydichloride |
| Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) |
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| Infobox references | |
Thionyl chloride is an inorganic compound with the formula SOCl2. It 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. Thionyl chloride is sometimes confused with sulfuryl chloride, SO2Cl2, but the properties of these compounds differ significantly. Approximately 45,000 tons/yr of SOCl2 were produced in the early 1990s.[2]
Contents |
The molecule SOCl2 is pyramidal, indicating the presence of a lone pair of electrons on the sulfur(IV) center. In contrast, the stoichiometrically related species COCl2 is planar. SOCl2 reacts with water to release hydrogen chloride and sulfur dioxide.
The major industrial synthesis involves the reaction of sulfur trioxide and sulfur dichloride:[3]
Other methods include syntheses from phosphorus pentachloride, chlorine, or phosgene:
The first of the above three 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.
Thionyl chloride is widely used in organic synthesis. For some applications, it requires purification.[4]. Classically, it converts carboxylic acids to acyl chlorides:[5]

Alcohols react with thionyl chloride to give the corresponding alkyl chlorides.[6]. This reaction proceeds via an internal nucleophilic substitution.


It is preferred over other reagents such as phosphorus pentachloride because the products of the thionyl chloride reactions, HCl and SO2, are gaseous, which simplies the purification of the product. Excess thionyl chloride can be readily removed by distillation.
Sulfonic acids react with thionyl chloride to produce sulfonyl chlorides.[7][8] Sulfonyl chlorides have also been prepared from the direct reaction of the corresponding diazonium salt with thionyl chloride.[9] Likewise, thionyl chloride will transform sulfinic acids into sulfinyl chlorides[10] and phosphonic acids into phosphoryl chlorides. Thionyl chloride will react with primary formamides to form isocyanides.[11] Amides will react with thionyl chloride to form imidoyl chlorides. However, primary amides under heating with thionyl chloride will continue on to form nitriles.[12]
Anhydrous metal chlorides may be obtained from hydrated metal chlorides by refluxing in freshly distilled thionyl chloride:[13]
Thionyl chloride is a component of prototype lithium-thionyl chloride batteries, where it forms the anode with lithium as the cathode.
SOCl2 is a reactive compound that can 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.
| Thionyl chloride | |
|---|---|
| Other names thionyl dichloride, sulfurous oxychloride, sulfurous dichloride, sulfinyl chloride, sulfinyl dichloride, dichlorosulfoxide, sulfur oxide dichloride, sulfur monoxide dichloride, sulfuryl(IV) chloride | |
| Identifiers | |
| CAS number | 7719-09-7 |
| EC number | 231-748-8 |
| UN number | 1836 |
| RTECS number | XM5150000 |
| Properties | |
| Molecular formula | SOCl2 |
| Molar mass | 118.97 g/mol |
| Appearance | clear to yellow odorous liquid |
| Density | 1.638 g/cm3, liquid |
| Melting point |
−104.5 °C |
| Boiling point |
74.6 °C |
| Solubility in water | reacts |
| Solubility | soluble in benzene, chloroform, CCl4 |
| Refractive index (nD) | 1.517 (20 °C) [1] |
| Viscosity | 0.6 cP |
| Structure | |
| Molecular shape | pyramidal |
| Dipole moment | 1.4 D |
| Hazards | |
| MSDS | External MSDS |
| EU Index | 016-015-00-0 |
| EU classification | Corrosive (C) |
| R-phrases | R14, R20/22, R29, R35 |
| S-phrases | (S1/2), S26, S36/37/39, S45 |
| NFPA 704 | |
| Flash point | Non-flammable |
| Related compounds | |
| Related thionyl halides | Thionyl fluoride Thionyl bromide |
| Related compounds | Sulfuryl chloride Selenium oxydichloride |
| (what is this?) (verify) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) | |
| Infobox references | |
Thionyl chloride is an inorganic compound with the formula SOCl2. It 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. Thionyl chloride is sometimes confused with sulfuryl chloride, SO2Cl2, but the properties of these compounds differ significantly. Approximately 45,000 tons/yr of SOCl2 were produced in the early 1990s.[2]
Contents |
The molecule SOCl2 is pyramidal, indicating the presence of a lone pair of electrons on the sulfur(IV) center. In contrast, the stoichiometrically related species COCl2 is planar. SOCl2 reacts with water to release hydrogen chloride and sulfur dioxide.
The major industrial synthesis involves the reaction of sulfur trioxide and sulfur dichloride:[3]
Other methods include syntheses from phosphorus pentachloride, chlorine, or phosgene:
The first of the above three 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.
Thionyl chloride is widely used in organic synthesis. For some applications, it requires purification.[4] Classically, it converts carboxylic acids to acyl chlorides:[5]
Alcohols react with thionyl chloride to give the corresponding alkyl chlorides. This method is known as Darzan's process. [6]. This reaction proceeds via an internal nucleophilic substitution.
It is preferred over other reagents such as phosphorus pentachloride because the products of the thionyl chloride reactions, HCl and SO2, are gaseous, which simplifies the purification of the product. Excess thionyl chloride can be readily removed by distillation.
Sulfonic acids react with thionyl chloride to produce sulfonyl chlorides.[7][8] Sulfonyl chlorides have also been prepared from the direct reaction of the corresponding diazonium salt with thionyl chloride.[9] Likewise, thionyl chloride will transform sulfinic acids into sulfinyl chlorides[10] and phosphonic acids into phosphoryl chlorides. Thionyl chloride will react with primary formamides to form isocyanides.[11] Amides will react with thionyl chloride to form imidoyl chlorides. However, primary amides under heating with thionyl chloride will continue on to form nitriles.[12]
Thionyl chloride can also produce nitriles from amides via E2 elimination.[13]
Anhydrous metal chlorides may be obtained from hydrated metal chlorides by refluxing in freshly distilled thionyl chloride:[14]
Thionyl chloride is a component of lithium-thionyl chloride batteries, where it acts as the positive electrode(cathode) with lithium as the negative electrode (anode).
SOCl2 is a reactive compound that can 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.
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