Triphosgene
Chemical compound
From Wikipedia, the free encyclopedia
Triphosgene (bis(trichloromethyl) carbonate (BTC)) is a chemical compound with the formula OC(OCCl3)2. It is used as a solid substitute for phosgene, which is a gas and diphosgene, which is a liquid.[5][6] Triphosgene is stable up to 200 °C.[7] Triphosgene is used in a variety of halogenation reactions.[8] Triphosgene is named this way because one equivalent of triphosgene behaves like three equivalents of phosgene. Triphosgene generates two equivalents of phosgene in situ, while the carbonate has the same reactivity as one equivalent of phosgene.
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| Names | |
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| Preferred IUPAC name
Bis(trichloromethyl) carbonate | |
| Other names
BTC | |
| Identifiers | |
3D model (JSmol) |
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| ChemSpider | |
| ECHA InfoCard | 100.046.336 |
PubChem CID |
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| UNII | |
CompTox Dashboard (EPA) |
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| Properties | |
| C3Cl6O3 | |
| Molar mass | 296.748 g/mol |
| Appearance | white solid |
| Density | 1.780 g/cm3 |
| Melting point | 80 °C (176 °F; 353 K) |
| Boiling point | 206 °C (403 °F; 479 K) |
| Reacts | |
| Solubility | *soluble in dichloromethane[1] |
| Hazards | |
| GHS labelling: | |
  [4] | |
| Danger | |
| H314, H330[4] | |
| P260, P280, P284, P305+P351+P338, P310[4] | |
| Safety data sheet (SDS) | SDS Triphosgene |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Preparation
This compound is commercially available. It is prepared by exhaustive free radical chlorination of dimethyl carbonate:[6]
- CH3OCO2CH3 + 6 Cl2 → CCl3OCO2CCl3 + 6 HCl
Triphosgene can be easily recrystallized from hot hexanes.
Uses
Triphosgene is used as a reagent in organic synthesis as a source of CO2+. It behaves like phosgene, to which it cracks thermally:
- OC(OCCl3)2 ⇌ 3 OCCl2
Alcohols are converted to carbonates. Primary and secondary amines are converted to ureas and isocyanates.[6][7][9][10]
Triphosgene has been used to synthesize chlorides.[8] Alkyl chlorides are produced from alcohols upon treatment with a mixture of triphosgene and pyridine. Alkyl dichlorides and trichlorides can similarly be prepared. Vinyl chlorides are synthesized from 2-epoxyketone using triphosgene and DMF to form the Vilsmeier reagent in situ.
Safety
The vapor pressure of Triphosgene is sufficiently high for it to reach concentrations that are considered toxicologically unsafe.[11] While several properties of triphosgene are not yet readily available, it is known that it is very toxic if inhaled. Toxic gases (phosgene and hydrogen chloride) are emitted when it comes in contact with water.[12] There is a lack of information and variability regarding the proper handling of triphosgene. It is assumed to have the same risks as phosgene.[13][14]