Triphosgene
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.<ref>Template:Cite book</ref><ref name="eckert">Template:Cite journal</ref> Triphosgene is stable up to 200 °C.<ref name=":0" /> Triphosgene is used in a variety of halogenation reactions.<ref name=":2" />
PreparationEdit
This compound is commercially available. It is prepared by exhaustive free radical chlorination of dimethyl carbonate:<ref name = eckert/>
- CH3OCO2CH3 + 6 Cl2 → CCl3OCO2CCl3 + 6 HCl
Triphosgene can be easily recrystallized from hot hexanes.
UsesEdit
Triphosgene is used as a reagent in organic synthesis as a source of CO2+. It behaves like phosgene, to which it cracks thermally:
Alcohols are converted to carbonates. Primary and secondary amines are converted to ureas and isocyanates.<ref name = eckert/><ref name=":0">Template:Cite journal</ref><ref name=":1">Template:Cite journal</ref><ref>Template:Cite journal</ref>
Triphosgene has been used to synthesize chlorides.<ref name=":2">Template:Cite journal</ref> Some Alkyl chlorides are prepared by treating alcohols with a mixture of triphosgene and pyridine. Alkyl dichlorides and trichlorides can similarly be synthesized using triphosgene. Vinyl chlorides are synthesized from ketones using triphosgene and DMF to form a Vilsmeier reagent, followed by a ring opening by chloride ions. Aryl chlorides can also be produced using a Vilsmeier reagent from triphosgene and DMF.
SafetyEdit
The vapor pressure of Triphosgene is sufficiently high for it to reach concentrations that are considered toxicologically unsafe.<ref name=":3">Template:Cite journal</ref> While several properties of triphosgene are not yet readily available, it is known that it is very toxic if inhaled. A toxic gas is emitted if it comes in contact with water.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> There is a lack of information and variability regarding the proper handling of triphosgene. It is assumed to have the same risks as phosgene.<ref>Template:Cite journal</ref><ref>Template:Cite journal</ref>