Triphosgene


Triphosgene carbonate''' is a chemical compound with the formula OC2. It is used as a safer substitute for phosgene, because, at room temperature, it is a solid, whereas phosgene is a gas. Triphosgene decomposes above 200 °C.

Preparation

This compound is commercially available. It is prepared by exhaustive free radical chlorination of dimethyl carbonate:
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:
Alcohols are converted to carbonates. Primary and secondary amines are converted to ureas and isocyanate.

Safety

The toxicity of triphosgene and phosgene are the same since the trimer decomposes to phosgene on heating and upon reaction with nucleophiles. Trace moisture leads to formation of phosgene. Therefore, this reagent can be safely handled if one takes all the precautions as for phosgene.