Tetrachlorocyclopropene

Tetrachlorocyclopropene is a chemical compound with the formula C3Cl4. A colorless liquid, the compound is a reagent used to prepare acetylene derivatives and in organic synthesis. It is prepared by addition of dichlorocarbene to trichloroethylene. It can react with water and alcohols rapidly.

The compound is used to prepare arylpropiolic acids:
 * C3Cl4 +  ArH  +  2 H2O  →  ArC2CO2H  +  4 HCl

Under some circumstances, diarylation occurs, giving diarylcyclopropenones, which decarbonylate to give diarylacetylenes. These reactions are thought to proceed via the intermediacy of trichlorocyclopropenium electrophile (C3Cl3+).