Hexafluorocyclobutene is the organofluorine compound with the formula (CF2)2(CF)2. A colorless gas, it is a precursor to a variety of compounds, including squaric acid. Hexafluorocyclobutene is prepared in two steps from chlorotrifluoroethylene. The thermal dimerization gives 1,2-dichloro-1,2,3,3,4,4-hexafluorocyclobutane. Dechlorination of the latter gives hexafluorocyclobutene:C4F6Cl2 + Zn → C4F6 + ZnCl2