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.^[1] It was first reported by Tobey and West.^[2] It is prepared by addition of dichlorocarbene to trichloroethylene and then further treating the resultant pentachlorocyclopropane with base to perform dehydrochlorination.^[3]

Tetrachlorocyclopropene

Identifiers
CAS Number	6262-42-6 Y
3D model (JSmol)	Interactive image
ChemSpider	72642
ECHA InfoCard	100.025.835
PubChem CID	80428
UNII	4161QF853X Y
CompTox Dashboard (EPA)	DTXSID6021660
InChI InChI=1S/C3Cl4/c4-1-2(5)3(1,6)7 Key: BLZOHTXDDOAASQ-UHFFFAOYSA-N
SMILES ClC1=C(Cl)C1(Cl)Cl
Properties
Chemical formula	C3Cl4
Molar mass	177.83 g·mol−1
Appearance	Colorless liquid
Density	1.45 g/mL
Boiling point	125 - 130 C
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

The compound is used to prepare arylcyclopropanones by a two-step, one-pot procedure beginning with a Friedel-Crafts-like arylation:^[1]

C₃Cl₄ + ArH → ArC₃Cl₃ + HCl (ArH = arene)

The aryltetrachlorocyclopropenes are then hydrolyzed to give the keto-alcohol:

ArC₃Cl₃ + 2 H₂O → ArC₃O(OH) + 3 HCl

The Friedel-Crafts-like arylation employs a Lewis acid catalyst. Treatment of tetrachlorocyclopropene with aluminium trichloride gives the trichlorocyclopropenium ion, which has been isolated as its tetrachloroaluminate salt. X-ray crystallography confirms the structure, revealing very short C-Cl bonds.^[4]