Tetrachlorocyclopropene

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Tetrachlorocyclopropene
Tetrachlorocyclopropene.svg
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.025.835 OOjs UI icon edit-ltr-progressive.svg
PubChem CID
UNII
  • InChI=1S/C3Cl4/c4-1-2(5)3(1,6)7
    Key: BLZOHTXDDOAASQ-UHFFFAOYSA-N
  • ClC1=C(Cl)C1(Cl)Cl
Properties
C3Cl4
Molar mass 177.83 g·mol−1
AppearanceColorless 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).

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]

Treatment with a good chloride-accepting Lewis acid affords trichlorocyclopropenium salts, a carbocation that is aromatic like other cyclopropenium ions, as predicted by Hückel's rule. Aluminum trichloride is most commonly used as the Lewis acid, giving the tetrachloroaluminate salt: [1] [4]

C3Cl4 + AlC3 → [C3Cl+3][AlCl−4]

The structure of trichlorocyclopropenium has been confirmed by X-ray crystallography of this salt. [5] Salts of hexachloroantimonate (SbCl−6), tetrachloroferrate (FeCl−4), and tetrachlorogallate (GaCl−4) have also been prepared from other Lewis acids. [4] Tetrachlorocyclopropene appears inert towards boron trifluoride and trichloride, but reacts with boron tribromide to give tetrabromocyclopropene, with gaseous boron trichloride leaving solution: [2]

3 C3Cl4 + 4 BBr3 → 3 C3Br4 + 4 BCl3

Arylpropiolate esters may be prepared from trichlorocyclopropenium by reacting with arenes, followed by hydrolysis in alcohols. [1] This can be done without isolating the trichlorocyclopropenium ion.

Trichlorocyclopropene is also used to prepare arylcyclopropanones by a two-step, one-pot procedure beginning with a Friedel-Crafts-like arylation, with trichlorocyclopropenium as an intermediate prepared in situ: [1]

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

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

ArC3Cl3 + 2 H2O → ArC3O(OH) + 3 HCl

References

  1. 1 2 3 4 Oliver Reiser; Armin de Meijere; Brittany M. Klootwyk; Gregory R. Boyce (2019). "Tetrachlorocyclopropene" . EEROS. doi:10.1002/047084289X.rt028. ISBN   978-0-471-93623-7.
  2. 1 2 Tobey, S. W.; West, R. (1963). "Tetrachlorocyclopropene and Hexachlorocyclopropane from Pentachlorocyclopropane" . Tetrahedron Letters. 4 (18): 1179–1182. doi:10.1016/S0040-4039(01)90799-3.
  3. ↑ Tobey, S. W.; West, R. (1966). "Tetrachlorocyclopropene, Tetrabromocyclopropene, and Some Fluorinated Cyclopropenes and Cyclopropanes" . Journal of the American Chemical Society. 88 (11): 2481–2488. Bibcode:1966JAChS..88.2481T. doi:10.1021/ja00963a023.
  4. 1 2 West, R.; Sadô, A.; Tobey, S. W. (1966). "Synthesis of Trihalocyclopropenium Salts and Normal Coordinate Analysis of C3Cl3+" . Journal of the American Chemical Society. 88 (11): 2488–2494. doi:10.1021/ja00963a024.
  5. ↑ Clark, George R.; Taylor, Michael J.; Steele, Derek (1993). "Crystal Structure Determination of C3Cl3+AlCl4- and ab initio Studies of the Structure and Vibrational Spectrum of the Trichlorocyclopropenium Cation". Journal of the Chemical Society, Faraday Transactions. 89 (19): 3597. doi:10.1039/ft9938903597.
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