Carbon tetraiodide

Last updated
Carbon tetraiodide
Stereo, skeletal formula of carbon tetraiodide Tetraiodmethan.svg
Stereo, skeletal formula of carbon tetraiodide
Carbon tetraiodide crystals and solution.jpg
  • Carbon tetraiodide crystals (left)
  • Solution in diethyl ether (right)
Ball and stick model of carbon tetraiodide Carbon-tetraiodide-3D-balls.png
Ball and stick model of carbon tetraiodide
Spacefill model of carbon tetraiodide Carbon-tetraiodide-3D-vdW.png
Spacefill model of carbon tetraiodide
Names
Preferred IUPAC name
Tetraiodomethane [1]
Identifiers
3D model (JSmol)
1733108
ChemSpider
ECHA InfoCard 100.007.335 OOjs UI icon edit-ltr-progressive.svg
EC Number
  • 208-068-5
PubChem CID
RTECS number
  • FG4960000
UNII
  • InChI=1S/CI4/c2-1(3,4)5 Yes check.svgY
    Key: JOHCVVJGGSABQY-UHFFFAOYSA-N Yes check.svgY
  • IC(I)(I)I
Properties
CI4
Molar mass 519.629 g·mol−1
AppearanceDark violet crystals
Density 4.32 g mL−1
−136·10−6 cm3/mol
Structure
Tetragonal
Tetrahedral
0 D
Thermochemistry
0.500 J K−1 g−1
384.0–400.4 kJ mol−1
−794.4 to −778.4 kJ mol−1
Hazards
Occupational safety and health (OHS/OSH):
Main hazards
toxic
GHS labelling:
GHS-pictogram-exclam.svg
Warning
H315, H319, H335
P261, P305+P351+P338
Related compounds
Other anions
Carbon tetrafluoride
Carbon tetrachloride
Carbon tetrabromide
Other cations
Silicon tetraiodide
Germanium tetraiodide
Tin(IV) iodide
Related alkanes
Related compounds
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
X mark.svgN  verify  (what is  Yes check.svgYX mark.svgN ?)

Carbon tetraiodide is a tetrahalomethane with the molecular formula CI4. Being bright red, it is a relatively rare example of a highly colored methane derivative. It is only 2.3% by weight carbon, although other methane derivatives are known with still less carbon.

Contents

Structure

The tetrahedral molecule features C-I distances of 2.12 ± 0.02 Å. [2] The molecule is slightly crowded with short contacts between iodine atoms of 3.459 ± 0.03 Å, and possibly for this reason, it is thermally and photochemically unstable.

Carbon tetraiodide crystallizes in tetragonal crystal structure (a 6.409, c 9.558 (.10−1 nm)). [3]

It has zero dipole moment due to its symmetrically substituted tetrahedral geometry.

Properties, synthesis, and uses

Carbon tetraiodide is slightly reactive towards water, giving iodoform and I2. It is soluble in nonpolar organic solvents. It decomposes thermally and photochemically to tetraiodoethylene, C2I4. Its synthesis entails AlCl3-catalyzed halide exchange, which is conducted at room temperature: [4]

CCl4 + 4 EtI → CI4 + 4 EtCl

The product crystallizes from the reaction solution.

Carbon tetraiodide is used as an iodination reagent, often upon reaction with bases. [5] Ketones are converted to 1,1-diiodoalkenes upon treatment with triphenylphosphine (PPh3) and carbon tetraiodide. Alcohols are converted in and to iodide, by a mechanism similar to the Appel reaction. In an Appel reaction, carbon tetrachloride is used to generate alkyl chlorides from alcohols.

Safety considerations

Manufacturers recommend that carbon tetraiodide be stored near 0 °C (32 °F). As a ready source of iodine, it is an irritant. Its LD50 on rats is 18 mg/kg. In general, perhalogenated organic compounds should be considered toxic, with the narrow exception of small perfluoroalkanes (essentially inert due to the strength of the C-F bond).

References

  1. "Tetraiodomethane - Compound Summary". PubChem Compound. USA: National Center for Biotechnology Information. 27 March 2005. Identification and Related Records. Retrieved 29 February 2012.
  2. Finbak, Chr.; Hassel, O. (1937). "Kristallstruktur und Molekülbau von CI4 und CBr4". Zeitschrift für Physikalische Chemie. B36: 301–308. doi:10.1515/zpch-1937-3621. S2CID   99718985.
  3. Pohl, S. (1982). "Die Kristallstruktur von CI4". Zeitschrift für Kristallographie. 159 (1–4): 211–216. doi:10.1524/zkri.1982.159.14.211. S2CID   102246815.
  4. McArthur, R. E.; Simons, J. H. (1950). "Carbon Tetraiodide". Inorganic Syntheses. Vol. III. pp. 37–39. doi:10.1002/9780470132340.ch8. ISBN   9780470132340.
  5. Schreiner, P. R.; Fokin, A. A. (2005). "Carbon Tetraiodide". In Paquette, L. (ed.). Carbon Tetraiodide. Encyclopedia of Reagents for Organic Synthesis. John Wiley & Sons, Ltd. doi:10.1002/047084289X.rn00604. ISBN   0-471-93623-5.

Further reading