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Carbon tetraiodide

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Carbon tetraiodide
Stereo, skeletal formula of carbon tetraiodide

Carbon tetraiodide crystals (left)
Solution in Et2O (right)
Ball and stick model of carbon tetraiodide
Ball and stick model of carbon tetraiodide
Spacefill model of carbon tetraiodide
Spacefill model of carbon tetraiodide
Names
Preferred IUPAC name
Tetraiodomethane[1]
Identifiers
3D model (JSmol)
1733108
ChemSpider
ECHA InfoCard 100.007.335 Edit this at Wikidata
EC Number
  • 208-068-5
RTECS number
  • FG4960000
UNII
  • InChI=1S/CI4/c2-1(3,4)5 checkY
    Key: JOHCVVJGGSABQY-UHFFFAOYSA-N checkY
  • IC(I)(I)I
Properties
CI4
Molar mass 519.629 g·mol−1
Appearance Dark 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–−778.4 kJ mol−1
Hazards
Occupational safety and health (OHS/OSH):
Main hazards
toxic
GHS labelling:
GHS07: Exclamation mark
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).
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Carbon tetraiodide is a tetrahalomethane with the molecular formula . 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.

Structure

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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, uses

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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]

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

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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

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  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. Inorganic Syntheses. Vol. III. pp. 37–39. doi:10.1002/9780470132340.ch8. ISBN 9780470132340.
  5. ^ P. R. Schreiner, A. A. Fokin (2005). "Carbon Tetraiodide". In L. Paquette (ed.). Encyclopedia of Reagents for Organic Synthesis. John Wiley & Sons, Ltd.

Further reading

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