Carbon tetraiodide

Carbon tetraiodide
Names
IUPAC name
Tetraiodomethane[1]
Identifiers
507-25-5 N
1733108
ChemSpider 10055 YesY
EC Number 208-068-5
Jmol interactive 3D Image
PubChem 10487
RTECS number FG4960000
Properties
CI4
Molar mass 519.63 g·mol−1
Appearance Dark violet crystals
Density 4.32 g mL−1
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
GHS pictograms
GHS signal word WARNING
H315, H319, H335
P261, P305+351+338
Xi
R-phrases R36/37/38
S-phrases S26, S36
Related compounds
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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Infobox references

Carbon tetraiodide is CI4, a tetrahalomethane. Being bright red, it is a relatively rare example of a highly colored methane derivative. It is only 2% by weight carbon, although other methane derivatives are known with still less carbon.

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

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 molecule.

Properties, synthesis, uses

CI4 is slightly reactive towards water, giving iodoform and I2. Otherwise it is soluble in nonpolar organic solvents. It decomposes thermally and photochemically to tetraiodoethylene, I2C=CI2. 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.

CI4 is used as an iodination reagent, often upon reaction with base. [5] Ketones are converted to 1,1-diiodoethenes upon treatment with PPh3 and CI4. 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 the chloride from alcohols.

Safety considerations

Manufacturers recommend that CI4 be stored near 0 °C (32 °F). As a ready source of iodine, it is an irritant. LD50: 178 mg.kg−1. 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. "Kristallstruktur und Molekülbau von CI4 und CBr4" Zeitschrift für Physikalische Chemie (1937), volume B36, page 301-8
  3. ↑ Pohl, S. "Die Kristallstruktur von CI4" Zeitschrift für Kristallographie (1982), volume 159, page 211-216 http://www.oldenbourg-link.com/doi/abs/10.1524/zkri.1982.159.1-4.211
  4. ↑ McArthur, R. E.; Simons, J. H., “Carbon Tetraiodide” Inorganic Syntheses 1950, volume III, 37–39
  5. ↑ P. R. Schreiner, A. A. Fokin, “Carbon Tetraiodide” in Encyclopedia of Reagents for Organic Synthesis (Ed: L. Paquette) 2005; John Wiley & Sons, Ltd

Further reading

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