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Carbon tetraiodide



Carbon tetraiodide
IUPAC name Tetraiodomethane
Carbon tetraiodide
Other names Carbon iodide
Identifiers
CAS number 507-25-5
PubChem 10487
EINECS number 208-068-5
RTECS number FG4960000
SMILES C(I)(I)(I)I
InChI InChI=1/CI4/c2-1(3,4)5
Properties
Molecular formula CI4
Molar mass 519.63 g/mol
Appearance Red crystals
Density 4.32 g/cm3
Melting point

171 °C (444 K) decomp.

Solubility in water Insoluble
Structure
Crystal structure Monoclinic
Molecular shape Tetrahedral
Hazards
EU classification Irritant (Xi)
R-phrases R36/37/38
S-phrases S26, S36
Except where noted otherwise, data are given for
materials in their standard state
(at 25 °C, 100 kPa)

Infobox disclaimer and 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. [1] 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 monoclinic crystal structure (a 22.39, b 12.93, c 25.85 (.10-1 nm), β 125.26°).

It has dipole moment of 0 Debyes due to its symmetrically substituted tetrahedral molecule.

Additional recommended knowledge

Contents

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:[2]

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. [3] 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. As a ready source of iodine, it is an irritant. LD50: 178 mg.kg–1. In general perhalogenated organic compounds should be considered toxic.

References

  1. ^ Finbak, Chr.; Hassel, O. "Kristallstruktur und Molekülbau von CI4 und CBr4" Zeitschrift für Physikalische Chemie (1937), volume B36, page 301-8
  2. ^ McArthur, R. E.; Simons, J. H., “Carbon Tetraiodide” Inorganic Syntheses 1950, volume III, 37–39
  3. ^ 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

Sorros, H., Hinkam J. B. , “The Redistribution Reaction. XI. Application to the Preparation of Carbon Tetraiodide and Related Halides” Journal of the American Chemical Society 1945, 67, 1643. DOI.

See also

 
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Carbon_tetraiodide". A list of authors is available in Wikipedia.
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