Carbon tetraiodide

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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 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.

Contents

[edit] 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.

[edit] 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.

[edit] 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

[edit] 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.

[edit] See also

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