Carbon tetraiodide
IUPAC name	Tetraiodomethane Carbon tetraiodide
Other names	Carbon iodide
Identifiers
CAS number	507-25-5
PubChem	10487
EC 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	519.6286 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 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 1 Properties, synthesis, uses 2 Safety considerations 3 References 4 Further reading

[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.

v • d • e Halomethanes Monosubstituted CH3F · CH3Cl · CH3Br · CH3I Disubstituted CH2F2 · CH2ClF · CH2BrF · CH2FI · CH2Cl2 · CH2BrCl · CH2ClI · CH2Br2 · CH2BrI · CH2I2 Trisubstituted CHF3 · CHClF2 · CHBrF2 · CHF2I · CHCl2F · C*HBrClF · C*HClFI · CHBr2F · C*HBrFI · CHFI2 · CHCl3 · CHBrCl2 · CHCl2I · CHBr2Cl · C*HBrClI · CHClI2 · CHBr3 · CHBr2I · CHBrI2 · CHI3 Tetrasubstituted CF4 · CClF3 · CBrF3 · CF3I · CCl2F2 · CBrClF2 · CClF2I · CBr2F2 · CBrF2I · CF2I2 · CCl3F · CBrCl2F · CCl2FI · CBr2ClF · C*BrClFI · CClFI2 · CBr3F · CBr2FI · CBrFI2 · CFI3 · CCl4 · CBrCl3 · CCl3I · CBr2Cl2 · CBrCl2I · CCl2I2 · CBr3Cl · CBr2ClI · CBrClI2 · CClI3 · CBr4 · CBr3I · CBr2I2 · CBrI3 · CI4 * Chiral compound.