Carbon tetraiodide

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Carbon tetraiodide
Stereo, skeletal formula of carbon tetraiodide
Ball and stick model of carbon tetraiodide Spacefill model of carbon tetraiodide
Identifiers
CAS number 507-25-5 N
PubChem 10487
ChemSpider 10055 YesY
EC number 208-068-5
RTECS number FG4960000
Beilstein Reference 1733108
Jmol-3D images Image 1
Properties
Molecular formula CI4
Molar mass 519.63 g mol−1
Appearance Dark violet crystals
Density 4.32 g mL−1
Structure
Crystal structure Tetragonal
Molecular shape Tetrahedral
Dipole moment 0 D
Thermochemistry
Specific
heat capacity
C
259.8 J K−1 mol−1
Std enthalpy of
formation
ΔfHo298
384.0–400.4 kJ mol−1
Std enthalpy of
combustion
ΔcHo298
−794.4–−778.4 kJ mol−1
Hazards
GHS pictograms The exclamation-mark pictogram in the Globally Harmonized System of Classification and Labelling of Chemicals (GHS)
GHS signal word WARNING
GHS hazard statements H315, H319, H335
GHS precautionary statements P261, P305+351+338
EU classification Irritant Xi
R-phrases R36/37/38
S-phrases S26, S36
Related compounds
Related alkanes
Related compounds
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
 N (verify) (what is: YesY/N?)
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. 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

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.