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
Names
IUPAC name
Tetraiodomethane[1]
Identifiers
3D model (JSmol)
1733108
ChemSpider
ECHA InfoCard 100.007.335
EC Number 208-068-5
RTECS number FG4960000
Properties
CI4
Molar mass 519.63 g·mol−1
Appearance Dark violet crystals
Density 4.32 g mL−1
-136·10−6 cm3/mol
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 The exclamation-mark pictogram in the Globally Harmonized System of Classification and Labelling of Chemicals (GHS)
GHS signal word WARNING
H315, H319, H335
P261, P305+351+338
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 a tetrahalomethane with the molecular formula CI4. 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.

Structure[edit]

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

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[edit]

Carbon tetraiodide is slightly reactive towards water, giving iodoform and I2. It is soluble in nonpolar organic solvents. It decomposes thermally and photochemically to tetraiodoethylene, C2I4. Its synthesis entails AlCl3-catalyzed halide exchange, which is conducted at room temperature:[4]

The product crystallizes from the reaction solution.

Carbon tetraiodide is used as an iodination reagent, often upon reaction with bases.[5] Ketones are converted to 1,1-diiodoalkenes upon treatment with triphenylphosphine (PPh3) and carbon tetraiodide. 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 alkyl chlorides from alcohols.

Safety considerations[edit]

Manufacturers recommend that carbon tetraiodide be stored near 0 °C (32 °F). As a ready source of iodine, it is an irritant. Its LD50 is 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[edit]

  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. (1937). "Kristallstruktur und Molekülbau von CI4 und CBr4". Zeitschrift für Physikalische Chemie. B36: 301–308. 
  3. ^ Pohl, S. (1982). "Die Kristallstruktur von CI4". Zeitschrift für Kristallographie. 159: 211–216. [permanent dead link]
  4. ^ McArthur, R. E.; Simons, J. H. (1950). "Carbon Tetraiodide". Inorganic Syntheses. III: 37–39. 
  5. ^ P. R. Schreiner, A. A. Fokin (2005). "Carbon Tetraiodide". In L. Paquette. Encyclopedia of Reagents for Organic Synthesis. John Wiley & Sons, Ltd. 

Further reading[edit]