Suvarna Garge (Editor)

Carbon tetraiodide

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Related compounds
  
PimagedineGuanidine

Melting point
  
171 °C

Density
  
4.32 g/cm³

Formula
  
CI4

Molar mass
  
519.6286 g/mol

Appearance
  
Dark violet crystals

Carbon tetraiodide httpsiytimgcomvisUBagAuOpgYmaxresdefaultjpg

Related alkanes
  
MethaneMethyl iodideDiiodomethaneIodoformEthaneEthyl iodide

Carbon tetraiodide meaning


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.

Contents

Structure

The tetrahedral molecule features C-I distances of 2.12 ± 0.02 Å. 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. Hexaiodoethane is unknown, probably for the same reason.

Carbon tetraiodide crystallizes in tetragonal crystal structure (a 6.409, c 9.558 (.10−1 nm)).

It has zero dipole moment due to its symmetrically substituted tetrahedral molecule.

Properties, synthesis, uses

Carbon tetraiodide is slightly reactive towards water, giving iodoform and I2>. Otherwise 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:

The product crystallizes from the reaction solution.

Carbon tetraiodide is used as an iodination reagent, often upon reaction with bases. 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

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

Carbon tetraiodide Wikipedia


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