Carbon tetraiodide is a

tetrahalomethane Tetrahalomethanes are fully halogenated methane derivatives of general formula CBrkCllFmInAtp, where:k+l+m+n+p=4Tetrahalomethanes are on the border of inorganic and organic chemistry, thus they can be assigned both inorganic and organic names by IU ...

with the molecular formula CI₄. Being bright red, it is a relatively rare example of a highly colored

methane Methane ( , ) is a chemical compound with the chemical formula (one carbon atom bonded to four hydrogen atoms). It is a group-14 hydride, the simplest alkane, and the main constituent of natural gas. The relative abundance of methane ...

derivative In mathematics, the derivative of a function of a real variable measures the sensitivity to change of the function value (output value) with respect to a change in its argument (input value). Derivatives are a fundamental tool of calculus. ...

. It is only 2.3% by weight carbon, although other methane derivatives are known with still less carbon.

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. Carbon tetraiodide crystallizes in

tetragonal In crystallography, the tetragonal crystal system is one of the 7 crystal systems. Tetragonal crystal lattices result from stretching a cubic lattice along one of its lattice vectors, so that the cube becomes a rectangular prism with a squar ...

crystal structure (''a'' 6.409, ''c'' 9.558 (.10⁻¹ nm)). It has zero dipole moment due to its symmetrically substituted

tetrahedral In geometry, a tetrahedron (plural: tetrahedra or tetrahedrons), also known as a triangular pyramid, is a polyhedron composed of four triangular faces, six straight edges, and four vertex corners. The tetrahedron is the simplest of all the ...

geometry.

Properties, synthesis, uses

Carbon tetraiodide is slightly reactive towards water, giving

iodoform Iodoform (also known as triiodomethane and, inaccurately, as carbon triiodide) is the organoiodine compound with the chemical formula C H I3. A pale yellow, crystalline, volatile substance, it has a penetrating and distinctive odor (in older ch ...

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: :CCl4 + 4 EtI -> CI4 + 4 EtCl The product crystallizes from the reaction solution. Carbon tetraiodide is used as an

iodination In chemistry, halogenation is a chemical reaction that entails the introduction of one or more halogens into a compound. Halide-containing compounds are pervasive, making this type of transformation important, e.g. in the production of polymers ...

reagent, often upon reaction with bases. Ketones are converted to 1,1-diiodoalkenes upon treatment with

triphenylphosphine Triphenylphosphine (IUPAC name: triphenylphosphane) is a common organophosphorus compound with the formula P(C6H5)3 and often abbreviated to P Ph3 or Ph3P. It is widely used in the synthesis of organic and organometallic compounds. PPh3 exists ...

(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 Carbon tetrachloride, also known by many other names (such as tetrachloromethane, also recognised by the IUPAC, carbon tet in the cleaning industry, Halon-104 in firefighting, and Refrigerant-10 in HVACR) is an organic compound with the chemi ...

is used to generate alkyl chlorides from alcohols.

Safety considerations

Manufacturers recommend that carbon tetraiodide be stored near . As a ready source of iodine, it is an irritant. Its LD₅₀ on rats is 18 mg/kg. 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).

Structure

Properties, synthesis, uses

Safety considerations

References

Further reading