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Carbon tetraiodide
	; Carbon tetraiodide crystals (left); Solution in Et2O (right)
Ball and stick model of carbon tetraiodide	Spacefill model of carbon tetraiodide
Names
	Preferred IUPAC name Tetraiodomethane
Identifiers
CAS Number	507-25-5 ;
3D model (JSmol)	Interactive image;
Beilstein Reference	1733108
ChemSpider	10055 ;
ECHA InfoCard	100.007.335
EC Number	208-068-5;
PubChem CID	10487;
RTECS number	FG4960000;
UNII	E22GNX36ZQ ;
CompTox Dashboard (EPA)	DTXSID0060145 ;
	InChI InChI=1S/CI4/c2-1(3,4)5 Key: JOHCVVJGGSABQY-UHFFFAOYSA-N ;
	SMILES IC(I)(I)I;
Properties
Chemical formula	CI4
Molar mass	519.629 g·mol−1
Appearance	Dark violet crystals
Density	4.32 g mL−1
Magnetic susceptibility (χ)	-136·10−6 cm3/mol
Structure
Crystal structure	Tetragonal
Molecular shape	Tetrahedral
Dipole moment	0 D
Thermochemistry
Heat capacity (C)	0.500 J K−1 g−1
Std enthalpy of; formation (ΔfH⦵298)	384.0–400.4 kJ mol−1
Std enthalpy of; combustion (ΔcH⦵298)	−794.4–−778.4 kJ mol−1
Hazards
	Occupational safety and health (OHS/OSH):
Main hazards	toxic
	GHS labelling:
Pictograms
Signal word	Warning
Hazard statements	H315, H319, H335
Precautionary statements	P261, P305+P351+P338
Related compounds
Other anions	Carbon tetrafluoride ; Carbon tetrachloride ; Carbon tetrabromide
Other cations	Silicon tetraiodide ; Germanium tetraiodide ; Tin(IV) iodide
Related alkanes	Methane; Methyl iodide; Diiodomethane; Iodoform; Ethane; Ethyl iodide;
Related compounds	Pimagedine; Guanidine;
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). verify (what is ?) Infobox references

Carbon tetraiodide is a tetrahalomethane with the molecular formula ${\ce {CI4}}$ . Being bright red, it is a relatively rare example of a highly colored methane derivative. 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.^[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 geometry.

Properties, synthesis, uses

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]

{\ce {CCl4 + 4 EtI -> CI4 + 4 EtCl}}

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

Manufacturers recommend that carbon tetraiodide be stored near 0 °C (32 °F). 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).

References

^ "Tetraiodomethane - Compound Summary". PubChem Compound. USA: National Center for Biotechnology Information. 27 March 2005. Identification and Related Records. Retrieved 29 February 2012.
^ Finbak, Chr.; Hassel, O. (1937). "Kristallstruktur und Molekülbau von CI₄ und CBr₄". Zeitschrift für Physikalische Chemie. B36: 301–308. doi:10.1515/zpch-1937-3621. S2CID 99718985.
^ Pohl, S. (1982). "Die Kristallstruktur von CI₄". Zeitschrift für Kristallographie. 159 (1–4): 211–216. doi:10.1524/zkri.1982.159.14.211. S2CID 102246815.
^ McArthur, R. E.; Simons, J. H. (1950). "Carbon Tetraiodide". Inorganic Syntheses. Vol. III. pp. 37–39. doi:10.1002/9780470132340.ch8. ISBN 9780470132340.
^ P. R. Schreiner, A. A. Fokin (2005). "Carbon Tetraiodide". In L. Paquette (ed.). Encyclopedia of Reagents for Organic Synthesis. John Wiley & Sons, Ltd.