Carbon tetraiodide
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| Names | |||
|---|---|---|---|
| IUPAC name
Tetraiodomethane[1] | |||
| Identifiers | |||
| 1733108 | |||
507-25-5  | |||
| ChemSpider | 10055  | ||
| EC number | 208-068-5 | ||
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| Jmol-3D images | Image | ||
| PubChem | 10487 | ||
| RTECS number | FG4960000 | ||
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| 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) |
0.500 J K−1 g−1 | ||
| Std enthalpy of formation (ΔfH |
384.0–400.4 kJ mol−1 | ||
| Std enthalpy of combustion (ΔcH |
−794.4–−778.4 kJ mol−1 | ||
| Hazards | |||
| GHS pictograms |  | ||
| GHS signal word | WARNING | ||
| H315, H319, H335 | |||
| P261, P305+351+338 | |||
| EU classification |  Xi | ||
| R-phrases | R36/37/38 | ||
| S-phrases | S26, S36 | ||
| Related compounds | |||
| Related alkanes |
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| Related compounds |
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| Except where noted otherwise, data is given for materials in their standard state (at 25 °C (77 °F), 100 kPa) | |||
| verify (what is: /?) | |||
| 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 (32 °F). 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
- ↑ "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. "Kristallstruktur und Molekülbau von CI4 und CBr4" Zeitschrift für Physikalische Chemie (1937), volume B36, page 301-8
- ↑ 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
- ↑ McArthur, R. E.; Simons, J. H., “Carbon Tetraiodide” Inorganic Syntheses 1950, volume III, 37–39
- ↑ 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.
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