Carbon tetraiodide
| Carbon tetraiodide | |
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Tetraiodomethane[1] |
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| Identifiers | |
| CAS number | 507-25-5  |
| PubChem | 10487 |
| ChemSpider | 10055  |
| EC number | 208-068-5 |
| RTECS number | FG4960000 |
| Beilstein Reference | 1733108 |
| Jmol-3D images | Image 1 |
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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 | |
| Std enthalpy of formation ΔfH |
384.0–400.4 kJ mol−1 |
| Std enthalpy of combustion ΔcH |
−794.4–−778.4 kJ mol−1 |
| Specific heat capacity, C | 259.8 J K−1 mol−1 |
| Hazards | |
| GHS pictograms |  |
| GHS signal word | WARNING |
| GHS hazard statements | H315, H319, H335 |
| GHS precautionary statements | P261, P305+351+338 |
| EU classification |  Xi |
| R-phrases | R36/37/38 |
| S-phrases | S26, S36 |
| Related compounds | |
| Related alkanes | |
| Related compounds | |
 (verify) (what is:  / ?)Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) |
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| 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.
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Properties, synthesis, uses[edit]
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]
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- 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[edit]
Manufacturers recommend that CI4 be stored near 0 °C. 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[edit]
- ^ "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[edit]
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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