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| Carbon tetraiodide | |
|---|---|
| General | |
| Systematic name | Carbon tetraiodide |
| Other names | Tetraiodomethane |
| Molecular formula | CI4 |
| SMILES | ? |
| Molar mass | 519.63 g/mol |
| Appearance | red crystals |
| CAS number | * |
| Properties | |
| Density and phase | 4.32 g/cm3 solid |
| Solubility in water | insoluble |
| Other solvents | non-polar organic solvents |
| Melting point | 171 °C with decomposition |
| Structure | |
| Molecular shape | tetrahedral |
| Crystal structure | monoclinic |
| Dipole moment | 0 D |
| Hazards | |
| MSDS | External MSDS |
| Main hazards | skin irritant |
| NFPA 704 | |
| R/S statement | R: 36/37/38 S: 26-36 |
| RTECS number | FG4960000 |
| Supplementary data page | |
| Structure and properties | n, εr, etc. |
| Thermodynamic data | Phase behaviour Solid, liquid, gas |
| Spectral data | UV, IR, NMR, MS |
| Related compounds | |
| Related compounds | CCl4CHI3 |
| Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Chemical infobox | |
Carbon tetraiodide is 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. The tetrahedral molecule features C-I distances of 2.12 ± 0.02 Å. Finbak, Chr.; Hassel, O. Kristallstruktur und Molekülbau von CI4 und CBr4" Zeitschrifte für Physikalische Chemie (1937), volume B36, page 301-8 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.
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:McArthur, R. E.; Simons, J. H., “Carbon Tetraiodide” Inorganic Syntheses 1950, volume III, 37–39
- CCl4 + 4 EtI → CI4 + 4 EtCl
CI4 is used as an iodination reagent, often upon reaction with base. P. R. Schreiner, A. A. Fokin, “Carbon Tetraiodide” in Encyclopedia of Reagents for Organic Synthesis (Ed: L. Paquette) 2005; John Wiley & Sons, Ltd Ketones are converted to 1,1-diiodoethenes upon treatment with PPh3 and CI4. Alcohols are converted in and to iodide, by an 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. As a ready source of iodine, it is an irritant. LD50: 178 mg kg–1. In general perhalogenated organic compounds should be considered toxic.
References
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.
External links
Inorganic carbon compounds | Iodides | Nonmetal halides | Reagents for organic chemistry
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"Carbon tetraiodide"