| Carbon tetraiodide | |
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Tetraiodomethane |
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Other names
Carbon iodide |
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| Identifiers | |
| CAS number | 507-25-5 |
| PubChem | 10487 |
| ChemSpider | 10055 |
| EC number | 208-068-5 |
| RTECS number | FG4960000 |
| Jmol-3D images | Image 1 Image 2 |
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| Properties | |
| Molecular formula | CI4 |
| Molar mass | 519.6286 g/mol |
| Appearance | red crystals |
| Density | 4.32 g/cm3 |
| Melting point |
171 °C (444 K) decomp. |
| Solubility in water | Insoluble |
| Structure | |
| Crystal structure | Monoclinic |
| Molecular shape | Tetrahedral |
| Hazards | |
| EU classification | Irritant (Xi) |
| R-phrases | R36/37/38 |
| S-phrases | S26, S36 |
| (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. [1] 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 monoclinic crystal structure (a 22.39, b 12.93, c 25.85 (.10-1 nm), β 125.26°).
It has dipole moment of 0 Debyes due to its symmetrically substituted tetrahedral molecule.
Contents |
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:[2]
The product crystallizes from the reaction solution.
CI4 is used as an iodination reagent, often upon reaction with base. [3] 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.
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.
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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