Chemistry:Diiodomethane
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| Names | |||
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| Preferred IUPAC name
Diiodomethane[1] | |||
| Identifiers | |||
3D model (JSmol)
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| 1696892 | |||
| ChemSpider | |||
| EC Number |
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| MeSH | methylene+iodide | ||
PubChem CID
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| RTECS number |
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| Properties | |||
| CH2I2 | |||
| Molar mass | 267.836 g·mol−1 | ||
| Appearance | Colorless liquid | ||
| Density | 3.325 g mL−1 (3325 kg/m3) | ||
| Melting point | 5.4 to 6.2 °C; 41.6 to 43.1 °F; 278.5 to 279.3 K | ||
| Boiling point | 182.1 °C; 359.7 °F; 455.2 K | ||
| 1.24 g L−1 (at 20 °C)[2] | |||
Henry's law
constant (kH) |
23 μmol Pa−1 kg−1 | ||
| -93.10·10−6 cm3/mol | |||
| Structure | |||
| Tetragonal | |||
| Tetrahedron | |||
| Thermochemistry | |||
Heat capacity (C)
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133.81 J K−1 mol−1 | ||
Std enthalpy of
formation (ΔfH⦵298) |
67.7–69.3 kJ mol−1 | ||
Std enthalpy of
combustion (ΔcH⦵298) |
−748.4–−747.2 kJ mol−1 | ||
| Hazards | |||
| Safety data sheet | hazard.com | ||
| GHS pictograms |  
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| GHS Signal word | DANGER | ||
| H302, H315, H318, H335 | |||
| P261, P280, P305+351+338 | |||
| NFPA 704 (fire diamond) | |||
| Flash point | 110 °C (230 °F; 383 K) | ||
| Related compounds | |||
Related alkanes/haloalkanes
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Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). | |||
 verify (what is   ?)
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| Infobox references | |||
Diiodomethane or methylene iodide, commonly abbreviated "MI", is an organoiodine compound. Diiodomethane is a very dense colorless liquid; however, it decomposes upon exposure to light liberating iodine, which colours samples brownish. It is slightly soluble in water, but soluble in organic solvents. It has a very high refractive index of 1.741, and a surface tension of 0.0508 N·m−1.[3]
Uses
Because of its high density, diiodomethane is used in the determination of the density of mineral and other solid samples. It can also be used as an optical contact liquid, in conjunction with the gemmological refractometer, for determining the refractive index of certain gemstones.
Diiodomethane is a reagent for installing the CH2 group. In the Simmons–Smith reaction, it is a source of methylene.[4] In fact the Simmons–Smith reaction does not produce free carbene but proceeds via Zn-CH2I intermediates.
Diiodomethane is also a source of the equivalent of CH22+. The synthesis of Fe2(CH2)(CO)8 illustrates this reactivity:[5]
- Na2Fe2(CO)8 + CH2I2 → Fe2(CH2)(CO)8 + 2 NaI
Preparation
Diiodomethane can be prepared from the widely available solvent dichloromethane by the action of sodium iodide in acetone in the Finkelstein reaction:[6]
- CH2Cl2 + 2 NaI → CH2I2 + 2 NaCl
It can also be prepared by reducing iodoform with elemental phosphorus[7] or sodium arsenite:[6]
- CHI3 + Na3AsO3 + NaOH → CH2I2 + NaI + Na3AsO4
Safety
Alkyl iodides are alkylating agents, which are potential mutagens.
References
- ↑ "methylene iodide - Compound Summary". PubChem Compound. USA: National Center for Biotechnology Information. 26 March 2005. Identification ad Related Records. https://pubchem.ncbi.nlm.nih.gov/summary/summary.cgi?cid=6346&loc=ec_rcs.
- ↑ "Diiodomethane". http://www.surface-tension.de/LIQUIDS/Diiodomethane3.htm.
- ↑ Website of Krüss (8.10.2009)
- ↑ Two cyclopropanation reactions: Smith, R. D.; Simmons, H. E.. "Norcarane". Organic Syntheses. http://www.orgsyn.org/demo.aspx?prep=cv5p0855.; Collective Volume, 5, pp. 855, Ito, Y.; Fujii, S.; Nakatuska, M.; Kawamoto, F.; Saegusa, T. (1988). "One-Carbon Ring Expansion Of Cycloalkanones To Conjugated Cycloalkenones: 2-Cyclohepten-1-one". Organic Syntheses. http://www.orgsyn.org/demo.aspx?prep=cv6p0327.; Collective Volume, 6, pp. 327
- ↑ Sumner, Charles E.; Riley, Paul E.; Davis, Raymond E.; Pettit, R. (1980). "Synthesis, Crystal Structure, and Chemical Reactivity of Octacarbonyl-μ-methylene-diiron". Journal of the American Chemical Society 102 (5): 1752–1754. doi:10.1021/ja00525a062.
- ↑ 6.0 6.1 Roger Adams; C. S. Marvel (1921). "Methylene Iodide". Organic Syntheses 1: 57. doi:10.15227/orgsyn.001.0057.
- ↑ Miller, William Allen (1880). Elements of Chemistry: Chemistry of carbon compounds (5th ed.). London: Longmans Green and Co.. p. 154. https://archive.org/details/elementschemist01grovgoog.
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