Diiodomethane

Diiodomethane or methylene iodide, commonly abbreviated “MI”, is an organoiodine compound. Diiodomethane is a 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 relatively high refractive index of 1.741, and a surface tension of 0.0508 N·m−1.[3]

Diiodomethane
Ball and stick model of diiodomethane
Spacefill model of diiodomethane
Names
IUPAC name
Diiodomethane[1]
Identifiers
3D model (JSmol)
1696892
ChemSpider
ECHA InfoCard 100.000.765
EC Number
  • 200-841-5
MeSH methylene+iodide
RTECS number
  • PA8575000
UNII
Properties
CH2I2
Molar mass 267.836 g·mol−1
Appearance Colorless liquid
Density 3.325 g mL−1
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]
23 μmol Pa−1 kg−1
-93.10·10−6 cm3/mol
Structure
Tetragonal
Tetrahedron
Thermochemistry
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
GHS Signal word Danger
GHS hazard statements
 H302, H315, H318, H335
P261, P280, P305+351+338
NFPA 704 (fire diamond)
Flammability code 1: Must be pre-heated before ignition can occur. Flash point over 93 °C (200 °F). E.g. canola oilHealth code 3: Short exposure could cause serious temporary or residual injury. E.g. chlorine gasReactivity code 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no code
1
3
0
Flash point 110 °C (230 °F; 383 K)
Related compounds
Related alkanes
Related compounds
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

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 in the Simmons–Smith reaction, serving as a source of the free radical methylene (carbene), :CH
2.[4]

Preparation

Diiodomethane can be prepared from the widely available solvent dichloromethane by the action of sodium iodide in acetone in the Finkelstein reaction:[5]

CH2Cl2 + 2 NaI → CH2I2 + 2 NaCl

It can also be prepared by reducing iodoform with elemental phosphorus[6] or sodium arsenite:[5]

CHI3 + Na3AsO3 + NaOH → CH2I2 + NaI + Na3AsO4

Safety

Alkyl iodides are alkylating agents and contact should be avoided.

References
  1. "methylene iodide - Compound Summary". PubChem Compound. USA: National Center for Biotechnology Information. 26 March 2005. Identification ad Related Records. Retrieved 27 February 2012.
  2. http://www.surface-tension.de/LIQUIDS/Diiodomethane3.htm
  3. Website of Krüss Archived 2013-12-01 at the Wayback Machine (8.10.2009)
  4. Two cyclopropanation reactions: Smith, R. D.; Simmons, H. E. "Norcarane". Organic Syntheses.CS1 maint: multiple names: authors list (link); Collective Volume, 5, p. 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.CS1 maint: multiple names: authors list (link); Collective Volume, 6, p. 327
  5. Roger Adams, C. S. Marvel (1941). "Methylene Iodide". Organic Syntheses.; Collective Volume, 1, p. 358
  6. Miller, William Allen (1880). Elements of Chemistry: Chemistry of carbon compounds 5th ed. London: Longmans Green and Co. p. 154.
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