Diiodomethane

Diiodomethane
Stereo, skeletal formula of diiodomethane with all explicit hydrogens added
Ball and stick model of diiodomethane
Ball and stick model of diiodomethane
Spacefill model of diiodomethane
Spacefill model of diiodomethane
Names
Preferred IUPAC name
Diiodomethane[1]
Identifiers
3D model (JSmol)
1696892
ChemSpider
ECHA InfoCard 100.000.765 Edit this at Wikidata
EC Number
  • 200-841-5
MeSH methylene+iodide
RTECS number
  • PA8575000
UNII
  • InChI=1S/CH2I2/c2-1-3/h1H2 checkY
    Key: NZZFYRREKKOMAT-UHFFFAOYSA-N checkY
  • ICI
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]
23 μmol Pa−1 kg−1
-93.10·10−6 cm3/mol
Structure
Tetragonal
Tetrahedron
Thermochemistry
133.81 J K−1 mol−1
67.7–69.3 kJ mol−1
−748.4–−747.2 kJ mol−1
Hazards
GHS labelling:
GHS05: Corrosive GHS07: Exclamation mark
Danger
H302, H315, H318, H335
P261, P280, P305+P351+P338
NFPA 704 (fire diamond)
NFPA 704 four-colored diamondHealth 3: Short exposure could cause serious temporary or residual injury. E.g. chlorine gasFlammability 1: Must be pre-heated before ignition can occur. Flash point over 93 °C (200 °F). E.g. canola oilInstability 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no code
3
1
0
Flash point 110 °C (230 °F; 383 K)
Safety data sheet (SDS) hazard.com
Related compounds
Related alkanes/haloalkanes
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
checkY verify (what is checkY☒N ?)

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 CH2+2. 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

  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. ^ "Diiodomethane".
  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; Collected Volumes, vol. 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; Collected Volumes, vol. 6, p. 327.
  5. ^ 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. ^ a b Roger Adams; C. S. Marvel (1921). "Methylene Iodide". Organic Syntheses. 1: 57. doi:10.15227/orgsyn.001.0057.
  7. ^ Miller, William Allen (1880). Elements of Chemistry: Chemistry of carbon compounds (5th ed.). London: Longmans Green and Co. p. 154.