Diiodomethane

Methylene iodide

Colorless to brown liquid with a characteristic odor

Liquid

3.325 g · cm -3

6 ° C

• 67-69 ° C ( 11 mmHg)
• 181 ° C ( decomposition)

Poorly in water ( 0.8 g · l-1 at 25 ° C)

1.7425 (20 ° C)

Risk

68.5 ± 0.8 kJ · mol -1

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Diiodomethane ( CH2I2 ), in the literature it is often the name of methylene iodide or the outdated version methylene iodide to be found, is a doubly iodinated derivative of methane and thus a halogenated hydrocarbon. In nature, this compound is given, for example in sea water at concentrations of a few pmol / mol.

Production and representation

Diiodomethane can similarly be obtained by the reaction of dibromomethane with iodoform sodium arsenite and sodium hydroxide.

It can also be prepared by halogen exchange with aluminum from dichloromethane.

Properties

In the fresh state diiodomethane is a colorless liquid that can turn brown due to decomposition reactions in the daylight over time. Both the density and the refractive index of diiodomethane are with 3.325 g · cm -3 and 1.7425 (20 ° C and 589.3 nm) exceptionally high. The surface tension of 0.0508 N · m -1.

Use

CH2I2 in organic synthesis can be used to represent carbenes, for example in the Simmons-Smith reaction. In addition, it is used as a source of iodine with a Sandmeyer -type reaction using, when working for example in systems in which inorganic iodides are not soluble.

In mineralogy, the heavy liquid is frequently used by means of the immersion method to determine the refractive index of minerals, as well as for the separation and determination of unknown density heavy minerals. Because of its indeterminate toxicity diiodomethane should no longer be used for this purpose, especially since it can be easily replaced in many cases by less heavy liquids.

The contact angle measurement diiodomethane is used as a reference liquid for determining the surface energy of solids, since it has a relatively high surface tension for a pure or predominantly non-polar liquid and therefore perfectly formed measurable contact angle.