Diiodomethane

Structural formula
General
Surname	Diiodomethane
other names	Methylene iodide
Molecular formula	CH 2 I 2
Brief description	light brown liquid with a characteristic odor
External identifiers / databases
EC number	200-841-5
ECHA InfoCard	100,000,765
PubChem	6346
Wikidata	Q425692
properties
Molar mass	267.84 g mol −1
Physical state	liquid
density	3.325 g cm −3
Melting point	6 ° C
boiling point	67-69 ° C (11 mmHg ); 181 ° C (decomposition);
solubility	poor in water (0.8 g l −1 at 25 ° C)
Refractive index	1.7425 (20 ° C)
safety instructions
GHS labeling of hazardous substances danger
H and P phrases	H: 301 + 311-332-315-319-335
	P: 280-302 + 352-305 + 351 + 338-308 + 310
Toxicological data	76 mg kg −1 ( LD 50 , rat , oral ) ; 830 mg kg −1 ( LD 50 , mouse , transdermal ) ; 1.3 mg l −1 (4h) ( LC 50 , rat , inh. ) ;
Thermodynamic properties
ΔH f 0	68.5 ± 0.8 kJ mol −1
	As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions . Refractive index: Na-D line , 20 ° C

Diiodomethane (CH ₂ I ₂ ), the name methylene iodide or the outdated version methylene iodide is more common in the literature , is a doubly iodinated derivative of methane and thus a halogenated hydrocarbon . In nature, this compound can be found, for example, in seawater in concentrations of a few pmol / mol.

Extraction and presentation

Like dibromomethane, diiodomethane can be obtained by reacting iodoform with sodium arsenite and sodium hydroxide .

{\ displaystyle \ mathrm {CHI_ {3} + Na_ {3} AsO_ {3} + NaOH \ rightarrow CH_ {2} I_ {2} + Na_ {3} AsO_ {4} + NaI}}

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

properties

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

use

In the organic synthesis CH can ₂ I ₂ for the preparation of carbenes are used, for example in the Simmons-Smith reaction . It is also used as a source of iodine in Sandmeyer-type reactions , for example when working in systems in which inorganic iodides are not soluble.

In mineralogy , the heavy liquid is often used with the aid of the immersion method to determine the refractive index of minerals , as well as to separate and determine the density of unknown heavy minerals. Because of its uncertain toxicity , diiodomethane should no longer be used for this purpose, especially since in many cases it can very easily be replaced by less dangerous heavy liquids.

In the contact angle measurement , diiodomethane is used as a reference liquid to determine the surface energy of solids, as it has a relatively high surface tension for a pure or predominantly non-polar liquid and therefore forms easily measurable contact angles.

Individual evidence

↑ ^a ^b ^c ^d ^e ^f Entry on methylene iodide in the GESTIS substance database of the IFA , accessed on January 8, 2018(JavaScript required) .
↑ ^a ^b ^c ^d CRC Handbook of Tables for Organic Compound Identification , Third Edition, 1984, ISBN 0-8493-0303-6 .
↑ ^a ^b ^c ^d data sheet diiodomethane (PDF) from Merck , accessed on July 5, 2007.
↑ Data sheet diiodomethane from Sigma-Aldrich , accessed on March 25, 2011 ( PDF ).
^ AS Carson, PG Laye, JB Pedley, Alison M. Welsby: The enthalpies of formation of iodomethane, diiodomethane, triiodomethane, and tetraiodomethane by rotating combustion calorimetry . In: The Journal of Chemical Thermodynamics , 1993 , 25 (2) , pp. 261-269; doi : 10.1006 / jcht.1993.1025 .
^ Vogt, Rainer et al .: Iodine chemistry and its role in halogen activation and ozone loss in the marine boundary layer: A model study. In: Journal of Atmospheric Chemistry 32.3 (1999): 375-395.
↑ Roger Adams and CS Marvel: Methylene Iodide In: Organic Syntheses . 1, 1921, p. 57, doi : 10.15227 / orgsyn.001.0057 ; Coll. Vol. 1, 1941, p. 358 ( PDF ).
↑ Krüss: Liquids , accessed on October 8, 2009.
^ HE Simmons, TL Cairns, SA Vladuchick, CM Hoiness: Review of its use in the cyclopropanation of olefins . In: Org. React. , 1973 , 20 , pp. 1-131.
^ V. Nair, S. Richardson: Modification of Nucleic Acid Bases via Radical Intermediates: Synthesis of Dihalogenated Purine Nucleosides . In: Synthesis , 1982 , pp. 670-672; doi : 10.1055 / s-1982-29896 .

[GESTIS-1] ↑ ^a ^b ^c ^d ^e ^f Entry on methylene iodide in the GESTIS substance database of the IFA , accessed on January 8, 2018(JavaScript required) .

[CRC-2] CRC Handbook of Tables for Organic Compound Identification , Third Edition, 1984, ISBN 0-8493-0303-6 .

[Merck-3] ta sheet diiodomethane (PDF) from Merck , accessed on July 5, 2007.

[Sigma-4] Data sheet diiodomethane from Sigma-Aldrich , accessed on March 25, 2011 ( PDF ).

[5] AS Carson, PG Laye, JB Pedley, Alison M. Welsby: The enthalpies of formation of iodomethane, diiodomethane, triiodomethane, and tetraiodomethane by rotating combustion calorimetry . In: The Journal of Chemical Thermodynamics , 1993 , 25 (2) , pp. 261-269; doi : 10.1006 / jcht.1993.1025 .

[6] Vogt, Rainer et al .: Iodine chemistry and its role in halogen activation and ozone loss in the marine boundary layer: A model study. In: Journal of Atmospheric Chemistry 32.3 (1999): 375-395.

[7] Roger Adams and CS Marvel: Methylene Iodide In: Organic Syntheses . 1, 1921, p. 57, doi : 10.15227 / orgsyn.001.0057 ; Coll. Vol. 1, 1941, p. 358 ( PDF ).

[KRÜSS-8] Krüss: Liquids , accessed on October 8, 2009.

[9] HE Simmons, TL Cairns, SA Vladuchick, CM Hoiness: Review of its use in the cyclopropanation of olefins . In: Org. React. , 1973 , 20 , pp. 1-131.

[10] V. Nair, S. Richardson: Modification of Nucleic Acid Bases via Radical Intermediates: Synthesis of Dihalogenated Purine Nucleosides . In: Synthesis , 1982 , pp. 670-672; doi : 10.1055 / s-1982-29896 .