Dibromomethane

This article is about dibromomethane, confusable with 1,2-dibromoethane (1,2-dibromo-ethane) .

Structural formula
Wedge line formula to clarify the geometry
General
Surname	Dibromomethane
other names	Methylene bromide Methylenedibromide
Molecular formula	CH 2 Br 2
Brief description	volatile colorless liquid with a sweetish odor
External identifiers / databases
CAS number 74-95-3 EC number 200-824-2 ECHA InfoCard 100,000,750 PubChem 3024 Wikidata Q421736
properties
Molar mass	173.83 g mol −1
Physical state	liquid
density	2.49 g cm −3
Melting point	−52 ° C
boiling point	97 ° C
Vapor pressure	46.2 h Pa (20 ° C) 76.8 hPa (30 ° C) 123 hPa (40 ° C)
solubility	slightly soluble in water (11.7 g l −1 at 15 ° C) soluble in most organic solvents
Refractive index	1.54-1.542
safety instructions
GHS hazard labeling from  Regulation (EC) No. 1272/2008 (CLP) , expanded if necessary Caution H and P phrases H: 332-412 P: 273
Toxicological data	108 mg kg −1 ( LD 50 ,  rat ,  oral )
Global warming potential	1 (based on 100 years)
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

Dibromomethane is a chemical compound from the group of aliphatic saturated halogenated hydrocarbons and organic bromine compounds . The compound is the disubstituted representative of the series of bromomethanes with bromomethane , dibromomethane, tribromomethane and tetrabromomethane .

Occurrence

Dibromomethane is naturally produced by some arctic macroalgae .

Extraction and presentation

The industrial production of dibromomethane takes place from dichloromethane by halogen exchange using bromine and aluminum

${\displaystyle \mathrm {6\,CH_{2}Cl_{2}+3\,Br_{2}+2\,Al\rightarrow 6\,CH_{2}BrCl+2\,Al_{2}O_{3}} }$ and

${\displaystyle \mathrm {6\,CH_{2}BrCl+3\,Br_{2}+2\,Al\rightarrow 6\,CH_{2}Br_{2}+2\,Al_{2}O_{3}} }$

or by means of hydrogen bromide in the presence of aluminum chloride

${\displaystyle \mathrm {CH_{2}Cl_{2}+HBr\xrightarrow {AlCl_{3}} \ CH_{2}BrCl+HCl} }$ and

${\displaystyle \mathrm {CH_{2}BrCl+HBr\xrightarrow {AlCl_{3}} \ CH_{2}Br_{2}+HCl} }$.

Both syntheses proceed via the intermediate product bromochloromethane . The yield of both products can be adjusted via the stoichiometry of the starting materials.

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

${\displaystyle \mathrm {CHBr_{3}+Na_{3}AsO_{3}+NaOH\rightarrow CH_{2}Br_{2}+Na_{3}AsO_{4}+NaBr} }$

Another way of production is the reaction of diiodomethane with bromine.

properties

Dibromomethane is a volatile, colorless to yellowish liquid with a sweetish odor. The compound boils at 97 ° C. under normal pressure . According to Antoine, the vapor pressure function results from log ₁₀ (P) = A− (B / (T + C)) (P in bar, T in K) with A = 4.51734, B = 1546.096 and C = −28.977 in the temperature range from 238 K to 372 K. The miscibility with water is only limited. As the temperature rises, the solubility of dibromomethane in water increases or the solubility of water in dibromomethane increases.

Miscibility between dibromomethane and water
temperature	° C	0	9.7	19.3	29.5	39.5	49.5	59.9	69.9	79.8	90.1
Dibromomethane in water	in%	1.17	1.13	1.28	1.14	1.20	1.27	1.36	1.36	1.61	1.51
Water in dibromomethane	in%		0.040	0.056	0.069	0.091	0.120	0.164	0.155	0.153	0.200

It decomposes when exposed to heat or light, producing bromine and bromine compounds.

use

Dibromomethane is an intermediate in the manufacture of herbicides and pesticides . It is also used in low concentrations in halogen lamps .

Web links

• Entry on dibromomethane in the Spectral Database for Organic Compounds (SDBS) of the National Institute of Advanced Industrial Science and Technology (AIST)

Individual evidence

1. ↑ ^{a b c d e f g h i j k l} Entry on dibromomethane in the GESTIS substance database of the IFA , accessed on April 5, 2018(JavaScript required) .
2. ↑ iclfr.com: dibromomethane  ( page no longer available , searching web archives )  Info: The link is automatically marked as defective. Please check the link according to the instructions and then remove this notice.  
3. ↑ Entry on dibromomethane at ChemBlink , accessed on February 25, 2011.
4. ↑ Entry on dibromomethane in the Classification and Labeling Inventory of the European Chemicals Agency (ECHA), accessed on February 1, 2016. Manufacturers or distributors can expand the harmonized classification and labeling .
5. ↑ Data sheet dibromomethane (PDF) from Merck , accessed on March 24, 2011.
6. ↑ G. Myhre, D. Shindell et al .: Climate Change 2013: The Physical Science Basis . Working Group I contribution to the IPCC Fifth Assessment Report. Ed .: Intergovernmental Panel on Climate Change . 2013, Chapter 8: Anthropogenic and Natural Radiative Forcing, pp. 24-39; Table 8.SM.16 ( PDF ).
7. ↑ F. Laturnus: Formation and release of short-chain halogenated hydrocarbons by macroalgae of the polar regions . In: Reports on polar research. Alfred Wegener Institute for Polar and Marine Research, 1993, 132, p. 188, ISSN  0176-5027 .
8. ↑ D. Yoffe; R. Frim; SD ukeles; MJ Dagani; HJ Barda; TJ Benya; DC Sanders: Bromine Compounds , in: Ullmanns Enzyklopädie der Technischen Chemie , Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim 2013; doi : 10.1002 / 14356007.a04_405.pub2 .
9. ^ W. Hartman, EE Dreger: Methylene Bromide In: Organic Syntheses . 9, 1929, p. 56, doi : 10.15227 / orgsyn.009.0056 ; Coll. Vol. 1, 1941, p. 357 ( PDF ).
10. ↑ Majer, V .; Svoboda, V .: Enthalpies of Vaporization of Organic Compounds: A Critical Review and Data Compilation , Blackwell Scientific Publications, Oxford, 1985, 300.
11. ↑ Stull, DR: Vapor Pressure of Pure Substances Organic Compounds in Ind. Eng. Chem. 39 (1947) 517-540, doi : 10.1021 / ie50448a022 .
12. ^ ^{A b} R. M. Stephenson: Mutual Solubilities: Water-Ketones, Water-Ethers, and Water-Gasoline-Alcohols in J. Chem. Eng. Data 37 (1992) 80-95, doi : 10.1021 / je00005a024 .
13. ↑ Hans Peter Latscha, Helmut Alfons Klein: Inorganische Chemie . Springer DE, 2002, ISBN 3-540-42938-7 , pp. 408 ( limited preview in Google Book search).