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1,2-Dibromoethylene

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1,2-Dibromoethylene
(Z)-1,2-Dibromoethylene
(E)-1,2-Dibromoethylene
Names
Preferred IUPAC name 1,2-Dibromoethene
Identifiers
CAS Number
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.007.953 Edit this at Wikidata
EC Number
  • 208-747-6
PubChem CID
UNII
CompTox Dashboard (EPA)
InChI
  • InChI=1S/C2H2Br2/c3-1-2-4/h1-2H/b2-1+Key: UWTUEMKLYAGTNQ-OWOJBTEDSA-N
SMILES
  • C(=CBr)Br
Properties
Chemical formula C2H2Br2
Molar mass 185.846 g·mol
Appearance colorless liquid
Density 2.246 g/cm
Boiling point 110 °C (230 °F; 383 K)
Hazards
Occupational safety and health (OHS/OSH):
Main hazards Toxic
GHS labelling:
Pictograms GHS05: CorrosiveGHS06: ToxicGHS07: Exclamation mark
Signal word Danger
Hazard statements H301, H314, H315, H319, H335
Precautionary statements P260, P261, P264, P270, P271, P280, P301+P310, P301+P330+P331, P302+P352, P303+P361+P353, P304+P340, P305+P351+P338, P310, P312, P321, P330, P332+P313, P337+P313, P362, P363, P403+P233, P405, P501
Except where otherwise noted, data are given for materials in their standard state (at 25 °C , 100 kPa). Infobox references
Chemical compound

1,2-Dibromoethylene, also known as 1,2-dibromoethene and acetylene dibromide, is a dihalogenated unsaturated compound with one bromine on each of the two carbon atoms. There are two isomers of this compound, cis and trans. Both isomers are colorless liquids.

Synthesis

1,2-Dibromoethylene can be synthesized by halogenation of acetylene (C2H2) with bromine (Br2). In order to prevent the formation of tetrahalogenated compounds, acetylene is used in excess, with Br2 as the limiting reagent.

Bromination of acetylene

Alternately, halogenation of this kind could also be achieved through the use of two equivalents of N-bromosuccinimide and lithium bromide (LiBr). N-Bromosuccinimide provides Br as an electrophile, which is followed by Br from LiBr.

References

  1. "Chapter 9: Addition Reactions of Alkynes". Organic Chemistry 4e Carey. McGraw-Hill. Archived from the original on April 12, 2016. Retrieved 9 June 2017.
  2. Shao, L.-X.; Shi, M. (2006). "N-Bromosuccinimide and Lithium Bromide: An Efficient Combination for the Dibromination of Carbon–Carbon Unsaturated Bonds" (PDF). Synlett. 2006 (8): 1269–1271. doi:10.1055/s-2006-941558.
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