1,2-Dibromoethylene

1,2-Dibromoethylene
(Z)-1,2-Dibromoethylene
(E)-1,2-Dibromoethylene
Names
IUPAC name
1,2-Dibromoethene
Identifiers
ChemSpider
Properties
C2H2Br2
Molar mass 185.85 g·mol−1
Density 2.246 g/cm3
Boiling point 110 °C (230 °F; 383 K)
Hazards
Main hazards Toxic
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

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. At room temperature, the mixture of two isomers is a clear colorless to yellow liquid.[1]

Synthesis

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

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.[3]

References

  1. ↑ "1,2-Dibromoethene product specification, Sigma Aldrich" (PDF). Sigma-Aldrich. Retrieved 9 June 2017.
  2. ↑ "Chapter 9: Alkynes". Retrieved 9 June 2017.
  3. ↑ Shao, L; Shi, M. "N-Bromosuccinimide and Lithium Bromide: An Efficient Combination for the Dibromination of Carbon–Carbon Unsaturated Bonds" (PDF). SYNLETT: 1269–1271. doi:10.1055/s-2006-941558.
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