1,2-Dibromoethylene

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1,2-Dibromoethylene
(Z)-1,2-Dibromoethene.png
(E)-1,2-Dibromoethene.png
Cis1,2-Dibromoethylene.png
(Z)-1,2-Dibromoethylene
Trans1,2-Dibromoethylene.png
(E)-1,2-Dibromoethylene
Names
Preferred IUPAC name
1,2-Dibromoethene
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.007.953 Edit this at Wikidata
EC Number
  • 208-747-6
UNII
  • InChI=1S/C2H2Br2/c3-1-2-4/h1-2H/b2-1+
    Key: UWTUEMKLYAGTNQ-OWOJBTEDSA-N
  • C(=CBr)Br
Properties
C2H2Br2
Molar mass 185.846 g·mol−1
Appearance colorless liquid
Density 2.246 g/cm3
Boiling point 110 °C (230 °F; 383 K)
Hazards
Occupational safety and health (OHS/OSH):
Main hazards
Toxic
GHS labelling:
GHS05: CorrosiveGHS06: ToxicGHS07: Exclamation mark
Danger
H301, H314, H315, H319, H335
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 [77 °F], 100 kPa).

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[edit]

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

Halogenation of Alynes (1).jpg

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.[2]

HalogenationLiBrNBS.png

References[edit]

  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.