1,2-Dibromoethylene

1,2-Dibromoethylene
(Z)-1,2-Dibromoethylene	(E)-1,2-Dibromoethylene
Names
	Preferred IUPAC name 1,2-Dibromoethene
Identifiers
CAS Number	590-11-4 (Z) ; 590-12-5 (E) ;
3D model (JSmol)	Interactive image;
ChemSpider	558875 (Z); 553502 (E);
ECHA InfoCard	100.007.953
EC Number	208-747-6;
PubChem CID	643776 (Z); 637929 (E);
UNII	0S4D0712FY (Z) ; 64UWX7EBVO (E) ;
CompTox Dashboard (EPA)	DTXSID3060241 ;
	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−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:
Pictograms
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 [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. Both isomers are colorless liquids.

Synthesis

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.

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]

References

↑ "Chapter 9: Addition Reactions of Alkynes". Organic Chemistry 4e Carey. McGraw-Hill. Archived from the original on April 12, 2016. Retrieved 9 June 2017.
↑ 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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[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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