Dibromoacetylene

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Dibromoacetylene
Dibromoacetylene.png
Names
Preferred IUPAC name
1,2-Dibromoethyne[1]
Identifiers
3D model (JSmol)
ChemSpider
  • InChI=1S/C2Br2/c3-1-2-4
    Key: JNFBOWNNNAHVNZ-UHFFFAOYSA-N
  • C(#CBr)Br
Properties
C2Br2
Molar mass 183.830 g·mol−1
Melting point −16.5 °C (2.3 °F; 256.6 K)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

Dibromoacetylene is a molecular chemical compound containing acetylene, with its hydrogen substituted by bromine.

Production[edit]

Dibromoacetylene can be made by reacting 1,1,2-tribromoethylene with potassium hydroxide. This method has a danger of causing explosions.[2]

Another way is to react acetylene with phenyl lithium (at −50 °C) to make lithium acetylide, which then reacts with bromine to yield the product.[3]

Yet another way is to react acetylene with sodium hypobromite NaOBr.[4]

Properties[edit]

Dibromoacetylene is explosive and sensitive to air.[4] Its appearance is a clear water like liquid. It has a sweetish smell, but makes a white fume in air that then smells like ozone, possibly because it forms ozone.[2] Dibromoacetylene is lachrymatory.[2]

Dibromoacetylene can be polymerised to polydibromoacetylene using catalysts like titanium tetrachloride and triethylaluminium. Polydibromoacetylene is black, electrically conducting, and stable in air to over 200 °C.[4]

The infrared spectrum has absorption at 2185 cm−1 due to symmetrical stretching on the C≡C bond, 832 cm−1 asymmetrical stretch on C-Br bond, 311 cm−1 bending on Z shape BrCC, 267 symmetrical stretch on all bonds, and 167 cm−1 for C shaped bending.[2]

Reactions[edit]

In air dibromoacetylene spontaneously inflames producing black sooty smoke and a red flame. When heated, it explodes, yielding carbon and other substances. A slower reaction with oxygen and water, yields oxalic acid and hydrobromic acid and other bromine containing substances. A reaction with hydrogen iodide yields dibromoiodoethylene. Dibromoacetylene reacts with bromine to yield tetrabromoethene.[5]

Dibromoacetylene reacts with Apiezon L, which is used as a vacuum grease in distillation, so its use is unsuitable with this chemical.[2]

References[edit]

  1. ^ "Dibromoacetylene". PubChem. National Library of Medicine. Retrieved 24 March 2022.
  2. ^ a b c d e Kloster-Jenson, Else (1971). "Preparation and physical characterization of pure hetero and homo dihaloacetylenes". Tetrahedron. 27 (1): 33–49. doi:10.1016/S0040-4020(01)92395-6.
  3. ^ Meijere, Armin de (2014). Science of Synthesis: Houben-Weyl Methods of Molecular Transformations Vol. 24: Three Carbon-Heteroatom Bonds: Ketene Acetals and Yne-X Compounds. Georg Thieme Verlag. pp. 1191–1192. ISBN 978-3-13-178171-0.
  4. ^ a b c Leben, S.; Janevski, A.; Šebenik, A.; Osredkar, U. (May 1992). "The synthesis and characterization of polydibromoacetylene" (PDF). Polymer Bulletin. 28 (3): 287–292. doi:10.1007/BF00294824. S2CID 94005740.
  5. ^ Sartori, Mario (1939). The War Gases Chemistry and Analysis. Translated by L. W. MARRISON. New York: D. Van Nostrand Co., Inc. p. 51.