Has anyone analyzed the products of the reaction of any simple alkyne (eg.: acetylene) with bromine water? Most online references state that a dihalo-addition or tetrahalo-addition happens, but the only experimentally-based reports I found are more than 90 years old and state that dihalooxy-addition happens (although with hypobromous acid), leading to α,α-dibromoaldehydes and α,α-dibromocarboxylic acids (I expect α,α-dibromoketones possible with internal alkynes). Any new data on that?

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    $\begingroup$ Well, why would they do more research on that? $\endgroup$
    – Mithoron
    Jul 18 at 14:37
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    $\begingroup$ Please reference those experimental reports $\endgroup$
    – Ritil
    Jul 18 at 20:50
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    $\begingroup$ Internal alkynes afford $\alpha$, $\alpha$-dibromoketones with tribromocyanuric acid in acetic acid. DOI: 10.2174/1570178615666180803152951 $\endgroup$
    – user55119
    Jul 18 at 21:58

1 Answer 1


There are 4 kinds of reactions which occur for sure:

  1. addition of dihalogen to alkene and alkyne in carbon tetrachloride gives vicinal dihalide(alkane and alkene respectively).
  2. addition of hydrohalic acid to alkene and alkyne gives monohalogenated alkane and alkene respectively.
  3. addition of dilute hydrobromic acid to alkene gives alpha-bromo alkanol
  4. addition of hydrohalous acid to alkene also gives the same product

If such kind of reactions are possible then I think that the reaction about you are talking should also be possible via tautomerism of alkenol, but I can't see how can carboxylic acids form.

Addition of HOBr across C=C I think this could be helpful


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