Addition of Halogen Acids to Alkynes

In case of unsymmetrical alkynes (which contain unequal number of H-atoms attached to the carbon atoms of the triple bonds), the addition of HX takes place according to the Markownikoff’s rule.

Addition of HBr to ethyne is as follows:

This rule states that in the addition of halogen acids to unsymmetrical alkynes, the halogen of HX goes to that carbon atom of C≡C bond which already has less H-atoms attached to it. Hydrogen atom of HX goes to the carbon atom with more number of H-atoms attached to it.