Additions to symmetrical alkynes:

 Alkynes go through electrophilic addition reactions with similar reagents like alkenes (for example halogens and hydrogen halides). Because there are two π bonds in alkynes, it is possible for the reaction to go one time or two times depending upon the amount of reagent added. For instance, reaction of 2-butyne with one equivalent of bromine provides an (E)-dibromoalkene. With two equal of bromine, the initially created (E)-dibromoalkene reacts further to provide a tetrabromoalkane.

Figure: Reaction of 2-butyne with (a) 1 equivalent of bromine; (b) 2 equivalents of bromine.