As a general rule, electrophiles undergo electrophilic addition reactions with alkynes much as they do with alkenes. Take the reaction of alkynes with HX, for example. The reaction often can be stopped after addition of 1 equivalent of HX, but reaction with an excess of HX leads to a dihalide product. For example, reaction of 1-hexyne with 2 equivalents of HBr yields 2,2-dibromohexane. As the following examples indicate, the regiochemistry of addition follows Markovnikov’s rule: Halogen adds to the less highly substituted side. Trans stereochemistry of H and X is normally(though not always) found in the product.