How can I illustrate Markovnikov's rule by the reaction of propene with hydrobromic acid?
Treat the acid as
As you know, the secondary carbocation is more stable than the primary carbocation. Because the carbocation intermediate is then going to react with the electrophile,
For further background see: Hughes, P. J. Chem. Ed. 2006 , 83 , 1152. Was Markovnikov's Rule an Inspired Guess? I can't get to this article, but your librarian should supply it. J. Chem. Ed. articles are generally very good.