Now, in the same way, when certain compounds react, different pathways are possible, and each pathway will lead us to a different compound. So let's examine the following example. Let's say we have the following two compounds. We have hydrochloric acid reacts with an alkene. Now, two different pathways are possible. In other words, this lewis base can take this H atom and follow pathway one, in which the H atom goes on this side of the carbon.