So let's imagine for a moment that we're taking a walk on a straight path and eventually we come to a fourth in a row. Now, at the fourth, we have several options. We can either take one pathway that will lead us to one place, or we can take a different pathway that will lead us to a different place. 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.