So if we place this molecule, let's say on the board and the board is our plane, then all these molecules will lie along the plane of that board. Now let's take a look at the following diagram. Something that we really haven't explained yet is the fact that we see predominantly the trans isomer configuration and not the CIS configuration. So in each one of these cases, the two alpha carbon groups pointed in opposite directions. They never pointed in the same directions. The question is why?