For example, the structure of 2-brombutane is
We can convert this to its enantiomer by interchanging any two groups.
We often interchange the groups on the wedges and dashes, as below.
It is not immediately obvious that these are mirror images of each other.
If we rotate the top structure 180 ° about the axis and put it below our original structure, we get
The red line represents a mirror plane that shows the enantiomers.
It is often easier to interconvert the bonds in the plane of the paper. This gives us
Here, the red line represents a vertical mirror plane with the two enantiomers.
There are other possibilities.
It just shows that we must practice viewing molecules in three dimensions.