text: Q:
  
  How to identify Enantiomers
  
  AP Biology Question
  So I know that enantiomers are like mirror images of each other, but not identical (superimposable) upon one another. On Wikipedia, I read that it was like our hands, similar but not identical (you can't rotate one hand into another. Makes sense. But I'm not sure how this would help me identify the enantiomers. All the molecules look identical.
  The answer is (D). 
  What is different about D? 
  
  A:
  
  The key point is that for four of the five pairs, the structure on the left can be rotated to make a structure exactly like the one on the right. For example, the left structure in (A), if rotated 120° about the C-CO$_2$H bond, is equivalent to the structure on the right.
  For two "enantiomeric" structures, it is not possible to do this. It might be helpful to draw every possible rotation of the structures in (D), to see that it is impossible to produce the structure on the right by rotating the one on the left.
  
  