How do you tell the difference between enantiomers and diasteromers?

1 Answer
Dec 12, 2015

A pair of enantiomers are non-suposable MIRROR images. Diastereomers are geometric isomers that are not mirror images.


Cis - trans isomerism is diastereomeric by this definition. For cis -2-butene, the connectivity is precisely the same as for trans -2-butene: #C_1# is connected to #C_2# is connected to #C_3# etc. Nevertheless the spatial geometry of each isomer is distinct. Of course I could propose diastereomers that have 2 or more chiral centres (i.e. #R,S# versus #R,R# etc.; these are diastereomeric but are clearly NOT enantiomeric), but this is much more difficult to represent meaningfully (good thing that I didn't split that last infinitive!).