Question

How do you tell the difference between enantiomers and diasteromers?

Answer 1

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

Explanation:

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!).