Question

How do you tell diastereomers from enantiomers?

Answer 1

Stereoisomers are molecules with the same connections, but different orientations in space.

The chirality center is where the spatial orientation can change.

Enantiomers are non-superimposable mirror images, whereas diastereomers are non-superimposable non-mirror images.

The former can occur with one chirality center, whereas the latter can only generally occur with more than one chirality center.

As a consequence of the preceding, when a molecule has more than one chirality center, its "family" will include `2^n` stereoisomers, where `n` indicates the number of chirality centers.

Relationally, an enantiomer only has one other enantiomer, but could have dozens of diastereomers.

For instance, these are enantiomers,

and, these are diastereomers,