Question

All epimers are diastereomers but all diastereomers are not epimers.
If true enter 1, else enter 0.

Answer 1

If two molecules are stereoisomers (same molecular formula, same connectivity, different arrangement of atoms in space) but are not enantiomers, then they are diastereomers by default. In practical terms, this means that at least one but not all of the chiral centers are opposite in a pair of diastereomers. Diastereomers which differ in only one stereocenter (out of two or more) are called epimers. Thus, we can say all epimers are diastereomers but all diastereomers are not epimers.