A diastereomer must have how many chiral centers?

Diastereomers are defined as stereoisomers that are not mirror images of each other. This occurs when two or more chiral centers are present in a molecule. For a compound with multiple chiral centers, it is possible for the configurations at some chiral centers to be the same while they differ at others, hence resulting in diastereomers.

Exactly one chiral center would lead to the formation of enantiomers when the configurations are changed, rather than diastereomers. It is important to have at least two chiral centers to facilitate the possibility of having one set of configurations that are the same while differing at another center, which defines the diastereomer relationship.

In essence, a molecule must have at least two chiral centers to have diastereomers, allowing for the combination of different stereoisomeric configurations that do not exhibit the mirror image relationship characteristic of enantiomers.