How do diastereomers differ from optical isomers?

Diastereomers and optical isomers (or enantiomers) are both types of stereoisomers, which means they have the same molecular formula and connectivity of atoms but differ in their spatial arrangement. Here’s how they differ:

Optical Isomers (Enantiomers):

Enantiomers are a type of optical isomer that are non-superimposable mirror images of each other. They are chiral, meaning they lack an internal plane of symmetry.
Enantiomers have identical physical properties (except for their interaction with plane-polarized light and their reactions with other chiral substances) but differ in their ability to rotate plane-polarized light in opposite directions (one clockwise, the other counterclockwise).
They are always found in pairs, known as enantiomeric pairs.
Diastereomers:

Diastereomers are stereoisomers that are not related as mirror images. They can have different physical properties and different reactivities.
They occur when a molecule has two or more chiral centers and the stereoisomers are not mirror images of each other.
Unlike enantiomers, diastereomers do not have a specific relationship in terms of optical activity; they may or may not both be optically active.
In summary, while optical isomers (enantiomers) are specifically related as non-superimposable mirror images, diastereomers are stereoisomers that are not mirror images of each other and may differ in more than just their optical activity.