meso compound

A meso compound is an achiral molecule that contains a stereogenic atom, meaning it has a carbon atom bonded to four different groups. Despite having a stereogenic center, the molecule itself is achiral because it possesses an internal plane of symmetry, making it superimposable on its mirror image.1

This is in contrast to enantiomers, which are stereoisomers that are non-superimposable mirror images of each other and are chiral. Meso compounds are often identified in molecules with multiple stereogenic atoms, where the symmetry cancels out the chirality. For example, 2,3-dichlorobutane can exist as a pair of enantiomers and a meso compound.1

The term "meso" can also relate to resonance in chemistry, as in "mesomeric," or to being intermediate, as in the prefix "meso-".23