MCAT Organic Chemistry Review 2018-2019

Figure 2.14. Example    of  a   Meso    Compound

As shown in this image, D- and L-tartaric acid are both optically active, but meso-tartaric acid has a
plane of symmetry and is not optically active. This means that even though meso-tartaric acid has
two chiral carbon atoms, the molecule as a whole does not display optical activity. Meso compounds
are essentially the molecular equivalent of a racemic mixture.

KEY CONCEPT

Meso    compounds   are made    up  of  two halves  that    are mirror  images. Thus,   as  a   whole   they

are not optically   active.

MCAT    Concept Check   2.2:

Before  you move    on, assess  your    understanding   of  the material    with    these   questions.

What    is  the difference  between a   conformational  and a   configurational isomer?

Conformational: 

Configurational: