Molecules containing asymmetric carbons
Crystallization and polymorphism - Physico-chemistry of polymorphism

When a molecule contains asymmetric carbons, there are several situations to consider. For simplicity's sake, let's take the case of a molecule containing a single asymmetric carbon. The product may be either the pure enantiomers R or S, or a racemate corresponding to a 50/50 mixture of the enantiomers.

The racemic product itself can give rise, as a general rule, to two different situations:

• the first case corresponds to the conglomerate, an equimolecular mixture of the two crystalline enantiomers R and S ;

• the second case corresponds to the true racemate, which is characterized by a unitary crystal lattice in which the two enantiomers coexist;

• the third case corresponds to the so-called pseudoracemate in the case of a 50/50 mixture. This term designates...