Stereochemistry refers to the shape of molecules and is important in under-standing how drugs interact with their molecular targets. The classical method of resolving racemates is to form diastereomeric derivatives of each enantiomer. If the chiral compound lacks a carboxylic acid or amine group, it is possible to form a diastereomeric derivative by temporarily linking a chiral compound to another functional group. Constitutional isomers have identical molecular formulae, but the atoms are linked together by different bonds. Configurational isomers are structures that have the same atoms and bonds. Optical isomers are compounds that can exist as two nonsuperimposable mirror images. The criteria for a good asymmetric synthesis are that the final product should be obtained in both a high chemical yield and a high optical yield. A chiral carboxylic acid can be treated with the single enantiomer of an optically active amine such as quinine.