2. General

Isomerism defines the structure of two substances with the same molecular formula, but different atomic bonds (e.g. 1-propanol and 2-propanol or isopropanol). These isomers have different molecular structures and physicochemical properties. Stereoisomerism is therefore defined as the case of compounds with an identical structure, but whose configuration (arrangement in space of the substituents) differs from optical isomerism or enantiomerism and geometric isomerism (cis/trans or Z/E).

Enantiomerism characterizes two stereoisomers that are non-superimposable images of each other in a mirror, known as enantiomers or optical antipodes. Enantiomers are able to deviate the plane of polarized light with the same absolute value, but with opposite signs.