Isomerism is the occurrence of such compounds.
Isomerism was first recognized by J. J. Berzelius in 1827. General Characteristics Isomers have the same number of atoms of each element in them and the same atomic weight but differ in other properties. Molecular disymmetry in optical isomers may come from some source other than an asymmetrical carbon atom, e.g., structural rigidity resulting from double bonds or ring structures within a molecule. For example, there are 16 stereoisomers of a simple sugar whose molecular formula is C6H12O4. Of these, only d -glucose is readily utilized in human metabolism.