In organic chemistry, Hantzsch–Widman nomenclature, also called the extended Hantzsch–Widman system (named for Arthur Rudolf Hantzsch and Karl Oskar Widman [sv; de]), is a type of systematic chemical nomenclature used for naming heterocyclic parent hydrides having no more than ten ring members.
[2][3] A Hantzsch–Widman name will always contain a prefix, which indicates the type of heteroatom present in the ring, and a stem, which indicates both the total number of atoms and the presence or absence of double bonds.
The heteroatom is assumed to have its standard bonding number for organic chemistry while the name is being constructed.
[4] In principle, lambda nomenclature could be used to specify a non-standard valence state for a heteroatom[3] but, in practice, this is rare.
The main criteria are: Notes on table: Hantzsch–Widman nomenclature is named after the German chemist Arthur Hantzsch and the Swedish chemist Oskar Widman, who independently proposed similar methods for the systematic naming of heterocyclic compounds in 1887 and 1888 respectively.