Nomenclature of Heterocycles

Systematic Nomenclature System (Hantzsch-Widman System)

 This is the most widely used systematic method and is used for naming three- to ten-membered mono cyclic heterocycles of various degree ofunsaturation containing one or more heteroatoms. This nomenclature system specifies the ring size and the nature, type and position(s) of the heteroatom(s). The heteromonocycles are named by using following revised rules!3 of Hantzsch-Widman nomenclature system.

(1) Combination of pretix( es) with stem The heteromonocyclic system is named by combining one or more 'a' prefixes for the heteroatom(s) with a stem indicating the size of the ring. If the stem begins with vowel, the terminal letter 'a' of the 'a' prefix is dropped. Pretixes : The prefixes indicate the heteroatoms present in the heterocyclic systems. The prefixes for different heteroatoms are presented in Table 1 in the preferential order.

Table 1.Prefixes for heteroatoms ('a' prefixes in decreasing order of priority)