The systematic name of the heterocycles is built from a prefix that indicates the type of heteroatom it contains, and a suffix that depends on the size of the cycle.

heterocycle nomenclature 01

[1] Aziridine

[2] Azirine

[3] Oxirane

heterocycle nomenclature 02

[4] Oxirene

[5] Phosphete

[6] Phosphethane

Table 1. Prefixes to indicate the heteroatoms of the heterocycle

Element Prefix Element Prefix
O oxa P phospha
S thia As arsa
Se selena Si sila
Te tellura Ge germa
N aza B bora

Table 2. Suffix to indicate the size of the ring of the heterocycle.

Ring size Unsaturated Saturated
3 irene (irine (1) ) irane (iridine (1) )
4 ete etane (etidine (1) )
5 ole olane(olidine (1) )
6 ine (inine (2) ) inane (ane (3) )
7 epine epane
8 ocine ocane
9 onine onane
10 ecina ecane

(1) Three-membered heterocycles with nitrogen terminate in irine (unsaturated) and iridine (saturated). In four-membered heterocycles with nitrogen, the ethane termination changes to etidine (saturated). Nitrogen five-membered heterocycles are terminated in olidine (saturated).
(2) The ine ending is changed to inine for the group of P, Ar, Sb and B in 6-unsaturated heterocycles.
(3) The group of O, S, Se, Te, Bi and Hg changes the ending inane to ane in saturated six-membered heterocycles.

azepine The heterocycle is named, according to this system, as "azepine". This first example illustrates the fundamental idea of the method: the name consists of a prefix (in red), which refers to the heteroatom present (if there are others, several prefixes are used) and which is selected in Table 1; and a suffix, which describes the size and unsaturated or saturated character of the molecule (in blue), and which is chosen from those in Table 2.

phosphinine There are exceptions for 3-, 4-, and 5-membered nitrogen heterocycles: irene is changed to irine; iran for iridine; ethane for etidine and olane for olidine. In the case of 6-membered heterocycles, the general rule for unsaturates is the ine termination, but phosphobenzene cannot be called phosphine (which is the common name for PH3 ), so it is called phosphinine, extending the inine termination the remaining elements of group 5A (As, Sb) and boron; the saturated ones end in inano, except those that have elements of group 6A (O, S, Se, Te), which end in ano.

triazocine Note the name of the heterocycle represented on the right, which allows us to understand how systems with more than one heteroatom of the same type in the ring are named. The numbering always begins in a heteroatom, so that the set of these is assigned the lowest possible locants; the quantity prefixes di, tri, tetra, etc. are used in the name.



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