Introduction to Organic Nomenclature: Heterocyclics (ii) Sytematic

Basic Organic Nomenclature

An Introduction

Dave Woodcock,
Associate Professor Emeritus UBC (Okanagan)
©1996,2000, 2008

8. Heterocyclics
(ii) Systematic Approach

Index

If you have been unable to find a name for your ring system from amongst the common names accepted by IUPAC, this page introduces the IUPAC approach to naming heterocyclic systems with from 3 to 10 atoms in a ring which contains oxygen, sulfur and/or nitrogen.

This systematic approach requires that the heteroatoms in the ring be named using prefixes which are followed by a ring-size root and a suffix indicating whether or not it contains the maximum number of double bonds. The number of different possibilities to look through make this a non-trivial exercise!

1. Heteroatom prefixes and order of priority.

The following table is in decreasing order of priority:

Heteroatom (valence) Prefix

O (II) oxa

S (II) thia

N (III) aza

Note that the final a of these prefixes is omitted before a vowel.

2. The suffix

Number of
Atoms in Ring
(Root Source) With N in Ring No N in Ring

With
double No
double With
double No
double

3
tri irine iridine irene irane

4*
tetra ete etidine ete etane

5* ole olidine ole olane

6 ine ** in ane

7
hept epine ** epin epane

8
oct ocine ** ocin ocane

9
non onine ** onin onane

10
dec ecine ** ecin ecane

* See table below
** use perhydro- + name with double bonds