4.7.2 Nomenclature of heterocyclic compounds
Most of the heterocycles are known by their trivial names, e.g. pyridine,
indole, quinoline, thiophene and so on. However, there are some general
rules to be followed in a heterocycle, especially in the use of suffixes to
indicate the ring size, saturation or unsaturation as shown in the following
table. For example, from the name, pyridine, where the suffix is -ine, one
can understand that this heterocyclic compound contains nitrogen, has a sixmembered ring system and is unsaturated.
Ring with nitrogen
Ring without nitrogen
Ring size Maximum unsaturation
Saturation
Maximum unsaturation
Saturation
3
irine
iridine
irene
irane
4
ete
etidine
ete
etane
5
ole
olidine
ole
olane
6
ine
–
ine
ane
7
epine
–
epine
epane
8
ocine
–
ocine
ocane
9
onine
–
onine
onane
10
ecine
–
ecine
ecane
Monocyclic heterocycles containing three to ten members, and one or more
hetero-atoms, are named systematically by using a prefix or prefixes to
indicate the nature of the hetero-atoms as presented in the following table.
For example, thiacyclobutane contains the hetero-atom sulphur (S).
Element
Prefix
Element
Prefix
Element
Prefix
O
oxa
P
phospha
Ge
germa
S
thia
As
arsa
Sn
stanna
Se
selena
Sb
stiba
Pb
plumba
Te
tellura
Bi
bisma
B
bora
N
aza
Si
sila
Hg
mercura
Two or more identical hetero-atoms are indicated by use of the multiplying
prefixes di-, tri- or tetra-. When more than one distinct hetero-atom is
present, the appropriate prefixes are cited in the name in descending order of
group number in the periodic table, e.g. oxa- takes precedence over aza-. If
both lie within the same group of the periodic table, then the order is
determined by increasing atomic number, e.g. oxa- precedes thia-.
In unsaturated heterocycles, if the double bonds can be arranged in more
than one way, their positions are defined by indicating the N or C atoms that
are not multiply bonded, and consequently carry an ‘extra’ hydrogen atom,
by 1H-, 2H- and so on, for example 1H-azepine and 2H-azepine.
144
CH4 ORGANIC FUNCTIONAL GROUPS
Most of the heterocycles are known by their trivial names, e.g. pyridine,
indole, quinoline, thiophene and so on. However, there are some general
rules to be followed in a heterocycle, especially in the use of suffixes to
indicate the ring size, saturation or unsaturation as shown in the following
table. For example, from the name, pyridine, where the suffix is -ine, one
can understand that this heterocyclic compound contains nitrogen, has a sixmembered ring system and is unsaturated.
Ring with nitrogen
Ring without nitrogen
Ring size Maximum unsaturation
Saturation
Maximum unsaturation
Saturation
3
irine
iridine
irene
irane
4
ete
etidine
ete
etane
5
ole
olidine
ole
olane
6
ine
–
ine
ane
7
epine
–
epine
epane
8
ocine
–
ocine
ocane
9
onine
–
onine
onane
10
ecine
–
ecine
ecane
Monocyclic heterocycles containing three to ten members, and one or more
hetero-atoms, are named systematically by using a prefix or prefixes to
indicate the nature of the hetero-atoms as presented in the following table.
For example, thiacyclobutane contains the hetero-atom sulphur (S).
Element
Prefix
Element
Prefix
Element
Prefix
O
oxa
P
phospha
Ge
germa
S
thia
As
arsa
Sn
stanna
Se
selena
Sb
stiba
Pb
plumba
Te
tellura
Bi
bisma
B
bora
N
aza
Si
sila
Hg
mercura
Two or more identical hetero-atoms are indicated by use of the multiplying
prefixes di-, tri- or tetra-. When more than one distinct hetero-atom is
present, the appropriate prefixes are cited in the name in descending order of
group number in the periodic table, e.g. oxa- takes precedence over aza-. If
both lie within the same group of the periodic table, then the order is
determined by increasing atomic number, e.g. oxa- precedes thia-.
In unsaturated heterocycles, if the double bonds can be arranged in more
than one way, their positions are defined by indicating the N or C atoms that
are not multiply bonded, and consequently carry an ‘extra’ hydrogen atom,
by 1H-, 2H- and so on, for example 1H-azepine and 2H-azepine.
144
CH4 ORGANIC FUNCTIONAL GROUPS