NOMENCLATURE OFHETEROCYCLIC COMPOUNDS

By : Vishal Sachan

1.1 NOMENCLATURE

• In heterocyclic chemistry there is a special name for each individual ring system and a trivial name for each compound. Trivial names convey little or no structural information but they are still widely used. The systematic name, in contrast, is designed so that one may deduce from it the structure of the compound. They tend to be long. However, a systematic nomenclature is still indispensable.

• In recent years the International Union of Pure and Applied Chemistry (IUPAC) has made efforts to systematize the nomenclature of heterocycliccompounds.

•According to this system single three-to-ten-membered rings are named by combining the appropriate prefix or prefixes (listed in Table 1.1) with a stem from Table 1.2.

Hetroatom valence Prefix

O

N

S

Se

P

As

Si

2

3

2

2

3 3

4

Oxa

Aza

Thia

Selena

Phospha

Arsa

Sila

Table 1.1 Prefix for Hetero Atoms

Table 1.2 Common Name Endings for Heterocyclic Compounds

Ring Size

Suffix for unsaturated compounds

Suffixes for fully saturated compounds

With ‘N’ With-out‘N’

With ‘N’

With- out ‘N’

3

4

5

6

7

-irene

-ete

-ole

-ine

-epine

-iren

-et(ete)

-ole(ol)

-in

-epin

-iredine

-etidine

-olidine

perhyd-ro ine

Perhyd-ro epine

-irane

-etane

-olane

-ane

-epane

8

9

10

-ocine

-onine

-ecine

-ocin

-onin

- Ecin

-perhydro ocine

-perhydro onine

-perhydro ecin

-ocane

--onan

-ecan

Accordingly some examples of compounds named on the basis of abovetwo tables are cited below:

N

1-Azabicyclo [4.2.0]octane

NH2

3

S1

4

6

5

7

8

10

9

2H-1,2-benzothiazine

2H-1,2,4-Benzothiadiazine

NHS

N

Examples: