IUPAC Nomenclature - Substituted Benzenes
Description:
Cyclic Compounds − A Saturated monocyclic compound is named by prefixing ‘cyclo’ to the corresponding straight chain alkane. The above mentioned rules apply if side chains are present.
IUPAC names of substituted benzenes follow the rules given below −
Naming is done by placing the substituent as prefix to the word benzene. Common names of benzene compounds are also widely used.
If the compound is disubstituted, the position of the substituent is assigned such that it receives the lowest numbers.
The terms ortho(o−),meta(m−) and para(p−) are used to denote 1,2;1,3 and 1,4 relative positions of the substituents.
If more than 2 substituents are present,
Substituents are named alphabetically;
Lowest number is assigned to groups according to the order of preference of functional groups.
| Disubstituted | Disubstituted with different groups | Polysubstituted benzene |
|---|---|---|
 |  |  |
| Also called meta − dibromobenzene | NH2 is given lowest numbering according to order of preference. NH2 > Br. It is also called 1 − amino − 3 − bromobenzene | According to order of preference, CH3 is given lowest number. CH3. Substituents are named alphabetically. Also called 2 − Chloro − 4 − nitrotoluene |