Basic Organic Nomenclature

Disubstituted Benzene

There are only three possible arrangements for two substituents on a benzene ring. They are located at atoms: 1,2; 1,3; or 1,4 according to the IUPAC numbering system. There is however another common way to name these arrangements using the prefixes: Examples of simply disubstituted benzenes:
Compound Name
Line Drawing
3D Model
1,2-dichlorobenzene
or
o-dichlorobenzene
1-chloro-3-ethylbenzene
or
m-chloroethylbenzene
1-fluoro-4-isopropylbenzene
or
p-fluoroisopropylbenzene

Often there is a common name for one of the substituents on the benzene ring, if so the one with the higher priority is used as the root name for the compound and the other substituent is named as a prefix.

Examples of common names for disubstituted benzenes:

Compound Name
Line Drawing
3D Model
2-methoxybenzoic acid
or
o-methoxybenzoic acid
3-methylaniline
or
m-methylaniline
 4-hydroxybenzaldehyde
or
p-hydroxybenzaldehyde

There are a number of common names for disubstituted benzene rings.
 

Compound Name
Line Drawing
o-xylene

(m- and p- isomers exist)
m-cymene

(o- and p- isomers exist)
 p-toluidine

(o- and m- isomers exist)
m-cresol

(o- and p- isomers exist)

phthalic acid

(1,3 isomer is isophthalic acid)
(1,4 isomer is terephthalic acid)

hydroquinone

(1,2 isomer is catechol)
(1,3 isomer is resorcinol)


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