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IUPAC naming Of Aromatic Compounds

Definition of Aromatic Compounds:

"Compounds containing benzene ring have distinctive fragrances. Hence, benzene family compounds are called Aromatic compounds. Example: Toluene, Aniline and Phenol".

IUPAC naming of Aromatic compunds.
Figure 1.1


Long form of IUPAC:

"International union of pure and applied chemistry".

Aromatic compounds having benzene in their structural formula have been important in Chemistry. In the IUPAC naming of  aromatic compounds common names of derivatives of benzene, such as Toluene, Aniline and Phenol, are used to name the whole compound.

Figure  below shows the structure of Toluene, Aniline and Phenol:

Let's see how these derivatives of benzene are named:

No.1) 

IUPAC naming of Aromatic compounds.
Figure 1.2

When benzene ring has only one substituent, there is no need of numbering. And as per IUPAC, first comes the name of substituent, followed by the common name  benzene. Example: Toluene, Aniline, and Phenol.

No.2) 

IUPAC naming of Aromatic compounds.
Figure 1.3


When benzene ring has more than one substituent, then, start numbering in a way that gives the lowest number to all substituents. Example: 1,2-Dichlorbenzene.(refer figure 1.3)

No.3) 

IUPAC naming of Aromatic compounds.
Figure 1.4


When common names such as toluene, aniline or phenol are used, start numbering from carbon attached to methyl, amine or hydroxyl group. Example: 2-Chlorotoluene.(refer figure 1.4)

No.4) 

IUPAC naming of Aromatic compounds.
Figure 1.5


Substituents are named in an alphabetical order.(refer figure 1.5)

Lets discuss IUPAC naming of 2,6-Dibromo-4-chlorotoluene:

IUPAC naming of Aromatic compounds.
Figure 1.6- 2,4-Dibromo-4-chlorotoluene

As per structure in the figure 1.6, above, we have to start numbering from carbon attached to  -CH3 substituent group. Thus, out of two -Br substituents, 1st -Br substituent is attached to second-carbon and 2nd -Br substituent group is attached to sixth carbon. And -Cl substituent group is attached to fourth-carbon. Thus, the Final name in an alphabetical order, is 2,6-Dibromo-4-chlorotoluene.
In case of two or more same substituents prefix di, tri, tetra is used. Example: 1,3,5- Trichlorobenzene, 4-Bromo-2-chlorotoluene, 2,6-Dibromo-4-chlorotoluene.( refer figure 1.6)

IUPAC naming of Aromatic compounds.
Figure 1.7


Example: 1,2-Dichlorobenzene, 1,3-Dichlorobenzene, 1,4-Dichlorobenzene.(refer figure 1.7)

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