Substituted Benzene Compounds: Nomenclature

Benzene is a hydrocarbon with the chemical formula C6H6. It has 6 carbon atoms joined in a ring and has 1 hydrogen atom attached to each of the carbon atoms. By replacing one or more of the hydrogen atoms with some functional group, we get several benzene compounds. While naming the substituted benzene compounds, we prefix the name of the substituent to the word benzene. In this article, we will learn the IUPAC nomenclature of the substituted benzene compounds.

Mono-substituted Benzene Compounds

For the benzene compounds consisting of a single substituent, we simply prefix the name of the substituent to benzene. Some examples along with their common names are listed below.

  • Methylbenzene or Toluene

Benzene Compounds - Toluene

Toluene

  • Hydroxybenzene or Phenol

Benzene Compounds - Phenol

Phenol

  • Aminobenzene or Aniline

Benzene Compounds - Aniline

Aniline

  • Ethylbenzene

Benzene Compounds

Di-substituted Benzene Compounds

When there are two substituents present in the compound, we number each of the carbon atoms in such a manner that the substituents are attached to the lowest possible numbered carbon atom.

  • 1,3-dinitrobenzene is the name of the following compound. Naming it as 1,5-dinitrobenzene is incorrect because the carbon atom would not be numbered lowest.

Benzene Compounds

  • 1,3-dichlorobenzene

Benzene Compounds

Moreover, when there is more than one substituent, we also name their positions as ortho- (o), meta- (m) and para- (p). They refer to the positions 1,2-;1,3- and 1,4- respectively. Thus, we can name the compound 1,3-dichlorobenzene as m-dichlorobenzene.

Poly-substituted Benzene Compounds

In case of poly-substituted compounds, if there is a base compound present, we assign it as the position 1. We then choose the next compound for numbering such that it gets the lowest number. However, if there are no special or base group present, we list them in the alphabetical order, giving them the lowest numbers.

  • 1-Bromo-2,4-dinitrobenzene

Benzene Compounds

  • For the following compound, aniline is the base compound. So, we name it as 3-Chloro-2-nitroaniline.

Benzene Compounds

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The IUPAC name of the following compound is 
(2009)