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Benzene Ring Nomenclature

Thenomenclature system of benzene ring compounds is not very systematic. While some of the benzene ring compounds are named based on the substitutes, there are many compounds that are given singular names and referred to by their singular names.


Benzene Ring Nomenclature


Thebenzene ring nomenclature system is not as systematic as the alkenes, alkanes and alkynes. Some of the compounds that are mono-substituted arenomenclated by benzene prefixed by the group name. Some examples are given below. Mainly, benzene ring compounds are referred to by their singular names. These names are unique.  These names need memorization. The following are a few examples for singular name benzene compounds.

 Benzen1


Thereare two commonly seen substituent groups which have benzene ring. Theseare phenyl which is abbreviated as Ph- along with benzyl which is abbreviated as Bn-.

The following are examples of some compounds that have phenyl and benzyl groups


 Benzen2


Whenthere ismore than one substituent on a benzene ring, then the position of the substitute needs to be found out. This is done by giving a numberto each of the carbons in the ring.

Incase the benzene ring has two substitute groups, ortho, meta & paraprefixes are used. Ortho is 1, 2- substitution, meta is 1, 3- substitution and para indicates 1, 3 1, 4- substitution.


Thefollowing examples show the names of different benzene compounds. Some tolueneswithtwo substitutes have singular names (e.g. toluidine, cresol &xylene). The isomers of these compounds are designated by the ortho, meta or para prefix.


Someof the disubstituted benzenes also have singular names given to particular isomers (e.g. salicylic acid & resorcinol). If a benzene ring has three or more substituent groups, the ring is numbered to assign the lowest possible numbers to the substituents; shown in the last row of examples. In the final name, the substituents are listed alphabetically. The numbering corresponds to the alphabetical order if the substitution is symmetrical.


 Benzen3

 

Here are a few more examples

Benzen4



Conclusion to to Benzene Ring Nomenclature


Benzenering nomenclature is less systemic as compared to other classificationsof hydrocarbons. Some of the compounds have singular names and some others are named based on the substitutes and the position of substitution.