The Nomenclature of Monosubstituted Benzenes

Some monosubstituted benzenes are named simply by adding the name of the substituent 

Some monosubstituted benzenes have names that incorporate the substituent. Unfortunately, these names have to be memorized. 

Recall that when a benzene ring is a substituent, it is called a phenyl group. A benzene ring with a methylene group is called a benzyl group (Section 9.5). 

With the exception of toluene, benzene rings with an alkyl substituent are named as alkyl-substituted benzenes (when the alkyl substituent has a name), or as phenyl-substituted alkanes (when the name of the alkyl substituent can be used). For example, 5 ec-pentyl cannot be used as a substituent name because both compounds that appear on the right would be called 5 ec-pentylbenzene, and a name must specify only one compound. 

Aryl (Ar) is the general term for either a phenyl group or a substituted phenyl group, just as alkyl (R) is the general term for a group derived from an alkane. Thus, ArOH could be used to designate any of the following phenols  

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