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In several places, I have seen that while naming benzene derivatives, no priority for substituents is followed. Eg: 2-hydroxy aniline= 2-amino phenol.

Is there no order? Or is the order different from aliphatic compounds?

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1  
Aniline is technically a trivial name. Phenol is IUPAC-approved, but it's still kind of trivial. The naming will depend on the person using it and the situation it's used in. – SendersReagent Mar 6 at 13:27
up vote 7 down vote accepted

According to the current version of Nomenclature of Organic Chemistry – IUPAC Recommendations and Preferred Names 2013 (Blue Book), the retained names “aniline” and “phenol” are preferred IUPAC names (PINs). Parent structures having retained names are called functional parent compounds.

aniline    phenol

For both retained names, substitution is permitted at any position. However, substitution of a functional parent compound is limited to substituent groups cited as prefixes in accordance with the seniority of the functional group that is explicitly expressed or implied in the functional parent compound name. (In systematic names, the presence of this characteristic group would normally be expressed as a suffix.)

P-15.1.8.2.1 Substitution rules for Type 2a retained names

Type 2a retained names include functional parent compounds whose name expresses or implies a characteristic group expressed as suffix in systematic names.

P-15.1.8.2.1.1 Substitution by substituent groups, expressed as prefixes, having a lower seniority than that denoted by the suffix is allowed.

(…)

P-15.1.8.2.1.2 The senior characteristic group or functional class name must be expressed in the name.

Therefore, the correct name for the compound given in the question is “2-aminophenol” (not “2-hydroxyaniline”) since hydroxy compounds are senior to amines.

2-aminophenol

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For the benefit of traffic from the HNQ sidebar, could you comment shortly on how seniority is handed out to compounds? Is there some objective criterion, or is it a sociological construct? – E.P. Mar 6 at 19:56
    
Thanks, and sorry for the late reply. In my text book they have named a compound as 2-amino toluene. Since nh2 has higher priority, this is wrong, right? Should it be 2-methyl aniline? – user93868 Mar 8 at 3:37
1  
@user93868 Yes, see chemistry.stackexchange.com/q/47562/7951 – Loong Mar 8 at 10:34

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