What will be the IUPAC name of the benzene ring compound with SO3H and COOH as substituents?


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According Section P-41 (seniority order for classes) and in more detail Section P-42 (seniority order for acids) of the current version of Nomenclature of Organic Chemistry – IUPAC Recommendations and Preferred Names 2013 (Blue Book), carboxylic acids $(\ce{-COOH})$ are senior to sulfonic acids $(\ce{-SO2-OH})$. Therefore, a compound that contains both functional groups is named as carboxylic acid. In case of benzenecarboxylic acid $(\ce{C6H5-COOH})$, the retained name ‘benzoic acid’ is the preferred IUPAC name (PIN).

Benzoic acid is substituted using the usual principles of substitutive nomenclature. In particular, a sulfonic acid group is expressed in substitutive nomenclature as follows.

P-65.3.2 Substitutive nomenclature, prefix mode for sulfonic, sulfinic, etc. acids

P- When another group is also present that has seniority for citation as principal group (see P-41, P-42, P-43), or when all groups cannot be expressed as suffixes, organic oxoacids of sulfur, selenium or tellurium are named by adding to the name of the parent compound the appropriate prefix given in Table 6.2. (…)

According to Table 6.2 in Subsection P-65.3.0, the preferred prefix used to denote a sulfonic acid group is ‘sulfo’. Therefore, a benzene ring with a carboxylic acid group and a sulfonic acid group is named as ‘sulfobenzoic acid’, for example: 4-sulfobenzoic acid.


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