I am trying to name the following compound:

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I thought the name would be: (E)-3-[(4-methylphenyl)methylideneamino]benzoic acid

I stayed away from benzylidene since P-57.1.2 indicates no substitution on this preferred prefix. However, Chemdraw shows the name as: (E)-3-((4-methylbenzylidene)amino)benzoic acid

Is my Chemdraw outdated? If so, is my name correct or is there a better way to name this compound? I am also a bit confused as to when to use parenthesis, brackets, or braces with substituent names, am I using them correctly? If not, why? Also should it be "amino" or "aza", I am confused as to when to use one or the other (similar to "oxa" vs "oxo", I think; unrelated but I also don't get the difference between those).


1 Answer 1


Your assessment is correct. The rules concerning the prefixes ‘benzyl’ and ‘benzylidene’ have been changed. In the 1993 IUPAC Recommandations, these prefixes could be substituted, but only on the ring. According to the current version of Nomenclature of Organic Chemistry – IUPAC Recommendations and Preferred Names 2013 (Blue Book), these prefixes cannot be substituted for preferred IUPAC names, although for general nomenclature restricted substitution is permitted (see P-29.6.2).

Except for the use of enclosing marks to set off parts of the name dealing with specific structural features, the suggested name is correct. The preferred IUPAC name is 3-{(E)-[(4-methylphenyl)methylidene]amino}benzoic acid.

3-{(E)-[(4-methylphenyl)methylidene]amino}benzoic acid

Note that enclosing marks are used around compound (see Rule P-29.1.2) and complex (see Rule P-29.1.3) prefixes. When multiple types of enclosing marks are required, the nesting order is {[({[( )]})]}, etc.

Concerning the use of ‘amino’ in this case instead of ‘aza’, Rule P-62.2.3 explains


Preferred IUPAC names for prefixes corresponding to $\ce{-NHR}$, $\ce{-NRR'}$, or $\ce{-NR2}$ are formed by prefixing the names of the groups $\ce{R}$ and $\ce{R'}$ to the prefix ‘amino’, for example ‘methylamino’ for $\ce{-NH-CH3}$. Prefixes such as azanyl and azanylidene may be used in general nomenclature.


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