Why is Formanilide not named N-benzamide in IUPAC Nomenclature

The preferred IUPAC name for formanilide is N-phenylformamide.


[![enter image description here](https://i.stack.imgur.com/qd3kf.png)](https://i.stack.imgur.com/qd3kf.png)


However, it is very similar to benzamide, except for the atom to which phenyl is attached


[![enter image description here](https://i.stack.imgur.com/dakU3.png)](https://i.stack.imgur.com/dakU3.png)


How does the bonding arrangement, in this case, change the parent group?




According to the current version of *[Nomenclature of Organic Chemistry – IUPAC Recommendations and Preferred Names 2013 (Blue Book)](http://dx.doi.org/10.1039/9781849733069),* amides are considered derivatives of the corresponding acids.



> 
> **P-66.1.0 Introduction**  
> 
> Amides are derivatives of organic oxoacids in which each hydroxy group has been
> replaced by an amino or substituted amino group. (…)
> 
> 
> 


Simple amide names (such as hexanamide) are generally formed by substitutive nomenclature.



> 
> **P-66-1.1.1.1.1** Alicyclic mono- and diamides are named substitutively by adding the suffix ‘amide’, to the appropriate parent hydride name, with elision of the final letter ‘e’ before ‘a’. The multiplying prefix ‘di’ is used to name diamides.
> 
> 
> 


A few amides, however, still have retained names that are derived from retained names of the corresponding carboxylic acids. This includes **benzamide** ($\ce{C6H5{-}CO{-}NH2}$, see Rule P-66.1.1.1.2.1) and **formamide** ($\ce{HCO{-}NH2}$, see Rule P-66.1.1.1.2.2).


Accordingly, formanilide is a substituted formamide and not a substituted benzamide since the acid part of formanilide is derived from formic acid and the amino part is derived from aniline. Thus, the correct name is ***N*-phenylformamide.**


Note that the name “*N*-benzamide” doesn't make sense anyway. *N* is a locant that does not describe anything here; so it reads like *N*-*what*-benzamide. It’s like writing “2-butane”.


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Put simply, formanilide is not N-benzamide because it is not a benzamide to begin with.


"Benzamide" refers to a derivative of benzoic acid, $\ce{C6H5 - C(O) - OH}$, in which the hydroxyl oxygen in the carboxyl group is replaced by nitrogen; the carbon atom outside the ring must be bonded directly to the ring as it is in the parent acid (thus, $\ce{C6H5 - C(O) - NR^{(1)}R^{(2)}}$). Formanilide has the ring joined to the nitrogen atom instead of to the seventh carbon atom and thus can never be a benzamide.


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