A nitro group effectively stabilizes a negative charge on an adjacent carbon atom through resonance:
Two of the following nitrophenols are much more acidic than phenol itself. The third compound is only slightly more acidic than phenol. Use resonance structures of the appropriate phenoxide ions to show why two of these anions should be unusually stable.
Here we have to calculate the resonance structures of the appropriate phenoxide ions and have to explain its stability .
The stability of a molecule can be explain by its resonance structure and probability of finding delocalization of electrons on the atom.
The resonance structure of phenoxide ion:-
Here the delocalization of -ve charge has been found on the benzene ring at C-2, C-4 and C-6.
Resonance structure of nitro group in position 2:-
Nitro group present in the 2nd position to the carbonyl group , delocalizes -ve charge .
Resonance structure of nitro group in position 3:-