Recently the other week, I was asked the following question:
Would you expect 4-aminophenol to have a higher or lower pKa than 4- bromophenol when measured in water?
And I thought about this on the way home, and decided to try and justify this using resonance.
My feeling was that Nitrogen couldn't handle 4 bonds and an extra lone pair on its atom, so the negative charge won't leave the benzene ring, whereas the Bromine could handle the double bond (I might have been mistaken with the negative charge on the Bromine - if so, do let me know please.)
Using this, I thought that this is the reason why 4-aminophenol would have a higher pKa than 4-bromophenol as its resonance form is not as extended as Bromine's, which is at a lower energy level to be able to handle the extra negative charge, plus all the carbons in the ring have 4 bonds as normal.
Is this a correct answer and justification?