Compare the acidity of o/p/m nitro phenol and benzoic acid
Answers
Answer:
Benzoic acid is more acidic than acetic acid, fomic acid is more acidic than benzoic acid, among monsoubstituted benzoic acid derivative, the ortho derivative is more acidic than meta and para substiued acid due to ortho effect.
Among the derivatives of phenols
Para nitro-phenol > Meta Nitro-phenol > Ortho Nitro-phenol
The ortho derivative has intramolecular hydrogen bonding so the only hydrogen capable of ejecting as H+ is bonded really well .
Para nitro-phenol is more acidic as the resonance due to -NO2 group favours the acidity as the -OH group is at the para position w.r.t the -NO2 group , while in meta nitro-phenol the resonance doesn't favours the acidity all that much as the -NO2 group is in meta position w.r.t the -OH group
Among the derivatives of benzoic acids
Ortho nitro-benzoic acid > Para nitro-benzoic acid > Meta nitro-benzoic acid
Ortho Nitro-benzoic acid doesn't have a very strong intramolecular hydrogen bonding , this is because vanderwaal's forces act at very short distances , and due to the steric repulsion between -COOH and the -NO2 the plane of -COOH Is out of conjugation with the benzene ring , along with that it's too far away for strong , well chelated hydrogen bonding ( I've shown this with a diagram in attachment ) . Also due to the strong negative inductive effect along with favoured resonance of -NO2 group at ortho position heavily increases the acidic strength of ortho nitro-benzoic acid
Again the same arguments stands with the meta and para derivatives
The resonance due to -NO2 group at para position heavily increases the acidic strength, while in meta position it doesn't , inductive effects are similar in both meta and para positions.
I've also included some of the canonical structures of para nitro-phenol in the attachment to show why resonance due to -NO2 group being at ortho and para positions favours acidity
