Give a reason for the following: o-nitrophenol is more acidic than o-methoxyphenol.
Answer: –NO₂ (−I, −M) withdraws electrons and stabilises the phenoxide; –OCH₃ (+M) donates electrons and destabilises it.
Solution
The nitro group pulls electron density from the ring (−I and −M), dispersing the phenoxide's negative charge — ionisation is favoured.
The methoxy group pushes electrons in (+M), intensifying the charge on the phenoxide oxygen — ionisation is opposed.
Hence o-nitrophenol ≫ o-methoxyphenol in acidity.
The methoxy group pushes electrons in (+M), intensifying the charge on the phenoxide oxygen — ionisation is opposed.
Hence o-nitrophenol ≫ o-methoxyphenol in acidity.
CBSE Class 12 Board · 2006 · All India · Subjective