Question

The correct order of acidic strength of (i) Alcohol (ii) Acetic acid (iii) 2,4,6-Trinitrophenol (iv) Phenol is

• A. (ii) > (iii) > (iv) > (i)
• B. (iii) > (ii) > (iv) > (i)
• C. (iii) > (iv) > (ii) > (i)
• D. (iv) > (iii) > (ii) > (i)

Answer 1

Answer: (A)

(ii) > (iii) > (iv) > (i)

Answer 2

Phenoxide ion is more stable than alkoxide ion due to resonance so, phenol is more acidic than alcohol. Also carboxylate ion is much more resonance stabilized than phenoxide ion. Therefore, acetic acid is stronger acid than phenol. Electron withdrawing grous increases acidity of phenols. Hence, the order of acidic strength is
{ \underset{\text{(ii)}}{{Acetic acid }}$> 2, 4, 6-$\underset{\text{(iii)}}{{Trinitrophenol }}$>$\underset{\text{(iv)}}{{Phenol }}$>$\underset{\text{(i)}}{{Alcohol }} }