is the most acidic, because of presence of e− withdrawing group that is,−NO2 at o- position to phenol, which makes the release of H+ ions easily. After the removal of H+;the conjugate base thus formed is stabilized by resonance as given below:
Whereas, e− releasing groups decreases the acidity of the substituted phenols and hence, make them less acidic than phenols but more acidic than alcohols.