AIIMS 2012 Chemistry Question Paper for free online practice with solutions

Phenols are much more acidic than alcohols due to the stabilisation of phenoxide ion be resonance.

ortho nitrophenol is most acidic because in it —NO2 electron attracting group is attached on ortho-position which helps in stabilizing of negative charge on the oxygen of phenoxide ion. Hence, due to this reason acidic character of phenol is increased, while on attachment of —CH3 group (electron donating group) acidic strength of phenol is decreased in cresol due to destabilization of phenoxide ion.