Question

Which one of the following compounds is most acidic?

• A.
• B.
• C.
• D.

Answer 1

Answer: (B)

Answer 2

Phenols are much more acidic than alcohols due to the stabilisation of phenoxide ion be resonance. ortho-nitrophenol is most acidic because in it $- NO _{2}$ 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 $- CH _{3}$ group (electron donating group) acidic strength of phenol is decreased in cresol due to destabilization of phenoxide ion.