The correct order of acid strength of the given phenols in aqueous medium at 298 K is -

Options

A. p-nitrophenol `lt` p-fluorophenol `lt` p-chlorpphenol
B. p-chlorophenol `lt` p-fluorophenol `lt` p-nitrophenol
C. p-flurorophenol `lt` p-chlorophenol `lt` p-nitrophendl
D. p-fluorophenol `lt` p-nitrophenol `lt` p-chlorophenol

Answer

C

Explanation

Due to almost identical sizes of 2p-orbitals of G and F, fR-effect and-I-effect of F almost balance each other and hence p-fluorophenol is almost as acidic as phenol. However, p-chlorophenoi and p-nitrpphenol are more acidic.than phenol. Further, due to stronger - R and -I-effect of `NO_2` group, p-nitrophenol is a much: stronger acid than p-chlorophenol in which. Cl has only weak + R and -I-effect