Question

Which of the following is most acidic?

• A. Benzyl alcohol
• B. Cyclohexanol
• C. Phenol
• D. m-Chlorophenol

Answer 1

Answer: (D)

m-Chlorophenol

Answer 2

Halogens have both +R and -I effect, but -I effect predominates over the +R effect. Hence, m-Chlorophenol is most acidic due to electron withdrawing -Cl group.

• Alcoholsare less acidic than phenol.
• Alpha carbon of benzyl alcohol and cyclohexanol is sp3 hybridized while in phenol and m-chlorophenol, it is sp2 hybridized.
• In m-chlorophenol, -Cl, the electron-withdrawing group is present at the meta position.