Which of the following is the wekest acid?

Options

A. Phenol
B. Catechol
C. Resorcinol
D. Hydroquinone

Answer

A

Explanation

In the ortho and para positions, `OH` is electron donating by resonance. In the meta position it is electron withdrawing by induction. Thus, resorcinaol is the strongest acid. The decresing order of acid strength is

Catechol is a stronger acid than hydroquinone on account of relatively stronger`-I_(effective)`. Both are stonger than phenol inspite of acid-weaking resonance effect because their ions are stabilized through hydrogen bonding.