The correct order of acidic strength of the following molecules is

detailed solution

Correct option is B

Unlike fluorine, chlorine has low lying vacant d -orbitals in which it can receive a pair of electrons. Therefore, chlorine can act as - M group and it can stabilise phenoxide ion (conjugate base) better than the fluorine does. The absence of electron withdrawing mesomeric effect in flourine becomes more important factor than their difference in the inductive effects. Both methoxy and methyl groups destabilize the phenoxide by their electron donating effects. When benzene ring has greater electron density, the extent of delocalization of lone pair (negative charge) on the oxygen in the phenoxide ion decreases. Therefore, stabilization of phenoxide ion decreases. Methoxy group can pump electron into the benzene ring better than the methyl group because methoxy group does it through electron donating mesomeric effect whereas methyl group does it through a weaker hyperconjugative and inductive effect. This makes para methoxy phenol weaker acid than para methyl phenol.Hence, the correct answer is (2).