Mark the correct order of decreasing acid strength of the following compounds.

Solution :
The electron withdrawing group $$\left( { - N{O_2}} \right)$$   increases the acidity of phenols and the electron donating group $$\left( { - OC{H_3}} \right)$$   decreases the acidity of phenols. The effect at $$p$$ - position is greater than at $$m$$ - position.