Question
The correct order of acidity for the following compounds is
The correct order of acidity for the following compounds is
A.
I > II > III > IV
B.
III > I > II > IV
C.
III > IV > II > I
D.
I > III > IV > II
Answer :
I > II > III > IV
Solution :
Due to $$ortho$$ - effect, (I) and (II) are stronger acids than (III) and (IV). Due to two $$ortho$$ hydroxyl groups in (I), it is stronger acid than (II). (III) is a stronger acid than (IV) because at $$m$$ - position, $$-OH$$ group cannot exert $$+R$$ effect but can only exert $$-I$$ effect while at $$p$$ - position, $$-OH$$ group exerts its strong $$+R$$ effect. Thus, the correct order of acidity is : I > II > III > IV.
Due to $$ortho$$ - effect, (I) and (II) are stronger acids than (III) and (IV). Due to two $$ortho$$ hydroxyl groups in (I), it is stronger acid than (II). (III) is a stronger acid than (IV) because at $$m$$ - position, $$-OH$$ group cannot exert $$+R$$ effect but can only exert $$-I$$ effect while at $$p$$ - position, $$-OH$$ group exerts its strong $$+R$$ effect. Thus, the correct order of acidity is : I > II > III > IV.