Question
Arrange the following in increasing order of their acidity ?
Arrange the following in increasing order of their acidity ?
(a) $$o-$$ cresol, (b) salicylic acid, (c) phenol
A.
c < a < b
B.
b < c < a
C.
a < b < a
D.
a < c < b
Answer :
a < c < b
Solution :
Electron releasing groups $$\left( { - C{H_3}, - OC{H_3}, - NC{H_3}\,{\text{etc}}} \right)$$ intensify the negative charge of phenoxide $$ion,$$ i.e., destablises it hence decreases ionization of parent phenol, therefore decreases acidity. While electron withdrawing groups $$\left( { - N{O_2}, - COOH, - CHO\,{\text{etc}}.} \right)$$ increases acidity.
Electron releasing groups $$\left( { - C{H_3}, - OC{H_3}, - NC{H_3}\,{\text{etc}}} \right)$$ intensify the negative charge of phenoxide $$ion,$$ i.e., destablises it hence decreases ionization of parent phenol, therefore decreases acidity. While electron withdrawing groups $$\left( { - N{O_2}, - COOH, - CHO\,{\text{etc}}.} \right)$$ increases acidity.