Key Point -I groups; if more in number and more close to - COOH group, more is the value of Ka while + I group if are more in number and close to - COOH group, decreases the value of Ka pKa∝
1
Ka
where, Ka= acidic ionisation constant. (a) It has one-(I) group (i.e. Cl ) at C−2 position. (b) It has also one (-)I group (i.e. Cl ) at C−3 position. (c) It has three (−) I groups (i.e. Cl )at C−2 position. (d) It has one (-)I group (i.e. Cl ) at C−2 position. Thus, option (c) is the correct answer.