question_answer

    Consider the acidity of the carboxylic acids  \[PhCOOH\]  \[o-N{{O}_{2}}{{C}_{6}}{{H}_{4}}COOH\]  \[p-N{{O}_{2}}{{C}_{6}}{{H}_{4}}COOH\]  \[m-N{{O}_{2}}{{C}_{6}}{{H}_{4}}COOH\] Which of the following order is correct?

A)  \[I>II>III>IV\]  

B)  \[II>IV>III>I\]

C)  \[II>IV>I>III\]  

D)  \[II>III>IV>I\]

Correct Answer: D

Solution :

                  (I)                         (II) (III)                       (IV) \[-N{{O}_{2}}\]group at any position shows electron withdrawing effect thus acid strength is increased. But o-nitro benzoate ion is stabilized by intramolecular H-bonding like forces hence its acid strength is maximum. Thus acid strength \[(II)>(III)>(IV)>(I)\]