Explain : 2-aminoethanoic acid exists as a dipolar ion as does p-amino sulphonic acid but p-amino benzoic acid does not.

Explanation

The aliphatic `–NH_(2)` group is sufficiently basic to accept an `H^(+)` from COOH group. The COOH group is not strong enough to donate `H^(+)` to the weakly basic `ArNH_(2)`, but `SO_(3)H` group sufficiently strong enough to donate `H^(+)` to weakly basic `ArNH_(2)`