. Which of the following does not exist as a Zwitter ion
(b) Glutamic acid
(c) Sulphanilic acid
(d) p-aminobenzoic acid
Solution: o- and p- aminobenzoic acids do not exist as a Zwitter ion. The lone pair of electrons on the ---NH2 group is donated towards the benzene ring due to resonance effect. As a result, acidic character of ----COOH group and basic character of ---NH2 group decrease. Therefore, the weakly acidic---COOH group cannot transfere a H+ ion to the weakly basic ---NH2 group. Thus o-or p- aminobenzoic acids do not exist as Zwitter ion.