Glycine exists as a zwitterion but o-and p-aminobenzoic acids do not-Give reason

Explanation

o- and p- aminobenzoic acids are resonance hybrids. In such reasonance, the lone pair on the amino nitrogen is involved in conjugation with the aromatic ring. This makes `-NH_(2)` group poorly basic and the `-COOH` group poorly acidic. Therefore the weakly acidic `-COOH` group cannot transfer a proton to the weakly basic `-NH_(2)` group. obviously o-and p- aminobenzoic acids do not exist as zwitterions

On the other hand, in glycine, no such benzene ring is present. Thus, `NH_(2)` group is sufficiently basic to accept a proton from the acidic `-COOH` group to form a zwitterion
`H_(2) overset(..)(N) - underset("Glycine")(CH_(2)) - COOH hArr underset("zwitterion")(H_(3) overset(oplus)(N)- CH_(2) - COO^(Θ))`