Question

Select the correct statements regarding zwitterion.

(i) Zwitterions can be formed from compounds that contain both acid groups and basic groups in their molecules.
(ii) A zwitterion can act either as a proton donor or proton acceptor.
(iii) A monoamine monocarboxylic $\alpha$-amino acid is a acid at high pH as both the groups (amino and carboxyl) lose a proton.
(iv) Amino acids in solution at neutral pH exist predominantly as dipolar ions, the amino group is protonated $\left(N{H}_3^{+}\right)$ and the carboxyl group is deprotonated $(-CO{O}^{-})$.

• A. iii and iv
• B. i, ii, iii, iv and v
• C. i, ii and v
• D. i, ii and iii

Answer 1

The correct option is B i, ii, iii, iv and v

A zwitterion is an ion that has a positive and negative charge on the same group of atoms. Amino acids in solution at neutral pH exist predominantly as zwitterions. In dipolar from the amino group is protonated $(-N{H}_2^{+})$ and the carboxyl group is deprotonated $(-CO{O}^{-})$. The ionization state of an amino acid varies with pH. In acid solution, the amino group is protonated $-N{H}_3^{+})$ and the carboxylic acid is the protonated amino group loses a proton.