Question

Give reasons for the following:

The melting points of α-amino acids are generally higher than that of the corresponding carboxylic acids.

Answer 1

The positively charged ammonium ion \[\ce{(-NH^+_3)}\]and the negatively charged carboxylate ion (−COO⁻) have significant electrostatic forces of attraction (ionic interactions) because amino acids are zwitterions in the solid state. In contrast to their comparable carboxylic acids, which primarily form weaker hydrogen bonds and have lower melting points, these strong electrostatic forces need more energy to break, resulting in higher melting points.