The melting points and solbility in water of amino acids are generally higher than that of the corresponding halo acids. Explain

Explanation

Due to the presence of both acidic and basic group in the molecule, amino acids exist as Zwitterions having dipolar structure with salt-like character.
`H_(2)overset(..)(N) - underset("Amino acid") (CHR - COOH) hArr underset("Zwitterion (dipolar structure)")(H_(3) overset(oplus)(N) - CHR - COoverset(Θ)O)`
Because of such Zwitterionic structure, molecules are held together by strong electrostatic force of attraction. Thus, amino acids have high melting point like ionic compounds. Further more, due to dipolar nature they interact strongly with `H_(2)O` molecules and hence, amino acids are highly soluble in water. On the other hand, corresponding halo acids cannot exist in the Zwitterionic form and hence they behave like simple carboxylic acids having relatively lower melting point and lower solubility in water.