The melting points of amino acids are higher than the corresponding halo-acids because

Options

A. amino acids exist as zwitter ions resulting in strong dipole-dipole attraction
B. amino acids are optically active
C. due to higher molecules mass of `-NH_2` group molecular mass of amino acids is higher.
D. they interact with water more than halo-acids and have salt like structure.

Answer

A

Explanation

Amino acids exist as zwitter ions, `H_3overset(+)N-OHR-COO^(-)`. Because of this dipolar salt-like character, they have strong dipole-dipole attractions. Hence, their melting points are higher than halo-acids.