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

Answer

The amino acids exist as zwitterions, `H_(3) overset(+)(N)-CHR-COO^(-)`. Due to this dipolar salt like character they have strong dipole-dipole attractions or elecrostatic. Therefore, their melting points are higher than haloacids which do not have salt like character. Further, due to salt like character, they interact strongly with `H_(2)O`. As a result, solubility in water of amino acids is higher than that of the corresponding haloacids.