Q.Write the Zwitter ion structure of alanine

In aqueous/solid-state amino acids, the -COOH proton transfers intramolecularly to the -NH$_2$ group, producing a dipolar (zwitterionic) structure, $H_3N^+-CHR-COO^-$, that is overall electrically neutral.

An amino acid has both an acidic carboxyl group (-COOH) and a basic amino group (-NH$_2$) on the same molecule. Because the -COOH is acidic enough and the -NH$_2$ is basic enough, an internal (intramolecular) proton transfer occurs: the carboxyl group loses its $H^+$ to become $-COO^-$, and that same proton is picked up by the amino group, becoming $-NH_3^+$. The resulting structure carries both a positive and a negative charge on the same molecule, with a net charge of zero — this is the zwitter ion (German 'zwitter' = hybrid). For a generic amino acid $H_2N-CHR-COOH$, the zwitterionic form is: $H_3N^+-CHR-COO^-$ This dipolar structure explains many of the characteristic physical properties of amino acids: their high melting points, water solubility, and b …