α-Amino acids have greater dipole moments than expected. Explain.

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A neutral H₂N-CHR-COOH structure would have only ordinary bond dipoles, but measured dipole moments of amino acids are far larger. The reason is the zwitterionic structure H₃N⁺-CHR-COO⁻ : the carboxyl group donates a proton to the amino group, giving a molecule with a full positive and a full negative charge separated by the α carbon. That charge separation accounts for the unexpectedly large dipole moment.

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