Different value of specific rotation of optically active amino acids are obtained at different pH. Explain.

Explanation

`underset(underset(underset((pH lt 7))("(conjugate acid)"))("Cation"))(R - overset(overset(overset(oplus)(N)H_(3))(|))(CH) - COOH) underset(OH^(Θ))overset(overset(oplus)(H))hArr underset(underset((pH = pl))("zwitterion"))(R - overset(overset(overset(oplus)(N)H_(3))(|))(CH) - COoverset(Θ)O) underset(overset(oplus)(H))overset(OH^(Θ))hArr underset(underset(underset((pH gt 7))("(conjugate base)"))("Anion"))(R - overset(overset(NH_(2))(|))(CH) - CO overset(Θ)O)`
The values of specific rotation of dipolar zwitterion, cation (conjugate acid) and anion (conjugate base) are different as the groups linked to the chiral carbon in each are different. A specific form exists at a particular pH. So, the specific rotation various according to the changes in pH of amino acids.