Within the list shown below, the correct pair of structures of alanine in pH range 2 – 4 and 9 – 11 is : (I) H3 N+ CH(CH3)CO2H (II) H2NCH(CH3)CO2– (III) H3 N+ CH(CH3)CO2

Engineering

Chemistry

pH Scale and Relative Strength of Acids

pH Calculation for Acids and Bases

Amino acids

Question

Within the list shown below, the correct pair of structures of alanine in pH range 2 – 4 and 9 – 11 is :
(I) H₃ N⁺CH(CH₃)CO₂H
(II) H₂NCH(CH₃)CO₂^–
(III) H₃ N⁺ CH(CH₃)CO₂^–
(IV) H₂NCH(CH₃)CO₂H

(I), (II)

(I), (III)

(II), (III)

(III), (IV)

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As the isoelectric point of Alanine is 6.1.
At pH below p^l it has NH₃^⊕,
At pH above p^l it has COO^⊖,
Option (A) is correct.