Chapter 27, Problem 27.28P

(a)

Interpretation Introduction

Interpretation:

The titration curves for the reaction of glutamic acid with $\text{NaOH}$ by taking $\text{pKa}$ values of the ionisable groups has to be sketched.

Concept Introduction:

In the titrations of amino acids, the most acidic group $\text{-COOH}$ will first react with the $\text{NaOH}$.  When 0.5 mol of $\text{NaOH}$ is added, the concentration of Zwitter ion and positive ion is equal.  Then 1.0 mol of $\text{NaOH}$ is added to the amino acid.  Here, the concentration of Zwitter ion is more.  Further adding of $\text{NaOH}$ neutralizes the amino groups.  At the end point, the concentration of anionic form of amino acid is more.

(b)

Interpretation Introduction

Interpretation:

The titration curves for the reaction of histidine with $\text{NaOH}$ by taking $\text{pKa}$ values of the ionisable groups has to be sketched.

Concept Introduction:

In the titrations of amino acids, the most acidic group $\text{-COOH}$ will first react with the $\text{NaOH}$.  When 0.5 mol of $\text{NaOH}$ is added, the concentration of Zwitter ion and positive ion is equal.  Then 1.0 mol of $\text{NaOH}$ is added to the amino acid.  Here, the concentration of Zwitter ion is more.  Further adding of $\text{NaOH}$ neutralizes the amino groups.  At the end point, the concentration of anionic form of amino acid is more.