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Biomolecules — Chemistry STD 12 Science — Question

Rajasthan BoardEnglish MediumSTD 12 ScienceChemistryBiomolecules3 Marks
Question
The monoamino monocarboxylic acids have two $\ce{pK_a}$ values.
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Answer

In aqueous solution, monoamino monocarboxylic acid behave like salt at isoelectric point.
At a $\ce{pH}$ lower than isoelectric point $($i.e., in acidic medium$)$ it showsone $\ce{pKa}$ value which corresponds to structure $\text{R}-\text{CH}-\text{COOH}\\ \ \ \ \ \ \ \ \ \ \text{|}\\\ \ \ \ \ ^+\text{NH}_3$ and at a $\ce{pH}$ higher than isoelectric point $($i.e., basic medium$),$ it shows another $\ce{pK_a}$​​​​​​​ value which corresponds to structure $\text{R}-\text{CH}-\text{COO}^-\\ \ \ \ \ \ \ \ \ \ \text{|}\\\ \ \ \ \ \text{NH}_2$

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