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Chapter 4: Problem 4

How is the \(\mathrm{p} K_{\mathrm{a}}\) of the \(\alpha\) - \(\mathrm{NH}_{3}+\) group affected by the presence on an amino acid of the \(\alpha-\mathrm{COO}^{-}\)?

Short Answer

Expert verified
The presence of an \(\alpha-\mathrm{COO}^{-}\) group on an amino acid increases the \(\mathrm{p} K_{\mathrm{a}}\) of the \(\alpha-\mathrm{NH}_{3}+\) group, making it act more acidic.

Step by step solution

01

Understanding the Biochemical Structure

In amino acids, \(\alpha-\mathrm{NH}_{3}+\) and \(\alpha-\mathrm{COO}^{-}\) are the amino and carboxyl groups. These groups are capable of donating or accepting protons, giving them acid-base properties.
02

Understand the Effect of Interaction

The presence of the \(\alpha-\mathrm{COO}^{-}\) (which is a basic group) near the \(\alpha-\mathrm{NH}_{3}+\) (an acidic group) would increase the \(\mathrm{p} K_{\mathrm{a}}\) of the \(\alpha-\mathrm{NH}_{3}+\) group. This is because when the \(\alpha-\mathrm{COO}^{-}\) group accepts a proton, it allows the \(\alpha-\mathrm{NH}_{3}+\) group to act more as an acid by donating a proton.
03

Summarizing the Final Impact

The more basic a group like \(\alpha-\mathrm{COO}^{-}\) is present in the vicinity or on the amino acid, the more it will raise the \(\mathrm{p} K_{\mathrm{a}}\) thus making the \(\alpha-\mathrm{NH}_{3}+\) act more acidic.

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