Question

Amino acids behave like salts rather than simple amines or carboxylic acids. Explain.

Answer 1

In aqueous solution, the –COOH group of an amino acid loses a proton and –NH₂ group accepts a proton to form zwitter ion (salt).

\[\begin{array}{cc}
\phantom{........}\ce{O}\phantom{........................}\ce{O}\phantom{.}\\
\phantom{........}||\phantom{........................}||\phantom{.}\\
\ce{H2N - CH - C - OH ⇌ H3\overset{+}{N} - CH - C - O-}\\
\phantom{........}|\phantom{.........................}|\phantom{.............}\\
\phantom{}\ce{\underset{Amino acid}{R}}\phantom{..............}\ce{\underset{Zwitter ion (inner salt)}{R}}\phantom{}
\end{array}\]