Question

Consider the following amino acid:

Which of the following options contain the correct structure of (A) and (B)?
 

• A.
• B.
• C.
• D.

Hint:

In acidic conditions (pH < 7), the amino group is protonated, and in basic conditions (pH > 7), the carboxyl group is deprotonated, forming the carboxylate ion.

Answer 1

The Correct Option is C

Step 1: At pH = 2 (Acidic condition)
At acidic pH, the amino group (-NH\(_2\)) of the amino acid will be protonated to form an ammonium ion (-NH\(_3^+\)) due to the availability of excess protons in the solution.
The carboxyl group (-COOH) will remain in its neutral form.
Therefore, at pH = 2, the structure of the amino acid will be: \[ \text{NH}_3^+ \, \text{CH} \, \text{COOH} \] This corresponds to (A) in the options.
Step 2: At pH = 10 (Basic condition)
At basic pH, the amino group (-NH\(_2\)) remains in its neutral form and the carboxyl group (-COOH) deprotonates to form the carboxylate ion (-COO\(^-\)).
Therefore, at pH = 10, the structure of the amino acid will be: \[ \text{NH}_2 \, \text{CH} \, \text{COO}^- \] This corresponds to (B) in the options.
Step 3: Conclusion
Thus, the correct structures are given by option (3), where (A) = \(\text{NH}_3^+ \, \text{CH} \, \text{COOH}\) and (B) = \(\text{NH}_2 \, \text{CH} \, \text{COO}^-\).