In basic medium, alanine exists as

Options

A. `{:(CH_(3)CH-NH_(3)^(+)),(" |"),(" "COOH):}`
B. `{:(CH_(3)CH-NH^(-)),(" |"),(" "COOH):}`
C. `{:(CH_(3)CH-NH_(2)),(" |"),(" "COO^(-)):}`
D. `{:(CH_(3)CH-NH_(3)^(+)),(" |"),(" "COO^(-)):}`

Explanation

To determine how alanine exists in a basic medium, we need to analyze its structure and the behavior of its functional groups in such an environment.

### Step-by-Step Solution:

1. **Identify the Structure of Alanine**:
- Alanine is an amino acid with the following structure:
\[ \text{NH}_2-\text{CH}(\text{COOH})-\text{CH}_3 \]
- It contains an amino group (\(-\text{NH}_2\)) and a carboxylic acid group (\(-\text{COOH}\)).

2. **Understand the Basic Medium**:
- A basic medium has a higher concentration of hydroxide ions (\(\text{OH}^-\)) and a lower concentration of hydrogen ions (\(\text{H}^+\)).
- In a basic medium, the acidic groups tend to lose their hydrogen ions.

3. **Behavior of the Carboxylic Group in Basic Medium**:
- The carboxylic acid group (\(-\text{COOH}\)) can donate a proton (\(\text{H}^+\)) in a basic environment, resulting in the formation of a carboxylate ion (\(-\text{COO}^-\)):
\[ \text{COOH} \rightarrow \text{COO}^- + \text{H}^+ \]

4. **Resulting Structure of Alanine in Basic Medium**:
- After the carboxylic group loses a proton, the structure of alanine in a basic medium becomes:
\[ \text{NH}_2-\text{C}(\text{COO}^-)-\text{CH}_3 \]
- Here, the amino group remains protonated as \(-\text{NH}_2\) since it does not gain a proton in basic conditions.

5. **Conclusion**:
- In a basic medium, alanine exists predominantly in its zwitterionic form where the carboxylic group is deprotonated, and the amino group remains unchanged. Thus, the structure can be represented as:
\[ \text{NH}_2-\text{C}(\text{COO}^-)-\text{CH}_3 \]

### Final Answer:
In a basic medium, alanine exists as \(\text{NH}_2-\text{C}(\text{COO}^-)-\text{CH}_3\).

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