Which of the following amines gives positively the carbylamine test?

Options

A. `C_(6)H_(5)-NH-CH_(3)`
B.
C. `C_(6)H_(5)-NH-C_(4)H_(9)`
D. `C_(6)H_(5)-N(C_(2)H_(5))_(2)`

Answer

To determine which amine gives a positive carbylamine test, we need to understand the characteristics of different types of amines and the conditions for the carbylamine test.

### Step-by-Step Solution:

1. **Understand the Carbylamine Test**:
- The carbylamine test is a qualitative test used to identify primary amines. It involves the reaction of a primary amine with chloroform (CHCl3) and a strong base (usually KOH) to form an isocyanide, which has a distinct foul smell.

2. **Identify Types of Amines**:
- Amines can be classified into three categories:
- **Primary amines (1°)**: Have one alkyl group and two hydrogen atoms attached to the nitrogen (R-NH2).
- **Secondary amines (2°)**: Have two alkyl groups and one hydrogen atom attached to the nitrogen (R2-NH).
- **Tertiary amines (3°)**: Have three alkyl groups attached to the nitrogen (R3-N).

3. **Analyze the Given Options**:
- We need to evaluate each option to determine whether it is a primary amine.
- **Option A**: Contains a nitrogen atom bonded to two alkyl groups and one hydrogen (R-NH-R). This is a secondary amine.
- **Option B**: Contains a nitrogen atom bonded to one alkyl group (methyl) and two hydrogens (NH2). This is a primary amine.
- **Option C**: Contains a nitrogen atom bonded to one alkyl group and one benzene ring (R-NH-R). This is a secondary amine.
- **Option D**: Contains a nitrogen atom bonded to two alkyl groups and one benzene ring (R-N-R). This is a tertiary amine.

4. **Conclusion**:
- From the analysis, only **Option B** is a primary amine (R-NH2). Therefore, it is the only compound that will give a positive carbylamine test.

### Final Answer:
**Option B** is the correct answer as it is the only primary amine that gives a positive carbylamine test.

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