A positive carbylamine test is given by:

Options

A. N,N-dimethylaniline
B. 2,4 Dimehtylaniline
C. N-methyl-o -methylaniline
D. p -methylbenzylamine

Answer

To determine which compounds give a positive carbylamine test, we need to analyze each option based on the nature of the amine present in the compound. The carbylamine test is a qualitative test used to identify primary amines, which react with chloroform and alcoholic potassium hydroxide to produce isocyanides (carbylamines).

### Step-by-Step Solution:

1. **Understand the Carbylamine Test**:
- The carbylamine test is specific for primary amines. When a primary amine is treated with chloroform and alcoholic KOH, it produces an isocyanide, which has a characteristic odor.

2. **Analyze Option 1: Anandimethyl Aniline**:
- Structure: Anandimethyl aniline is a tertiary amine.
- Conclusion: Tertiary amines do not give a positive carbylamine test.
- Result: **Not correct**.

3. **Analyze Option 2: 2,4-Dimethyl Aniline**:
- Structure: This compound has an amino group (-NH2) directly attached to the benzene ring, making it a primary amine.
- Conclusion: Primary amines give a positive carbylamine test.
- Result: **Correct**.

4. **Analyze Option 3: N-Methyl Ortho Methyl Aniline**:
- Structure: This compound has a methyl group attached to the nitrogen, making it a secondary amine.
- Conclusion: Secondary amines do not give a positive carbylamine test.
- Result: **Not correct**.

5. **Analyze Option 4: Para-Methylbenzylamine**:
- Structure: This compound has an amino group attached to a benzyl group, making it a primary amine.
- Conclusion: Primary amines give a positive carbylamine test.
- Result: **Correct**.

### Final Conclusion:
The compounds that give a positive carbylamine test are:
- **Option 2: 2,4-Dimethyl Aniline**
- **Option 4: Para-Methylbenzylamine**