Amine that cannot be prepared by Gabriel - phthalimide synthesis is:

Options

A. Aniline
B. Benzyl amine
C. Methyl amine
D. Iso - butylamine

Explanation

To determine which amine cannot be prepared by the Gabriel phthalimide synthesis, we first need to understand the mechanism of this synthesis and the types of amines that can be formed through it.

### Step-by-Step Solution:

1. **Understanding Gabriel Phthalimide Synthesis**:
- The Gabriel phthalimide synthesis involves the use of phthalimide, which is treated with a strong base (such as potassium hydroxide) to generate a nucleophilic nitrogen species. This nitrogen can then react with an alkyl halide to form a primary amine.

2. **Formation of the Nucleophile**:
- When phthalimide is treated with a strong base, it abstracts a proton from the nitrogen, resulting in a negatively charged nitrogen (N⁻). This nucleophile can then attack an alkyl halide.

3. **Reaction with Alkyl Halides**:
- The nucleophilic nitrogen attacks the carbon atom of the alkyl halide, leading to the formation of a new C-N bond. This results in the formation of a primary amine after hydrolysis.

4. **Types of Amines Formed**:
- The Gabriel synthesis can effectively produce primary amines. However, it is important to note that it cannot produce secondary or tertiary amines or amines that involve aryl halides due to the resonance stabilization of the aryl group, which makes the C-X bond stronger and less reactive.

5. **Identifying the Amine**:
- The question asks for an amine that cannot be prepared by this method.
- **Aniline (C6H5NH2)** is an example of an amine that cannot be prepared using Gabriel phthalimide synthesis because it involves an aryl halide (halobenzene), which cannot be effectively reacted due to the resonance stabilization of the benzene ring.

6. **Conclusion**:
- Therefore, the amine that cannot be prepared by Gabriel phthalimide synthesis is **Aniline**.

### Final Answer:
**Aniline cannot be prepared by Gabriel phthalimide synthesis.**

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