Amine that cannot be prepared by Gabriel phthalimide synthesis is

Options

A. Benzyl amine
B. Aniline
C. iso - butylamine
D. tertiary - butylamine

Answer

To determine which amine cannot be prepared by the Gabriel phthalimide synthesis, we need to understand the mechanism and limitations of this method.

### Step-by-Step Solution:

1. **Understanding Gabriel Phthalimide Synthesis**:
- Gabriel phthalimide synthesis is a method used to prepare primary amines. It involves the reaction of phthalimide with an alkyl halide in the presence of a strong base (usually KOH) to form a potassium salt of phthalimide, which then undergoes hydrolysis to yield the primary amine.

2. **Identifying the Type of Amines Produced**:
- The key aspect of this synthesis is that it primarily produces primary amines from alkyl halides. The alkyl halide can be either aliphatic or aromatic, but the reaction mechanism is crucial.

3. **Limitations of the Reaction**:
- Aromatic amines (like aniline) cannot be prepared using this method. This is because the reaction mechanism involves an SN2 nucleophilic substitution, which does not occur with aryl halides due to their stable double bond character (sp² hybridization). The resonance stabilization in aromatic compounds makes it difficult for nucleophiles to attack.

4. **Conclusion**:
- Therefore, among the options provided, the amine that cannot be prepared by Gabriel phthalimide synthesis is the aromatic amine, specifically aniline (C6H5NH2).

### Answer:
The amine that cannot be prepared by Gabriel phthalimide synthesis is **aniline**.

---