Best method for preparing primary amines from alkyl halides without changing the number of carbon atoms in the chain is

Options

A. Hofmann bromamide reaction
B. Gabriel phthalimide
C. Sandmeyer reaction
D. reaction with `Nnh_(3)`

Explanation

To prepare primary amines from alkyl halides without changing the number of carbon atoms in the chain, we can use the Gabriel phthalimide synthesis method. Here’s a step-by-step breakdown of the process:

### Step 1: Understanding the Reactants
- **Phthalimide**: This is the starting material, which has the structure of a benzene ring with two carbonyl groups (C=O) at the ortho positions and an amine group (NH).
- **Alkyl Halide (RX)**: This is the alkyl halide that we will react with phthalimide. Here, R represents an alkyl group and X represents a halogen (like Cl, Br, or I).

### Step 2: Formation of Potassium Phthalimide
- When phthalimide is treated with alcoholic KOH, it undergoes deprotonation to form potassium phthalimide.
- This involves the removal of a hydrogen atom from the nitrogen atom of phthalimide, resulting in a negatively charged nitrogen.

### Step 3: Nucleophilic Attack
- The negatively charged nitrogen in potassium phthalimide acts as a nucleophile and attacks the alkyl halide (RX).
- The halogen (X) is displaced, leading to the formation of an N-alkyl phthalimide.

### Step 4: Hydrolysis of N-alkyl Phthalimide
- The N-alkyl phthalimide is then hydrolyzed to produce the primary amine and phthalic acid.
- Hydrolysis can be performed either in acidic or basic conditions. In both cases, heating is often required.
- The hydrolysis reaction breaks the bond between the nitrogen and the phthalimide ring, resulting in the release of the primary amine (RNH2) and phthalic acid.

### Step 5: Final Products
- The final products of the reaction are the primary amine (RNH2) and phthalic acid.
- Importantly, the number of carbon atoms in the primary amine remains the same as that in the original alkyl halide, fulfilling the requirement of the question.

### Conclusion
Therefore, the best method for preparing primary amines from alkyl halides without changing the number of carbon atoms in the chain is **Gabriel phthalimide synthesis**.

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