Which is the best method of preparing `2^(@)` amine ?

Options

A. `CHCl_(3) + NH_(3) to`
B. `CH_(3)Cl overset(KCN)to overset(Sn//HCl)to`
C. `CH_(3)Cloverset(AgCN)to overset(LiAlH_(4)to `
D. `CH_(3)NH_(2)overset(CH_(3)NH_(2))to overset(Sn//HCl)to`

Answer

To prepare a 2° amine, the best method involves starting from a 1° amine and using a specific reaction sequence. Here’s the step-by-step solution:

### Step 1: React 1° Amine with CHCl3 in Basic Medium
- Start with a 1° amine (RnH2).
- React it with chloroform (CHCl3) in the presence of a strong base like KOH.
- This reaction leads to the formation of an isocyanide (RNC) and produces three molecules of KCl and three molecules of water (H2O).

### Step 2: Formation of Isocyanide
- The reaction can be summarized as:
\[ RNH_2 + CHCl_3 + 3KOH \rightarrow RNC + 3KCl + 3H_2O \]
- Here, the chloroform undergoes alpha elimination to form CCl2, which then reacts with the 1° amine.

### Step 3: React Isocyanide with Tin and HCl
- The isocyanide (RNC) is then treated with tin (Sn) in the presence of hydrochloric acid (HCl).
- This reaction converts the isocyanide into a 2° amine:
\[ RNC + Sn + HCl \rightarrow RNHCH_3 \]
- The product formed is a 2° amine (RNHCH3).

### Final Product
- The final product of this reaction sequence is the desired 2° amine, which is RNHCH3.

### Summary
The best method for preparing a 2° amine is by reacting a 1° amine with chloroform in a basic medium to form an isocyanide, followed by reduction with tin and HCl.

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