`A overset(Cl_(2))(rarr) B overset("AgCN")(rarr) C overset([H])(rarr) (CH_(3))_(2)` NH Reactant [ A ] is :

Options

A. Methane
B. Ethane
C. Ethene
D. Propane

Answer

To solve the question, we need to identify the reactant A that leads to the final product (CH₃)₂NH through a series of reactions. Let's break down the steps:

### Step 1: Identify the Final Product
The final product given is (CH₃)₂NH, which is a secondary amine. This indicates that the reactant A must be capable of forming a secondary amine through the reactions described.

**Hint:** A secondary amine has two carbon groups attached to the nitrogen atom.

### Step 2: Determine the Structure of Reactant A
Since (CH₃)₂NH is a secondary amine, the reactant A must have at least two carbon atoms. The simplest structure that can lead to a secondary amine upon reaction is propane (C₃H₈), which has the structure CH₃-CH₂-CH₃.

**Hint:** Look for a reactant that can provide the necessary carbon skeleton for a secondary amine.

### Step 3: Reaction with Cl₂
When propane reacts with Cl₂ (in the presence of heat or light), it undergoes a free radical substitution reaction. The chlorine will preferentially attach to the secondary carbon to form a more stable radical. The major product formed will be isopropyl chloride (CH₃-CHCl-CH₃).

**Hint:** Remember that free radical halogenation favors the formation of more stable radicals.

### Step 4: Reaction with AgCN
The isopropyl chloride (product B) then reacts with silver cyanide (AgCN). This reaction is a nucleophilic substitution where the chlorine atom is replaced by the cyanide ion (CN⁻), forming isopropyl cyanide (CH₃-CH(CN)-CH₃).

**Hint:** Nucleophilic substitution reactions often involve the replacement of a leaving group with a nucleophile.

### Step 5: Reduction of the Cyanide
The final step involves the reduction of isopropyl cyanide (product C) to form the secondary amine (CH₃)₂NH. This reduction can be achieved using hydrogen (H₂) in the presence of a reducing agent.

**Hint:** Reducing agents can convert nitriles (like cyanides) into amines.

### Conclusion
After analyzing the reactions and the structures involved, we conclude that the reactant A is propane (C₃H₈).

**Final Answer:** The reactant [A] is propane (C₃H₈).

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