A chlorocompound (A) on reduction with Zn-Cu and ethanol gives the hydrocarbon (B) with five carbon atoms. When (A) is dissolved in dry ether and treated with sodium metal it gave 2,2,5,5,-tetramethylhexane. The treatment of A as
`A overset(alc. KCN)to C`
The reation of A with aq. KOH will preferably favour

Options

A. `S_(N)1` mechanism
B. `S_(N)2` mechanism
C. `E_(1)` mechanism
D. `E_(2)` mechanism

Answer

To solve the problem step by step, we will analyze the information provided about the chlorocompound (A) and its reactions.

### Step 1: Identify the structure of compound A
The compound A is a chlorocompound that, upon reduction with Zn-Cu and ethanol, yields a hydrocarbon (B) with five carbon atoms. This suggests that compound A contains more than five carbons, and the reduction removes the chlorine atom and adds hydrogen.

**Hint:** Look for a chlorocompound that can yield a five-carbon hydrocarbon upon reduction.

### Step 2: Determine the structure of compound B
Since compound B has five carbon atoms, we can assume it is likely a straight-chain alkane or branched alkane. The reduction process suggests that compound A could be a chlorinated derivative of a hydrocarbon with more than five carbons.

**Hint:** Consider common alkanes with five carbons, such as pentane or its isomers.

### Step 3: Analyze the reaction with sodium metal in dry ether
The reaction of compound A with sodium metal in dry ether produces 2,2,5,5-tetramethylhexane. This indicates that compound A must have a structure that allows for the formation of this specific hydrocarbon through a coupling reaction, known as the Wurtz reaction.

**Hint:** The Wurtz reaction typically involves the coupling of alkyl halides.

### Step 4: Deduce the structure of compound A
From the information gathered, we can deduce that compound A is likely 2,2-dimethyl-1-chloro-3-pentane. This structure can yield 2,2,5,5-tetramethylhexane through the Wurtz reaction.

**Hint:** Draw the structure of A and ensure it has the necessary groups to yield the products mentioned.

### Step 5: Reaction of A with alcoholic KCN
When compound A is treated with alcoholic KCN, a nucleophilic substitution reaction occurs, leading to the formation of a nitrile (C). The chlorine atom is replaced by a cyanide group.

**Hint:** Remember that nucleophilic substitution reactions can lead to the formation of new functional groups.

### Step 6: Reaction of A with aqueous KOH
When compound A is treated with aqueous KOH, the reaction will favor an elimination mechanism (E2) rather than substitution (SN1 or SN2) due to the presence of a strong base and the structure of compound A. The elimination will lead to the formation of an alkene.

**Hint:** Consider the stability of the resulting alkene and the mechanism that would be favored under these conditions.

### Final Answer
The treatment of compound A with aqueous KOH will preferably favor an elimination reaction, leading to the formation of an alkene.