Identify the final product in that follow sequence of reactions.
`CH_(2)=CH_(2)overset(Br_(2))rarr(X)overset(KCN)rarr (Y) overset(H_(3)O^(+))rarr (Z)`

Options

A. `CH_(3)BrCH_(2)COOH`
B. `HOOC CH_(2)COOH`
C. `HOOC CH_(2)CH_(2)COOH`
D. `HOOC CH(CH_(3))COOH`

Answer

To identify the final product (Z) in the given sequence of reactions, we will go through each step systematically.

### Step 1: Reaction of Ethene with Bromine
- **Starting Compound**: Ethene (CH₂=CH₂)
- **Reaction**: Ethene reacts with bromine (Br₂) in a non-polar solvent like carbon tetrachloride (CCl₄).
- **Mechanism**: The reaction proceeds via the formation of a bromonium ion intermediate. The double bond in ethene attacks one of the bromine atoms, leading to the formation of a cyclic bromonium ion. The other bromine atom then attacks the more substituted carbon atom (since ethene is symmetrical, it can attack either carbon).
- **Product (X)**: The final product of this reaction is 1,2-dibromoethane (Br-CH₂-CHBr).

### Step 2: Reaction of Product X with Potassium Cyanide
- **Starting Compound**: 1,2-dibromoethane (Br-CH₂-CHBr)
- **Reaction**: This compound reacts with potassium cyanide (KCN).
- **Mechanism**: The cyanide ion (CN⁻) acts as a nucleophile and attacks the electrophilic carbon atoms that are bonded to bromine. This leads to the substitution of bromine with the cyanide group.
- **Product (Y)**: The product formed is 1,2-dicyanoethane (CN-CH₂-CH(CN)).

### Step 3: Hydrolysis of Product Y
- **Starting Compound**: 1,2-dicyanoethane (CN-CH₂-CH(CN))
- **Reaction**: The compound undergoes hydrolysis in the presence of an acid (H₃O⁺).
- **Mechanism**: The cyanide groups are hydrolyzed to form carboxylic acids. Each cyanide group (CN) is converted to a carboxylic acid (COOH).
- **Product (Z)**: The final product is butane-1,4-dicarboxylic acid (HOOC-CH₂-CH₂-COOH).

### Final Answer
The final product (Z) is **butane-1,4-dicarboxylic acid**.

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