Major product of the following reaction
`CH_(3)-CH_(2)-Broverset(KCN)tounderset(H_(2)O)overset(overline(O)H)tounderset(Delta)overset(PCl_(5))to` product

Options

A. `CH_(3)-CH_(2)-Cl`
B. `H_(3)C-CH_(2)-underset(O)underset(||)(C)-Cl`
C. `CH_(3)-CH_(2)-CN`
D. `CH_(3)-underset(O)underset(||)(C)-NH_(2)`

Answer

To determine the major product of the reaction involving `CH3-CH2-Br` with `KCN`, followed by hydrolysis with `H2O`, and then treatment with `PCl5`, we can break down the steps as follows:

### Step-by-Step Solution:

1. **Identify the Starting Material**:
The starting material is `CH3-CH2-Br` (ethyl bromide). Bromine is a good leaving group.

**Hint**: Recognize that bromine can easily leave, allowing for nucleophilic substitution.

2. **Nucleophilic Substitution with KCN**:
When `KCN` is added, the cyanide ion (`CN⁻`) acts as a nucleophile. It attacks the carbon atom bonded to bromine, leading to the displacement of bromine.

The reaction can be represented as:
\[ CH3-CH2-Br + KCN \rightarrow CH3-CH2-CN + KBr \]
The major product at this stage is `CH3-CH2-CN` (ethyl cyanide).

**Hint**: Remember that nucleophiles attack electrophilic centers, resulting in the substitution of the leaving group.

3. **Hydrolysis of Ethyl Cyanide**:
Next, the product `CH3-CH2-CN` undergoes hydrolysis when treated with water (`H2O`). The cyanide group (`CN`) is converted into a carboxylic acid group (`COOH`).

The reaction can be represented as:
\[ CH3-CH2-CN + H2O \xrightarrow{H^+} CH3-CH2-COOH \]
The product formed is `CH3-CH2-COOH` (propanoic acid).

**Hint**: Hydrolysis involves the addition of water, which converts nitriles to carboxylic acids.

4. **Conversion to Acid Chloride with PCl5**:
Finally, when `PCl5` is added to `CH3-CH2-COOH`, it converts the carboxylic acid into an acyl chloride.

The reaction can be represented as:
\[ CH3-CH2-COOH + PCl5 \rightarrow CH3-CH2-C(=O)Cl + POCl3 + HCl \]
The major product of this step is `CH3-CH2-C(=O)Cl` (ethyl acyl chloride or ethanoic chloride).

**Hint**: The reaction with PCl5 replaces the hydroxyl group of the carboxylic acid with a chlorine atom, forming an acid chloride.

### Final Product:
The final major product of the entire reaction sequence is `CH3-CH2-C(=O)Cl`, which is ethyl acyl chloride.