End product D of reaction sequence is `CH_3Broverset(KCN)rarrAoverset(H_2"O"//H^+)rarrBoverset(SOCl_2)rarrCoverset((C_2H_5)_2Cd)rarrD`

Options

A. `CH_3CH_2-O-C_2H_5`
B. `C_2H_5COOCH_3`
C. `CH_3COOC_2H_5`
D. `CH_3COOC_2H_5`

Answer

To solve the problem step-by-step, we will follow the sequence of reactions described in the question.

### Step 1: Reaction of CH₃Br with KCN
- **Reaction**: CH₃Br + KCN → CH₃CN (A)
- **Explanation**: In this reaction, KCN dissociates into K⁺ and CN⁻. The CN⁻ acts as a nucleophile and attacks the carbon atom in CH₃Br, resulting in the substitution of the bromine atom with the cyanide group. Therefore, the product formed is acetonitrile (CH₃CN), which we will denote as compound A.

### Step 2: Hydrolysis of CH₃CN
- **Reaction**: CH₃CN + H₂O/H⁺ → CH₃COOH (B)
- **Explanation**: The next step involves the hydrolysis of acetonitrile (CH₃CN). When acetonitrile is treated with water in the presence of an acid (H⁺), it undergoes hydrolysis to form acetic acid (CH₃COOH). This compound will be denoted as compound B.

### Step 3: Reaction of CH₃COOH with SOCl₂
- **Reaction**: CH₃COOH + SOCl₂ → CH₃COCl (C) + SO₂ + HCl
- **Explanation**: In this step, acetic acid (CH₃COOH) reacts with thionyl chloride (SOCl₂). This reaction converts the carboxylic acid into an acyl chloride (acetyl chloride, CH₃COCl). The byproducts of this reaction are sulfur dioxide (SO₂) and hydrochloric acid (HCl), both of which are gases and escape from the reaction mixture. We denote this product as compound C.

### Step 4: Reaction of CH₃COCl with (C₂H₅)₂Cd
- **Reaction**: CH₃COCl + (C₂H₅)₂Cd → CH₃C(O)C₂H₅ (D) + CdCl₂
- **Explanation**: The final step involves the reaction of acetyl chloride (CH₃COCl) with diethyl cadmium ((C₂H₅)₂Cd). In this reaction, the nucleophilic carbon from diethyl cadmium attacks the electrophilic carbon of the carbonyl group in acetyl chloride. This results in the formation of a ketone, specifically 3-pentanone (CH₃C(O)C₂H₅), which we denote as compound D. The byproduct of this reaction is cadmium chloride (CdCl₂).

### Final Product
- The end product D of the reaction sequence is 3-pentanone (CH₃C(O)C₂H₅).

### Summary of Steps:
1. **Substitution reaction**: CH₃Br + KCN → CH₃CN (A)
2. **Hydrolysis**: CH₃CN + H₂O/H⁺ → CH₃COOH (B)
3. **Formation of acyl chloride**: CH₃COOH + SOCl₂ → CH₃COCl (C)
4. **Formation of ketone**: CH₃COCl + (C₂H₅)₂Cd → CH₃C(O)C₂H₅ (D)