End product S of the reaction sequence is
`CH_3-CH_2Broverset(KCN)(rarr)P overset(H_2O //H^+)(rarr)Q overset(SOCl_2)(rarr) R overset((C_2H_5)_(2)Cd)(rarr)S`

Options

A. `CH_3CH_2-CH_2-O-C_2H_5`
B. `C_2H_5COOCH_2-CH_3`
C. `CH_3-CH_2-COC_2H_5`
D. `CH_3COOC_2H_5`

Answer

To solve the reaction sequence and identify the end product S, we will go through each step of the reaction one by one.

### Step 1: Identify P
The first reaction involves the reaction of ethyl bromide (CH₃CH₂Br) with potassium cyanide (KCN).

**Reaction:**
\[ \text{CH}_3\text{CH}_2\text{Br} + \text{KCN} \rightarrow \text{CH}_3\text{CH}_2\text{CN} \]

**Product P:**
- The product formed is propionitrile (CH₃CH₂CN).

### Step 2: Identify Q
Next, P (propionitrile) reacts with water (H₂O) in the presence of an acid (H⁺).

**Reaction:**
\[ \text{CH}_3\text{CH}_2\text{CN} + \text{H}_2\text{O} \xrightarrow{\text{H}^+} \text{CH}_3\text{CH}_2\text{COOH} \]

**Product Q:**
- The product formed is propanoic acid (CH₃CH₂COOH).

### Step 3: Identify R
Now, Q (propanoic acid) reacts with thionyl chloride (SOCl₂).

**Reaction:**
\[ \text{CH}_3\text{CH}_2\text{COOH} + \text{SOCl}_2 \rightarrow \text{CH}_3\text{CH}_2\text{COCl} + \text{SO}_2 + \text{HCl} \]

**Product R:**
- The product formed is propanoyl chloride (CH₃CH₂COCl).

### Step 4: Identify S
Finally, R (propanoyl chloride) reacts with diethyl cadmium ((C₂H₅)₂Cd).

**Reaction:**
\[ \text{CH}_3\text{CH}_2\text{COCl} + (C_2H_5)_2\text{Cd} \rightarrow \text{CH}_3\text{CH}_2\text{C}(C_2H_5)=\text{C}(C_2H_5) \]

**Product S:**
- The product formed is 3-ethyl-3-pentene (CH₃CH₂C(C₂H₅)=C(C₂H₅)).

### Final Answer:
The end product S of the reaction sequence is 3-ethyl-3-pentene.

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