Which of the following reactions represents `SN` reaction ?

Options

A. `EtCl + EtSNa rarr EtSEt + NaCl`
B. `EtCl + NaOH rarr EtOH + KCl`
C. `EtCl + AgCN rarr Et - overset (oplus) N -= overset (Ө) C + AgCl`
D. `EtCl + H_2 rarr C_2 H_6 + HCl`

Explanation

To determine which of the given reactions represents an SN (nucleophilic substitution) reaction, we will analyze each reaction step by step.

### Step 1: Identify the Reactions
We have four reactions to analyze:
1. **C2H5Cl + NaSC2H5**
2. **C2H5Cl + NaOH**
3. **C2H5Cl + AgCN**
4. **C2H5Cl + H2**

### Step 2: Analyze Each Reaction

#### Reaction 1: C2H5Cl + NaSC2H5
- **Description**: Ethyl chloride (C2H5Cl) reacts with sodium ethyl mercaptide (NaSC2H5).
- **Mechanism**: The chloride ion (Cl-) is replaced by the ethyl mercaptide group (SC2H5).
- **Conclusion**: This is a nucleophilic substitution reaction (SN).

#### Reaction 2: C2H5Cl + NaOH
- **Description**: Ethyl chloride reacts with sodium hydroxide (NaOH).
- **Mechanism**: The hydroxyl ion (OH-) replaces the chloride ion (Cl-).
- **Conclusion**: This is also a nucleophilic substitution reaction (SN).

#### Reaction 3: C2H5Cl + AgCN
- **Description**: Ethyl chloride reacts with silver cyanide (AgCN).
- **Mechanism**: The cyanide ion (CN-) replaces the chloride ion (Cl-).
- **Conclusion**: This is another nucleophilic substitution reaction (SN).

#### Reaction 4: C2H5Cl + H2
- **Description**: Ethyl chloride reacts with hydrogen (H2).
- **Mechanism**: This reaction involves the reduction of ethyl chloride to ethane (C2H6) and hydrochloric acid (HCl).
- **Conclusion**: This is not a nucleophilic substitution reaction; it is a reduction reaction (hydrogenolysis).

### Step 3: Final Conclusion
The reactions that represent SN reactions are:
1. C2H5Cl + NaSC2H5
2. C2H5Cl + NaOH
3. C2H5Cl + AgCN

The reaction that does not represent an SN reaction is:
4. C2H5Cl + H2

### Summary
The correct options that represent SN reactions are the first three reactions.

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