Which of the following reactions does not take place?

Options

A. `C_2H_5Br+KNO_2toC_2H_5-O-N=O+KBr`
B.
C. `C_2H_5Br+AgCNtoC_2H_5NC+AgBr`
D. `C_2H_5Br+KCNtoC_2H_5NC+KBr`

Explanation

To determine which of the following reactions does not take place, we will analyze each reaction step by step.

### Step 1: Analyze Reaction A
**Reaction:** C2H5Br + K + O2 → Product

- Ethyl bromide (C2H5Br) reacts with potassium (K) and oxygen (O2).
- The potassium ion (K+) interacts with the bromide ion (Br-) from ethyl bromide.
- The oxygen acts as an electron donor, attacking the carbon atom and leading to the formation of a product with a nitrogen-oxygen double bond.
- **Conclusion:** This reaction is feasible.

### Step 2: Analyze Reaction B
**Reaction:** C2H5Br + AgNO2 → Product

- Ethyl bromide (C2H5Br) reacts with silver nitrite (AgNO2).
- Due to Fajan's rule, the covalent character increases in the AgNO2 compound, making nitrogen a better electron donor.
- The nitrogen donates a lone pair to the ethyl group, leading to the removal of bromine and the formation of a product with a nitrogen-oxygen double bond.
- **Conclusion:** This reaction is feasible.

### Step 3: Analyze Reaction C
**Reaction:** C2H5Br + AgCN → Product

- Ethyl bromide (C2H5Br) reacts with silver cyanide (AgCN).
- Again, due to Fajan's rule, the covalent character increases, and nitrogen becomes a better electron donor.
- The nitrogen donates a lone pair, leading to the removal of bromine and the formation of isocyanide (C2H5NC).
- **Conclusion:** This reaction is feasible.

### Step 4: Analyze Reaction D
**Reaction:** C2H5Br + KCl → Product

- Ethyl bromide (C2H5Br) reacts with potassium chloride (KCl).
- KCl is purely ionic, and there is no covalent character to facilitate the donation of electrons from nitrogen.
- In this case, the carbon atom in ethyl bromide is a better electron donor than nitrogen.
- The reaction leads to the formation of ethyl chloride (C2H5Cl) and potassium bromide (KBr).
- However, the question states that nitrogen donates electrons, which is incorrect in this context.
- **Conclusion:** This reaction is not feasible as described.

### Final Conclusion
The reaction that does not take place is **Reaction D** (C2H5Br + KCl).

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