Which of the following reactions are feasible ?

Options

A.
B.
C.
D.

Explanation

To determine the feasibility of the given reactions, we need to analyze each one based on the presence of alpha hydrogens and the nature of the reactants involved. Here’s a step-by-step breakdown of the reactions:

### Step 1: Analyze Reaction A
**Reaction:** Chlorobenzene + KNS2 + NH3

1. **Identify the structure:** Chlorobenzene has a chlorine atom attached to a benzene ring.
2. **Check for alpha hydrogens:** Alpha hydrogens are the hydrogens on the carbon adjacent to the carbon bearing the leaving group (in this case, chlorine). Chlorobenzene has no alpha hydrogens since the benzene ring does not have any carbon adjacent to the carbon with chlorine that has hydrogen atoms.
3. **Conclusion:** Since there are no alpha hydrogens, the reaction is not feasible.

### Step 2: Analyze Reaction B
**Reaction:** Chlorobenzene + KNS2 + NH3 (with a methyl group)

1. **Identify the structure:** This is a substituted chlorobenzene with a methyl group (C6H5-CH3).
2. **Check for alpha hydrogens:** The methyl group has three alpha hydrogens (the three hydrogens on the carbon adjacent to the carbon with chlorine).
3. **Conclusion:** Since there are alpha hydrogens present, the reaction can proceed, resulting in the substitution of chlorine with the NS2 group.

### Step 3: Analyze Reaction C
**Reaction:** Bromobenzene + KNS2 + NH3 (with an ethyl group)

1. **Identify the structure:** Bromobenzene with an ethyl group (C6H5-CH2-CH3).
2. **Check for alpha hydrogens:** The ethyl group has two alpha hydrogens, but the bromobenzene itself does not have any alpha hydrogens.
3. **Conclusion:** Since bromobenzene lacks alpha hydrogens, the reaction is not feasible.

### Step 4: Analyze Reaction D
**Reaction:** Chlorobenzene + KNS2 + NH3 (with two methyl groups)

1. **Identify the structure:** This is another chlorobenzene with two methyl groups (C6H5-CH3-CH3).
2. **Check for alpha hydrogens:** The two methyl groups provide six alpha hydrogens.
3. **Conclusion:** Since there are alpha hydrogens present, the reaction can proceed, resulting in the substitution of chlorine with the NS2 group.

### Summary of Feasibility
- **Reaction A:** Not feasible (no alpha hydrogens).
- **Reaction B:** Feasible (alpha hydrogens present).
- **Reaction C:** Not feasible (no alpha hydrogens).
- **Reaction D:** Feasible (alpha hydrogens present).