Which of the following is having most acidic `alpha`-Hydrogen?

Options

A. `CH_(3)-NO_(2)`
B. `underset(NO_(2))underset(|)(CH_(2))-NO_(2)`
C. `NO_(2)-underset(NO_(2))underset(|)(CH)-NO_(2)`
D.

Answer

To determine which of the given compounds has the most acidic alpha-hydrogen, we will analyze each option based on the presence and effect of electron-withdrawing groups (EWGs) on the stability of the conjugate base formed after deprotonation.

### Step 1: Identify the alpha-hydrogens in each compound.
- **Option A: CH3NO2**
- The alpha-hydrogen is the one attached to the carbon adjacent to the nitro group (NO2).

- **Option B: CH2(NO2)2**
- The alpha-hydrogen is the one attached to the carbon adjacent to the two nitro groups.

- **Option C: CH(NO2)3**
- The alpha-hydrogen is the one attached to the carbon adjacent to three nitro groups.

- **Option D: CH3C(=O)CH2NO2**
- The alpha-hydrogens are the ones attached to the carbon adjacent to the carbonyl (C=O) and the nitro group.

### Step 2: Analyze the effect of electron-withdrawing groups on acidity.
- **Option A: CH3NO2**
- When the alpha-hydrogen is removed, it forms CH2-NO2. The nitro group is an EWG and stabilizes the negative charge through resonance, but there is only one nitro group.

- **Option B: CH2(NO2)2**
- When the alpha-hydrogen is removed, it forms CH(NO2)2. Here, two nitro groups are present, which can stabilize the negative charge even more effectively than in option A.

- **Option C: CH(NO2)3**
- When the alpha-hydrogen is removed, it forms C(NO2)3. With three nitro groups, the negative charge can be delocalized over three electron-withdrawing groups, leading to a highly stable conjugate base.

- **Option D: CH3C(=O)CH2NO2**
- The alpha-hydrogens are adjacent to a carbonyl group and a nitro group. However, the presence of the carbonyl group (C=O) does not provide the same level of stabilization as multiple nitro groups.

### Step 3: Compare the stability of the conjugate bases.
- The stability of the conjugate base directly correlates with the acidity of the alpha-hydrogen. The more electron-withdrawing groups present, the more stable the conjugate base will be.

- **Option A** has one EWG, **Option B** has two, **Option C** has three, and **Option D** has a combination that does not provide as much stabilization as option C.

### Conclusion:
Based on the analysis, **Option C (CH(NO2)3)** has the most acidic alpha-hydrogen due to the presence of three electron-withdrawing nitro groups, which provide maximum stabilization to the conjugate base formed after deprotonation.

### Final Answer:
**C (CH(NO2)3)** has the most acidic alpha-hydrogen.

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