In which compund `D-` exchange is possible in presence of `OD^(-) // D_(2)O` ?

Explanation

To determine in which compound D-exchange is possible in the presence of OD⁻ and D₂O, we need to identify compounds that have acidic alpha hydrogens. These acidic alpha hydrogens can participate in the exchange reaction with deuterium.

### Step-by-Step Solution:

1. **Understanding D-exchange**: D-exchange refers to the process where hydrogen atoms (H) in a compound are replaced by deuterium (D). This typically occurs at acidic alpha hydrogens adjacent to carbonyl groups.

2. **Identifying Acidic Alpha Hydrogens**:
- Acidic alpha hydrogens are those that can be easily removed as protons (H⁺) to form a stable carbanion or enolate.
- The presence of a carbonyl group (C=O) increases the acidity of the hydrogen atoms on the adjacent carbon (alpha carbon).

3. **Analyzing the Options**:
- **Option A**: CH₃C(=O)Ph (Acetophenone)
- The alpha hydrogens (H on the CH₃ group) are acidic due to the adjacent carbonyl group. Thus, D-exchange is possible.
- **Option B**: CH₃CH₂C(=O)Ph (Butyrophenone)
- The alpha hydrogens here (on the CH₃ and CH₂ groups) are not sufficiently acidic for D-exchange due to the lack of stabilization from the carbonyl.
- **Option C**: CH₂=CHC(=O)Ph (Vinyl phenyl ketone)
- The alpha hydrogens are on sp² hybridized carbons, which are not acidic enough for D-exchange.
- **Option D**: (CH₃)₂C(=O)Ph (Acetone derivative)
- The alpha hydrogens here are also not acidic enough to facilitate D-exchange.

4. **Conclusion**: The only compound that allows for D-exchange due to the presence of acidic alpha hydrogens is **Option A**: CH₃C(=O)Ph.

### Final Answer:
**The correct answer is Option A: CH₃C(=O)Ph (Acetophenone).**