`{:(" "O^(16)),(" ||"),(CH_(3)-C-H overset(D_(2)O^(18))underset(D^(o+))to CH_(3)-C-H),(" ||"),(" "._(18)O):}`
Give the following reaction intermediate is :

Options

A. A. `{:(" ".^(18)OD),(" |"),(CH_(3)-C-D),(" |"),(" "._(16)OD):}`
B. B. `{:(" ".^(18)OD),(" |"),(CH_(3)-C-H),(" |"),(" "._(16)OD):}`
C. C. `{:(" ".^(16)OD),(" |"),(CH_(3)-C-H),(" |"),(" "._(16)OD):}`
D. D. `{:(" ".^(18)OD),(" |"),(CH_(3)-C-H),(" |"),(" "._(18)OD):}`

Answer

To determine the reaction intermediate for the given reaction involving aldehydes and ketones, we will analyze the steps involved in the reaction.

### Step-by-Step Solution:

1. **Identify the Reactants:**
The reactants in the reaction are:
- **Aldehyde:** CH₃C=O (with O being the oxygen-16 isotope)
- **Reagent:** D₂O (heavy water, which contains oxygen-18)

2. **Understanding the Mechanism:**
In the presence of D₂O, the carbonyl carbon of the aldehyde will undergo nucleophilic attack by the oxygen atom from D₂O. This is due to the presence of lone pairs on the oxygen atom.

3. **Formation of the Intermediate:**
During the nucleophilic attack:
- The oxygen from D₂O will attack the carbonyl carbon (C=O), leading to the formation of a tetrahedral intermediate.
- This intermediate will have the following structure:
- The carbon will still be bonded to the methyl group (CH₃).
- The original oxygen (O) will now have a negative charge (O⁻).
- The oxygen from D₂O (which is now part of the intermediate) will be bonded to the carbon and will carry the oxygen-18 isotope (O-18).
- The hydrogen atom from the aldehyde remains unchanged.

4. **Final Structure of the Intermediate:**
The resulting structure of the intermediate can be represented as:
- **Intermediate:** CH₃C(OH)(O-18)⁻
- Here, the carbonyl carbon is now bonded to:
- Methyl group (CH₃)
- Hydroxyl group (OH)
- An oxygen atom with an oxygen-18 isotope (O-18)

5. **Addition of D⁺:**
In the next step, the D⁺ ion from D₂O will attach to the hydroxyl group, replacing the hydrogen atom:
- This leads to the final intermediate structure:
- **Final Intermediate:** CH₃C(OD)(O-18)

### Conclusion:
The reaction intermediate formed in this reaction is **CH₃C(OD)(O-18)**.