Which reaction is not an example of nucleophilic addition reaction?

Options

A. `CH_(3)-CHOunderset((2)H_(2)O)overset((1)LiAID_(4))toH_(3)C-underset(H)underset(|)overset(OH)overset(|)(C)-D`
B. `H_(3)C-CHOoverset(HCN)rarroverset(OH)overset(|)(H_(3)C-CH-CN`
C. `H_(3)C-CHOunderset((2)H_(2)O)overset((1)CH_(3)MgBr)tooverset(OH)overset(|)(H_(3)C-CH-CH_(3)`
D. `H_(3)C-COOCH_(3)underset(-CH_(3)O^(-))overset(NH_(2)^(-))to H_(3)C-CONH_(2)`

Explanation

To determine which reaction is not an example of a nucleophilic addition reaction, we will analyze each of the provided reactions step by step.

### Step-by-Step Solution:

1. **Identify the Reactions:**
We have four reactions to analyze. Let's denote them as Reaction 1, Reaction 2, Reaction 3, and Reaction 4.

2. **Analyze Reaction 1:**
- **Reactants:** Acetaldehyde (CH3CHO) and LiAlD4 (a nucleophile).
- **Mechanism:** The nucleophile attacks the carbonyl carbon of acetaldehyde, leading to the shifting of pi electrons towards oxygen, creating a negatively charged oxygen and a positively charged carbon. This results in the formation of a negatively charged intermediate.
- **Conclusion:** This is a nucleophilic addition reaction.

3. **Analyze Reaction 2:**
- **Reactants:** Acetaldehyde (CH3CHO) and CN- (cyanide ion).
- **Mechanism:** Similar to Reaction 1, the nucleophile CN- attacks the carbonyl carbon, causing the same electron shift and formation of an intermediate. Protonation occurs to yield cyanohydrins.
- **Conclusion:** This is also a nucleophilic addition reaction.

4. **Analyze Reaction 3:**
- **Reactants:** Acetaldehyde (CH3CHO) and a Grignard reagent (like CH3MgBr).
- **Mechanism:** The Grignard reagent acts as a nucleophile, attacking the carbonyl carbon, leading to the formation of an intermediate and subsequent hydrolysis to form an alcohol.
- **Conclusion:** This is a nucleophilic addition reaction.

5. **Analyze Reaction 4:**
- **Reactants:** Methyl acetate (CH3COOCH3) and NH2- (amide ion).
- **Mechanism:** In this case, the nucleophile NH2- attacks the carbonyl carbon, but instead of adding to the carbon, it results in the removal of the methoxy group (OCH3) as CH3O-. This indicates a substitution rather than an addition.
- **Conclusion:** This is a nucleophilic substitution reaction.

6. **Final Conclusion:**
- The reaction that is not an example of a nucleophilic addition reaction is **Reaction 4**. Therefore, the correct answer is **Option D**.