Which of the following will undergo self aldol reaction on heating with dil. NaOH

Options

A.
B.
C. Methanol
D. Pivaldehyde

Explanation

To determine which of the given compounds will undergo a self-aldol reaction when heated with dilute NaOH, we need to analyze each compound for the presence of alpha hydrogens. The self-aldol reaction occurs when a compound has at least one alpha hydrogen that can participate in the reaction.

### Step-by-Step Solution:

1. **Identify the Compounds**:
We have several compounds to analyze. Let's denote them as follows:
- Option 1: Hydroxybenzaldehyde (Benzaldehyde with a hydroxyl group)
- Option 2: A ketone with three alpha hydrogens
- Option 3: Methanol
- Option 4: Pivaldehyde

2. **Check for Alpha Hydrogens**:
- **Option 1 (Hydroxybenzaldehyde)**:
- Structure: This compound has a benzaldehyde group with a hydroxyl (-OH) group at the alpha position.
- Alpha Hydrogens: There are no alpha hydrogens present because the carbon adjacent to the carbonyl carbon (the alpha carbon) is bonded to a hydroxyl group instead of hydrogen.
- Conclusion: **Cannot undergo self-aldol reaction**.

- **Option 2 (Ketone)**:
- Structure: This compound is a ketone with three alpha hydrogens.
- Alpha Hydrogens: Since it has three alpha hydrogens, it can undergo a self-aldol reaction.
- Conclusion: **Can undergo self-aldol reaction**.

- **Option 3 (Methanol)**:
- Structure: Methanol is an alcohol.
- Alpha Hydrogens: Methanol does not have a carbonyl group; therefore, it cannot undergo a self-aldol reaction.
- Conclusion: **Cannot undergo self-aldol reaction**.

- **Option 4 (Pivaldehyde)**:
- Structure: Pivaldehyde has a carbonyl group but is connected to three other carbons.
- Alpha Hydrogens: There are no alpha hydrogens present on the carbon adjacent to the carbonyl carbon.
- Conclusion: **Cannot undergo self-aldol reaction**.

3. **Final Conclusion**:
The only compound that can undergo a self-aldol reaction when heated with dilute NaOH is **Option 2 (the ketone with three alpha hydrogens)**.

### Summary:
The compound that will undergo a self-aldol reaction on heating with dilute NaOH is **Option 2**.