Which undergoes aldol condensation in the presence of dilute NaOH?

Options

A. Salicylaldehyde
B. Benzophenone
C. Benzaldehyde
D. Acetaldehyde and formaldehyde mixture.

Explanation

To determine which compound undergoes aldol condensation in the presence of dilute NaOH, we need to identify the presence of alpha hydrogen in each compound. Here’s a step-by-step solution:

### Step 1: Understand the Requirements for Aldol Condensation
Aldol condensation requires the presence of alpha hydrogen atoms adjacent to the carbonyl group (C=O). If a compound has alpha hydrogen, it can participate in the aldol reaction.

**Hint:** Look for hydrogen atoms attached to the carbon next to the carbonyl carbon.

### Step 2: Analyze Each Compound
1. **Salicylaldehyde:**
- Structure: Contains a benzene ring with a -CHO group and -OH group in ortho position.
- Check for alpha hydrogen: The carbon adjacent to the carbonyl carbon has no hydrogen atoms (it is fully substituted).
- Conclusion: **No alpha hydrogen present. Cannot undergo aldol condensation.**

**Hint:** Examine the carbon next to the carbonyl; if it has no hydrogen, it can't participate.

2. **Benzophenone:**
- Structure: Contains two benzene rings with a ketone (C=O) group.
- Check for alpha hydrogen: The carbon adjacent to the carbonyl carbon also has no hydrogen atoms (it is fully substituted).
- Conclusion: **No alpha hydrogen present. Cannot undergo aldol condensation.**

**Hint:** Remember that both sides of the carbonyl must be checked for hydrogen presence.

3. **Benzaldehyde:**
- Structure: Contains a benzene ring with a -CHO group.
- Check for alpha hydrogen: The carbon adjacent to the carbonyl carbon has no hydrogen atoms.
- Conclusion: **No alpha hydrogen present. Cannot undergo aldol condensation.**

**Hint:** Similar to the previous compounds, check the adjacent carbon for hydrogen.

4. **Aldehyde Mixture (Acetaldehyde and Formaldehyde):**
- Structures: Acetaldehyde (CH3CHO) has three alpha hydrogens, and formaldehyde (HCHO) has none.
- Check for alpha hydrogen: Acetaldehyde has alpha hydrogens, while formaldehyde does not affect the aldol reaction.
- Conclusion: **Alpha hydrogen present in acetaldehyde. Can undergo aldol condensation.**

**Hint:** Look for the total number of alpha hydrogens in the mixture; only one compound needs to have them.

### Step 3: Final Conclusion
The only compound that can undergo aldol condensation in the presence of dilute NaOH is the mixture of acetaldehyde and formaldehyde (option D).

**Final Answer:** **D (Aldehyde mixture of acetaldehyde and formaldehyde) undergoes aldol condensation.**