Which of the following are examples of aldol condensation ?

Options

A. `2CH_(3)CHO overset(Dil.NaOH)rarr CH_(3)CHOHCH_(2)CHO`
B. `2CH_(3)COCH_(3) overset(Dil.NaOH)rarr (CH_(3))_(2)C(HO)CH_(2)COCH_(3)`
C. `2HCHO overset(Dil.NaOH)rarr CH_(3)OH` + HCOONa
D. `C_(6)H_(5)CHO+HCHO overset(Dil.NaOH)rarr C_(6)H_(5)CH_(2)OH`

Explanation

To determine which of the given reactions are examples of aldol condensation, we need to understand the concept of aldol condensation and identify the compounds involved. Here's a step-by-step solution:

### Step 1: Understand Aldol Condensation
Aldol condensation is a reaction that occurs between aldehydes or ketones that possess alpha hydrogens. In this reaction, one molecule of an aldehyde or ketone reacts with another molecule of the same or different aldehyde or ketone in the presence of a base (usually OH-) to form a β-hydroxy aldehyde or ketone, which can further dehydrate to yield an α,β-unsaturated carbonyl compound.

**Hint:** Look for compounds with alpha hydrogens (hydrogens on the carbon adjacent to the carbonyl group) to identify potential aldol condensation reactions.

### Step 2: Analyze the Given Compounds
1. **Acetaldehyde (CH3CHO)**:
- Acetaldehyde has three alpha hydrogens (from the CH3 group).
- It can undergo aldol condensation.

2. **Acetone (CH3COCH3)**:
- Acetone has six alpha hydrogens (three from each CH3 group).
- It can also undergo aldol condensation.

3. **Formaldehyde (HCHO)**:
- Formaldehyde has no alpha hydrogens (there are no carbons adjacent to the carbonyl).
- It cannot undergo aldol condensation; instead, it undergoes the Cannizzaro reaction.

4. **Benzaldehyde (C6H5CHO)**:
- Benzaldehyde also has no alpha hydrogens (the carbonyl carbon is directly attached to a phenyl group).
- It cannot undergo aldol condensation; it also undergoes the Cannizzaro reaction.

### Step 3: Conclusion
Based on the analysis:
- **Acetaldehyde** and **Acetone** can undergo aldol condensation because they have alpha hydrogens.
- **Formaldehyde** and **Benzaldehyde** cannot undergo aldol condensation due to the absence of alpha hydrogens.

Thus, the examples of aldol condensation from the given options are **Acetaldehyde and Acetone**.

**Final Answer:** The examples of aldol condensation are **Acetaldehyde and Acetone**.

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