`Ph-overset(O)overset(||)(C)-CH_(3)+underset("(excess)")(CH_(2)=O) overset(OH^(Theta))toPh-overset(O)overset(||)(C)-C(CH_(2)OH)_(3)`
In the above reaction how times of aldol reaction takes place ?

Explanation

To solve the problem of how many times aldol reaction takes place in the given reaction, let's break it down step by step.

### Step-by-Step Solution:

1. **Identify the Reactants**:
The reactants given are:
- **Benzaldehyde (Ph-CHO)**: This is the aromatic aldehyde.
- **Acetaldehyde (CH₂=O)**: This is the aliphatic aldehyde, and it is in excess.

2. **Understand the Aldol Reaction**:
The aldol reaction involves the formation of a β-hydroxy aldehyde or ketone from the reaction of two aldehydes or ketones in the presence of a base (OH⁻). The reaction typically proceeds through the formation of an enolate ion, which then attacks the carbonyl carbon of another aldehyde or ketone.

3. **First Aldol Reaction**:
- The enolate ion is formed from acetaldehyde (CH₂=O) by deprotonation in the presence of OH⁻.
- This enolate ion then attacks the carbonyl carbon of benzaldehyde (Ph-CHO).
- The product of this step is a β-hydroxy aldehyde.

4. **Second Aldol Reaction**:
- The β-hydroxy aldehyde formed can undergo dehydration (loss of water) to form an α,β-unsaturated carbonyl compound.
- Now, this product can react with another molecule of acetaldehyde (CH₂=O) in the presence of OH⁻.
- This leads to the formation of a new β-hydroxy compound.

5. **Third Aldol Reaction**:
- The newly formed β-hydroxy compound can again undergo dehydration to form another α,β-unsaturated carbonyl compound.
- This compound can react with another molecule of acetaldehyde (CH₂=O) in the presence of OH⁻.
- This results in a final product that has multiple hydroxymethyl groups attached.

6. **Count the Aldol Reactions**:
- The aldol reaction occurs three times in total:
- First reaction: Benzaldehyde + Acetaldehyde
- Second reaction: First product + Acetaldehyde
- Third reaction: Second product + Acetaldehyde

### Final Answer:
The aldol reaction takes place **three times**.

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