Predict the product of following aldol condensation reaction :
`(a)CH_(3)-CH_(2)-CHO overset(OH^(-)//Delta)to " " (b) Ph-CO-CH_(3) overset(OH^(-)//Delta)to`

Answer

To predict the products of the given aldol condensation reactions, we will follow a systematic approach for each reaction.

### Reaction (a): CH₃-CH₂-CHO

1. **Identify the Reactants**: The reactant is butanal (CH₃-CH₂-CHO), which is an aldehyde. It has an alpha hydrogen (the hydrogen on the carbon adjacent to the carbonyl group).

2. **Formation of Enolate Ion**: The base (OH⁻) abstracts the alpha hydrogen from the aldehyde, forming an enolate ion:
\[ \text{CH}_3\text{CH}_2\text{CHO} \rightarrow \text{CH}_3\text{CH}(-) + \text{H}_2\text{O} \]
The enolate ion can be represented as CH₃-CH=O⁻.

3. **Nucleophilic Attack**: The enolate ion attacks the carbonyl carbon of another molecule of butanal:
\[ \text{CH}_3\text{CH}(-) + \text{CH}_3\text{CH}_2\text{CHO} \rightarrow \text{CH}_3\text{CH}_2\text{C(OH)(CH}_3)\text{CHO} \]

4. **Formation of β-Hydroxyaldehyde**: This results in the formation of a β-hydroxyaldehyde (3-hydroxybutanal):
\[ \text{CH}_3\text{CH}_2\text{C(OH)(CH}_3)\text{CHO} \]

5. **Dehydration**: Upon heating, the β-hydroxyaldehyde undergoes dehydration (loss of water) to form an α,β-unsaturated aldehyde:
\[ \text{CH}_3\text{CH}=\text{CH-CHO} \]

6. **Final Product**: The final product of the aldol condensation reaction is crotonaldehyde (CH₃-CH=CH-CHO).

### Reaction (b): Ph-CO-CH₃

1. **Identify the Reactants**: The reactant is acetophenone (Ph-CO-CH₃), which is a ketone. It also has an alpha hydrogen on the methyl group.

2. **Formation of Enolate Ion**: The base (OH⁻) abstracts the alpha hydrogen from acetophenone, forming an enolate ion:
\[ \text{Ph-CO-CH}_3 \rightarrow \text{Ph-CO-CH}(-) + \text{H}_2\text{O} \]
The enolate ion can be represented as Ph-CO-CH₂⁻.

3. **Nucleophilic Attack**: The enolate ion attacks the carbonyl carbon of another molecule of acetophenone:
\[ \text{Ph-CO-CH}(-) + \text{Ph-CO-CH}_3 \rightarrow \text{Ph-CO-CH}_2\text{C(OH)(Ph-CO)}\text{CH}_3 \]

4. **Formation of β-Hydroxyketone**: This results in the formation of a β-hydroxyketone (3-hydroxy-1,3-diphenylpropan-1-one):
\[ \text{Ph-CO-CH}_2\text{C(OH)(Ph-CO)}\text{CH}_3 \]

5. **Dehydration**: Upon heating, the β-hydroxyketone undergoes dehydration (loss of water) to form an α,β-unsaturated ketone:
\[ \text{Ph-CO-CH}=\text{C(Ph)}\text{CH}_3 \]

6. **Final Product**: The final product of the aldol condensation reaction is chalcone (Ph-CH=CH-CO-Ph).

### Summary of Products:
- (a) Crotonaldehyde (CH₃-CH=CH-CHO)
- (b) Chalcone (Ph-CH=CH-CO-Ph)