Assertion : Cross aldol condensation of ethanal and propanal gives a mixture of four products.
Reason : Ethanal and propanal, both contain `alpha`- hydrogen atom.

Options

A. If both assertion and reason are true and reason is the correct explanation of assertion.
B. If both assertion and reason are true but reason is not the correct explanation of assertion.
C. If assertion is true but reason is false.
D. If both assertion and reason are false.

Answer

To solve the question regarding the assertion and reason related to the cross aldol condensation of ethanal (acetaldehyde) and propanal, we will analyze the statements step by step.

### Step 1: Understanding Aldol Condensation
Aldol condensation is a reaction between two aldehydes or ketones that contain alpha-hydrogens. In this reaction, one molecule acts as a nucleophile (the enolate ion) and the other as an electrophile (the carbonyl compound). The reaction typically occurs in the presence of a base, such as sodium hydroxide (NaOH).

### Step 2: Identifying the Reactants
The reactants in this case are:
- Ethanal (acetaldehyde): CH3CHO
- Propanal: CH3CH2CHO

Both of these compounds contain alpha-hydrogens, which are crucial for the aldol condensation reaction.

### Step 3: Formation of Enolate Ion
In the presence of a base (NaOH), the alpha-hydrogens of ethanal and propanal can be deprotonated to form enolate ions.
- From ethanal: CH3C(=O)H → CH3C(−) + OH−
- From propanal: CH3CH2C(=O)H → CH3CH2C(−) + OH−

### Step 4: Cross Aldol Reaction
The enolate ion formed from one aldehyde can attack the carbonyl carbon of the other aldehyde:
1. The enolate from ethanal attacks propanal.
2. The enolate from propanal attacks ethanal.

### Step 5: Products Formation
The cross aldol condensation of ethanal and propanal will yield four products:
1. **Product 1**: From ethanal enolate attacking propanal.
2. **Product 2**: From propanal enolate attacking ethanal.
3. **Product 3**: From the self-condensation of ethanal.
4. **Product 4**: From the self-condensation of propanal.

### Step 6: Summary of Products
The four products formed are:
1. **3-Hydroxybutanal** (from ethanal enolate + propanal)
2. **3-Hydroxy-2-methylbutanal** (from propanal enolate + ethanal)
3. **But-2-enal** (from dehydration of 3-Hydroxybutanal)
4. **4-Methylpent-3-enal** (from dehydration of 3-Hydroxy-2-methylbutanal)

### Conclusion
Thus, the assertion that cross aldol condensation of ethanal and propanal gives a mixture of four products is **true**. The reason that both ethanal and propanal contain alpha-hydrogen atoms is also **true** and explains why the reaction occurs.

### Final Answer
- **Assertion**: True
- **Reason**: True
- **Conclusion**: Both the assertion and reason are correct, and the reason supports the assertion.

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