The cross aldol product formed when propanal acts as the electrophile and butanal as nucleophile is

Options

A. 3-hydroxy-2-methylpentanal
B. 3-hydroxy-2-methylhexanal
C. 2-ethyl-3-hydroxypentanal
D. 2-ethyl-3-hydroxyhexanal

Explanation

To solve the question regarding the cross aldol product formed when propanal acts as the electrophile and butanal as the nucleophile, we will follow these steps:

### Step 1: Identify the Reactants
- **Propanal (Electrophile)**: The structure of propanal is CH3-CH2-CHO.
- **Butanal (Nucleophile)**: The structure of butanal is CH3-CH2-CH2-CHO.

### Step 2: Determine the Active Hydrogen
- In butanal, the alpha hydrogens (the hydrogens attached to the carbon adjacent to the carbonyl group) are the ones that will be removed. Butanal has three alpha hydrogens.

### Step 3: Formation of Enolate Ion
- Remove one alpha hydrogen from butanal to form the enolate ion. The structure will now be:
- CH3-CH2-CH=O⁻ (the negative charge is on the carbon adjacent to the carbonyl).

### Step 4: Nucleophilic Attack
- The enolate ion will attack the carbonyl carbon of propanal. The carbonyl group in propanal will open up, leading to the formation of a new bond:
- The resulting structure will be:
- CH3-CH2-CH(O⁻)-CH2-CHO.

### Step 5: Protonation
- The negatively charged oxygen will then pick up a proton (H⁺) from the medium, resulting in the formation of the aldol product:
- CH3-CH2-CH(OH)-CH2-CHO.

### Step 6: Naming the Product
- Now, we need to name the product:
- The longest carbon chain contains five carbons (pentane).
- There is a hydroxyl group (OH) on the third carbon and an aldehyde group (CHO) on the first carbon.
- Therefore, the compound is named 3-hydroxy-2-pentanal.

### Final Answer
The cross aldol product formed when propanal acts as the electrophile and butanal as the nucleophile is **3-hydroxy-2-pentanal**.

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