What is the reaction of acetaldehyde with concentraed sulphuric acid

Options

A. No reaction
B. Decomposition
C. Charred to black residue
D. Polymerisation

Explanation

### Step-by-Step Solution

1. **Identify the Reactants**: The reaction involves acetaldehyde (CH₃CHO) and concentrated sulfuric acid (H₂SO₄).

2. **Understand the Role of Concentrated Sulfuric Acid**: Concentrated sulfuric acid acts as a dehydrating agent. This means it can remove water (H₂O) from the acetaldehyde, leading to dehydration.

3. **Initial Protonation**: When acetaldehyde reacts with concentrated sulfuric acid, the carbonyl oxygen of acetaldehyde can be protonated by H⁺ from sulfuric acid, forming a more reactive species.

\[ \text{CH}_3\text{CHO} + \text{H}^+ \rightarrow \text{CH}_3\text{C(OH)}^+ \]

4. **Formation of Carbocation**: The protonation leads to the formation of a carbocation, which is a positively charged carbon species. This carbocation can further react with another molecule of acetaldehyde.

5. **Nucleophilic Attack**: The carbocation formed can act as an electrophile and can react with another acetaldehyde molecule. The nucleophilic carbon of another acetaldehyde attacks the carbocation.

\[ \text{CH}_3\text{C}^+ + \text{CH}_3\text{CHO} \rightarrow \text{CH}_3\text{C(OH)(CH}_3\text{)}\text{CHO} \]

6. **Polymerization**: The reaction can lead to polymerization, where multiple acetaldehyde units can join together. This can form either linear or cyclic structures depending on the conditions and the number of acetaldehyde molecules involved.

7. **Final Products**: The final products may include oligomers or polymers of acetaldehyde, which can be in the form of linear chains or cyclic compounds. The exact structure will depend on the reaction conditions.