Reaction of acetaldehyde with HCN followed by hydrolysis gives a compound which shows

Options

A. Optical isomerism
B. Geometrical isomerism
C. Metamerism
D. Tautomerism

Explanation

To solve the question regarding the reaction of acetaldehyde with HCN followed by hydrolysis, we can break it down into clear steps:

### Step 1: Identify the reactants
The reactants in this reaction are acetaldehyde (CH₃CHO) and hydrogen cyanide (HCN).

### Step 2: Nucleophilic addition reaction
When acetaldehyde reacts with HCN, a nucleophilic addition reaction occurs. The cyanide ion (CN⁻) acts as a nucleophile and attacks the electrophilic carbon atom of the carbonyl group in acetaldehyde.

**Reaction:**
\[ \text{CH}_3CHO + \text{HCN} \rightarrow \text{CH}_3C(OH)(CN) \]

Here, the product formed is a cyanohydrin, specifically 2-hydroxy-2-methylpropanenitrile.

### Step 3: Hydrolysis of the cyanohydrin
The next step is hydrolysis of the cyanohydrin. In the presence of water, the cyanide group (CN) is converted into a carboxylic acid group (COOH).

**Reaction:**
\[ \text{CH}_3C(OH)(CN) + \text{H}_2O \rightarrow \text{CH}_3C(OH)(COOH) \]

The product formed after hydrolysis is 2-hydroxybutanoic acid.

### Step 4: Analyze the final product
The final product, 2-hydroxybutanoic acid, has one chiral carbon atom. This is because it has four different groups attached to it:
1. Hydroxyl group (OH)
2. Carboxylic acid group (COOH)
3. Methyl group (CH₃)
4. Hydrogen atom (H)

### Step 5: Determine the optical activity
Since the compound has one chiral center, it exhibits optical isomerism. This means that it can exist in two enantiomeric forms that are non-superimposable mirror images of each other.

### Conclusion
The compound formed from the reaction of acetaldehyde with HCN followed by hydrolysis shows optical isomerism due to the presence of a chiral carbon atom.