Ethanal reacts with HCN and the addition product so obtained is hydrolyzed to form a new compound. This compound shows

Options

A. optical isomerism
B. geometrical isomerism
C. tautomerism
D. metamerism

Answer

To solve the problem step by step, let's analyze the reaction of ethanal (acetaldehyde) with HCN and the subsequent hydrolysis of the addition product.

### Step 1: Understand the Reactants
- The reactant is ethanal, which has the molecular formula CH3CHO. It consists of a methyl group (CH3) and a carbonyl group (C=O).

### Step 2: Reaction with HCN
- When ethanal reacts with HCN, the nucleophilic cyanide ion (CN⁻) attacks the electrophilic carbon of the carbonyl group (C=O).
- The reaction can be represented as follows:
\[ \text{CH}_3\text{CHO} + \text{HCN} \rightarrow \text{CH}_3\text{C(OH)(CN)} \]
- The product formed is called a cyanohydrin, specifically 2-cyanoethanol.

### Step 3: Hydrolysis of the Cyanohydrin
- The cyanohydrin can be hydrolyzed in the presence of water (H2O) and an acid or base to convert the cyano group (CN) into a carboxylic acid (COOH).
- The hydrolysis reaction can be represented as:
\[ \text{CH}_3\text{C(OH)(CN)} + H_2O \rightarrow \text{CH}_3\text{C(OH)(COOH)} \]
- The product formed is 2-hydroxybutanoic acid (or 2-hydroxypropanoic acid).

### Step 4: Identify the New Compound
- The new compound formed after hydrolysis is 2-hydroxybutanoic acid, which has the following structure:
\[ \text{CH}_3\text{C(OH)(COOH)} \]

### Step 5: Determine the Isomerism
- To determine the type of isomerism, we need to check if the compound has a chiral center.
- A chiral center is a carbon atom that is attached to four different groups. In this case, the carbon atom that is attached to the hydroxyl group (OH), the carboxylic acid (COOH), the methyl group (CH3), and a hydrogen atom (H) is indeed a chiral center.
- Since there is a chiral center, the compound can exhibit optical isomerism (enantiomers).

### Conclusion
- The compound formed after hydrolysis of the addition product shows optical isomerism.

### Final Answer
- The new compound shows **optical isomerism**.