`H - C = C- H underset(H_2SO_4) overset(HgSO_4)to (A) underset((2) H_3O^(o+)) overset((1) NH_3 + HCN)to(B)`, Product (B) of given reaction is :

Options

A. Glycine
B. Alanine
C. valine
D. Leucine

Explanation

To solve the problem, we will break down the reactions step by step and identify the products formed at each stage.

### Step 1: Hydration of Ethyne
1. **Starting Material**: Ethyne (C₂H₂) is our starting compound.
2. **Reagents**: We are using sulfuric acid (H₂SO₄) and mercuric sulfate (HgSO₄) as a catalyst.
3. **Reaction**: The reaction involves the hydration of ethyne, which means adding water (H₂O) across the double bond.
4. **Product Formation**: The product formed from this reaction is acetaldehyde (CH₃CHO), which is also known as ethanal. This is product A.

### Step 2: Reaction of Acetaldehyde with Ammonia and Hydrogen Cyanide
1. **Starting Material**: The product A (acetaldehyde, CH₃CHO) is now reacted with ammonia (NH₃) and hydrogen cyanide (HCN) in the presence of hydronium ions (H₃O⁺).
2. **Mechanism**:
- The carbonyl group (C=O) of acetaldehyde is attacked by the nucleophile (HCN), leading to the formation of a cyanohydrin.
- The reaction can be summarized as follows:
- The H⁺ from H₃O⁺ adds to the oxygen of the carbonyl group, making it more electrophilic.
- The CN⁻ from HCN attacks the carbon atom of the carbonyl, forming a cyanohydrin intermediate (CH₃CH(OH)CN).
3. **Product Formation**:
- The cyanohydrin can then react with excess ammonia.
- The ammonia attacks the carbon atom, and a water molecule is eliminated, leading to the formation of an alpha-amino nitrile.
- Upon hydrolysis (adding water), the alpha-amino nitrile will convert to an amino acid.
- The final product formed is alanine (CH₃CH(NH₂)COOH), which is product B.

### Conclusion
The product (B) of the given reaction is alanine (CH₃CH(NH₂)COOH).

### Final Answer
Product (B) is **alanine**.

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