The reaction of acetaldehyde and HCN, followed by complete acid hydrolysis gives

Options

A. `CH_(2)=CH-COOH`
B. `CH_(3)-CH(OH)CONH_(2)`
C. `CH_(3)CH(OH)COOH`
D. `CH_(2)=CHCONH_(2)`

Answer

To solve the problem of the reaction between acetaldehyde and HCN followed by complete acid hydrolysis, we will proceed step by step.

### Step 1: Understand the Reactants
Acetaldehyde is represented by the formula CH3CHO. HCN (hydrogen cyanide) contains the cyanide ion (CN⁻), which acts as a nucleophile.

**Hint:** Identify the functional groups in the reactants. Acetaldehyde has a carbonyl group (C=O) which is reactive towards nucleophiles.

### Step 2: Nucleophilic Addition
When HCN reacts with acetaldehyde, the cyanide ion (CN⁻) attacks the electrophilic carbon of the carbonyl group in acetaldehyde. This results in the formation of a cyanohydrin.

The reaction can be depicted as:
\[ \text{CH}_3\text{CHO} + \text{HCN} \rightarrow \text{CH}_3\text{C(OH)(CN)} \]

**Hint:** Remember that the nucleophile attacks the carbonyl carbon, leading to the formation of a new carbon-oxygen bond.

### Step 3: Formation of Cyanohydrin
The product formed after the nucleophilic attack is called a cyanohydrin, which has the structure:
\[ \text{CH}_3\text{C(OH)(CN)} \]

**Hint:** Recognize that the cyanohydrin contains both a hydroxyl group (-OH) and a cyanide group (-CN).

### Step 4: Acid Hydrolysis
Next, we perform complete acid hydrolysis. In this step, the cyanohydrin undergoes hydrolysis in the presence of an acid (H⁺) and water (H₂O). The -CN group will be converted into a carboxylic acid (-COOH).

The hydrolysis reaction can be summarized as:
\[ \text{CH}_3\text{C(OH)(CN)} + H_2O \rightarrow \text{CH}_3\text{C(OH)(COOH)} \]

**Hint:** During hydrolysis, the cyanide group is converted into a carboxylic acid, and water plays a crucial role in this transformation.

### Step 5: Final Product
After complete hydrolysis, the final product will be:
\[ \text{CH}_3\text{C(OH)(COOH)} \]

This compound is 2-hydroxybutanoic acid (or lactic acid).

**Hint:** Ensure you can identify the final product's structure and functional groups.

### Conclusion
The final product obtained from the reaction of acetaldehyde with HCN followed by complete acid hydrolysis is 2-hydroxybutanoic acid (lactic acid).

**Final Answer:** 2-hydroxybutanoic acid (lactic acid).