In the given reaction `CH_3CHOoverset((i) HCN//Ca(CN)_2)underset((ii) H_3O^+)rarr[X]` [X] will be

Options

A. Malonic acid
B. Lactic acid
C. Tartaric acid
D. Mandelic acid

Answer

To solve the given reaction step by step, we will follow the process of nucleophilic addition and hydrolysis.

### Step 1: Identify the Reactants
The reactants in the reaction are:
- **CH₃CHO** (acetaldehyde)
- **HCN** (hydrogen cyanide) in the presence of **Ca(CN)₂** (calcium cyanamide)

### Step 2: Nucleophilic Attack
In the first step, the nucleophile (CN⁻ from HCN) attacks the electrophilic carbonyl carbon of the aldehyde (CH₃CHO). The carbonyl carbon is electron-deficient due to the electronegative oxygen atom.

**Reaction:**
- The CN⁻ ion attacks the carbonyl carbon of CH₃CHO.
- This results in the formation of a tetrahedral intermediate.

### Step 3: Formation of Cyanohydrin
After the nucleophilic attack, the tetrahedral intermediate collapses, leading to the formation of a cyanohydrin. The oxygen atom of the carbonyl group gets protonated, resulting in the following compound:

**Intermediate:**
- **CH₃C(OH)(CN)H** (2-cyano-1-ol)

### Step 4: Hydrolysis
In the second step, we perform hydrolysis of the cyanohydrin. The CN group undergoes hydrolysis to form a carboxylic acid.

**Hydrolysis Reaction:**
- The CN group is converted to a carboxylic acid (–COOH) through the addition of water (H₂O) and the action of H₃O⁺ (acidic conditions).

### Step 5: Final Product
The final product after hydrolysis is **lactic acid** (2-hydroxypropanoic acid), which has the following structure:

**Final Product:**
- **CH₃C(OH)COOH** (lactic acid)

### Conclusion
Thus, the compound [X] formed in the reaction is **lactic acid**.

### Answer:
**[X] = Lactic Acid (2-hydroxypropanoic acid)**

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