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 analyze the reaction of acetaldehyde (CH₃CHO) with HCN in the presence of calcium cyanamide (Ca(CN)₂) followed by hydrolysis.

### Step 1: Identify the Reactants
The reactants are:
- Acetaldehyde (CH₃CHO)
- HCN (Hydrogen cyanide)
- Ca(CN)₂ (Calcium cyanamide)

### Step 2: Nucleophilic Addition
In the first step, HCN acts as a nucleophile. The carbonyl carbon in acetaldehyde (C=O) is electrophilic due to the partial positive charge on it. The cyanide ion (CN⁻) from HCN attacks this carbon atom.

- The reaction can be represented as:
\[ CH₃CHO + HCN \rightarrow CH₃C(OH)(CN) \]
- Here, the carbonyl oxygen will become negatively charged (alkoxide ion), and the cyanide group will be attached to the carbon.

### Step 3: Protonation
After the nucleophilic addition, the alkoxide ion (C-O⁻) will be protonated by the H⁺ from HCN or from the solvent, leading to the formation of a hydroxyl group.

- The product after this step is:
\[ CH₃C(OH)(CN) \]

### Step 4: Hydrolysis
In the second step, the product undergoes hydrolysis. The cyanide group (CN) will be converted into a carboxylic acid (COOH) group in the presence of water (H₂O).

- The hydrolysis can be represented as:
\[ CH₃C(OH)(CN) + H₂O \rightarrow CH₃C(OH)(COOH) \]
- The final product after hydrolysis is:
\[ CH₃C(OH)(COOH) \]

### Step 5: Identify the Final Product
The final product is 2-hydroxypropanoic acid, which is commonly known as lactic acid.

### Final Answer
Thus, the compound [X] formed in the reaction is:
\[ \text{[X] = CH}_3\text{C(OH)(COOH) (Lactic Acid)} \]

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