Give reasons for the following :
(ii) Treatment of `C_(6)H_(5)CHO` with HCN gives a mixture of two isomers which cannot be separted even by fractional distillation.

Explanation

To understand why the treatment of benzaldehyde (C6H5CHO) with hydrogen cyanide (HCN) results in a mixture of two isomers that cannot be separated by fractional distillation, let's break down the process step by step.

### Step 1: Reaction of Benzaldehyde with HCN
When benzaldehyde (C6H5CHO) reacts with hydrogen cyanide (HCN), the nucleophile (CN⁻) attacks the electrophilic carbon of the carbonyl group (C=O) in benzaldehyde. This leads to the formation of a cyanohydrin.

### Step 2: Formation of Two Isomers
The carbon atom in the carbonyl group is sp² hybridized and planar. This allows the nucleophile (CN⁻) to attack from either above or below the plane of the carbonyl group. As a result, two different stereoisomers (enantiomers) are formed:

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