To determine the compound (X) that forms a cyanohydrin which, upon hydrolysis, yields an alpha-hydroxy acid that shows optical activity, we can follow these steps:
### Step 1: Understand the Formation of Cyanohydrins
Cyanohydrins are formed by the reaction of carbonyl compounds (aldehydes or ketones) with hydrogen cyanide (HCN). The reaction involves the nucleophilic attack of the cyanide ion (CN⁻) on the carbonyl carbon, leading to the formation of a cyanohydrin.
### Step 2: Identify the Characteristics of the Product
The problem states that the hydrolysis of the cyanohydrin results in an alpha-hydroxy acid that exhibits optical activity. For a compound to show optical activity, it must have a chiral carbon atom, meaning that it must have four different substituents attached to it.
### Step 3: Evaluate Each Compound
We will evaluate the given options: acetone, formaldehyde, diethyl ketone, and acetyl aldehyde.
1. **Acetone (CH₃COCH₃)**:
- Cyanohydrin formed: CH₃C(OH)(CN)CH₃
- Upon hydrolysis, it forms: CH₃C(OH)COOH
- The carbon bearing the hydroxyl group is not chiral (two CH₃ groups), so it does not show optical activity.
2. **Formaldehyde (HCHO)**:
- Cyanohydrin formed: H₂C(OH)(CN)
- Upon hydrolysis, it forms: H₂C(OH)COOH
- The carbon bearing the hydroxyl group is not chiral (two H atoms), so it does not show optical activity.
3. **Diethyl Ketone (CH₃COC₂H₅)**:
- Cyanohydrin formed: C₂H₅C(OH)(CN)CH₃
- Upon hydrolysis, it forms: C₂H₅C(OH)COOH
- The carbon bearing the hydroxyl group is not chiral (two C₂H₅ groups), so it does not show optical activity.
4. **Acetyl Aldehyde (Acetaldehyde, CH₃CHO)**:
- Cyanohydrin formed: CH₃C(OH)(CN)H
- Upon hydrolysis, it forms: CH₃C(OH)COOH
- The carbon bearing the hydroxyl group is chiral (one CH₃, one H, one OH, and one COOH), so it shows optical activity.
### Conclusion
The compound (X) that forms a cyanohydrin which, upon hydrolysis, yields an alpha-hydroxy acid that shows optical activity is **Acetyl Aldehyde (Acetaldehyde)**.
### Final Answer
The compound (X) is **Acetyl Aldehyde (Acetaldehyde)**.
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