Cyanohydrin formation requires a carbonyl and asymmetric addition for chirality

Steps:

• Hydrogen cyanide (HCN) adds to aldehydes/ketones, converting the planar carbonyl carbon to a tetrahedral carbon with OH and CN groups.
• The product is a cyanohydrin; chirality occurs if this carbon has four different substituents.
• Examine each compound: alcohols lack carbonyls and do not form cyanohydrins, while symmetric carbonyls yield achiral products.
• Identify the option where the carbonyl carbon gains four distinct groups post-reaction.

Why C is correct:

• CH3CHO (acetaldehyde) reacts to form CH3CH(OH)CN; the central carbon bonds to H, CH3, OH, and CN—all different, creating a chiral center per the definition of chirality (four unique substituents).

Why the others are wrong:

• A: CH3CHOHCH3 is an alcohol with no carbonyl, so no cyanohydrin forms.
• B: CH3COCH3 (acetone) forms (CH3)2C(OH)CN; central carbon has two identical CH3 groups, so achiral.
• D: HCHO (formaldehyde) forms CH2(OH)CN; central carbon has two H atoms, so achiral.

Final answer: C