Chiral Center Formation in Organic Reactions

Steps:

• Determine the major product for each reagent pair using standard reaction mechanisms.
• Examine the product's structure for a tetrahedral carbon atom bonded to four different substituents.
• Confirm chirality by ensuring no plane of symmetry or identical groups on the potential stereocenter.
• Select the option where the product introduces a new chiral carbon.

Why C is correct:

• CH3CHO + HCN forms CH3CH(OH)CN via nucleophilic addition; the central carbon bonds to H, OH, CH3, and CN—four different groups, defining a chiral center per stereochemistry rules.

Why the others are wrong:

• A: CH3CH=CH2 + HBr yields CH3CHBrCH3 (Markovnikov addition); the central carbon has two CH3 groups, so achiral.
• B: (CH3)2CHBr + NaBH4 gives (CH3)2CH2 (reduction); propane has no chiral carbon.
• D: CH3COOH + CH3OH produces CH3COOCH3 (esterification); the structure lacks a tetrahedral carbon with four different substituents.

Final answer: C