When an aldehyde is reacted with hydrogen cyanide a " Cyanihydrin" is formed. This process is best termed as __________?
Correct answer: C. Nucleophilic addition
- A. Electrophilic addition
- B. Electrophilic substitution
- C. Nucleophilic addition
- D. Necleophilic substitution
Explanation
The cyanide ion from HCN attacks the electrophilic carbonyl carbon of the aldehyde, followed by protonation to give a cyanohydrin, so the reaction is nucleophilic addition. Students may choose electrophilic addition because HCN adds across a double bond-like carbonyl group, but the attacking species is the nucleophile CN−.
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About Nucleophilic Addition Reactions
Nucleophilic addition occurs at the polar carbonyl group of aldehydes and ketones, where a nucleophile attacks the electron-deficient carbon atom. Reactions with hydrogen cyanide, sodium bisulfite, alcohols and Grignard reagents are explained through tetrahedral intermediates, acid or base catalysis, and the different reactivity of aldehydes and ketones.
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