What organic transformation occurs when benzaldehyde (having no alpha-hydrogen atoms) is treated with concentrated (50%) sodium hydroxide?
Answer and explanation
Correct answer: D. Cannizzaro disproportionation yielding benzyl alcohol and sodium benzoate
- Step 1: Aldehydes lacking alpha hydrogens cannot form enolates in base. Step 2. Under concentrated alkaline conditions, they undergo redox disproportionation (Cannizzaro reaction): one molecule is reduced to an alcohol and the other is oxidized to a carboxylate salt. Answer: Cannizzaro disproportionation yielding benzyl alcohol and sodium benzoate. Why not the others: Aldol requires alpha hydrogens; Clemmensen uses Zn(Hg)/HCl; HVZ halogenates carboxylic acids.
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