Arrange the following compounds in decreasing order of their reactivity towards reduction by NaBH ₄ : (I) (II) (III)

Step-by-step solution

The reactivity of carbonyl compounds towards nucleophilic addition (such as reduction by NaBH ₄ ) depends on the electrophilicity of the carbonyl carbon and steric hindrance. Compound (I) is formaldehyde ( HCHO ), (II) is acetaldehyde ( CH₃CHO ), and (III) is N,N-dimethylacetamide ( CH₃CON(CH₃)₂ ). NaBH ₄ is a mild reducing agent that readily reduces aldehydes and ketones but does not reduce amides. Thus, the amide (III) is the least reactive. Comparing the aldehydes, the methyl group in acetaldehyde (II) exerts an