Which of the following reagent is not used to convert aldehyde into alcohol?
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → $Sn/HCl$
Conversion of an aldehyde to alcohol is a reduction reaction:
R–CHO → R–CH₂OH
So we must identify which reagents can reduce aldehydes to primary alcohols.
Option Analysis
Option 1: H₂/Pd
Catalytic hydrogenation using hydrogen gas in presence of palladium reduces aldehydes to primary alcohols.
R–CHO + H₂ → R–CH₂OH
Hence, this reagent is used for conversion.
Option 2: LiAlH₄
Lithium aluminium hydride is a strong reducing agent. It easily reduces aldehydes to primary alcohols by hydride transfer.
R–CHO → R–CH₂OH
Hence, this reagent is used.
Option 3: NaBH₄
Sodium borohydride is a milder reducing agent but is highly effective for reducing aldehydes to alcohols. It selectively reduces carbonyl compounds without affecting many other functional groups.
R–CHO → R–CH₂OH
Hence, this reagent is also used.
Option 4: Sn/HCl
Tin in hydrochloric acid is not a reducing agent for aldehydes. It is specifically used for reduction of nitro compounds into amines.
Example: Nitrobenzene → Aniline
It does not convert aldehydes into alcohols.