Which of the following reagent is not used to convert aldehyde into alcohol?

$Sn/HCl$

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.