Question:
Shown below are four possible synthesis of propionaldehyde. Which one would not work?
Shown below are four possible synthesis of propionaldehyde. Which one would not work?
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LiAlH$_4$ is strong → reduces esters to alcohols, not aldehydes.
Updated On: Apr 23, 2026
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The Correct Option is B
Solution and Explanation
Concept:
Different reducing agents give different products depending on their strength.
Step 1: Option (a): Primary alcohol $\xrightarrow{PCC}$ aldehyde → valid reaction.
Step 2: Option (b): Ester $\xrightarrow{LiAlH_4}$ gives primary alcohol, not aldehyde.
Step 3: Option (c): Ester $\xrightarrow{DIBAL-H}$ (controlled) gives aldehyde → valid.
Step 4: Option (d): Acid chloride $\xrightarrow{LiAlH(O-tBu)_3}$ gives aldehyde → valid.
Conclusion:
Only option (b) does not give propionaldehyde.
Step 1: Option (a): Primary alcohol $\xrightarrow{PCC}$ aldehyde → valid reaction.
Step 2: Option (b): Ester $\xrightarrow{LiAlH_4}$ gives primary alcohol, not aldehyde.
Step 3: Option (c): Ester $\xrightarrow{DIBAL-H}$ (controlled) gives aldehyde → valid.
Step 4: Option (d): Acid chloride $\xrightarrow{LiAlH(O-tBu)_3}$ gives aldehyde → valid.
Conclusion:
Only option (b) does not give propionaldehyde.
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