JEE MainChemistryAldehydes and Ketones
Identify the correct sequence of reagents to achieve the following transformation: 4-oxohexanal 4-hydroxyhexanoic acid
Options
- A(i) [ Ag ( NH ₃)₂]^+ OH ^- ; (ii) NaBH ₄ , EtOH , followed by H ₃ O ^+
- B(i) NaBH ₄ , EtOH ; (ii) [ Ag ( NH ₃)₂]^+ OH ^- , followed by H ₃ O ^+
- C(i) K ₂ Cr ₂ O ₇ , H ^+ ; (ii) LiAlH ₄ , ether , followed by H ₃ O ^+
- D(i) LiAlH ₄ , ether , followed by H ₃ O ^+ ; (ii) KMnO ₄ , H ^+
Correct answer
A. (i) [ Ag ( NH ₃)₂]^+ OH ^- ; (ii) NaBH ₄ , EtOH , followed by H ₃ O ^+
Step-by-step solution
To convert 4-oxohexanal to 4-hydroxyhexanoic acid, the aldehyde group must be oxidized to a carboxylic acid and the ketone group must be reduced to a secondary alcohol. If a reducing agent like NaBH ₄ is used first, both the aldehyde and ketone groups will be reduced to alcohols, and Tollens' reagent cannot oxidize alcohols. Therefore, the aldehyde must be selectively oxidized first. Tollens' reagent ( [ Ag ( NH ₃)₂]^+ OH ^- ) is a mild oxidizing agent that selectively oxidizes aldehydes to carboxylate salts withou