Chemistry Aldehydes & Ketones MDCAT 2017
PMDC Verified Question 72 of 94
Which reagent is responsible for the conversion of ketone to secondary alcohol:
A
\( NaAlH_4 \)
B
\( Al \)
C
\( NaBH_4 \)
D
Red P
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option C: \( NaBH_4 \)
Concept:

To convert a ketone back into a secondary alcohol, a reduction reaction is required, which adds hydrogen across the \( C=O \) double bond.

Solution:

  • Sodium borohydride (\( NaBH_4 \)) is a classic, mild hydride reducing agent.


  • It selectively attacks the partially positive carbonyl carbon, transferring a hydride ion (\( H^- \)). After protonation, the ketone is successfully reduced to a secondary alcohol.


Why other options are incorrect:

Red Phosphorus is used in extreme reductions to alkanes (often with HI). \( Al \) metal alone is not a standard reducing agent for this. \( NaAlH_4 \) is highly reactive and less commonly used compared to \( NaBH_4 \) or \( LiAlH_4 \) for this specific selective reduction.

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