Stereochemistry of Ketone Reduction

Hard Organic Chemistry Carbonyl Chemistry

Consider the synthetic route to convert a ketone into an alcohol through reduction. In this scenario, we are interested in the reaction conditions that not only dictate the efficiency of the reduction but also influence the stereochemistry of the resultant alcohol.

When reducing the ketone using specific reducing agents, the facial selectivity or approach of the nucleophile plays an important role. One particular reducing agent, sodium borohydride (NaBH4), is known to selectively reduce ketones without affecting other functional groups. However, the reduction must be conducted under conditions that favor the formation of the desired stereoisomer.

Given this context, which of the following statements regarding the stereochemical outcome of the reduction of ketones is true?

Sodium borohydride will always produce only the R isomer of the alcohol.

The reaction produces a racemic mixture of alcohols regardless of the ketone's configuration.

Facial selectivity is influenced by sterics and electronics of the ketone.

Only lithium aluminum hydride can produce a stereoselective reduction of ketones.

Hint

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