Organic Chemistry MCAT Practice Exam 2025 – 400 Free Practice Questions to Pass the Exam

The correct answer for the reduction of ketones to secondary alcohols is sodium borohydride (NaBH4). Sodium borohydride is a milder reducing agent that specifically targets ketones and aldehydes, providing a straightforward pathway for converting these carbonyl compounds into their corresponding alcohols.

NaBH4 donates a hydride ion (H-) to the carbonyl carbon of the ketone, breaking the π bond and reforming a single bond while concurrently generating an alkoxide intermediate. Subsequent protonation of the alkoxide leads to the formation of the secondary alcohol.

Although lithium aluminum hydride (LiAlH4) is also a potent reducing agent capable of reducing ketones to alcohols, it is more reactive and can reduce a wider variety of carbonyl compounds, including esters and carboxylic acids. This level of reactivity may lead to undesired side reactions when a more selective approach (like that with NaBH4) is preferred.

Grignard reagents can also be used to form alcohols through a reaction with ketones, leading to tertiary alcohols rather than secondary alcohols. Therefore, while both Grignard reagents and lithium aluminum hydride can reduce ketones, they do not