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Addition of NaBH4 to ketones to give secondary alcohols

Description:  Addition of sodium borohydride (NaBH4) to ketones gives secondary alcohols (after addition of acid) [private_ReactionGuide]

Notes: The precise type of acid isn’t crucial for this reaction; H2O, H+, H3O(+) or other acids might be used.

Examples:

Notes:  Again, many different acids can be used in the last step. It’s not crucial which specific acid is used, just that something is present that can donate a proton to form the alcohol.

Mechanism:  NaBH4 is a source of hydride (H–)  and the reaction begins with 1,2 addition of hydride to the carbonyl of the ketone (Step 1, arrows A and B). Upon addition of acid, the oxygen is protonated (Step 2, arrows C and D) to give the neutral alcohol.

 

Notes: Again, the choice of H2O /H2SO4 as acid isn’t crucial.

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