Treatment of a ketone or aldehyde with LiAlH4 or NabH4 reduces the
Carbonyl group and yields an alcohol (Section 17.5). Although the exact details of carbonyl-group reduction are complex, LiAlH4 and NaBH4 act as if they were donors of hydride ion, :H_ , and the key step is a nucleophilic addition reaction (Figure 19.7). Addition of water or aqueous acid after the hydride addition step protonates the tetrahedral alkoxide intermediate and
Gives the alcohol product