- The Lewis acid Mg2+ first forms an acid-base complex with the basic oxygen atom of the aldehyde or ketone, thereby making the carbonyl group a better acceptor.
- Nucleophilic addition of an alkyl group :R_ to the aldehyde or ketone produces a tetrahedral magnesium alkoxide intermediate . . .
- . . . which undergoes hydrolysis when water is added in a separate step. The final product is a neutral alcohol.