How do Grignard reagents react with formaldehyde to produce primary alcohols?

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periodic table with group numbers and the s, p, d, and f blocks — organometallic compound The periodic table of the elements, displaying the group numbers and the s, p, d, and f blocks. Elements in the shaded area are the metals of organometallic chemistry.

Grignard reagents (RMgX) act as strong nucleophiles that add to the carbonyl group of formaldehyde to produce magnesium alkoxides. This addition reaction effectively links the organic radical (R) of the reagent to the carbonyl carbon of the formaldehyde.12

Following this addition, the resulting magnesium alkoxide intermediate is hydrolyzed—typically through treatment with an aqueous acid—to yield a primary alcohol. Because formaldehyde provides the simplest carbonyl structure, this process results in a primary alcohol that contains one additional carbon atom compared to the original alkyl halide used to synthesize the Grignard reagent.12