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How do Grignard reagents react with aldehydes to form secondary alcohols?
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organohalogen compound
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Grignard reagents (RMgX) act as strong nucleophiles in synthetic organic chemistry, behaving similarly to carbanions due to the carbon-metal bond.12
To form a secondary alcohol, a Grignard reagent is added to an aldehyde other than formaldehyde. The reaction process involves the following steps:13
- Nucleophilic Attack: The nucleophilic carbon of the Grignard reagent attacks the electrophilic carbon atom of the aldehyde's carbonyl group, forming a new carbon-carbon bond.34
- Intermediate Formation: This attack results in an intermediate where the carbonyl oxygen carries a negative charge.4
- Acidification: Subsequent treatment with aqueous acid provides a hydrogen ion to the negatively charged oxygen, yielding the final secondary alcohol.34
While this reaction is a fundamental method for assembling complex carbon skeletons, it is important to note that Grignard reagents cannot be prepared from halides that contain functional groups such as aldehydes or ketones, as the reagent would react with itself.5