Organomagnesium halides, commonly known as Grignard reagents, convert acid halides to tertiary alcohols. The reaction requires two equivalents of the Grignard reagent and proceeds via a ketone intermediate.
Grignard reagents are a source of carbanions and function as nucleophiles. The mechanism begins with the nucleophilic attack by the carbanion at the carbonyl carbon of the acid halide to form a tetrahedral intermediate. Next, the carbonyl group is re-formed, and the halide ion departs, forming a ketone. The addition of another equivalent of the carbanion generates a tertiary alkoxide ion. Protonation of the alkoxide gives a tertiary alcohol as the final product.
In addition to lithium aluminum hydride, organomagnesium halides, known as Grignard reagents, convert acid halides to alcohols.
Unlike the first approach, where the final product is a primary alcohol, reduction with the Grignard reagent yields a tertiary alcohol.
The reaction requires two equivalents of the Grignard reagent and proceeds via a ketone intermediate.
Since the alkyl–magnesium bond is highly polar, the alkyl carbon acquires a carbanionic character and functions as a nucleophile.
The first step of the mechanism begins with a nucleophilic attack by the Grignard reagent at the carbonyl carbon, forming a tetrahedral intermediate.
In the second step, the carbon–oxygen double bond is reconstructed, and the halide ion departs as a leaving group to yield a ketone.
Next, the ketone is attacked by another equivalent of the Grignard reagent, generating an alkoxide intermediate.
Lastly, protonation of the alkoxide drives the reaction to completion, forming a tertiary alcohol as the final product.
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