Answer :
a) The reaction mechanism between a Grignard reagent and a ketone involves the nucleophilic addition of the Grignard reagent to the carbonyl carbon of the ketone followed by protonation.
- Nucleophilic Addition: The Grignard reagent, which is an organomagnesium compound, acts as a nucleophile and the nucleophilic addition results in the formation of a carbon-carbon bond between the Grignard reagent and the ketone, while the oxygen of the carbonyl group becomes negatively charged.
- Protonation: The negatively charged oxygen is protonated by a source of protons, such as water or an acid and protonation neutralizes the negative charge on the oxygen, resulting in the formation of the final product.
b) To determine the major product produced from each reaction, we need to consider the reactivity and regioselectivity of the reactant:
- If the ketone has an alpha-hydrogen, a nucleophilic addition reaction will occur at the carbonyl carbon, resulting in the formation of an alcohol.
- The major product will be determined by the steric hindrance and electronic effects of the ketone and the Grignard reagent.
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