Answer :
Final answer:
A cyclic acetal is treated with a Grignard reagent, there is no reaction because the acetal serves as a protecting group for the ketone, preventing reaction with the Grignard reagent.
Explanation:
When a cyclic acetal is treated with a Grignard reagent, there is no reaction; the cyclic acetal is protected from Grignard attack. Cyclic acetals are commonly used as protecting groups for ketones because Grignard reagents, which are strong nucleophiles that attack electrophilic carbon atoms, do not react with acetals.
Instead, the acetal plays a protective role by preventing the Grignard reagent from reacting with the sensitive ketone. In a typical reaction sequence, a ketone is first converted into a cyclic acetal using a diol such as ethylene glycol. After the ketone is protected, other reactions like those with Grignard reagents can occur on other functional groups without affecting the ketone. Once the desired reactions have taken place, the acetal protection can be removed by acidic hydrolysis to regenerate the ketone. Therefore, the correct answer to the question is d) No reaction has occurred; the cyclic acetal is protected from Grignard attack.
