Answer :
Final answer:
A ketone is formed from a nitrile and a Grignard reagent by first creating an imine salt intermediate, which is then hydrolyzed to yield the ketone. The Grignard reagent attacks the electrophilic carbon in the nitrile, and the subsequent hydrolysis converts the CN group into a CO group. This process is essential in synthetic organic chemistry for building complex molecules.
Explanation:
The reaction of a Grignard reagent with a nitrile to form a ketone involves the formation of an imine salt intermediate. When the Grignard reagent attacks the electrophilic carbon atom of the nitrile, it adds to the nitrile forming the imine anion, which is then protonated to give the imine salt. This intermediate is stable due to the negative charge on nitrogen, which prevents further nucleophilic addition. Hydrolysis of this imine salt with water results in the formation of a ketone, wherein the CN triple bond of the nitrile is converted into a CO double bond of the ketone.
For synthesis planning, one must consider the nitrile as the starting material and the organometallic species - either the Grignard or an organolithium reagent - as the agent that will ultimately form the new carbon-carbon bond. This reaction is especially useful for creating complex molecular architectures as it allows for the formation of a C-C bond and conversion to a ketone, providing access to a wider variety of organic compounds.
