Question

Without looking back, propose a mechanism for the hydrolysis of this iminium salt to the alkylated ketone. The first step is attack by water, followed by loss of a proton to give a carbinolamine. Protonation on nitrogen allows pyrrolidine to leave, giving the protonated ketone.

Accepted Answer

Identify the iminium salt structure. The iminium ion typically has a positively charged nitrogen atom double-bonded to a carbon atom. This is the reactive center for the hydrolysis reaction. Initiate the mechanism with the nucleophilic attack by water (H₂O) on the carbon atom of the iminium ion. This step involves the lone pair of electrons on the oxygen atom of water attacking the electrophilic carbon, forming a bond between the oxygen and carbon. Following the nucleophilic attack, a proton transfer occurs. The oxygen atom of the water molecule, now bonded to the carbon, will lose a proton (H⁺) to form a carbinolamine intermediate. This step stabilizes the intermediate by neutralizing the charge on the oxygen. Protonation of the nitrogen atom in the carbinolamine intermediate occurs next. This step involves the nitrogen atom accepting a proton (H⁺), which increases the leaving group ability of the pyrrolidine ring attached to the nitrogen. Finally, the pyrrolidine group leaves, resulting in the formation of a protonated ketone. The nitrogen atom, now positively charged, facilitates the departure of the pyrrolidine, leaving behind the alkylated ketone structure.

Without looking back, propose a mechanism for the hydrolysis of this iminium salt to the alkylated ketone. The first step is attack by water, followed by loss of a proton to give a carbinolamine. Protonation on nitrogen allows pyrrolidine to leave, giving the protonated ketone.

Verified video answer for a similar problem:

Key Concepts

Iminium Salt

Nucleophilic Attack

Proton Transfer