What functional group forms in an acid-catalyzed reaction between a secondary amine and a ketone?

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11ecba2d_128d_2f8f_a3bf_e114c2e9c5b5_MD0008_00 Ketones and aldehydes react with primary (1°) and secondary (2°) amines to form a carbon-nitrogen bond. The reaction begins with an acid-catalyzed addition of the amine to the carbonyl, which involves protonation of the carbonyl, nucleophilic attack of the carbonyl by the amine, and deprotonation of the amine. This forms an intermediate known as an α-aminoalcohol. The second part of the reaction is an acid-catalyzed dehydration involving protonation of the -OH group, loss of H₂O, and deprotonation. The product formed is dependent on the type of amine used (1° or 2°). If a 1° amine is used, an imine (nitrogen analogue to ketones and aldehydes) is formed because the nitrogen has a proton available for removal in the last step, permitting C=N bond formation. If a 2° amine is used, an enamine (nitrogen analogue to an enol) is formed because the nitrogen does not have a proton available to be removed in the last step. Therefore, a proton is removed from the α-carbon, forming a C=C bond. (Choice B) A carbon-nitrogen bond is formed in the reaction, but the functional group is not a nitrile because the bond between carbon and nitrogen is a single bond rather than a triple bond. (Choice C) If a ketone reacts with a 1° amine rather than a 2° amine, an imine would form. (Choice D) Although a carbon-carbon double bond is formed in the reaction, an alkene indicates that the functional group contains only a double bond. Because a nitrogen atom is bonded to the sp² carbon, the functional group would be classified as an enamine rather than an alkene. Educational objective: Ketones and aldehydes undergo acid-catalyzed addition of 1° and 2° amines to form imines or enamines, respectively. Like ketones and aldehydes, imines contain a carbon-heteroatom double bond (nitrogen in imines, oxygen in ketones and aldehydes). Enamines are the nitrogen analogue to enols, containing a carbon-carbon double bond.

What Functional Group Forms in an Acid-Catalyzed Reaction Between a Secondary