What types of functional groups react to form the imine intermediate in the Strecker synthesis of amino acids?

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11ecba2d_12b9_975d_a3bf_db985b8ad0ae_MD0008_00 Ketones and aldehydes react with ammonia (NH₃) or primary (1°) amines to form imines, which are ketone and aldehyde analogues that contain a carbon-nitrogen double 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 Strecker synthesis is used to make α-amino acids from aldehydes using NH₃ and potassium cyanide (KCN). The first step of the reaction proceeds with protonation of the carbonyl oxygen by H₃O⁺, followed by nucleophilic attack of the carbonyl carbon by NH₃, resulting in dehydration and imine formation. Therefore, an aldehyde and NH₃ are used to form the imine intermediate in the Strecker synthesis. (Choice B) An aldehyde and a secondary amine react to form an enamine via an acid-catalyzed addition of the amine followed by an acid-catalyzed dehydration. This reaction does not form an imine. (Choices C and D) Ketones can be used in the formation of imines. However, tertiary and quaternary amines are not suitable for imine synthesis because tertiary amines do not have an available hydrogen for deprotonation and quaternary amines cannot act as nucleophiles and add the ketone (or aldehyde) carbonyl. Educational objective: An imine is an analogue of ketones and aldehydes that contains a carbon-nitrogen double bond. Imines are formed from a ketone or aldehyde and NH₃ or a primary amine via an acid-catalyzed addition of the amine followed by an acid-catalyzed dehydration.

What Types of Functional Groups React to Form the Imine