(c) Diethyl ketone (structure given below) is subjected to reaction with the amines shown below in the presence of dilute acid.
(i) Which of the three reactions will give an imine as a product? Explain your reasoning.
(ii) Draw the structure of an imine formed and the mechanism of its formation.
(iii) Briefly explain why the other two amines will not form an imine.

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Accepted Answer

∻Solution∻ ‖ 1 ⋮ **Identify the reaction**: Diethyl ketone reacts with primary amines in the presence of dilute acid to form imines. The general reaction is: $$ ext{R}_2 ext{C=O} + ext{RNH}_2 ightarrow ext{R}_2 ext{C=NR} + ext{H}_2 ext{O} $$ where $ ext{R}_2 ext{C=O}$ is the ketone and $ ext{RNH}_2$ is the primary amine. ‖ ‖ 2 ⋮ **Determine the suitable amine**: Among the three amines provided, only primary amines can form imines. Secondary and tertiary amines do not form imines because they lack the necessary hydrogen atom on the nitrogen to form water during the reaction. ‖ ‖ 3 ⋮ **Draw the structure of the imine**: The imine formed from diethyl ketone and a primary amine (let's assume the primary amine is $ ext{RNH}_2$) will have the structure: $$ ext{CH}_3 ext{CH}_2 ext{C=NR} $$ where $ ext{R}$ is the alkyl group from the primary amine. ‖ ‖ 4 ⋮ **Mechanism of imine formation**: 1. **Nucleophilic attack**: The nitrogen of the primary amine attacks the carbonyl carbon of the diethyl ketone, forming a tetrahedral intermediate. 2. **Proton transfer**: A proton is transferred from the nitrogen to the oxygen, forming a protonated alcohol intermediate. 3. **Dehydration**: The intermediate loses a molecule of water, forming a double bond between the carbon and nitrogen, resulting in the imine. The mechanism can be summarized as: $$ ext{R}_2 ext{C=O} + ext{RNH}_2 ightarrow ext{R}_2 ext{C(OH)NHR} ightarrow ext{R}_2 ext{C=NR} + ext{H}_2 ext{O} $$ ‖ ‖ 5 ⋮ **Explain why other amines do not form imines**: Secondary amines ($ ext{R}_2 ext{NH}$) and tertiary amines ($ ext{R}_3 ext{N}$) do not form imines because they do not have a hydrogen atom on the nitrogen that can be lost as water during the dehydration step. Without this hydrogen, the formation of the imine double bond is not possible. ‖ ∻Answer∻ ⚹ The reaction of diethyl ketone with a primary amine will give an imine as a product. The structure of the imine formed is $ ext{CH}_3 ext{CH}_2 ext{C=NR}$, and the mechanism involves nucleophilic attack, proton transfer, and dehydration. Secondary and tertiary amines do not form imines because they lack the necessary hydrogen atom on the nitrogen. ⚹ ∻Key Concept∻ ⚹ Primary amines react with ketones to form imines. ⚹ ∻Explanation∻ ⚹ Only primary amines can form imines with ketones because they have a hydrogen atom on the nitrogen that is necessary for the dehydration step in the mechanism. Secondary and tertiary amines do not have this hydrogen and thus cannot form imines. ⚹◊What is the general reaction mechanism for the formation of an imine from diethyl ketone and an amine in the presence of dilute acid?⍭ Generate me a similar question◊

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