Ch. 22 - Condensations and Alpha Substitutions of Carbonyl Compounds

Wade9th EditionOrganic ChemistryISBN: 9780135213728Not the one you use?Change textbook

Wade 9th Edition

Ch. 22 - Condensations and Alpha Substitutions of Carbonyl Compounds

Problem 8a

Chapter 22, Problem 8a

Give the expected products of the following acid-catalyzed reactions.
(a) acetophenone + methylamine

Verified step by step guidance

Step 1: Recognize the functional groups in acetophenone. Acetophenone contains a ketone group (C=O) attached to a benzene ring.

Step 2: Understand the role of methylamine (CH₃NH₂) in the reaction. Methylamine is a nucleophile due to the lone pair of electrons on the nitrogen atom.

Step 3: Recall the mechanism of acid-catalyzed nucleophilic addition to a ketone. The acid catalyst protonates the carbonyl oxygen, increasing the electrophilicity of the carbonyl carbon.

Step 4: The nucleophilic nitrogen of methylamine attacks the electrophilic carbonyl carbon, forming a tetrahedral intermediate.

Step 5: The intermediate undergoes dehydration (loss of water) to form an imine (Schiff base), where the carbonyl oxygen is replaced by a double-bonded nitrogen attached to the methyl group.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Acid-Catalyzed Reactions

Acid-catalyzed reactions involve the use of an acid to increase the rate of a chemical reaction. In organic chemistry, acids can protonate reactants, making them more electrophilic and facilitating nucleophilic attacks. This is particularly important in reactions involving carbonyl compounds, where the carbonyl carbon becomes more reactive towards nucleophiles in the presence of an acid.

Nucleophilic Addition

Nucleophilic addition is a fundamental reaction mechanism in organic chemistry where a nucleophile attacks an electrophilic carbon atom, typically found in carbonyl groups. In the case of acetophenone and methylamine, the nitrogen in methylamine acts as a nucleophile, attacking the electrophilic carbon of the carbonyl group in acetophenone, leading to the formation of an intermediate that can further react to yield the final product.

Imine Formation

Imine formation is a specific type of nucleophilic addition reaction where a primary amine reacts with a carbonyl compound to form an imine. This process involves the condensation of the amine with the carbonyl compound, resulting in the elimination of water. In the reaction between acetophenone and methylamine, the expected product is an imine, which is characterized by a C=N bond.

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Imine Mechanism

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Textbook Question

Propose a mechanism for the acid-catalyzed reaction of cyclohexanone with pyrrolidine.

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Textbook 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.

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Textbook Question

Give the expected products of the following acid-catalyzed reactions.

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Textbook Question

Give the expected products of the following acid-catalyzed reactions.

(d) cyclohexanone + piperidine

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Textbook Question

Predict the major products of the following reactions.

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Textbook Question