Ch. 15 - Reactions of Carboxylic Acids and Carboxylic Acid Derivatives

Bruice8th EditionOrganic ChemistryISBN: 9780135213711Not the one you use?Change textbook

Bruice 8th Edition

Ch. 15 - Reactions of Carboxylic Acids and Carboxylic Acid Derivatives

Problem 34a

Chapter 16, Problem 34a

Which of the following reactions lead to the formation of an amide?

Verified step by step guidance

Step 1: Understand the functional groups involved in the reactions. In both reactions, the starting materials include a carboxylic acid derivative (reaction A: carboxylic acid, reaction B: ester) and a nucleophile (methylamine, CH3NH2). Amides are formed when a carboxylic acid derivative reacts with an amine or ammonia.

Step 2: Analyze reaction A. The carboxylic acid (RC=O(OH)) reacts with methylamine (CH3NH2). This reaction typically leads to the formation of an amide, but it requires a dehydrating agent or heat to remove water (H2O) formed during the reaction. Without these conditions, the reaction may not proceed efficiently.

Step 3: Analyze reaction B. The ester (RC=O(OCH3)) reacts with methylamine (CH3NH2) under heat (Δ). This is an example of aminolysis of an ester, where the amine acts as a nucleophile and replaces the alkoxy group (-OCH3) to form an amide. The heat provided facilitates this substitution reaction.

Step 4: Compare the two reactions. Reaction A may lead to the formation of an amide if appropriate conditions (e.g., heat or a dehydrating agent) are applied. Reaction B, under the given conditions (Δ), is more likely to proceed efficiently to form an amide due to the reactivity of esters with amines under heat.

Step 5: Conclude that reaction B is more favorable for the formation of an amide under the given conditions. Reaction A may also form an amide but requires additional conditions to drive the reaction forward.

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Key Concepts

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

Amide Formation

Amides are formed when a carboxylic acid reacts with an amine, resulting in the replacement of the hydroxyl group (-OH) of the acid with an amine group (-NH2). This reaction typically involves the condensation of the two reactants, leading to the release of water. Understanding this process is crucial for identifying which reactions yield amides.

Nucleophilic Acyl Substitution

Nucleophilic acyl substitution is a fundamental reaction mechanism in organic chemistry where a nucleophile attacks the electrophilic carbon of a carbonyl group (C=O). In the context of amide formation, the amine acts as the nucleophile, attacking the carbonyl carbon of the carboxylic acid or its derivatives. This mechanism is essential for understanding how amides can be synthesized from various carbonyl-containing compounds.

Reactivity of Carbonyl Compounds

Different carbonyl compounds exhibit varying reactivities based on their substituents. For instance, carboxylic acids and their derivatives (like acid chlorides and esters) are more reactive than simple aldehydes or ketones. Recognizing the reactivity of these compounds is vital for predicting which reactions will successfully lead to amide formation, as the presence of specific functional groups can significantly influence the outcome.

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Related Practice

Textbook Question

Write the mechanism for the acid-catalyzed reaction of an amide with an alcohol to form an ester.

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Textbook Question

Propose a mechanism for the following reaction. (Hint: Number the carbons to help you see where they end up in the product.)

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Textbook Question

Rank the following amides from greatest reactivity to least reactivity toward acid-catalyzed hydrolysis:

Textbook Question

Show how each of the following esters could be prepared using a carboxylic acid as one of the starting materials:

a. methyl butyrate (odor of apples)

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Textbook Question

What acyl chloride and amine are required to synthesize the following amides?

a. N-ethylbutanamide

b. N,N-dimethylbenzamide

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Textbook Question

What alkyl bromide would you use in a Gabriel synthesis to prepare each of the following amines?

a. pentylamine

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