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 72

Chapter 16, Problem 72

When butanoic acid and ¹⁸O-labeled methanol react under acidic conditions, what compounds are labeled when the reaction has reached equilibrium?

Verified step by step guidance

Identify the reaction type: This is a Fischer esterification reaction, where a carboxylic acid (butanoic acid) reacts with an alcohol (18^O-labeled methanol) under acidic conditions to form an ester and water.

Write the general reaction mechanism: The carboxylic acid (butanoic acid) reacts with the alcohol (18^O-labeled methanol) in the presence of an acid catalyst. The hydroxyl group (-OH) of the carboxylic acid is replaced by the alkoxy group (-OCH3) from the alcohol, forming an ester (methyl butanoate). Water is also produced as a byproduct.

Track the labeled oxygen atom: The 18^O label in methanol is part of the -OCH3 group. During the reaction, this labeled oxygen becomes part of the ester product (methyl butanoate). The water molecule formed will contain the oxygen atom originally from the carboxylic acid (-OH group).

Consider equilibrium: At equilibrium, both the ester (methyl butanoate) and water are present. The labeled oxygen (18^O) will be found in the ester product, specifically in the -OCH3 group, while the water molecule will not contain the labeled oxygen.

Summarize the labeled compounds: At equilibrium, the compound labeled with 18^O is the ester (methyl butanoate), as the labeled oxygen from methanol is incorporated into the ester structure.

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Key Concepts

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

Acid-Base Reactions

Acid-base reactions involve the transfer of protons (H+) between reactants. In the context of butanoic acid and methanol, the acidic conditions facilitate the protonation of the alcohol, making it a better nucleophile. Understanding this concept is crucial for predicting how the reactants will interact and form new products.

Isotope Labeling

Isotope labeling, such as using 18^O in methanol, allows chemists to track the movement of atoms during a chemical reaction. In this case, the 18^O label will help identify which compounds incorporate the oxygen from methanol after the reaction. This concept is essential for understanding how the labeled atoms are distributed among the products.

Equilibrium in Chemical Reactions

Chemical equilibrium occurs when the rates of the forward and reverse reactions are equal, resulting in constant concentrations of reactants and products. In the reaction between butanoic acid and methanol, knowing how equilibrium affects the distribution of labeled and unlabeled compounds is vital for predicting the final outcome of the reaction.

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Textbook Question

An aqueous solution of a primary or secondary amine reacts with an acyl chloride to form an amide as the major product. However, if the amine is tertiary, an amide is not formed. What product is formed? Explain.

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Textbook Question

Phosgene (COCl₂) was used as a poison gas in World War I. What product would be formed from the reaction of phosgene with each of the following reagents?

c. excess propylamine

d. excess water

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Textbook Question

When a student treated butanedioic acid with thionyl chloride, she was surprised to find that the product she obtained was an anhydride rather than an acyl chloride. Propose a mechanism to explain why she obtained an anhydride.

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Textbook Question

a. When a carboxylic acid is dissolved in isotopically labeled water (H₂O¹⁸) and an acid catalyst is added, the label is incorporated into both oxygens of the acid. Propose a mechanism to account for this.

c. If an ester is dissolved in isotopically labeled water (H₂O¹⁸) and an acid catalyst is added, where will the label reside in the product?

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Textbook Question

a. Identify the two products obtained from the following reaction:

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Textbook Question

What are the products of the following reactions?

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