Textbook Question
Propose a mechanism for the following ring-opening transesterification. Use the mechanism in Problem 21-13 as a model.
1
views
Ch. 21 - Carboxylic Acid Derivatives
Wade9th EditionOrganic ChemistryISBN: 9780135213728
Not the one you use?Change textbookSelect a different textbook
Table of contents
- Ch.1 - Structure and Bonding107
- Ch. 2 - Acids and Bases; Functional Groups115
- Ch.3 - Structure and Stereochemistry of Alkanes100
- Ch.4 - The Study of Chemical Reactions99
- Ch.5 - Stereochemistry93
- Ch.6 - Alkyl Halides; Nucleophilic Substitution118
- Ch. 7 - Structure and Synthesis of Alkenes; Elimination158
- Ch.8 - Reactions of Alkenes171
- Ch.9 - Alkynes91
- Ch.10 - Structure and Synthesis of Alcohols143
- Ch.11 - Reactions of Alcohols104
- Ch. 12 - Infrared Spectroscopy and Mass Spectrometry22
- Ch. 13 - Nuclear Magnetic Resonance Spectroscopy45
- Ch. 14 - Ethers, Epoxides, and Thioethers72
- Ch. 15 - Conjugated Systems, Orbital Symmetry, and Ultraviolet Spectroscopy89
- Ch. 16 - Aromatic Compounds74
- Ch. 17 - Reactions of Aromatic Compounds126
- Ch. 18 - Ketones and Aldehydes193
- Ch. 19 - Amines129
- Ch. 20 - Carboxylic Acids77
- Ch. 21 - Carboxylic Acid Derivatives141
- Ch. 22 - Condensations and Alpha Substitutions of Carbonyl Compounds175
- Ch. 23 - Carbohydrates and Nucleic Acids93
- Ch. 24 - Amino Acids, Peptides, and Proteins54
Chapter 21, Problem 14
Propose a mechanism for the acid-catalyzed hydrolysis of phenylalanine ethyl ester.
Verified step by step guidance1
Step 1: Protonation of the ester group - In the presence of an acid catalyst, the carbonyl oxygen of the ester group in phenylalanine ethyl ester gets protonated. This increases the electrophilicity of the carbonyl carbon, making it more susceptible to nucleophilic attack.
Step 2: Nucleophilic attack by water - A water molecule acts as a nucleophile and attacks the electrophilic carbonyl carbon of the protonated ester, forming a tetrahedral intermediate.
Step 3: Proton transfer - A proton transfer occurs within the tetrahedral intermediate to stabilize the structure. This step involves the movement of a proton from the water molecule to one of the oxygen atoms.
Step 4: Collapse of the tetrahedral intermediate - The tetrahedral intermediate collapses, leading to the cleavage of the C-O bond between the carbonyl carbon and the ethyl group. This results in the formation of a carboxylic acid group and an ethanol molecule.
Step 5: Deprotonation of the carboxylic acid - The final step involves the deprotonation of the carboxylic acid group to regenerate the acid catalyst and yield phenylalanine as the product.
Verified video answer for a similar problem:
This video solution was recommended by our tutors as helpful for the problem above.
Was this helpful?
Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Acid-Catalyzed Hydrolysis
Acid-catalyzed hydrolysis involves the reaction of a compound with water in the presence of an acid, which donates protons (H+) to facilitate the breaking of bonds. In this process, the acid increases the electrophilicity of the substrate, making it more susceptible to nucleophilic attack by water. This mechanism is crucial for understanding how esters, like phenylalanine ethyl ester, can be converted into their corresponding acids and alcohols.
Recommended video:
Guided course
03:09
Acid Catalyzed
Mechanism of Ester Hydrolysis
The mechanism of ester hydrolysis typically involves two main steps: protonation of the carbonyl oxygen followed by nucleophilic attack by water. The protonation enhances the carbonyl carbon's electrophilicity, allowing water to act as a nucleophile, leading to the formation of a tetrahedral intermediate. This intermediate then collapses, resulting in the release of the alcohol and the formation of the carboxylic acid.
Recommended video:
0:48Hydrolysis of Phosphate Esters Concept 2
Phenylalanine Ethyl Ester Structure
Phenylalanine ethyl ester is an ester derived from phenylalanine, an amino acid, and ethanol. Its structure includes a phenyl group, a carboxylate moiety, and an ethyl group. Understanding its structure is essential for predicting how it will react under acid-catalyzed hydrolysis, as the presence of the aromatic ring can influence the stability of intermediates and the overall reaction pathway.
Recommended video:
Guided course
02:39Ester Nomenclature
Related Practice
Textbook Question
Propose a mechanism for the reaction of benzyl acetate with methylamine. Label the attacking nucleophile and the leaving group, and draw the transition state in which the leaving group leaves.
1
views
Textbook Question
When ethyl 4-hydroxybutyrate is heated in the presence of a trace of a basic catalyst (sodium acetate), one of the products is a lactone. Propose a mechanism for formation of this lactone.
6
views
Textbook Question
Acid-catalyzed transesterification:
Complete the mechanism for this acid-catalyzed transesterification by drawing out all the individual steps. Draw the important resonance contributors for each resonance-stabilized intermediate.
3
views
Textbook Question
1. Propose a mechanism for the acid-catalyzed reaction of salicylic acid with acetic anhydride.
2. Explain why a single drop of sulfuric acid dramatically increases the reaction rate.
1
views
Textbook Question
Suppose we have some optically pure (R)-2-butyl acetate that has been 'labeled' with the heavy 18O isotope at one oxygen atom as shown.
(a) Draw a mechanism for the hydrolysis of this compound under basic conditions. Predict which of the products will contain the 18O label. Also predict whether the butan-2-ol product will be pure (R), pure (S), or racemized.
1
views