Textbook Question
Draw the product(s) you'd expect when each of these alkenes is treated first with O3, then with CH3SCH3
(c)
Ch. 9 - Alkenes II: Oxidation and Reduction
Mullins1st EditionOrganic Chemistry: A Learner Centered ApproachISBN: 9780137566471
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Table of contents
- Ch. 2 - General Chemistry Translated: Finding the Electrons114
- Ch. 3 - Alkanes and Cycloalkanes: Properties and Conformational Analysis109
- Ch. 4 - Acids and Bases: Electron Flow144
- Ch. 5 - Chemical Reaction Analysis: Thermodynamics and Kinetics118
- Ch. 6 - Stereoisomerism: Arrangement of Atoms in Space112
- Ch. 7 - Principles of Green (Organic) Chemistry3
- Ch. 8 - Alkenes I: Properties and Electrophilic Additions158
- Ch. 9 - Alkenes II: Oxidation and Reduction150
- Ch. 10 - Alkynes: Electrophilic Addition and Redox Reactions101
- Ch. 11 - Properties and Synthesis of Alkyl Halides: Radical Reactions108
- Ch. 12 - Substitution and Elimination: Reactions of Haloalkanes172
- Ch. 13 - Alcohols, Ethers and Related Compounds: Substitution and Elimination239
- Ch. 14 - Structural Identification I: Infrared Spectroscopy and Mass Spectrometry54
- Ch. 15 - Structural Identification II: Nuclear Magnetic Resonance Spectroscopy93
- Ch. 16 - Metals in Organic Chemistry48
- Ch. 17 - Carbonyl Addition Reactions: Aldehydes and Ketones45
- Ch. 18 - Nucleophilic Acyl Substitution I: Carboxylic Acids18
- Ch. 19 - Nucleophilic Acyl Substitution II: Carboxylic Acid Derivatives39
- Ch. 20 - Enolates: Carbonyl Addition and Substitution13
- Ch. 21 - Conjugated Systems I: Stability and Addition Reactions56
- Ch. 22 - Conjugated Systems II: Pericyclic Reactions54
- Ch. 23 - Benzene I: Aromatic Stability and Substitution Reactions64
- Ch. 24 - Benzene II: Reactions Influenced by the Aromatic Ring62
- Ch. 25 - Amines: Structure, Reactions, and Synthesis27
- Ch. 26 - Amino Acids, Proteins, and Peptide Synthesis9
- Ch. 27 - Carbohydrates, Nucleic Acids, and Lipids54
Mullins1st EditionOrganic Chemistry: A Learner Centered ApproachISBN: 9780137566471Not the one you use?Change textbook
Chapter 8, Problem 28
Despite it being equally favorable, opening of the epoxide does not happen in the absence of an acid catalyst. How does acid make the reaction faster? Demonstrate this concept by directly comparing the reaction coordinate diagram for both situations A and B.
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In Situation A (without acid), the epoxide ring opens via a nucleophilic attack by water. However, the oxygen in the epoxide is not protonated, so the ring strain is not significantly reduced, and the reaction proceeds slowly due to the high activation energy required to break the epoxide bond.
In Situation B (with acid), the epoxide oxygen is first protonated by the acid, forming a positively charged oxonium ion. This protonation increases the electrophilicity of the epoxide carbon atoms, making them more susceptible to nucleophilic attack.
The protonation in Situation B also reduces the activation energy of the reaction by stabilizing the transition state. This is because the positive charge on the oxonium ion delocalizes, lowering the energy barrier for the ring-opening step.
The reaction coordinate diagram for Situation A would show a higher activation energy peak compared to Situation B. In Situation B, the protonation step creates an intermediate with lower energy, resulting in a smaller energy difference between the reactants and the transition state.
Overall, the acid catalyst in Situation B accelerates the reaction by both increasing the electrophilicity of the epoxide and lowering the activation energy, as demonstrated by the lower energy barrier in the reaction coordinate diagram.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Epoxide Reactivity
Epoxides are three-membered cyclic ethers that are highly strained, making them reactive towards nucleophiles. The strain in the epoxide ring creates a tendency for the ring to open, but this reaction can be significantly influenced by the presence of catalysts, particularly acids, which stabilize the transition state.
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General properties of epoxidation.
Acid Catalysis
Acid catalysis involves the use of an acid to increase the rate of a chemical reaction. In the case of epoxide opening, the acid protonates the oxygen atom in the epoxide, increasing its electrophilicity. This makes the carbon atoms in the epoxide more susceptible to nucleophilic attack, thereby accelerating the reaction.
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Reaction Coordinate Diagram
A reaction coordinate diagram visually represents the energy changes during a chemical reaction. It illustrates the energy of reactants, products, and transition states. By comparing diagrams for acid-catalyzed and uncatalyzed reactions, one can observe how the presence of an acid lowers the activation energy barrier, facilitating a faster reaction.
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Related Practice
Textbook Question
Predict the product(s) of each of the following reactions, making sure to indicate the relative stereochemical outcome. Indicate any racemic mixtures by drawing both enantiomers.
(c)
3
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Textbook Question
Draw the product(s) you'd expect when each of these alkenes is treated first with O3, then with CH3SCH3
(b)
1
views
Textbook Question
Draw the product(s) you'd expect when each of these alkenes is treated first with O3, then with CH3SCH3
(a)
Textbook Question
Predict the product(s) of each of the following reactions, making sure to indicate the relative stereochemical outcome. Indicate any racemic mixtures by drawing both enantiomers.
(d)
7
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Textbook Question
In Assessment 9.26, what is the relationship between the enantiomers of compound A and the enantiomers of compound B?
1
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