Table of contents

1. A Review of General Chemistry5h 5m
2. Molecular Representations1h 14m
3. Acids and Bases2h 46m
4. Alkanes and Cycloalkanes4h 17m
5. Chirality3h 39m
6. Thermodynamics and Kinetics1h 22m
7. Substitution Reactions1h 48m
8. Elimination Reactions2h 30m
9. Alkenes and Alkynes2h 9m
10. Addition Reactions3h 19m
11. Radical Reactions1h 58m
12. Alcohols, Ethers, Epoxides and Thiols2h 42m
13. Alcohols and Carbonyl Compounds2h 17m
14. Synthetic Techniques1h 26m
15. Analytical Techniques:IR, NMR, Mass Spect7h 3m
16. Conjugated Systems6h 13m
17. Ultraviolet Spectroscopy51m
18. Aromaticity2h 34m
19. Reactions of Aromatics: EAS and Beyond5h 1m
20. Phenols55m
21. Aldehydes and Ketones: Nucleophilic Addition4h 56m
22. Carboxylic Acid Derivatives: NAS2h 51m
23. The Chemistry of Thioesters, Phophate Ester and Phosphate Anhydrides1h 10m
24. Enolate Chemistry: Reactions at the Alpha-Carbon1h 53m
25. Condensation Chemistry2h 9m
26. Amines1h 43m
27. Heterocycles2h 0m
28. Carbohydrates5h 53m
29. Amino Acids4h 20m
30. Peptides and Proteins2h 42m
31. Catalysis in Organic Reactions1h 30m
32. Lipids 2h 50m
33. The Organic Chemistry of Metabolic Pathways2h 52m
34. Nucleic Acids1h 32m
35. Transition Metals6h 14m
36. Synthetic Polymers1h 49m

10. Addition Reactions

Epoxidation

Organic Chemistry

10. Addition Reactions

Epoxidation

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5:41 minutes

Problem 46

Textbook Question

Rank the reactivity of the following alkenes with mCPBA ( 1 = most reactive , 5 least reactive ).

Verified step by step guidance

Identify the structure of each alkene provided in the problem. Look for features such as electron-donating or electron-withdrawing groups attached to the double bond, as these influence reactivity with mCPBA (meta-chloroperoxybenzoic acid).

Recall that mCPBA is an electrophilic oxidizing agent used to convert alkenes into epoxides. Alkenes with electron-donating groups (e.g., alkyl groups) are more reactive because they increase the electron density on the double bond, making it more nucleophilic.

Rank the alkenes based on the presence and strength of electron-donating or electron-withdrawing groups. For example, alkenes with alkyl substituents will generally be more reactive than those with electron-withdrawing groups (e.g., halogens, nitro groups).

Consider steric hindrance around the double bond. Alkenes with less steric hindrance are more accessible to the mCPBA molecule and will react more readily.

Combine the effects of electronic and steric factors to assign a reactivity ranking (1 = most reactive, 5 = least reactive). Ensure that you carefully evaluate each alkene based on these principles.

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Key Concepts

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

Alkenes and Their Reactivity

Alkenes are hydrocarbons that contain at least one carbon-carbon double bond (C=C). Their reactivity is influenced by the stability of the double bond and the substituents attached to the carbon atoms. Generally, more substituted alkenes are more stable and less reactive, while less substituted alkenes are more reactive due to their higher strain and lower stability.

mCPBA and Epoxidation

mCPBA (meta-Chloroperbenzoic acid) is a peracid commonly used in organic chemistry for the epoxidation of alkenes. This reaction involves the formation of a three-membered cyclic ether called an epoxide, which is a highly reactive intermediate. The reactivity of alkenes with mCPBA depends on their substitution pattern, with less hindered alkenes typically reacting more readily.

Steric Hindrance

Steric hindrance refers to the prevention of reactions at a particular location in a molecule due to the size of substituent groups. In the context of alkenes, bulky groups around the double bond can impede the approach of mCPBA, reducing the rate of epoxidation. Understanding steric effects is crucial for predicting the reactivity of different alkenes in reactions with mCPBA.

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Related Practice

Textbook Question

Predict the product(s) that would result when the alkenes are allowed to react under the following conditions: (vii) 1. mCPBA 2. H₂SO₄, H₂O

(h)

Textbook Question

Predict the product(s) that would result when the alkenes are allowed to react under the following conditions: (v) mCPBA;

(k)

Textbook Question

Predict the product(s) when each of the following are reacted with mCPBA, making sure to indicate the relative stereochemical outcome. Indicate any racemic mixtures by drawing both enantiomers.

(a)

Textbook Question

When producing a chiral molecule, epoxide formation still results in a mixture of enantiomers, despite its stereospecificity.

(b) How is it that a reaction can be stereospecific while still producing two enantiomers?

Textbook Question

One way to think about concerted reactions is to imagine them as being stepwise reactions where, besides the slowest step, all others have infinitesimally small activation energies. Considering the hypothetical stepwise mechanism and actual concerted mechanism of epoxide formation, show what a reaction coordinate diagram might look like for each possibility.

(a) Stepwise, hypothetical mechanism:

Textbook Question

(b) Concerted , actual mechanism (butterfly transition state:

Textbook Question

How does the carbonyl in mCPBA weaken the O―O σ bond (i.e., make a better leaving group)?

Textbook Question

Calculate the atom economy of the reaction in Figure 9.24. [Catalysts are not included in the atom economy calculation.]

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