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

7. Substitution Reactions

SN1 Reaction

Organic Chemistry

7. Substitution Reactions

SN1 Reaction

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5:15 minutes

Problem 41a

Textbook Question

Allylic halides have the structure

a. Show how the first-order ionization of an allylic halide leads to a resonance-stabilized cation.

Verified step by step guidance

Step 1: Recognize the structure of an allylic halide. The given structure contains a halogen atom (X) attached to a carbon atom that is adjacent to a double bond. This is characteristic of an allylic halide.

Step 2: Understand the first-order ionization process. In this process, the bond between the halogen (X) and the carbon atom breaks heterolytically, resulting in the formation of a carbocation and a halide ion (X⁻).

Step 3: Analyze the resulting carbocation. The carbon atom that loses the halogen becomes positively charged, forming an allylic carbocation. This carbocation is resonance-stabilized due to the delocalization of the positive charge over the π-electron system of the double bond.

Step 4: Draw the resonance structures. The positive charge can shift between the two carbons of the double bond, creating two resonance structures. Use curved arrows to show the movement of electrons from the π-bond to the positively charged carbon.

Step 5: Explain the stabilization. Resonance stabilization occurs because the positive charge is delocalized over multiple atoms, reducing the energy of the carbocation and making it more stable compared to a non-resonance-stabilized carbocation.

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Key Concepts

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

Allylic Halides

Allylic halides are organic compounds where a halogen atom is bonded to a carbon atom adjacent to a carbon-carbon double bond. This structure allows for unique reactivity patterns, particularly in nucleophilic substitution reactions, due to the presence of the double bond which can stabilize intermediates formed during reactions.

First-Order Ionization

First-order ionization refers to a reaction mechanism where a single molecule undergoes a transformation to form an ion, typically involving the departure of a leaving group. In the case of allylic halides, the halogen leaves, generating a carbocation that can be stabilized by resonance with the adjacent double bond.

Resonance Stabilization

Resonance stabilization occurs when a molecule can be represented by multiple valid Lewis structures, allowing for the delocalization of electrons. In allylic halides, the carbocation formed after ionization can be stabilized by resonance with the π electrons of the adjacent double bond, leading to a more stable cationic intermediate.

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Related Practice

Textbook Question

A reluctant first-order substrate can be forced to ionize by adding some silver nitrate (one of the few soluble silver salts) to the reaction. Silver ion reacts with the halogen to form a silver halide (a highly exothermic reaction), generating the cation of the alkyl group.

Give mechanisms for the following silver-promoted rearrangements.

(b)

Textbook Question

Propose a mechanism involving a hydride shift or an alkyl shift for each solvolysis reaction. Explain how each rearrangement forms a more stable intermediate.

Hint: Most rearrangements convert 2° (or incipient 1°) carbocations to 3° or resonance-stabilized carbocations.

(c)

Textbook Question

Choose the member of each pair that will react faster by the SN1 mechanism.

c. n-propyl bromide or allyl bromide

d. 1-bromo-2,2-dimethylpropane or 2-bromopropane

Textbook Question

Predict the compound in each pair that will undergo solvolysis (in aqueous ethanol) more rapidly.

(c)

(d)

Textbook Question

Often, compounds can be synthesized by more than one method. Show how this 3° alcohol can be made from the following:

(d) a 3° alkyl bromide

Textbook Question

Give the substitution products expected from solvolysis of each compound by heating in ethanol.

(c)

(d)

Textbook Question

Propose a mechanism for the reaction of benzyl bromide with ethanol to give benzyl ethyl ether.

Textbook Question

Propose a mechanism involving a hydride shift or an alkyl shift for each solvolysis reaction. Explain how each rearrangement forms a more stable intermediate.

Hint: Most rearrangements convert 2° (or incipient 1°) carbocations to 3° or resonance-stabilized carbocations.

(d)

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Allylic halides have the structurea. Show how the first-order ionization of an allylic halide leads to a resonance-stabilized cation.

Key Concepts

Allylic Halides

First-Order Ionization

Resonance Stabilization

Watch next

Allylic halides have the structure

a. Show how the first-order ionization of an allylic halide leads to a resonance-stabilized cation.