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

Good Leaving Groups

Organic Chemistry

7. Substitution Reactions

Good Leaving Groups

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4:37 minutes

Problem 114

Textbook Question

Explain why the rate of the reaction of 1-bromo-2-butene with ethanol is increased if silver nitrate is added to the reaction mixture.

Verified step by step guidance

The reaction involves 1-bromo-2-butene, which is an alkyl halide, and ethanol, which acts as a nucleophile. The reaction mechanism is likely to proceed via a substitution reaction, specifically an SN1 mechanism due to the nature of the substrate.

Silver nitrate (AgNO₃) plays a crucial role in this reaction. Silver ions (Ag⁺) have a strong affinity for halide ions (such as Br⁻). When AgNO₃ is added, the Ag⁺ ions react with the bromide ion (Br⁻) from 1-bromo-2-butene to form an insoluble silver bromide (AgBr) precipitate.

The removal of Br⁻ as AgBr shifts the equilibrium of the reaction, effectively increasing the rate of the ionization step where the carbocation intermediate is formed. This is because the formation of the carbocation is now more favorable due to the removal of the leaving group (Br⁻).

The carbocation intermediate formed during the reaction is stabilized by resonance, as the positive charge can delocalize over the double bond in 1-bromo-2-butene. This stabilization further facilitates the SN1 mechanism.

With the carbocation intermediate formed, ethanol (acting as a nucleophile) can attack the carbocation, leading to the formation of the substitution product. The overall rate of the reaction is increased due to the role of AgNO₃ in removing Br⁻ and promoting carbocation formation.

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Key Concepts

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

Nucleophilic Substitution Reactions

Nucleophilic substitution reactions involve the replacement of a leaving group in a molecule by a nucleophile. In the case of 1-bromo-2-butene, the bromine atom acts as a leaving group, and ethanol serves as the nucleophile. Understanding the mechanism of these reactions, particularly whether they proceed via an SN1 or SN2 pathway, is crucial for analyzing the reaction rate.

Role of Silver Nitrate

Silver nitrate (AgNO3) plays a significant role in enhancing the reaction rate by forming a complex with the bromide ion (Br-) released during the reaction. This complexation effectively removes Br- from the solution, shifting the equilibrium and promoting the nucleophilic attack by ethanol. The presence of AgNO3 thus increases the concentration of the reactive species in the solution.

Reaction Rate and Equilibrium

The rate of a chemical reaction is influenced by the concentration of reactants and the presence of catalysts or inhibitors. In this scenario, the addition of silver nitrate alters the equilibrium by reducing the concentration of the leaving group (Br-), which accelerates the reaction. Understanding Le Chatelier's principle helps explain how changes in concentration can affect the rate and direction of the reaction.

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