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

SN2 Reaction

Organic Chemistry

7. Substitution Reactions

SN2 Reaction

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1:59 minutes

Problem 20e

Textbook Question

Draw a perspective structure or a Fischer projection for the products of the following S_N2 reactions.
(e)

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Identify the type of reaction: This is an SN2 reaction, which involves a single-step mechanism where the nucleophile attacks the electrophilic carbon, displacing the leaving group in a backside attack. This results in inversion of configuration at the carbon center.

Analyze the reactants: The substrate is a secondary alkyl halide (2-bromobutane), and the nucleophile is methoxide ion (CH3O⁻) in methanol (CH3OH). Methoxide is a strong nucleophile, favoring the SN2 mechanism.

Determine the stereochemistry of the substrate: The carbon bonded to the bromine atom is a chiral center. In the given structure, the substituents are CH3, H, CH2CH2CH3, and Br. Assign the configuration (R or S) to this carbon using the Cahn-Ingold-Prelog priority rules.

Predict the product: In an SN2 reaction, the nucleophile (CH3O⁻) will attack the carbon from the side opposite to the leaving group (Br), leading to inversion of configuration. Draw the product with the methoxy group (OCH3) replacing the bromine atom and inverted stereochemistry at the chiral center.

Choose the representation: Draw the product as either a perspective structure (showing the 3D arrangement of groups) or a Fischer projection (a 2D representation where horizontal lines represent bonds coming out of the plane and vertical lines represent bonds going into the plane). Ensure the stereochemistry is correctly represented in the chosen format.

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Key Concepts

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

SN2 Mechanism

The SN2 mechanism is a type of nucleophilic substitution reaction where a nucleophile attacks an electrophile, resulting in the simultaneous displacement of a leaving group. This reaction occurs in a single concerted step, leading to the inversion of configuration at the carbon center. It is favored by primary and some secondary substrates due to steric accessibility.

Fischer Projection

A Fischer projection is a two-dimensional representation of a three-dimensional organic molecule, particularly useful for depicting stereochemistry. In this format, vertical lines represent bonds that project away from the viewer, while horizontal lines represent bonds that project towards the viewer. Fischer projections are commonly used to illustrate the stereochemistry of carbohydrates and amino acids.

Nucleophiles and Electrophiles

Nucleophiles are species that donate an electron pair to form a chemical bond, while electrophiles are electron-deficient species that accept an electron pair. In SN2 reactions, the nucleophile attacks the electrophile, leading to the substitution of the leaving group. Understanding the nature of these species is crucial for predicting the outcome of organic reactions.

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Related Practice

Textbook Question

How will the rate of each of the following S_N2 reactions change if it is carried out in a more polar solvent?

Textbook Question

Show all the products, including their configurations, that are obtained from the above reaction.

Textbook Question

You were told in [SECTION 7.11] that is best to use a methyl halide or a primary alkyl halide for the reaction of an acetylide ion with an alkyl halide. Explain why this is so.

Textbook Question

Would you expect acetate ion (CH₃CO₂⁻) to be a better nucleophile in an S_N2 reaction with an alkyl halide carried out in methanol or in dimethyl sulfoxide?

Textbook Question

Draw a perspective structure or a Fischer projection for the products of the following S_N2 reactions.

(f)

Textbook Question

Predict the compound in each pair that will undergo the S_N2 reaction faster.

(c)

(d)

Textbook Question

For each pair of compounds, state which compound is the better S_N2 substrate.

c. 2-bromobutane or isopropyl bromide

d. 1-chloro-2,2-dimethylbutane or 2-chlorobutane

e. 1-iodobutane or 2-iodopropane

Textbook Question

Triethyloxonium tetrafluoroborate, (CH₃CH₂)₃O⁺ BF₄^–, is a solid with melting point 91–92°C. Show how this reagent can transfer an ethyl group to a nucleophile (Nuc:⁻) in an S_N2 reaction. What is the leaving group? Why might this reagent be preferred to using an ethyl halide? (Consult Table 6-2)

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Draw a perspective structure or a Fischer projection for the products of the following SN2 reactions.(e)

Key Concepts

S<sub>N</sub>2 Mechanism

Fischer Projection

Nucleophiles and Electrophiles

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Draw a perspective structure or a Fischer projection for the products of the following S_N2 reactions.
(e)