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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4:37 minutes

Problem 18

Textbook Question

Draw a transition state for the following substitution reaction.

Verified step by step guidance

Identify the type of substitution reaction: This is an SN2 reaction, as the nucleophile (acetylide ion, H₃C―C≡C⁻) directly attacks the electrophilic carbon in the methyl chloride (H₃C―Cl), leading to a single-step mechanism.

Understand the transition state: In an SN2 reaction, the transition state involves simultaneous bond formation and bond breaking. The nucleophile forms a new bond with the electrophilic carbon while the leaving group (Cl⁻) begins to detach.

Draw the structure of the transition state: Represent the central carbon atom of the methyl chloride as partially bonded to both the nucleophile (H₃C―C≡C⁻) and the leaving group (Cl⁻). Use dashed lines to indicate partial bonds in the transition state.

Include the geometry of the transition state: The central carbon in the transition state adopts a trigonal bipyramidal geometry, with the nucleophile and leaving group positioned opposite each other (anti-periplanar) to minimize steric hindrance.

Label charges and partial bonds: Indicate the negative charge on the acetylide ion (H₃C―C≡C⁻) and the partial negative charge on the leaving group (Cl⁻). Ensure the transition state reflects the simultaneous bond-making and bond-breaking process.

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Key Concepts

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

Transition State

A transition state is a high-energy, unstable arrangement of atoms that occurs during a chemical reaction. It represents the point at which reactants are transformed into products, and it cannot be isolated. In the context of a substitution reaction, the transition state is crucial for understanding the mechanism and energy changes involved as the nucleophile attacks the electrophile.

Nucleophilic Substitution

Nucleophilic substitution is a fundamental reaction in organic chemistry where a nucleophile replaces a leaving group in a molecule. In this case, the acetylide ion (H₃C―C ≡ C⁻) acts as the nucleophile, attacking the carbon atom bonded to chlorine in H₃C―Cl. Understanding the mechanism of this reaction, whether it follows an SN1 or SN2 pathway, is essential for predicting the structure of the transition state.

Reaction Mechanism

A reaction mechanism describes the step-by-step process by which reactants are converted into products, detailing the bonds that are broken and formed. In substitution reactions, the mechanism can influence the stereochemistry and kinetics of the reaction. Analyzing the mechanism helps in visualizing the transition state and understanding the factors that affect the reaction rate and outcome.

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Related Practice

Textbook Question

Rank the following alkyl bromides from most reactive to least reactive in an S_N2 reaction:

1-bromo-2-methylbutane, 1-bromo-3-methylbutane, 2-bromo-2-methylbutane, and 1-bromopentane.

Textbook Question

Which alkyl halide is more reactive in an S_N2 reaction with a given nucleophile?

Textbook Question

Does increasing the energy barrier for an S_N2 reaction increase or decrease the magnitude of the rate constant for the reaction?

Textbook Question

The rate of the reaction of methyl iodide with quinuclidine was measured in nitrobenzene, and then the rate of the reaction of methyl iodide with triethylamine was measured in the same solvent. The concentration of the reagents was the same in both experiments.

a.Which reaction had the larger rate constant?

Textbook Question

Predict the major products of the following reactions.

(a) ethyl tosylate + potassium tert-butoxide

(b) isobutyl tosylate + NaI

Textbook Question

Practice your electron-pushing skills by drawing a mechanism for the following S_N2 reactions.

(a)

Textbook Question

Practice your electron-pushing skills by drawing a mechanism for the following S_N2 reactions.

(b)

Textbook Question