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

9. Alkenes and Alkynes

Zaitsev Rule

Organic Chemistry

9. Alkenes and Alkynes

Zaitsev Rule

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6:34 minutes

Problem 33(3)

Textbook Question

a. What is the major product obtained when each of the following compounds undergoes an E2 reaction with methoxide ion? Show the configuration of the product.
b. Does the product obtained depend on whether you start with the R or S enantiomer of the reactant?
3.

Verified step by step guidance

Step 1: Identify the type of reaction. The problem specifies an E2 elimination reaction, which is a bimolecular elimination mechanism. In E2 reactions, a strong base (methoxide ion in this case) removes a proton from a β-carbon, and simultaneously, the leaving group (chlorine here) departs from the α-carbon, forming a double bond.

Step 2: Analyze the structure of the reactant. The compound provided is a benzylic halide with a chlorine atom attached to a secondary carbon. The β-hydrogens are located on the adjacent carbons to the α-carbon (the carbon bonded to chlorine).

Step 3: Determine the stereochemical requirement for E2 elimination. E2 reactions require the β-hydrogen and the leaving group to be anti-periplanar (in opposite planes). This stereochemical alignment ensures the elimination proceeds efficiently.

Step 4: Predict the major product. The elimination will result in the formation of a double bond between the α-carbon and the β-carbon. Since the β-carbon adjacent to the benzene ring is more substituted, the major product will follow Zaitsev's rule, favoring the more substituted alkene. The configuration of the product will depend on the anti-periplanar arrangement of the β-hydrogen and chlorine during elimination.

Step 5: Address the stereochemical question. The product obtained does not depend on whether the starting material is the R or S enantiomer because the E2 mechanism is stereospecific and depends only on the anti-periplanar geometry of the β-hydrogen and leaving group, not the absolute configuration of the reactant.

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Key Concepts

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

E2 Reaction Mechanism

The E2 (bimolecular elimination) reaction is a type of elimination reaction where a base removes a proton from a substrate while a leaving group departs simultaneously. This concerted mechanism results in the formation of a double bond. The stereochemistry of the product is influenced by the anti-periplanar arrangement of the leaving group and the hydrogen being removed.

Stereochemistry and Configuration

Stereochemistry refers to the spatial arrangement of atoms in molecules and how this affects their chemical behavior. In the context of E2 reactions, the configuration of the starting material (R or S) can influence the stereochemical outcome of the product. Understanding how to depict and interpret configurations is crucial for predicting the major product.

Enantiomers and Reaction Outcomes

Enantiomers are pairs of molecules that are non-superimposable mirror images of each other. In E2 reactions, the starting enantiomer can lead to different products based on the stereochemical orientation of the reactant. This means that the product may vary depending on whether the reaction starts with the R or S enantiomer, affecting the final configuration of the product.

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