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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5:40 minutes

Problem 45c

Textbook Question

What products will be obtained from the E2 reaction of the following alkyl halides?
c.

Verified step by step guidance

Step 1: Identify the alkyl halide structure. The given compound is 3-chloro-2-methyl-2-pentene. The chlorine atom is attached to the third carbon, and there is a double bond between the second and third carbons.

Step 2: Understand the E2 elimination mechanism. E2 reactions require a strong base and proceed via a single-step mechanism where the base abstracts a proton from a β-carbon (adjacent to the carbon bearing the leaving group), and the leaving group (Cl) departs simultaneously, forming a double bond.

Step 3: Determine the β-hydrogens available for elimination. In this molecule, the β-carbons are the first and fourth carbons relative to the carbon bearing the chlorine atom. The first carbon has three hydrogens, while the fourth carbon has one hydrogen.

Step 4: Consider the stereoelectronic requirement for E2 elimination. The β-hydrogen and the leaving group must be anti-periplanar (opposite sides of the same plane). This geometry will dictate which β-hydrogen can be abstracted by the base.

Step 5: Predict the products. Depending on the β-hydrogen abstracted, elimination will result in the formation of different alkenes. If a hydrogen from the first carbon is abstracted, the product will be 2-methyl-1-pentene. If the hydrogen from the fourth carbon is abstracted, the product will be 2,3-dimethyl-2-pentene. Both products are possible depending on the reaction conditions.

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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 reaction is a type of elimination reaction where a base removes a proton from a β-carbon, leading to the simultaneous departure of a leaving group, typically a halide. This concerted mechanism results in the formation of a double bond between the α and β carbons. Understanding the stereochemistry and the requirement for anti-periplanar geometry is crucial for predicting the products.

Alkyl Halides

Alkyl halides are organic compounds containing a carbon atom bonded to a halogen atom (such as chlorine, bromine, or iodine). The reactivity of alkyl halides in elimination reactions depends on their structure, including whether they are primary, secondary, or tertiary. The type of alkyl halide influences the mechanism and the products formed during the E2 reaction.

Stereochemistry in E2 Reactions

Stereochemistry plays a significant role in E2 reactions, as the elimination must occur in an anti-periplanar arrangement for optimal overlap of orbitals. This means that the hydrogen atom being removed and the leaving group must be on opposite sides of the molecule. Recognizing the spatial arrangement of substituents is essential for predicting the correct alkene products formed from the reaction.

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Related Practice

Textbook Question

Predict the products of E1 elimination of the following compounds. Label the major products.

(a)

Textbook Question

When using sulfuric acid, but in the absence of other nucleophiles like water or bromide ion, less stable alkenes can be isomerized to their more stable isomer. Provide a mechanism for these acid-catalyzed isomerization reactions. [This is one illustration of the principle of microscopic reversibility.]

(b)

Textbook Question

For each of the following reactions, draw the major elimination product; if the product can exist as stereoisomers, indicate which stereoisomer is obtained in greater yield.

e. 3-bromo-3-methylpentane + high concentration of CH₃CH₂O⁻

f. 3-bromo-3-methylpentane + CH₃CH2OH

Textbook Question

Which alkyl halide in each pair is more reactive in an E2 reaction with hydroxide ion?

Textbook Question

Draw the elimination products for each of the following E2 reactions; if the products can exist as stereoisomers, indicate which stereoisomers are obtained.

d. (2R,3R)-2-chloro-3-methylpentane + high concentration of CH₃O^-

Textbook Question

What is the major elimination product obtained from an E2 reaction of each of the following alkyl halides with hydroxide ion?

Multiple Choice

What is the major product of the reaction?

Multiple Choice

What is the major product of the reaction?

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