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

Dehydrohalogenation

Organic Chemistry

9. Alkenes and Alkynes

Dehydrohalogenation

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1:14 minutes

Problem 50e

Textbook Question

Predict the products formed by sodium hydroxide-promoted dehydrohalogenation of the following compounds. In each case, predict which will be the major product.
e. trans-1-bromo-2-methylcyclohexane

Verified step by step guidance

Identify the type of reaction: Sodium hydroxide (NaOH) is a strong base, and the reaction involves dehydrohalogenation, which is an elimination reaction (E2 mechanism). This means a β-hydrogen will be removed along with the halogen (bromine) to form a double bond.

Locate the β-hydrogens: In trans-1-bromo-2-methylcyclohexane, the bromine atom is attached to carbon-1. The β-hydrogens are located on the carbons adjacent to carbon-1 (i.e., carbon-2 and carbon-6).

Determine the stereochemistry: Since the compound is trans, the β-hydrogen and the bromine atom must be anti-periplanar (in opposite planes) for the E2 elimination to occur. Analyze the chair conformation of the cyclohexane ring to identify which β-hydrogen satisfies this condition.

Predict the possible products: Removing a β-hydrogen from carbon-2 or carbon-6 will result in the formation of a double bond. This will lead to the formation of two possible alkenes: one with the double bond between carbon-1 and carbon-2, and the other with the double bond between carbon-1 and carbon-6.

Determine the major product: According to Zaitsev's rule, the more substituted alkene (the one with more alkyl groups attached to the double-bonded carbons) is typically the major product. Compare the substitution patterns of the two possible alkenes to predict the major product.

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Key Concepts

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

Dehydrohalogenation

Dehydrohalogenation is an elimination reaction where a hydrogen halide (HX) is removed from a molecule, typically resulting in the formation of a double bond. In the context of organic chemistry, this reaction often occurs in the presence of a strong base, such as sodium hydroxide, which abstracts a proton from the carbon adjacent to the halogen, leading to the formation of alkenes.

Zaitsev's Rule

Zaitsev's Rule states that in elimination reactions, the more substituted alkene is generally the major product. This is because more substituted alkenes are more stable due to hyperconjugation and the inductive effect. Understanding this rule is crucial for predicting the major product in dehydrohalogenation reactions, especially when multiple elimination products are possible.

Stereochemistry of Alkenes

Stereochemistry refers to the spatial arrangement of atoms in molecules and is particularly important in the formation of alkenes. In the case of trans-1-bromo-2-methylcyclohexane, the stereochemical configuration will influence the stability and formation of the alkene product. The formation of cis or trans alkenes can affect their reactivity and physical properties, making it essential to consider stereochemistry when predicting products.

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Related Practice

Textbook Question

Predict the dehydrohalogenation product(s) that result when the following alkyl halides are heated in alcoholic KOH. When more than one product is formed, predict the major and minor products.

(a)

(b)

(c)

Textbook Question

Predict the dehydrohalogenation product(s) that result when the following alkyl halides are heated in alcoholic KOH. When more than one product is formed, predict the major and minor products.

(f)

Textbook Question

Predict the products formed by sodium hydroxide-promoted dehydrohalogenation of the following compounds. In each case, predict which will be the major product.

a. 1-bromobutane

b. 2-chlorobutane

c. 3-bromopentane

Textbook Question

Predict the products formed by sodium hydroxide-promoted dehydrohalogenation of the following compounds. In each case, predict which will be the major product.

d. cis-1-bromo-2-methylcyclohexane

Textbook Question

What halides would undergo E2 dehydrohalogenation to give the following pure alkenes?

d. methylenecyclohexane

Textbook Question

What halides would undergo E2 dehydrohalogenation to give the following pure alkenes?

e. 4-methylcyclohexene

Multiple Choice

Predict the major, organic product for the following reaction.

Multiple Choice

Predict the major, organic product for the following reaction.

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