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

11. Radical Reactions

Radical Selectivity

Organic Chemistry

11. Radical Reactions

Radical Selectivity

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3:20 minutes

Problem 43(3)a,b

Textbook Question

For each alkane, which monobrominated derivatives could you form in good yield by free-radical bromination?
a. Cyclopentane
b. Methylcyclopentnae

Verified step by step guidance

Identify the structure of the given alkanes: Cyclopentane is a cyclic alkane with five carbon atoms in a ring, and Methylcyclopentane is a cyclopentane ring with a single methyl group attached to one of the carbons.

Understand the concept of free-radical bromination: Bromination occurs at the most stable radical intermediate, which is determined by the stability of the carbon radical formed during the reaction. Radical stability follows the order: tertiary > secondary > primary > methyl.

For Cyclopentane: All hydrogens in cyclopentane are equivalent because of the symmetry of the molecule. Bromination at any carbon will yield the same product, 1-bromocyclopentane.

For Methylcyclopentane: The hydrogens are not equivalent due to the presence of the methyl group. Identify the different types of hydrogens: (1) Hydrogens on the methyl group (primary hydrogens), (2) Hydrogens on the carbon adjacent to the methyl group (secondary hydrogens), and (3) Hydrogens on the other carbons in the ring (secondary hydrogens). Bromination will preferentially occur at the secondary carbon adjacent to the methyl group because it forms the most stable radical.

Conclude the products: For Cyclopentane, the product is 1-bromocyclopentane. For Methylcyclopentane, the major product is bromination at the secondary carbon adjacent to the methyl group, forming 1-bromo-2-methylcyclopentane. Minor products may form from bromination at other secondary or primary positions, but these are less favored.

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Key Concepts

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

Free-Radical Bromination

Free-radical bromination is a reaction mechanism where bromine (Br2) reacts with alkanes in the presence of heat or light to form brominated products. This process involves the generation of bromine radicals, which abstract hydrogen atoms from the alkane, leading to the formation of alkyl radicals. These alkyl radicals can then react with bromine molecules to yield monobrominated derivatives. The selectivity of this reaction is influenced by the stability of the resulting radicals.

Alkane Structure and Reactivity

Alkanes are saturated hydrocarbons characterized by single carbon-carbon bonds. Their reactivity in free-radical bromination depends on the structure of the alkane, including the presence of branching and cyclic structures. For example, cyclopentane and methylcyclopentane have different reactivity patterns due to their unique structures, which affect the stability of the radicals formed during bromination. Understanding these structural features is crucial for predicting the products of the reaction.

Monobrominated Derivatives

Monobrominated derivatives are organic compounds formed when one hydrogen atom in an alkane is replaced by a bromine atom. The formation of these derivatives during free-radical bromination can lead to multiple products, especially in branched or cyclic alkanes, due to the presence of different hydrogen environments. Identifying the possible monobrominated products requires analyzing the alkane's structure and the positions where bromination can occur, which is essential for understanding the yields of the reaction.

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