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

10. Addition Reactions

Markovnikov

Organic Chemistry

10. Addition Reactions

Markovnikov

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4:24 minutes

Problem 6a,b

Textbook Question

To which compound is the addition of HBr more highly regioselective?
a.
b.

Verified step by step guidance

Step 1: Understand the concept of regioselectivity in addition reactions. Regioselectivity refers to the preference for the formation of one constitutional isomer over another in a chemical reaction. In the case of HBr addition to alkenes, the Markovnikov rule applies, which states that the hydrogen atom from HBr will add to the carbon with more hydrogen atoms (less substituted), and the bromine atom will add to the carbon with fewer hydrogen atoms (more substituted).

Step 2: Analyze the first pair of compounds (CH3CH2C=CH2 vs CH3C=CHCH3). In CH3CH2C=CH2, the double bond is terminal, meaning one of the carbons in the double bond is bonded to only one other carbon atom. In CH3C=CHCH3, the double bond is internal, meaning both carbons in the double bond are bonded to other carbon atoms. Terminal alkenes generally exhibit higher regioselectivity because the difference in substitution between the two carbons in the double bond is more pronounced.

Step 3: Analyze the second pair of compounds (cyclohexene with CH2 vs cyclohexene with CH3). In the first compound, the double bond is terminal, with one carbon bonded to only one other carbon atom. In the second compound, the double bond is internal, with both carbons bonded to other carbon atoms. Similar to the first pair, terminal alkenes tend to show higher regioselectivity due to the greater difference in substitution between the two carbons in the double bond.

Step 4: Compare the regioselectivity of HBr addition to the compounds in each pair. For both pairs, the terminal alkenes (CH3CH2C=CH2 and cyclohexene with CH2) are expected to exhibit higher regioselectivity because the Markovnikov addition of HBr is more pronounced when there is a clear difference in substitution between the two carbons in the double bond.

Step 5: Conclude that the addition of HBr is more highly regioselective to the terminal alkenes in both pairs of compounds. This is due to the greater difference in substitution between the carbons in the double bond, which makes the Markovnikov rule more applicable.

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Key Concepts

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

Regioselectivity

Regioselectivity refers to the preference of a chemical reaction to occur at one location over another in a molecule. In the context of electrophilic addition reactions, such as the addition of HBr to alkenes, regioselectivity determines which carbon atom of the double bond will bond with the bromine atom and which will bond with the hydrogen atom, leading to different products.

Markovnikov's Rule

Markovnikov's Rule states that in the addition of HX (where X is a halogen) to an alkene, the hydrogen atom will attach to the carbon with the greater number of hydrogen atoms already attached. This rule helps predict the major product of the reaction, as it indicates the regioselectivity based on the stability of the carbocation intermediates formed during the reaction.

Carbocation Stability

Carbocation stability is a key factor in determining the outcome of electrophilic addition reactions. More stable carbocations, such as tertiary carbocations, are favored during the reaction process. The stability is influenced by factors such as the degree of substitution and resonance, which can affect the regioselectivity of the addition of HBr to alkenes.

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