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

15. Analytical Techniques:IR, NMR, Mass Spect

1H NMR:Number of Signals

Organic Chemistry

15. Analytical Techniques:IR, NMR, Mass Spect

1H NMR:Number of Signals

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7:10 minutes

Problem 70

Textbook Question

How can ¹H NMR be used to prove that the addition of HBr to propene follows the rule that says that the electrophile adds to the sp² carbon bonded to the most hydrogens?

Verified step by step guidance

Understand the reaction: The addition of HBr to propene follows Markovnikov's rule, which states that the electrophile (H⁺) adds to the sp² carbon with the most hydrogens, forming 2-bromopropane as the major product.

Analyze the products: If Markovnikov's rule is followed, the major product will be 2-bromopropane. If the rule is not followed, the product would be 1-bromopropane. These two products have distinct ¹H NMR spectra.

Identify key signals in the ¹H NMR spectrum: For 2-bromopropane, the methyl group attached to the brominated carbon will show a doublet due to splitting by the adjacent methine proton. The methine proton will appear as a multiplet. For 1-bromopropane, the methylene group adjacent to the bromine will show a triplet, and the terminal methyl group will show a triplet as well.

Compare the integration of peaks: The integration of the peaks in the ¹H NMR spectrum will correspond to the number of protons in each environment. For 2-bromopropane, the integration ratio will match the expected proton counts for the methyl, methine, and other groups. For 1-bromopropane, the integration will differ due to the different proton environments.

Conclude based on the spectrum: If the ¹H NMR spectrum matches the expected pattern for 2-bromopropane, it confirms that the addition of HBr to propene followed Markovnikov's rule, with the electrophile (H⁺) adding to the sp² carbon bonded to the most hydrogens.

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Key Concepts

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

1H NMR Spectroscopy

1H NMR (Proton Nuclear Magnetic Resonance) spectroscopy is a powerful analytical technique used to determine the structure of organic compounds. It provides information about the number of hydrogen atoms in different environments within a molecule, allowing chemists to infer connectivity and functional groups. In the context of propene and HBr addition, 1H NMR can reveal the relative positions of hydrogen atoms, helping to confirm the regioselectivity of the reaction.

Electrophilic Addition Mechanism

The electrophilic addition mechanism describes how electrophiles react with alkenes, such as propene, to form more saturated products. In this process, the electrophile (HBr) adds to the sp2 carbon of the alkene, which is more electron-rich. According to Markovnikov's rule, the electrophile will preferentially add to the carbon atom that is bonded to the most hydrogens, leading to the formation of the more stable carbocation intermediate.

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 outcome of reactions involving alkenes and is crucial for understanding regioselectivity. In the case of propene reacting with HBr, applying this rule allows chemists to anticipate the major product formed and verify it through 1H NMR analysis.

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