Predict the products you would get when the following alkenes undergo (i) hydroboration–oxidation (1. BH 3 2. NaOH, H 2 O 2 or (ii) oxymercuration–reduction [1. Hg(OAc) 2 , H 2 O 2. NaBH 4 ]. (a)

Hello, everyone. Today, we have the following problem. More products are generated when the given compound is treated with the following reagents. So first, we have our bora that is reacting with sodium hydroxide and we have our hydrogen peroxide. So this essentially is hydro beration oxidation wherein our hydroxy group is added to the less substituted carbon. So if we were to draw out our products, we would have our hydroxy group on the less substituted carbon of our alkanna circle. And since we are forming a stereo isomers, we will have a rece mixture with the following where we have our hydroxy group on a wedge and on a dash. And then the other group is added in the, in the same fashion. For our second reaction, we have essentially oxy meer operation reduction reaction where we used mercury, water and sodium bore hydro. And this will add hydroxyl group to the more substituted carbon as indicated by the square on the reactant. So what that looks like is essentially we have our hydroxyl group that will also be on a wedge again at a dash as we have formed a reca mixture. So we perform the following as our products and with that, we have solved the problem overall, I hope this helped and until next time.

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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

Hydroboration

Organic Chemistry

10. Addition Reactions

Hydroboration

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7:09 minutes

Problem 54a

Textbook Question

Predict the products you would get when the following alkenes undergo (i) hydroboration–oxidation (1. BH₃ 2. NaOH, H₂O₂ or (ii) oxymercuration–reduction [1. Hg(OAc)₂, H₂O 2. NaBH₄].
(a)

Verified step by step guidance

Step 1: Analyze the given alkene structure. The molecule contains a phenyl group (Ph) attached to a carbon chain with a double bond located between the second and third carbons in the chain.

Step 2: For hydroboration–oxidation (1. BH3, 2. NaOH, H2O2), the reaction proceeds via anti-Markovnikov addition of water across the double bond. The boron atom initially adds to the less substituted carbon of the double bond, followed by oxidation to replace the boron with a hydroxyl group (-OH). This results in the alcohol being formed at the less substituted carbon.

Step 3: For oxymercuration–reduction (1. Hg(OAc)2, H2O, 2. NaBH4), the reaction proceeds via Markovnikov addition of water across the double bond. The mercury intermediate forms at the more substituted carbon, and during reduction, the mercury is replaced with a hydroxyl group (-OH). This results in the alcohol being formed at the more substituted carbon.

Step 4: Consider stereochemistry. Hydroboration–oxidation typically results in syn addition (both the hydrogen and hydroxyl group add to the same face of the double bond), while oxymercuration–reduction does not involve stereospecificity.

Step 5: Predict the products. For hydroboration–oxidation, the alcohol will form at the less substituted carbon of the double bond. For oxymercuration–reduction, the alcohol will form at the more substituted carbon of the double bond. Ensure the phenyl group remains unaffected in both reactions.

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Key Concepts

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

Hydroboration-Oxidation

Hydroboration-oxidation is a two-step reaction that converts alkenes into alcohols. In the first step, BH₃ adds to the alkene, forming a trialkylborane intermediate. This is followed by oxidation with hydrogen peroxide (H₂O₂) and a base (NaOH), which converts the boron to an alcohol. This reaction is stereospecific and results in anti-Markovnikov addition, meaning the hydroxyl group attaches to the less substituted carbon.

Oxymercuration-Reduction

Oxymercuration-reduction is another method for converting alkenes to alcohols, involving two steps. Initially, the alkene reacts with mercuric acetate (Hg(OAc)₂) in the presence of water, leading to the formation of a mercurial intermediate. The subsequent reduction with sodium borohydride (NaBH₄) replaces the mercury with a hydrogen atom, yielding an alcohol. This reaction follows Markovnikov's rule, where the hydroxyl group attaches to the more substituted carbon.

Markovnikov's Rule

Markovnikov's rule is a principle in organic chemistry that predicts the outcome of electrophilic addition reactions to alkenes. It states that when HX (where X is a halogen or hydroxyl group) adds to an asymmetric alkene, the more stable carbocation will form, leading to the more substituted carbon receiving the electrophile. This rule is crucial for understanding the regioselectivity of reactions like oxymercuration-reduction, where the product distribution is influenced by the stability of the intermediates formed.

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