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Ch. 8 - Alkenes I: Properties and Electrophilic Additions
Mullins - Organic Chemistry: A Learner Centered Approach 1st Edition
Mullins1st EditionOrganic Chemistry: A Learner Centered ApproachISBN: 9780137566471Not the one you use?Change textbook
All textbooksMullins 1st EditionCh. 8 - Alkenes I: Properties and Electrophilic AdditionsProblem 55d
Chapter 7, Problem 55d

Suggest an alkene to undergo hydroboration–oxidation (1. BH3 2. NaOH, H2O2) to give exclusively the alcohols shown. Pay close attention to the relative (but not absolute) stereochemical outcome.
(d) Chemical structure of an alcohol derived from hydroboration-oxidation, featuring a five-membered ring and a hydroxyl group.

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1
Identify the alcohol product(s) formed after hydroboration–oxidation. Hydroboration–oxidation of an alkene results in an anti-Markovnikov addition of water, where the hydroxyl group (-OH) attaches to the less substituted carbon of the double bond.
Analyze the stereochemistry of the alcohol product(s). Hydroboration–oxidation proceeds with syn addition, meaning that the hydrogen (H) and hydroxyl group (-OH) are added to the same face of the alkene. This stereochemical outcome must be considered when proposing the starting alkene.
Propose a potential alkene structure. The starting alkene should have a double bond positioned such that the anti-Markovnikov addition of water leads to the observed alcohol product(s) with the correct stereochemistry.
Verify the stereochemical relationship between the proposed alkene and the alcohol product(s). Ensure that the syn addition mechanism of hydroboration–oxidation aligns with the relative stereochemistry of the alcohol product(s).
Confirm that the proposed alkene is consistent with the reaction conditions and the exclusive formation of the given alcohol product(s). If necessary, adjust the structure of the alkene to ensure it matches the observed outcome.

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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, borane (BH₃) adds across the double bond of the alkene, resulting in a trialkylborane intermediate. The second step involves oxidation with hydrogen peroxide (H₂O₂) in a basic solution, which replaces the boron atom with a hydroxyl group, yielding an alcohol. This reaction is notable for its syn-addition mechanism, leading to specific stereochemical outcomes.
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General properties of hydroboration-oxidation.

Stereochemistry

Stereochemistry refers to the spatial arrangement of atoms in molecules and how this affects their chemical behavior. In the context of hydroboration-oxidation, the reaction proceeds with syn-addition, meaning that the boron and hydrogen atoms add to the same side of the double bond. This results in a specific stereochemical configuration of the resulting alcohol, which is crucial for predicting the product's properties and reactivity.
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Regioselectivity

Regioselectivity is the preference of a chemical reaction to yield one structural isomer over others when multiple possibilities exist. In hydroboration-oxidation, the boron atom adds to the less substituted carbon of the alkene, leading to the formation of the more stable, less sterically hindered alcohol. Understanding regioselectivity is essential for predicting the outcome of the reaction and ensuring the desired alcohol is produced.
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Related Practice
Textbook Question

Unlike hydroboration–oxidation, the addition of H2O catalyzed by H3O+ is not stereospecific. Thinking carefully about the mechanism of the reaction, give two reasons why.

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Textbook Question

The first step of oxymercuration–reduction is stereospecific, and yet this fact wasn't emphasized in that discussion. Show the stereospecificity of the first step for the following alkene and then explain why the stereospecificity becomes unimportant after the second step.

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Textbook Question

Suggest an alkene to undergo hydroboration–oxidation (1. BH3 2. NaOH, H2O2) to give exclusively the alcohols shown. Pay close attention to the relative (but not absolute) stereochemical outcome.

(c)

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Textbook Question

Predict the major product(s) of the following elimination reactions, paying close attention to the stereochemical outcome of the reactions.

(e) 

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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)

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Textbook Question

Predict the products you would get when the following alkenes undergo (ii) oxymercuration–reduction [1. Hg(OAc)2 , H2O 2. NaBH4 ].

(b)

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