Textbook Question
What stereoisomers are obtained from hydroboration–oxidation of the following compounds? Assign an R or S configuration to each asymmetric center.
c. cis-2-butene
10. Addition Reactions
Hydroboration
4:37 minutesProblem 13c
Textbook Question
Predict the major products of the following reactions. Include stereochemistry where applicable.
(c) 
Verified step by step guidance1
Step 1: Recognize the reaction type. The given reaction involves hydroboration-oxidation, which is a two-step process used to convert alkenes into alcohols. The first step uses BH3⋅THF (borane in tetrahydrofuran) to add boron and hydrogen across the double bond, and the second step uses H2O2 and OH⁻ to replace the boron with a hydroxyl group.
Step 2: Understand the regioselectivity. Hydroboration-oxidation follows anti-Markovnikov addition, meaning the hydroxyl group (-OH) will be added to the less substituted carbon of the double bond, while the hydrogen will be added to the more substituted carbon.
Step 3: Consider stereochemistry. Hydroboration-oxidation proceeds with syn addition, meaning both the hydrogen and hydroxyl group will be added to the same face of the molecule. This is important for determining the stereochemistry of the product.
Step 4: Analyze the structure of the starting material. The starting material is a bicyclic compound with a double bond. The double bond is between a bridgehead carbon and a secondary carbon. The hydroxyl group will be added to the secondary carbon (less substituted), and the hydrogen will be added to the bridgehead carbon (more substituted).
Step 5: Predict the major product. After the reaction, the hydroxyl group will be added to the less substituted carbon of the double bond, and the hydrogen will be added to the more substituted carbon. Both groups will be added to the same face of the molecule, resulting in a syn addition product. Ensure stereochemistry is properly represented in the final structure.
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Video duration:
4mKey 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 process used to convert alkenes into alcohols. In the first step, borane (BH3) adds across the double bond of the alkene in a syn addition, resulting in an organoborane intermediate. The second step involves oxidation with hydrogen peroxide (H2O2) and hydroxide (OH-), which replaces the boron atom with a hydroxyl group, yielding an alcohol with anti-Markovnikov orientation.
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General properties of hydroboration-oxidation.
Stereochemistry
Stereochemistry refers to the study of the spatial arrangement of atoms in molecules and how this affects their chemical behavior. In reactions involving chiral centers, the stereochemistry of the products can be crucial. For hydroboration-oxidation, the syn addition of borane leads to specific stereochemical outcomes, which must be considered when predicting the major products of the reaction.
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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 the context of hydroboration-oxidation, the reaction is regioselective for the formation of alcohols at the less substituted carbon of the alkene, following the anti-Markovnikov rule. Understanding regioselectivity is essential for predicting the major products in reactions involving unsymmetrical alkenes.
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