Textbook Question
Devise a synthesis for each compound, starting with methylenecyclohexane and any other reagents you need.
b. cyclohexylmethanol
10. Addition Reactions
Hydroboration
2:42 minutesProblem 57a(10)
Textbook Question
a. Show the reagents required to form the primary alcohol in each of the following reactions.
Verified step by step guidance1
Step 1: Analyze the starting material and the product. The starting material is an alkene (propene), and the product is a primary alcohol (propan-1-ol). This indicates that the reaction involves the addition of an -OH group to the terminal carbon of the alkene.
Step 2: Recognize the type of reaction. To convert an alkene to a primary alcohol, hydroboration-oxidation is a common method. This reaction proceeds via anti-Markovnikov addition, where the -OH group is added to the less substituted carbon.
Step 3: Identify the reagents for hydroboration-oxidation. The first step requires a borane reagent, such as BH₃·THF (borane-tetrahydrofuran complex), to perform hydroboration. The second step involves oxidation using hydrogen peroxide (H₂O₂) in the presence of a base, such as sodium hydroxide (NaOH).
Step 4: Describe the mechanism briefly. In the hydroboration step, the borane adds to the alkene in a concerted mechanism, forming an organoborane intermediate. In the oxidation step, the organoborane reacts with H₂O₂ and NaOH to replace the boron atom with an -OH group, yielding the primary alcohol.
Step 5: Summarize the reaction conditions. The overall reaction requires two steps: (1) hydroboration with BH₃·THF, and (2) oxidation with H₂O₂ and NaOH. These reagents ensure the formation of the primary alcohol via anti-Markovnikov addition.
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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 process used to convert alkenes into alcohols. In the first step, an alkene reacts with diborane (B2H6) to form a trialkylborane intermediate. This step is characterized by the addition of boron across the double bond in a syn fashion, leading to the formation of a primary alcohol upon oxidation in the second step, typically using hydrogen peroxide (H2O2) in a basic solution.
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Regioselectivity
Regioselectivity refers to the preference of a chemical reaction to yield one structural isomer over others when multiple possibilities exist. In hydroboration, the boron atom adds to the less substituted carbon of the alkene, resulting in the formation of a primary alcohol. This regioselectivity is crucial for synthesizing specific alcohols from alkenes, as it determines the final product's structure.
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Primary Alcohols
Primary alcohols are organic compounds where the hydroxyl (-OH) group is attached to a carbon atom that is bonded to only one other carbon atom. They are typically formed from the hydroboration-oxidation of alkenes, where the reaction favors the formation of the least substituted alcohol. Understanding the structure and properties of primary alcohols is essential for predicting their reactivity and applications in organic synthesis.
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