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Ch.11 - Reactions of Alcohols
Wade - Organic Chemistry 9th Edition
Wade9th EditionOrganic ChemistryISBN: 9780135213728당신이 사용하는 게 아니라요?교과서 변경
모든 교과서Wade 9th EditionCh.11 - Reactions of Alcohols문제 60
11장, 문제 60

The Williamson ether synthesis involves the displacement of an alkyl halide or tosylate by an alkoxide ion. Would the synthesis shown be possible by making a tosylate and displacing it? If so, show the sequence of reactions. If not, explain why not and show an alternative synthesis that would be more likely to work.

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Step 1: Analyze the starting material and the product. The starting material is an alcohol (-OH group) attached to a bicyclic structure, and the product is an ether (-OCH₃ group) attached to the same bicyclic structure. The Williamson ether synthesis involves converting the alcohol into a good leaving group (e.g., tosylate) and then performing an SN2 reaction with an alkoxide ion.
Step 2: Consider the feasibility of the SN2 reaction. The bicyclic structure in the starting material is highly sterically hindered, which makes an SN2 reaction difficult. In an SN2 reaction, the nucleophile must approach the electrophilic carbon directly from the opposite side of the leaving group, but steric hindrance in this structure would block such an approach.
Step 3: Propose an alternative synthesis. Since the SN2 reaction is unlikely to succeed due to steric hindrance, an alternative method such as the use of an alkyl halide and silver oxide (Ag₂O) to form the ether might be more effective. This method avoids the steric hindrance issues associated with the SN2 mechanism.
Step 4: Outline the alternative synthesis. First, convert the alcohol into an alkyl halide using a reagent like thionyl chloride (SOCl₂) or phosphorus tribromide (PBr₃). Then, react the alkyl halide with methanol (CH₃OH) in the presence of silver oxide (Ag₂O) to form the desired ether.
Step 5: Summarize the reasoning. The tosylate approach is not feasible due to steric hindrance preventing the SN2 displacement. The alternative synthesis using an alkyl halide and silver oxide is more likely to succeed in forming the ether product.

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주요 개념

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Williamson Ether Synthesis

The Williamson ether synthesis is a method for creating ethers through the nucleophilic substitution of an alkyl halide or tosylate by an alkoxide ion. This reaction typically requires a strong nucleophile and is favored by primary alkyl halides to minimize steric hindrance, which can lead to elimination reactions instead of substitution.
추천 영상:
03:50
The Mechanism of Williamson Ether Synthesis.

Tosylate Formation

Tosylates are derivatives of alcohols formed by reacting an alcohol with tosyl chloride, making the alcohol a better leaving group. This transformation is crucial in the Williamson ether synthesis as it allows for the use of secondary or tertiary alcohols, which would otherwise be less reactive in nucleophilic substitution due to steric hindrance.
추천 영상:
02:26
Formation of Enolates

Nucleophilic Substitution Mechanisms

Nucleophilic substitution can occur via two main mechanisms: SN1 and SN2. The SN2 mechanism involves a single concerted step where the nucleophile attacks the electrophile, displacing the leaving group. In contrast, the SN1 mechanism involves the formation of a carbocation intermediate, making it more favorable for tertiary substrates but less so for primary ones due to steric hindrance.
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01:47
Nucleophiles and Electrophiles can react in Substitution Reactions.
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