Ch.11 - Reactions of Alcohols

Wade9th EditionOrganic ChemistryISBN: 9780135213728당신이 사용하는 게 아니라요?교과서 변경

Wade 9th Edition

Ch.11 - Reactions of Alcohols

문제 63b

11장, 문제 63b

Alcohols combine with ketones and aldehydes to form interesting derivatives, which we will discuss in Chapter 18. The following reactions show the hydrolysis of two such derivatives. Propose mechanisms for these reactions.
(b)

검증된 단계별 안내

Step 1: Analyze the starting material and product. The starting material is a cyclic acetal (a compound with two ether groups attached to the same carbon), and the product is a ketone with a hydroxyl group attached to the adjacent carbon. This indicates hydrolysis of the acetal under acidic conditions.

Step 2: Protonation of the acetal oxygen. In the presence of acid (H⁺), one of the ether oxygen atoms in the acetal is protonated, increasing its electrophilicity and making the carbon attached to it more susceptible to nucleophilic attack.

Step 3: Water attacks the protonated acetal. A molecule of water (H₂O) acts as a nucleophile and attacks the electrophilic carbon, leading to the formation of a tetrahedral intermediate.

Step 4: Cleavage of the acetal bond. The tetrahedral intermediate undergoes bond cleavage, releasing one of the ether groups as an alcohol and forming a hemiacetal intermediate.

Step 5: Further hydrolysis of the hemiacetal. The hemiacetal undergoes another round of protonation and nucleophilic attack by water, leading to the formation of the final product: a ketone and an alcohol group.

비슷한 문제에 대한 검증된 영상 답변:

이 영상 해법은 위 문제에 도움이 된다고 튜터들이 추천한 것입니다.

영상 길이:

주요 개념

질문에 올바르게 답하기 위해 반드시 이해해야 하는 핵심 개념들은 다음과 같습니다.

Nucleophilic Addition

Nucleophilic addition is a fundamental reaction in organic chemistry where a nucleophile attacks an electrophilic carbon atom, typically found in carbonyl groups of aldehydes and ketones. This process leads to the formation of a tetrahedral intermediate, which can further react to yield various products, including alcohols. Understanding this mechanism is crucial for analyzing how alcohols interact with carbonyl compounds to form derivatives.

Hydrolysis Reactions

Hydrolysis reactions involve the breaking of chemical bonds through the reaction with water, often resulting in the formation of alcohols and acids. In the context of the question, hydrolysis of derivatives formed from alcohols and carbonyl compounds is essential to understand how these compounds revert to their original forms or transform into new products. Recognizing the conditions and mechanisms of hydrolysis is key to proposing accurate reaction mechanisms.

Reaction Mechanisms

A reaction mechanism is a step-by-step description of the pathway taken during a chemical reaction, detailing the sequence of elementary steps and the intermediates formed. Understanding reaction mechanisms is vital for predicting the products of reactions and for proposing how specific transformations occur. In this case, analyzing the mechanisms of hydrolysis for the derivatives formed from alcohols and carbonyls will help elucidate the overall reaction process.

관련 실천

교과서 질문

(b) Under the same conditions, an optically active sample of trans-2-bromocyclopentanol reacts with concentrated aqueous HBr to give an optically inactive product, (racemic) trans-1,2-dibromocyclopentane. Propose a mechanism to show how this reaction goes with apparently complete retention of configuration, yet with racemization. (Hint: Draw out the mechanism of the reaction of cyclopentene with Br₂ in water to give the starting material, trans-2- bromocyclopentanol. Consider how parts of this mechanism might be involved in the reaction with HBr.)

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교과서 질문

(a) The reaction of butan-2-ol with concentrated aqueous HBr goes with partial racemization, giving more inversion than retention of configuration. Propose a mechanism that accounts for racemization with excess inversion.

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교과서 질문

Under normal circumstances, tertiary alcohols are not oxidized. However, when the tertiary alcohol is allylic, it can undergo a migration of the double bond (called an allylic shift) and subsequent oxidation of the alcohol. A particularly effective reagent for this reaction is Bobbitt's reagent, similar to TEMPO used in many oxidations. (M. Shibuya et al., J. Org. Chem., 2008, 73, 4750.)

Show the expected product when each of these 3° allylic alcohols is oxidized by Bobbitt's reagent.

(a)

(b)

Show the expected product when each of these 3° allylic alcohols is oxidized by Bobbitt’s reagent

(c)

(d)

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교과서 질문

Alcohols combine with ketones and aldehydes to form interesting derivatives, which we will discuss in Chapter 18. The following reactions show the hydrolysis of two such derivatives. Propose mechanisms for these reactions.

(a)

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Alcohols combine with ketones and aldehydes to form interesting derivatives, which we will discuss in Chapter 18. The following reactions show the hydrolysis of two such derivatives. Propose mechanisms for these reactions.(b)

비슷한 문제에 대한 검증된 영상 답변:

주요 개념

Nucleophilic Addition

Hydrolysis Reactions

Reaction Mechanisms

Alcohols combine with ketones and aldehydes to form interesting derivatives, which we will discuss in Chapter 18. The following reactions show the hydrolysis of two such derivatives. Propose mechanisms for these reactions.
(b)