Predict the major product(s) that would result when molecules (a)–(i) are allowed to react under the following conditions. (iv) chlorocyclopentane, AlCl3, (v) 1-chloro-1-methylcyclohexane , AlCl3, (vi) PhCOCl, AlCl3. If no reaction will occur, indicate by writing NR.(a)

Ch. 23 - Benzene I: Aromatic Stability and Substitution Reactions

Mullins - Organic Chemistry: A Learner Centered Approach 1st Edition

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Ch. 23 - Benzene I: Aromatic Stability and Substitution Reactions

Problem 72a

Chapter 22, Problem 72a

Predict the major product(s) that would result when molecules (a)–(i) are allowed to react under the following conditions. (iv) chlorocyclopentane, AlCl₃, (v) 1-chloro-1-methylcyclohexane , AlCl₃, (vi) PhCOCl, AlCl₃. If no reaction will occur, indicate by writing NR.
(a)

Verified step by step guidance

Identify the type of reaction: The presence of AlCl3 suggests a Friedel-Crafts reaction, which is a type of electrophilic aromatic substitution.

Analyze the reactants: The image shows a benzene ring, which is a common substrate for Friedel-Crafts reactions.

Consider the electrophile: In the case of chlorocyclopentane with AlCl3, the electrophile is a cyclopentyl cation formed by the interaction of chlorocyclopentane with AlCl3.

Predict the reaction: The cyclopentyl cation will attack the benzene ring, leading to the formation of a cyclopentylbenzene product.

Evaluate the conditions: Ensure that the reaction conditions are suitable for the Friedel-Crafts alkylation to occur, such as the presence of a strong Lewis acid (AlCl3) and an aromatic substrate (benzene).

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Friedel-Crafts Alkylation

Friedel-Crafts alkylation is a reaction that introduces an alkyl group into an aromatic ring using an alkyl halide and a Lewis acid catalyst like AlCl3. The catalyst helps generate a carbocation from the alkyl halide, which then attacks the electron-rich aromatic ring, forming a new carbon-carbon bond. This reaction is useful for synthesizing alkylbenzenes but can lead to polyalkylation and carbocation rearrangements.

Friedel-Crafts Acylation

Friedel-Crafts acylation involves the introduction of an acyl group into an aromatic ring using an acyl chloride and a Lewis acid catalyst such as AlCl3. This reaction forms a ketone and is generally more controlled than alkylation, as it avoids carbocation rearrangements and polyacylation. The acylium ion, generated in situ, is the electrophile that attacks the aromatic ring, leading to the formation of an aryl ketone.

Aromaticity and Electrophilic Aromatic Substitution

Aromatic compounds, like benzene, are characterized by their stability due to delocalized π-electrons. Electrophilic aromatic substitution (EAS) is a common reaction mechanism where an electrophile replaces a hydrogen atom on the aromatic ring. The stability of the aromatic system is temporarily disrupted during the formation of a sigma complex, but restored upon re-aromatization. Understanding EAS is crucial for predicting the outcome of reactions involving aromatic compounds.

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