Ch. 17 - Reactions of Aromatic Compounds

Wade9th EditionOrganic ChemistryISBN: 9780135213728Not the one you use?Change textbook

Wade 9th Edition

Ch. 17 - Reactions of Aromatic Compounds

Problem 60e

Chapter 17, Problem 60e

Electrophilic aromatic substitution usually occurs at the 1-position of naphthalene, also called the 1-position. Predict the major products of the reactions of naphthalene with the following reagents.

(e) cyclohexanol and BF₃

Verified step by step guidance

Step 1: Understand the reaction type. The problem involves electrophilic aromatic substitution, which is a reaction where an electrophile replaces a hydrogen atom on an aromatic ring. Naphthalene is the aromatic compound in this case.

Step 2: Identify the reagents. Cyclohexanol and BF3 are provided as reagents. BF3 acts as a Lewis acid, which can activate cyclohexanol to form a carbocation. This carbocation will serve as the electrophile in the reaction.

Step 3: Determine the site of substitution. In naphthalene, the alpha position (1-position) is more reactive due to its higher electron density and stability of the intermediate carbocation formed during the reaction. Thus, substitution is expected to occur at the alpha position.

Step 4: Predict the product formation. The carbocation generated from cyclohexanol will attack the alpha position of naphthalene, leading to the formation of a new bond between the naphthalene ring and the cyclohexyl group.

Step 5: Consider resonance stabilization. After the electrophilic attack, the intermediate formed will undergo resonance stabilization, ensuring the aromaticity of the naphthalene ring is restored in the final product.

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Key Concepts

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

Electrophilic Aromatic Substitution (EAS)

Electrophilic Aromatic Substitution is a fundamental reaction in organic chemistry where an electrophile replaces a hydrogen atom on an aromatic ring. This reaction is crucial for modifying aromatic compounds, allowing for the introduction of various functional groups. The mechanism involves the formation of a sigma complex, where the aromaticity is temporarily lost, followed by deprotonation to restore aromaticity.

Naphthalene Structure and Reactivity

Naphthalene is a polycyclic aromatic hydrocarbon consisting of two fused benzene rings. Its structure allows for electrophilic substitution primarily at the 1-position (α position) and 2-position (β position). The reactivity of naphthalene is influenced by its electron-rich nature, making it susceptible to electrophiles, with the α position being favored due to steric and electronic factors.

Role of Lewis Acids in EAS

Lewis acids, such as BF3, are often used in electrophilic aromatic substitution reactions to enhance the electrophilicity of the reacting species. In the presence of a Lewis acid, the electrophile can become more reactive, facilitating the substitution process. This is particularly important when the electrophile is weak, as the Lewis acid can stabilize the transition state and promote the reaction.

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Related Practice

Textbook Question

The most common selective herbicide for killing broadleaf weeds is 2,4-dichlorophenoxyacetic acid (2,4-D). Show how you would synthesize 2,4-D from benzene, chloroacetic acid (ClCH₂COOH), and any necessary reagents and solvents.

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Textbook Question

Furan undergoes electrophilic aromatic substitution more readily than benzene; mild reagents and conditions are sufficient. For example, furan reacts with bromine to give 2-bromofuran.

a. Propose mechanisms for the bromination of furan at the 2-position and at the 3-position. Draw the resonance forms of each sigma complex, and compare their stabilities.

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Textbook Question

Furan undergoes electrophilic aromatic substitution more readily than benzene; mild reagents and conditions are sufficient. For example, furan reacts with bromine to give 2-bromofuran.

b. Explain why furan undergoes bromination (and other electrophilic aromatic substitutions) primarily at the 2-position.

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Textbook Question

Electrophilic aromatic substitution usually occurs at the 1-position of naphthalene, also called the a position. Predict the major products of the reactions of naphthalene with the following reagents.

(d) isobutylene and HF

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Textbook Question

α-Tetralone undergoes Birch reduction to give an excellent yield of a single product. Predict the structure of the product, and propose a mechanism for its formation.

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Textbook Question

(a) HNO₃, H₂SO₄

(b) Br₂, FeBr₃

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Electrophilic aromatic substitution usually occurs at the 1-position of naphthalene, also called the 1-position. Predict the major products of the reactions of naphthalene with the following reagents.(e) cyclohexanol and BF3

Verified video answer for a similar problem:

Key Concepts

Electrophilic Aromatic Substitution (EAS)

Naphthalene Structure and Reactivity

Role of Lewis Acids in EAS

Electrophilic aromatic substitution usually occurs at the 1-position of naphthalene, also called the 1-position. Predict the major products of the reactions of naphthalene with the following reagents.

(e) cyclohexanol and BF₃