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 60d

Chapter 17, Problem 60d

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

Verified step by step guidance

Step 1: Understand the reaction type. The problem involves electrophilic aromatic substitution (EAS), a reaction where an electrophile replaces a hydrogen atom on an aromatic ring. Naphthalene, a polycyclic aromatic hydrocarbon, undergoes EAS preferentially at the 1-position (α position) due to its higher electron density and stability of the intermediate carbocation.

Step 2: Analyze the reagents. Isobutylene (CH₂=C(CH₃)₂) and HF are used in this reaction. HF acts as a catalyst to protonate isobutylene, generating a carbocation (CH₃-C⁺(CH₃)-CH₃), which serves as the electrophile in the EAS reaction.

Step 3: Predict the site of attack. The carbocation electrophile will attack the α position (1-position) of naphthalene because this position leads to the formation of the most stable intermediate carbocation during the reaction.

Step 4: Draw the intermediate. After the electrophile attacks the α position, a resonance-stabilized carbocation intermediate is formed. This intermediate redistributes the positive charge across the aromatic system, stabilizing the structure.

Step 5: Complete the reaction. The final product is formed when the intermediate loses a proton, restoring aromaticity to the naphthalene ring. The major product will be naphthalene substituted at the α position with the isobutyl group (CH₂-C(CH₃)₂).

Verified video answer for a similar problem:

This video solution was recommended by our tutors as helpful for the problem above.

Video duration:

Was this helpful?

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 typically occurs at positions that are more reactive due to the stability of the aromatic system. In naphthalene, the 1-position (alpha position) is particularly reactive due to its ability to stabilize the positive charge formed during the reaction.

Naphthalene Structure and Reactivity

Naphthalene is a polycyclic aromatic hydrocarbon consisting of two fused benzene rings. Its structure allows for multiple substitution positions, with the 1-position being the most favorable for electrophilic attack. Understanding the reactivity of naphthalene is crucial for predicting the products of reactions, especially when considering steric and electronic effects.

Reagents in EAS Reactions

In the context of EAS reactions, reagents such as isobutylene and HF can influence the outcome of the substitution. Isobutylene can act as a source of a carbocation, while HF can provide a protonation step. The nature of these reagents affects the stability of the intermediates and the final products, making it essential to analyze their roles in the reaction mechanism.

Recommended video:

3:22

EAS Reactions of Pyridine Concept 3

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.

views

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.

views

Textbook Question

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

views

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.

views

Textbook Question

Show the products you expect when each compound reacts with NBS with light shining on the reaction.

(d)

views

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.

(a) HNO₃, H₂SO₄

(b) Br₂, FeBr₃

views

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

Verified video answer for a similar problem:

Key Concepts

Electrophilic Aromatic Substitution (EAS)

Naphthalene Structure and Reactivity

Reagents in EAS Reactions

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