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

검증된 단계별 안내

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).

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주요 개념

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

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.

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