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

1. 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.
2. 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.
3. 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.
4. 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.
5. 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.

Key Concepts

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.