Naphthalene

Structure of Naphthalene:

• Naphthalene is a polycyclic aromatic hydrocarbon consisting of two fused benzene rings.

• The molecular formula is.

• The structure is planar, and it has alternating double and single bonds, which are characteristic of aromatic compounds.

Structure of Naphthalene

Synthesis:

From Coal Tar:

• Naphthalene is primarily obtained from coal tar, which is distilled to separate it from other components.

Laboratory Synthesis (Haworth Reaction):

• Formation of 1-Tetralone: Benzene is first reacted with succinic anhydride to form 1-tetralone via the Friedel-Crafts acylation.

• Cyclization: The intermediate is cyclized to form naphthol.

• Dehydration and Aromatization: Finally, dehydration and aromatization produce naphthalene.

Benzene + Succinic anhydride → AlCl3 (reagents) → 1-Tetralone → Cyclization Naphthalene

Reactions:

Electrophilic Substitution:

• Nitration: Naphthalene reacts with nitric acid (HNO3 HNO_3HNO3​) to form nitronaphthalene.

C10H8 + HNO3 → H2SO4 (reagents) C10H7NO2 + H2O

• Sulfonation: Naphthalene reacts with sulfuric acid (H2SO4H_2SO_4H2​SO4​) to form naphthalene sulfonic acid.

C10H8 + H2SO4 → C10H7SO3H + H2O

Oxidation:

• Naphthalene can be oxidized to phthalic anhydride using oxidizing agents like vanadium pentoxide (V2O5​).

C10H8+4O2→V2O5C6H4(CO)2O+2H2O

Derivatives:

1. Naphthols (1-Naphthol, 2-Naphthol): These are important derivatives used in dye manufacture.

2. Naphthylamines (1-Naphthylamine, 2-Naphthylamine): These are precursors to various azo dyes.

Medicinal Uses:

• Mothballs: Naphthalene is used in mothballs due to its insect-repellent properties.

• Derivatives: Some derivatives of naphthalene, such as naphthoquinones, have antibacterial and antifungal properties. However, the direct medicinal use of naphthalene is limited due to its toxic nature.