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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.
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_4H2SO4) 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
Naphthols (1-Naphthol, 2-Naphthol): These are important derivatives used in dye manufacture.
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.
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