Naphthalene is an organic compound with formula C10H8. It is the simplest polycyclic aromatic hydrocarbon, and is a white crystalline solid with a characteristic odor that is detectable at concentrations as low as 0.08 ppm by mass. As an aromatic hydrocarbon, naphthalene’s structure consists of a fused pair of benzene rings. It is best known as the main ingredient of traditional mouthballs.
Naphthaline, as it had been derived from a kind of Naphtha (a broad term encompassing any volatile, flammable liquid hydrocarbon mixture, including coal tar).
Naphthalene is the most abundant single component of coal tar. Although the composition of coal tar varies with the coal from which it is produced, typical coal tar is about 10% naphthalene by weight. In industrial practice, distillation of coal tar yields an oil containing about 50% naphthalene, along with twelve other aromatic compounds.
This oil, after being washed with aqueous sodium hydroxide to remove acidic components (chiefly various phenols), and with sulfuric acid to remove basic components, undergoes fractional distillation to isolate naphthalene. The crude naphthalene resulting from this process is about 95% naphthalene by weight.
The chief impurities are the sulfur-containing aromatic compound benzothiophene (< 2%), indane (0.2%), indene (< 2%), and methylnaphthalene (< 2%). Petroleum-derived naphthalene is usually purer than that derived from coal tar. Where required, crude naphthalene can be further purified by crystallization from any of a variety of solvents, resulting in 99% naphthalene by weight, referred to as 80 °C (melting point). Approximately 1.3M tons are produced annually.
Naphthalene is used mainly as a precursor to other chemicals. The single largest use of naphthalene is the industrial production of phthalic anhydried, although more phthalic anhydride is made from o-xylene.
Wetting agent and Surfactant
Alkyl naphthalene sulfonates (ANS) are used in many industrial applications as nondetergent wetting agents that effectively disperse colloidal systems in aqueous media. The major commercial applications are in the agricultural chemical industry, which uses ANS for wettable powder and wettable granular (dry-flowable) formulations, and the textile and fabric industry, which utilizes the wetting and defoaming properties of ANS for bleaching and dyeing operations.
As a fumigant
Naphthalene has been used as a household fumigant. It was once the primary ingredient in mouthballs, although its use has largely been replaced in favor of alternatives such as 1,4-dichlorobenzene. In a sealed container containing naphthalene pellets, naphthalene vapors build up to levels toxic to both the adult and larval forms of many moths that attack textiles. Other fumigant uses of naphthalene include use in soil as a fumigant pesticide, in attic spaces to repel animals and insects, and in museum storage-drawers and cupboards to protect the contents from attack by insect pests. Naphthalene is a repellent to opossums.
It is used in pyrotechnic special effects such as the generation of black smoke and simulated explosions. It is used to create artificial pores in the manufacture of high-porosity grinding wheels. In the past, naphthalene was administered orally to kill parasitic worms in livestock. Naphthalene and its Alkyl Homologs are the major constituents of creosote. Naphthalene is used in engineering to study heat transfer using mass sublimation.