description
Naphthalene is a white solid chemical that vaporizes easily. It has a strong smell. You can sometimes smell naphthalene in the air or in water. Called white tar and tar camphor, naphthalene is used in mothballs and moth flakes. Petroleum and coal contain naphthalene.
Naphthalene, the simplest of the fused or condensed ring hydrocarbon compounds composed of two benzene rings sharing two adjacent carbon atoms. Naphthalene is the most abundant single constituent of coal tar, a volatile product from the destructive distillation of coal, and is also formed in modern processes for the high-temperature cracking (breaking up of large molecules) of petroleum.
1-Methylnaphthalene and 2-methylnaphthalene are naphthalene-related compounds. 1-Methylnaphthalene is a clear liquid and 2-methylnaphthalene is a solid; both can be smelled in air and in water at very low concentrations. 1-Methylnaphthalene and 2-methylnaphthalene are used to make other chemicals such as dyes and resins. 2-Methylnaphthalene is also used to make vitamin K.
Chemical Properties
Naphthalene is a crystalline, white, flammable, polycyclic aromatic hydrocarbon consisting of two fused benzene rings. It has a pungent odor and sublimes readily above its melting point; it has been traditionally used in moth balls and is responsible for the moth balls characteristic odor. Naphthalene is a natural component of fossil fuels and is the single most abundant component of coal tar, accounting for approximately 11% of dry coal tar.
Uses
- In industry, naphthalene is used to manufacture a plastic called polyvinyl chloride (PVC). In public restrooms, naphthalene can be found in toilet deodorant blocks. At home, naphthalene can be found in moth repellents.
- Naphthalene balls are extensively used as household preservative of woolen clothes and as a deodorant tablet for the toilets, urinals, bathrooms etc. These are manufactured from naphthalene flakes by a tabletmaking machine having its ball shape die.
- Naphthalene is an important hydrocarbon raw material and is primarily used to manufacture phthalic anhydride and polyvinyl chloride (PVC) plastics, but is also used in moth repellents and toilet deodorant blocks.
- Naphthalene was used in liquid-phase exfoliation of graphite in organic solvents for the production of graphene sheets. It was used in preparation of carbon-coated Si 70 Sn 30 nanoparticles.
- It was used as fluorescent probe to study the aggregation behavior of sodium cholate.
- It was used to investigate influence of added short chain linear and branched alcohols on the binding of 1:1 complex of naphthalene and β-cyclodextrin.
Health Hazard
Most of the data available on the toxic effects of naphthalene have been derived from animal studies conducted either in vivo or with in vitro preparations.
Rats and mice breathing naphthalene vapors daily for a lifetime had irritated noses and nose tumors and irritated lungs. Some female mice had lung tumors. Some animals got cloudy eyes after ingesting it.
It is not clear if naphthalene causes reproductive problems in animals. Although there is no direct data showing that naphthalene can cause cancer in people, naphthalene exposure can lead to cancer in animals.
Exposure to large amounts of naphthalene may damage or destroy red blood cells, a condition called hemolytic anemia. Symptoms of hemolytic anemia are feeling very tired or restless, lack of appetite, and pale skin. Exposure to large amounts of naphthalene may also cause upset stomach, diarrhea, blood in the urine,and yellow-colored skin. Very young children and unborn children are at higher risk if they are exposed to naphthalene, especially if they ingest the chemical. Some infants have become ill when they were close to clothing or blankets stored in naphthalene mothballs.
Toxicity
Naphthalene is a white solid substance with a strong smell. Poisoning from naphthalene destroys or changes red blood cells so they cannot carry oxygen. This can cause organ damage.
In humans, naphthalene is broken down to alpha-naphthol, which is linked to the development of hemolytic anemia. Kidney and liver damage may also occur. Alpha-naphthol and other metabolites are excreted in urine.
In animals, naphthalene breaks down into other compounds including alpha-naphthol, which may affect the lungs and eyes. Naphthalene was found in the milk of exposed cows, but the residues disappeared quickly after the cows were no longer exposed. Nearly all the naphthalene was broken down into other compounds and excreted in their urine.
Description
Naphthalene occurs as transparent prismatic plates also available as white scales, powder
balls, or cakes with a characteristic mothball or strong coal tar and aromatic odour. It is
sparingly soluble in water but soluble in methanol/ethanol and very soluble in ether.
Naphthalene is a commercially important aromatic hydrocarbon. Naphthalene occurs as
a white solid or powder. Naphthalene occurs in coal tar in large quantities and is easily
isolated from this source in pure condition. It volatilises and sublimes at room temperature
above the melting point. The primary use for naphthalene is in the production of
phthalic anhydride, also of carbamate insecticides, surface active agents and resins, as a
dye intermediate, as a synthetic tanning agent, as a moth repellent, and in miscellaneous
organic chemicals. Naphthalene is used in the production of phthalic anhydride; it is also
used in mothballs. Naphthalene is also used in the manufacture of phthalic and anthranilic
acids to make indigo, indanthrene, and triphenyl methane dyes, for synthetic resins,
lubricant, celluloid, lampblack, smokeless powder, and hydronaphthalenes. Naphthalene
is also used in dusting powders, lavatory deodorant discs, wood preservatives, fungicide,
and as an insecticide. It has been used as an intestinal antiseptic and vermicide and in
the treatment of pediculosis and scabies.
Chemical Properties
Naphthalene is a colorless to brown crystalline solid with a characteristic “moth ball” odor. It evaporates easily and has a strong odor of tar or mothballs. Solubility in water is low (31.7 mg/l at 25 °C), and it is soluble in benzene, alcohol, ether, and acetone (ATSDR, 2005). Shipped as a molten solid.
History
In 1819, naphthalene was obtained as white crystals during the pyrolysis of coal tar by John
Kidd (1775–1851), a British physician and chemist, and Alexander Garden (1757–1829), an
American living in Britain. Kidd described the properties of the white crystals he obtained
from coal tar and proposed the named naphthaline for the substance; naphthaline was
derived from naphtha, a general term for a volatile, fl ammable, hydrocarbon liquid. Michael
Faraday (1791–1867) determined the correct empirical formula for naphthalene in 1825,
and Richard August Carl Emil Erlenmeyer (1825–1909) proposed the fused benzene ring
structure in 1866.
Uses
In addition to oxidation and reduction reactions, naphthalene readily undergoes substitutionreactions such as nitration, halogenation, sulfonation, and acylation to produce a varietyof other substances, which are used in the manufacture of dyes, insecticides, organic solvents,and synthetic resins. The principal use of naphthalene is for the production of phthalic anhydride,C8H4O3.
Naphthalene is catalytically oxidized to phthalic anhydride: 2C10H8 + 9O2 → 2C4H8O3 +4CO2 + 4H2O using metal oxide catalysts. Phthalic anhydride is used to produce plastics,phthalate plasticizers, insecticides, pharmaceuticals, and resins. Sulfonation of naphthalene withsulfuric acid produces naphthalenesulfonic acids, which are used to produce naphthalene sulfonates.Naphthalene sulfonates are used in various formulations as concrete additives, gypsumboard additives, dye intermediates, tanning agents, and polymeric dispersants. Naphthalene isused to produce carbamate insecticides such as carbaryl, which is a wide-spectrum, generalpurposeinsecticide.
Uses
Naphthalene occurs naturally in fossil fuels such as coal and petroleum. It is commonly produced from the distillation and fractionation of coal tar. Naphthalene is used as an intermediate in the production of phthalate plasticizers, other plastics and resins, and other products such as dyes, wood preservatives, explosives, lubricants, pharmaceuticals, deodorizers, and insect repellants. Moth balls and other moth repellants, and some solid block deodorizers used for toilets and diaper pails, are made of crystalline naphthalene (ATSDR, 2005).
Production Methods
Naphthalene is produced from coal tar or petroleum. It is made from petroleum by dealkylationof methylnaphthalenes in the presence of hydrogen at high temperature and pressure.Petroleum was a major source of naphthalene until the 1980s, but now most naphthaleneis produced from coal tar. The pyrolysis of bituminous coal produces coke and coke ovengases. Naphthalene is condensed by cooling the coke gas and then separated from the gas.
Definition
naphthalene: A white volatilesolid, C
10H
8; r.d. 1.025;m.p. 80.55°C; b.p. 218°C. Naphthaleneis an aromatic hydrocarbon withan odour of mothballs and is obtainedfrom crude oil. It is a raw materialfor making certain syntheticresins.
Definition
ChEBI: An aromatic hydrocarbon comprising two fused benzene rings. It occurs in the essential oils of numerous plant species e.g. magnolia.
General Description
Heterogeneous ozonolysis of naphthalene adsorbed on XAD-4 resin has been studied using annular denuder technique.
Air & Water Reactions
Highly flammable. Insoluble in water.
Reactivity Profile
Vigorous reactions, sometimes amounting to explosions, can result from the contact between aromatic hydrocarbons, such as Naphthalene, and strong oxidizing agents. They can react exothermically with bases and with diazo compounds. Substitution at the benzene nucleus occurs by halogenation (acid catalyst), nitration, sulfonation, and the Friedel-Crafts reaction. Naphthalene, camphor, glycerol, or turpentine will react violently with chromic anhydride [Haz. Chem. Data 1967. p 68]. Friedel-Crafts acylation of Naphthalene using benzoyl chloride, catalyzed by AlCl3, must be conducted above the melting point of the mixture, or the reaction may be violent [Clar, E. et al., Tetrahedron, 1974, 30, 3296].
Hazard
Toxic by inhalation. Upper respiratory tract
irritant, cataracts and hemolytic anemia. Possible
carcinogen.
Health Hazard
Inhalation of naphthalene vapor may causeirritation of the eyes, skin, and respiratorytract, and injury to the cornea. Other symptoms are headache, nausea, confusion, andexcitability. The routes of exposure of thiscompound into the body are inhalation, ingestion, and absorption through the skin; andthe organs that may be affected are the eyes,liver, kidney, blood, skin, and central nervoussystem.
The most severe toxic effects from naphthalene, however, may come from oral intakeof large doses of this compound. In animals, as well as in humans, ingestion of largeamounts may cause acute hemolytic anemiaand hemoglobinuria attributed to its metabolites, 1- and 2-naphthol and naphthoquinones.Infants are more sensitive than adults becauseof their lower capacity for methemoglobinreduction. Other symptoms from ingestion ofnaphthalene are gastrointestinal pain and kidney damage. The LD50 values reported inthe literature show variation among differentspecies. In mice, an oral LD50 value may beon the order of 600 mg/kg. Symptoms of respiratory depression and ataxia were noted.
Chronic exposure to naphthalene vapormay affect the eyes, causing opacities of thelens and optical neuritis. The acute effectsfrom inhalation of its vapors at high concentrations are nausea and vomiting.
Inhalation studies have shown positivetumorigenic response in mice. Studies conducted under National Toxicology Program(NTP) show clear evidence of carcinogenicityin rats resulting from inhalation of naphthalene vapors (NTP 2000). Increased incidencesof respiratory epithelial adenoma and olfactory epithelial neuroblastoma in the nose wereobserved in both the sexes of rats. On thebasis of these findings IARC has reevaluatednaphthalene and reclassified it under Group2B carcinogen, as possibly carcinogenic tohumans (IARC 2002)..
Fire Hazard
Flammable/combustible material. May be ignited by friction, heat, sparks or flames. Some may burn rapidly with flare burning effect. Powders, dusts, shavings, borings, turnings or cuttings may explode or burn with explosive violence. Substance may be transported in a molten form at a temperature that may be above its flash point. May re-ignite after fire is extinguished.
Flammability and Explosibility
Flammable
Safety Profile
Human poison by
ingestion. Experimental poison by ingestion, intravenous, and intraperitoneal routes.
Moderately toxic by subcutaneous route. An
experimental teratogen. Experimental
reproductive effects. An eye and skin
irritant. Can cause nausea, headache,
daphoresis, hematuria, fever, anemia, liver
damage, vomiting, convulsions, and coma.
Poisoning may occur by ingestion of large
doses, inhalation, or skin absorption.
Questionable carcinogen with experimental
tumorigenic data. Flammable when exposed
to heat or flame; reacts with oxidizing
materials. Explosive reaction with dinitrogen
pentaoxide. Reacts violently with CrOs,
aluminum chloride + benzoyl chloride. Fires
in the benzene scrubbers of coke oven gas
plants have been attributed to oxidation of
naphthalene. Explosive in the form of vapor
or dust when exposed to heat or flame. To
fight fire, use water, CO2, dry chemical.
When heated to decomposition it emits
acrid smoke and irritating fumes.
Potential Exposure
Naphthalene is used as a chemical
intermediate or feedstock for synthesis of phthalic, anthranilic,
hydroxyl (naphthols), amino (naphthylamines), and sulfonic
compounds; which are used in the manufacture of
various dyes and in the preparation of phthalic anhydride, 1-naphthyl-N-methyl carbonate; and β-naphthol. Naphthalene
is also used in the manufacture of hydronaphthalenes, synthetic
resins; lampblack, smokeless powder; and celluloid.
Naphthalene has been used as a moth repellent.
Approximately 100 million people worldwide have G6PD
deficiency which would make them more susceptible to
hemolytic anemia on exposure to naphthalene. At present,
more than 80 variants of this enzyme deficiency have been
identified. The incidence of this deficiency is 0.1% in
American and European Caucasians, but can range as high
as 20% in American blacks and greater than 50% in certain
Jewish groups. Newborn infants have a similar sensitivity
to the hemolytic effects of naphthalene, even without
G6PD deficiency.
Carcinogenicity
Naphthalene is reasonably anticipated to be a human carcinogenbased on sufficient evidence from studies in experimental animals.
Shipping
UN1334 Naphthalene, crude or Naphthalene,
refined, Hazard Class: 4.1; Labels: 4.1-Flammable solid.
UN2304 (molten) Hazard Class: 4.1; Labels: 4.1-Flammable
solid.
Purification Methods
Crystallise naphthalene once or more times from the following solvents: EtOH, MeOH, CCl4, *C6H6, glacial acetic acid, acetone or diethyl ether, followed by drying at 60o in an Abderhalden drying apparatus. It has also been purified by vacuum sublimation and by fractional crystallisation from its melt. Other purification procedures include refluxing in EtOH over Raney Ni and chromatography of a CCl4 solution on alumina with *benzene as eluting solvent. Baly and Tuck [J Chem Soc 1902 1908] purified naphthalene for spectroscopy by heating with conc H2SO4 and MnO2, followed by steam distillation (repeating the process), and formation of the picrate which, after recrystallisation (m 150o) is decomposed with base and the naphthalene is steam distilled. It is then crystallised from dilute EtOH. It can be dried over P2O5 under vacuum (take care not to make it sublime). Also purify it by sublimation and subsequent crystallisation from cyclohexane. Alternatively, it has been washed at 85o with 10% NaOH to remove phenols, with 50% NaOH to remove nitriles, with 10% H2SO4 to remove organic bases, and with 0.8g AlCl3 to remove thianaphthalenes and various alkyl derivatives. Then it is treated with 20% H2SO4, 15% Na2CO3 and finally distilled. [Gorman et al. J Am Chem Soc 107 4404 1985.] Zone refining purified naphthalene from anthracene, 2,4-dinitrophenylhydrazine, methyl violet, benzoic acid, methyl red, chrysene, pentacene and indoline. [Beilstein 5 IV 1640.]
Toxicity evaluation
Systemic absorption of naphthalene vapor may result in
cataracts. The biochemical basis for naphthalene cataract has
been investigated. Naphthalene is metabolized in the liver to
1,2-dihydro-1,2-dihydroxynaphthalene. Lenticular catechol
reductase biotransforms 1,2-dihydro-1,2-dihydroxynaphthalene
to 1,2-dihydroxynaphthalene, which, in turn, is
auto-oxidized in air at neutral pH to 1,2-naphthoquinone
and hydrogen peroxide. Ascorbic acid reverses the latter
reaction and forms dehydroascorbic acid, which diffuses out
of the lens very slowly. Dehydroascorbic acid has been
shown to accumulate in the lens of rabbits that were fed
naphthalene and lens incubated in vitro with 1,2-dihydro-
1,2-dihydroxynaphthalene. The sequence of reactions
involves the reduction of ascorbic acid by 1,2-naphthoquinone
in the aqueous humor to dehydroascorbic acid,
which rapidly penetrates the lens and is reduced by glutathione.
Oxidized glutathione and 1,2-naphthoquinone may
compete for enzyme glutathione reductase, which normally
maintains high reticular levels of reduced glutathione. A
reduction in the concentration of these coupled with the
removal of oxygen from the aqueous humor due to the autooxidation
of 1,2-dihydroxynaphthalene may make the lens
sensitive to naphthalene toxicity.
Incompatibilities
Dust may form explosive mixture with
air. Incompatible with oxidizers (chlorates, nitrates, peroxides,
permanganates, perchlorates, chlorine, bromine, fluorine,
etc.); contact may cause fires or explosions. Keep
away from alkaline materials, strong bases, strong acids,
oxoacids, epoxides. Violent reactions with chromium(III)
oxide, dinitrogen pentoxide; chromic anhydride.
Waste Disposal
Dissolve or mix the material
with a combustible solvent and burn in a chemical incinerator
equipped with an afterburner and scrubber. All federal,
state, and local environmental regulations must be
observed. Consult with environmental regulatory agencies
for guidance on acceptable disposal practices. Generators
of waste containing this contaminant (≥100 kg/mo) must
conform with EPA regulations governing storage, transportation,
treatment, and waste disposal.
