Naphthalene 99426 223151883 2008-07-02T20:10:05Z 131.252.182.142 /* References */ {{Chembox new | Name = Naphthalene | ImageFile = Naphthalene.svg | ImageSize = 114px | ImageFile1 = Naphthalene-3D-balls.png | ImageFile2 = Naphthalene-3D-vdW.png | IUPACName = Naphthalene | OtherNames = Tar Camphor, White Tar, Moth Flakes | Section1 = {{Chembox Identifiers | SMILES = c1cccc2c1cccc2 | CASNo = 91-20-3 | EINECS = 202-049-5 | RTECS = QJ0525000 }} | Section2 = {{Chembox Properties | Formula = C<sub>10</sub>H<sub>8</sub> | MolarMass = 128.17052 g/mol | Appearance = White solid crystals/flakes,<br />strong odor of coal tar | Density = 1.14 g/cm³ | Solubility = approximately 30 mg/L | MeltingPt = 80.26 °C | BoilingPt = 218 °C }} | Section7 = {{Chembox Hazards | MainHazards = [[Flammable]], [[sensitizer]], possible<br />[[carcinogen]]. Dust can form<br /> [[explosive]] mixtures with [[air]] | NFPA-H = 2 | NFPA-F = 2 | NFPA-R = | FlashPt = 79 - 87 °C | Autoignition = 525 °C | RPhrases = {{R22}}, {{R40}}, {{R50/53}} | SPhrases = {{S2}}, {{S36/37}}, {{S46}}, {{S60}}, {{S61}} }} }} '''Naphthalene''' (not to be confused with [[naphtha]]), also known as '''naphthalin''', '''naphthaline''', '''napthene''', '''tar camphor''', '''white tar''', '''albocarbon''', or '''antimite''' is a crystalline, [[Aromaticity|aromatic]], white, solid [[hydrocarbon]], best known as the traditional, primary ingredient of [[mothball]]s. It is volatile, forming a flammable [[vapor]], and readily [[sublimation (physics)|sublimes]] at room temperature, producing a characteristic odor that is detectable at concentrations as low as 0.08&nbsp;[[parts per million|ppm by mass]].<ref name="">{{cite journal | title=Odor as an aid to chemical safety: Odor thresholds compared with threshold limit values and volatiles for 214 industrial chemicals in air and water dilution | author=Amoore J E and Hautala E | journal=J Appl Toxicology | volume=3 | issue=6 | pages=272–290 | year=1983 | doi=10.1002/jat.2550030603 }}</ref> ==History== In 1819&ndash;1820, at least two chemists reported a white solid with a pungent odor derived from the distillation of coal tar. In 1821, [[John Kidd]] described many of this substance's properties and the means of its production, and proposed the name ''naphthaline'', as it had been derived from a kind of [[naphtha]] (a broad term encompassing any volatile, flammable liquid hydrocarbon mixture, including coal tar).<ref>{{cite journal | author = John Kidd | year = 1821 | title = Observations on Naphthaline, a peculiar substance resembling a concrete essential oil, which is apparently produced during the decomposition of coal tar, by exposure to a red heat | journal = Philosophical Transactions | volume = 111 | pages = 209–221 | doi = 10.1098/rstl.1821.0017}}</ref> Naphthaline's chemical formula was determined by [[Michael Faraday]] in 1826. The structure of two fused benzene rings was proposed by [[Emil Erlenmeyer]] in 1866,<ref>{{cite journal | title = Studien über die s. g. aromatischen Säuren | author = Emil Erlenmeyer | journal = [[Annalen der Chemie und Pharmacie]] | volume = 137 | issue = 3 | pages = 327–359 | year = 1866 | url = | doi = 10.1002/jlac.18661370309 }}</ref> and confirmed by [[Carl Graebe]] three years later. ==Structure and reactivity== A naphthalene molecule is composed of two fused benzene rings. (In [[organic chemistry]], rings are ''fused'' if they share two or more atoms.) Accordingly, naphthalene is classified as a benzenoid [[polycyclic aromatic hydrocarbon]] (PAH). There are two sets of equivalent hydrogens: the ''alpha'' positions are positions 1, 4, 5, and 8 on the drawing below, and the ''beta'' positions are positions 2, 3, 6, and 7. Unlike highly-symmetrical [[aromatic]]s, such as [[benzene]], the carbon-carbon bonds in naphthalene are not of the same length. The bonds C1–C2, C3–C4, C5–C6 and C7–C8 are about 1.36 Å (136 pm) in length, whereas the other carbon-carbon bonds are about 1.42 Å (142 pm) long. This has been verified by [[x-ray diffraction]], and is consistent with the [[valence bond theory|valence bond]] model of bonding in napthalene which involves three [[resonance structure]]s (as shown below); while the bonds C1–C2, C3–C4, C5–C6 and C7–C8 are double in ''two'' of the three structures, the others are double in only one. [[Image:naphthalene resonance.PNG|Resonace structures of naphthalene]] Like benzene, naphthalene can undergo [[electrophilic aromatic substitution]]. For many electrophilic aromatic substitution reactions, naphthalene is more reactive than benzene, reacting under milder conditions than does benzene. For example, whereas both benzene and naphthalene react with [[chlorine]] in the presence of a [[ferric chloride]] or [[aluminium chloride]] catalyst, naphthalene and chlorine can react to form 1-chloronaphthalene even without a catalyst. Similarly, while both benzene and naphthalene can be alkylated using [[Friedel-Crafts reaction]]s, naphthalene can also be alkylated by reaction with [[alkene]]s or [[alcohol]]s, with [[sulfuric acid|sulfuric]] or [[phosphoric acid]] as the catalyst. Two [[isomer]]s are possible for mono-substituted naphthalenes, corresponding to substitution at an alpha or beta position. Usually, electrophiles attack at the alpha position. The selectivity for alpha over beta substitution can be rationalized in terms of the resonance structures of the intermediate: for the alpha substitution intermediate, seven resonance structures can be drawn, of which four preserve an aromatic ring. For beta substitution, the intermediate has only six resonance structures, and only two of these are aromatic. Sulfonation, however, gives a mixture of the "alpha" product 1-naphthalenesulfonic acid and the "beta" product 2-naphthalenesulfonic acid, with the ratio dependent on reaction conditions. The 1-isomer forming predominantly at 25<sup>O</sup>C, and the 2-isomer at 160<sup>O</sup>C. Naphthalene can be [[hydrogenate]]d under high pressure with metal [[catalyst]]s to give 1,2,3,4-tetrahydronaphthalene or [[tetralin]] (C<sub>10</sub>H<sub>12</sub>). Further hydrogenation yields [[decahydronaphthalene]] or decalin (C<sub>10</sub>H<sub>18</sub>). [[Oxidation]] with [[chromate]] or [[permanganate]], or catalytic oxidation with O<sub>2</sub> and a [[vanadium]] [[catalyst]], gives [[phthalic acid]]. ==Production== Most naphthalene is derived from [[coal tar]]. From the 1960s until the 1990s, significant amounts of naphthalene were also produced from heavy petroleum fractions during [[petroleum refining]], but today petroleum-derived naphthalene represents only a minor component of naphthalene production. Naphthalene is the most abundant single component of coal tar. While 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 a variety of other [[aromatic compound]]s. This oil, after being washed with aqueous [[sodium hydroxide]] to remove [[acid]]ic components (chiefly various [[phenol]]s), and with [[sulfuric acid]] to remove [[base (chemistry)|basic]] components, is [[fractional distillation|fractionally distilled]] to isolate naphthalene. The crude naphthalene resulting from this process is about 95% naphthalene by weight, often referred to as 78<sup>0</sup>C (melting point). The chief impurities are the sulfur-containing aromatic compound [[benzothiophene]] (<2%), [[indane]] (0.2%), [[indene]] (<2%), and methylnapthalene (<2%). Petroleum-derived naphthalene is usually purer than that derived from coal tar. Where required, crude naphthalene can be further purified by [[recrystallization]] from any of a variety of solvents, resulting in 99% naphthalene by weight, referred to as 80<sup>0</sup>C (melting point). In North America, coal tar producers are [[Koppers]] Inc. and Recochem Inc., and petroleum-derived producer is Advanced Aromatics, L.P.. ==Incidence in nature== Trace amounts of naphthalene are produced by [[magnolia]]s and specific types of [[deer]]. Naphthalene has also been found in the [[Formosan subterranean termite]], possibly as a repellant against "ants, poisonous fungi and nematode worms." [http://news.bbc.co.uk/1/hi/sci/tech/76115.stm] ==Uses== Naphthalene's most familiar use is as a household [[fumigant]], such as in [[mothball]]s (although [[1,4-dichlorobenzene]] (or ''p''-dichlorobenzene) is now more widely used). In a sealed container containing naphthalene pellets, naphthalene vapors build up to levels toxic to both the adult and larval forms of many [[moth]]s 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. 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 vapour can also slow the onset of [[rust]]{{Fact|date=December 2007}}, such as the use of moth balls in a tool box. Naphthalene and its alkyl [[homolog (chemistry)|homologs]] are the major constituents of [[creosote]]. ===Use as a chemical intermediate=== Larger volumes of naphthalene are used as a chemical intermediate to produce other chemicals. The single largest use of naphthalene is the industrial production of [[phthalic anhydride]] (although more phthalic anhydride is made from [[o-xylene]] than from naphthalene). Other naphthalene-derived chemicals include alkyl naphthalene sulfonate [[surfactant]]s, and the [[insecticide]] [[carbaryl|1-naphthyl-N-methylcarbamate (''carbaryl'')]]. Naphthalenes substituted with combinations of strongly electron-donating [[functional group]]s, such as [[alcohol]]s and [[amine]]s, and strongly electron-withdrawing groups, especially [[sulfonic acid]]s, are intermediates in the preparation of many synthetic [[dye]]s. The hydrogenated naphthalenes [[tetrahydronaphthalene]] (tetralin) and [[decahydronaphthalene]] (decalin) are used as low-volatility [[solvent]]s. Naphthalene sulfonic acids are used in the manufacture of naphthalene sulfonate polymer [[plasticizer]]s which are used to produce [[concrete]] and [[plasterboard]] ([[wallboard]] or [[drywall]]). They are also used as [[dispersant]]s in synthetic and natural rubbers, and as [[tanning|tanning agents]] in leather industries. Naphthalene sulfonate polymers are produced by reacting naphthalene with sulfuric acid and polymerizing this with formaldehyde, followed by neutralization with sodium hydroxide. Naphthalene is also used in the synthesis of [[2-naphthol]], and of miscellaneous chemicals and pharmaceuticals. ==Health effects== Exposure to large amounts of naphthalene may damage or destroy [[red blood cell]]s. Humans, particularly children, have developed this condition, known as [[hemolytic anemia]], after ingesting mothballs or deodorant blocks containing naphthalene. Symptoms include fatigue, lack of appetite, restlessness, and pale [[skin]]. Exposure to large amounts of naphthalene may cause [[nausea]], vomiting, [[diarrhea]], [[blood]] in the [[urine]], and [[jaundice]] (yellow coloration of the skin). When the U.S. National Toxicology Program exposed male and female rats and mice to naphthalene vapors on weekdays for two years,<ref>{{cite web | title=NTP Technical Reports 410 and 500 | work=NTP Technical Reports 410 and 500, available from NTP: Long-Term Abstracts & Reports| url=http://ntp.niehs.nih.gov/INDEX.CFM?OBJECTID=0847DDA0-F261-59BF-FAA04EB1EC032B61| accessmonthday=March 6 | accessyear=2005}}</ref> male and female rats exhibited: evidence of carcinogenic activity, based on increased incidences of adenoma and neuroblastoma of the nose, female mice exhibited some evidence of carcinogenic activity, based on increased incidences of alveolar and bronchiolar adenomas of the lung, and male mice exhibited no evidence of carcinogenic activity. The International Agency for Research on Cancer (IARC)<ref>{{cite web | title=IARC Monographs on the Evaluation of Carcinogenic Risks to Humans | work=Monographs on the Evaluation of Carcinogenic Risks to Humans, Some Traditional Herbal Medicines, Some Mycotoxins, Naphthalene and Styrene, Vol. 82 (2002) (p. 367)| url=http://www-cie.iarc.fr/htdocs/monographs/vol82/82-06.html | accessmonthday=March 9 | accessyear=2005}}</ref> classifies naphthalene as possibly carcinogenic to humans [Group 2B]. The IARC also points out that acute exposure causes cataracts in humans, rats, rabbits, and mice, and that hemolytic anemia, described above, can occur in children and infants after oral or inhalation exposure or after maternal exposure during pregnancy. Over 400 million people have an inherited condition called [[glucose-6-phosphate dehydrogenase deficiency]]. Exposure to naphthalene is more harmful for these people and may cause hemolytic anemia at lower doses. ==See also== *[[Decahydronaphthalene]] (the fully saturated analog of naphthalene) *[[Naphthol]] * Classic naphthalene synthesis: the [[Wagner-Jauregg reaction]] ==References== <references/> CRC Handbook of Chemistry and Physics 87th edition ==External links== *[http://npic.orst.edu/capro/Mothballs1.pdf National Pesticide Information Center - Mothballs Case Profile] *[http://www.epa.gov/ttn/atw/hlthef/naphthal.html Naphthalene] - EPA Air Toxics Web Site *[http://www.inchem.org/documents/pims/chemical/pim363.htm Naphthalene (PIM 363)] - mostly on toxicity of naphthalene *Koppers Inc.[http://www.koppers.com/] *Recochem Inc.[http://www.recochem.com/] *Advanced Aromatics, L.P.[http://www.advancedaromatics.com/] [[Category:Hydrocarbons]] [[Category:Simple aromatic rings]] [[Category:Hazardous air pollutants]] [[Category:Insecticides]] [[Category:Antiseptics]] [[Category:Aromatic compounds]] [[ar:نفثالين]] [[cs:Naftalen]] [[da:Naftalin]] [[de:Naphthalin]] [[es:Naftalina]] [[eo:Naftalino]] [[fa:نفتالین]] [[fr:Naphtalène]] [[it:Naftalene]] [[he:נפטלין]] [[lv:Naftalīns]] [[hu:Naftalin]] [[nl:Naftaleen]] [[ja:ナフタレン]] [[no:Naftalen]] [[pl:Naftalen]] [[pt:Naftalina]] [[ro:Naftalină]] [[ru:Нафталин]] [[simple:Naphthalene]] [[sk:Naftalén]] [[fi:Naftaleeni]] [[sv:Naftalen]] [[th:แนฟทาลีน]] [[vi:Naphtalen]] [[tr:Naftalin]] [[zh:萘]]