naphthalene

Structural formula
General
Surname	naphthalene
other names	Naphthalene (IUPAC)
Molecular formula	C 10 H 8
Brief description	colorless solid with a smell of moth powder / tar
External identifiers / databases
CAS number 91-20-3 EC number 202-049-5 ECHA InfoCard 100.001.863 PubChem 931 Wikidata Q179724
properties
Molar mass	128.17 g mol −1
Physical state	firmly
density	1.14 g cm −3 (20 ° C)
Melting point	80 ° C
boiling point	218 ° C
Vapor pressure	7.2 Pa (20 ° C)
solubility	very bad in water (31 mg l −1 at 20 ° C)
safety instructions
GHS hazard labeling from  Regulation (EC) No. 1272/2008 (CLP) , expanded if necessary danger H and P phrases H: 228-302-351-410 P: 210-280-301 + 312 + 330-370 + 378
MAK	repealed as a suspected carcinogenic effect Switzerland: 10 ml m −3 or 50 mg m −3
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Naphthalene [ naftaˈliːn ] (from ancient Greek νάφθα naphtha = petroleum; name according to IUPAC : naphthalene ) is a colorless solid with the empirical formula C ₁₀ H ₈ , which sublimes even at room temperature . It is a bicyclic aromatic hydrocarbon with a characteristic smell of moth powder / tar. Naphthalene is harmful to health and the environment.

history

In 1819 naphthalene was isolated independently from coal tar by the British chemists William Thomas Brande (1788–1866), Alexander Garden († 1829) and John Kidd . The name comes from Kidd. In 1826 Michael Faraday found the empirical formula. In 1866 Emil Erlenmeyer established the naphthalene formula for the first time. Traditionally, naphthalene is also counted among the polycyclic aromatic hydrocarbons (PAHs). The naphthalene molecule consists of two fused benzene rings ; its chemical behavior is similar to that of the other PAHs.

Occurrence in nature

Traces of naphthalene are produced by magnolias and some species of deer . The substance was also found in a species of termite that apparently uses it as a defense against natural enemies such as ants and poisonous fungi.

Extraction and presentation

Naphthalene is obtained from the middle oil fraction of the coal tar (up to 11%), as well as lignite and wood tar , cracked gas oil or from coal , if this is coked . In terms of quantity, it is the largest component in coal tar. It is also found in petroleum and other fossil fuels and is also produced when wood or tobacco is burned. Naphthalene is emitted from gasworks and wood impregnation plants, and it is also produced in landfills.

In 1987 about one million tons of naphthalene was produced. Western Europe is the main producer of naphthalene with 250,000 tons, followed by Eastern Europe (200,000 tons), Japan (200,000 tons) and the USA (125,000 tons).

properties

Physical Properties

Naphthalene is largely insoluble in water, at room temperature only 0.032 g of naphthalene dissolves in one liter of water. It is poorly soluble in short-chain alcohols , but readily soluble in non-polar solvents such as benzene  (1.130 g / l), carbon sulfide , ether , toluene  (910 g / l), xylene  (783 g / l), and chloroform . Naphthalene forms white crystal flakes that melt at 80 ° C to form a colorless liquid that boils at 218 ° C. It has a characteristic, intensely aromatic, tar-like odor; the odor threshold is 0.14 to 125 mg / m ^3, depending on the person . Naphthalene has a burning taste. The vapors are flammable, the flash point is 80 ° C and the ignition temperature is 540 ° C. The density is 1.14 g / cm ³ , therefore naphthalene sinks in water.

Chemical properties

Chopstick model

Dome model

Naphthalene burns with a glowing, sooty flame. It reacts violently with oxidizing agents such as chromium trioxide and nitrogen oxides . The chemical behavior is very similar to that of benzene, but due to its molecular structure it is more reactive than benzene, but less reactive than tricyclic aromatics such as anthracene . The naphthalene molecule has 10 π electrons. Like benzene, it enters into electrophilic substitution reactions . Azulene , also an aromatic hydrocarbon, is an isomer of naphthalene, it consists of a five and a seven carbon ring; however, due to a dipolar structure, it is deep blue and significantly more reactive than naphthalene.

Naphthalene can be hydrogenated to tetralin (C ₁₀ H ₁₂ ) under moderate conditions . Further hydrogenation under more drastic conditions leads to decalin (C ₁₀ H ₁₈ ).

Naphthalene represented by reduction with alkali metals in aprotic solvents (eg. As tetrahydrofuran , 1,2-dimethoxyethane ) Alkalinaphthalide . With sodium, the result is a deep green salt. It is a radical anion that has an ESR signal at g = 2.0. The reduction potential is −2.5 V (against standard hydrogen electrode (SHE)). The green color is caused by absorption bands at 463 and 735 nm.

The anion is a strong base, it reacts with protic solvents to form dihydronaphthalene :

${\displaystyle \mathrm {2\ NaC_{10}H_{8}+2\ H_{2}O\longrightarrow C_{10}H_{10}+C_{10}H_{8}+2\ NaOH} }$

With concentrated nitric acid , naphthalene forms 1-nitronaphthalene or 2-nitronaphthalene, depending on the reaction conditions chosen .

proof

Oxidation with chromates and permanganates or, on an industrial scale, with oxygen over a catalyst produces phthalic acid . Naphthalene can be detected by UV spectroscopy or by high-performance liquid chromatography .

The emission measurement of naphthalene can be done by GC / MS . The immission measurement is carried out with high-resolution mass spectrometry (HRMS).

Due to its volatility, naphthalene can only be determined with limited reliability by means of biomonitoring .

use

Naphthalene used to be the main component of mothballs , but is now often replaced by other substances because of its unpleasant smell. Furthermore, naphthalene is hardly insecticidal. It is also hardly effective for disinfecting collections of insects , although it has been used for a long time.

Naphthalene was also found in the illuminating gas used at the beginning of the 20th century and often clogged the gas pipes because it separated out as a solid. Despite its potential health hazards, it was used medically, for example, to disinfect the intestines.

Naphthalene is mainly used for the synthesis of phthalic anhydride , which is processed into solvents, plastics and fuels. Also for the production of the solvents and fuel additives decalin and tetralin it is required for the preparation of azo dyes , for the synthesis of the wood preservative chloronaphthalene , of insecticides ( carbamates ) and of PVC - plasticizer -Zwischenprodukten, also for the production of Alkylnaphthalinsulfaten used as soaps . Further industrially important derivatives are the naphthols , bromonaphthalenes , naphthylamines and nitronaphthalenes . Another application of naphthalene is as a pore former in the manufacture of abrasives .

Biological importance

In the microsomes of human liver cells , naphthalene is metabolized by cytochrome P450 . The oxidation leads to the primary metabolites via the short-lived epoxide intermediate stage :

• trans -1,2-dihydro-1,2-naphthalenediol ("dihydrodiol")
• 1-naphthol and
• 2-naphthol

The cytochrome subtype CYP1A2 mainly produces the dihydrodiol and 1-naphthol, while the subtype CYP3A4 mainly produces 2-naphthol. 2,6- and 1,7-dihydroxynaphthalene are formed directly from 2-naphthol as secondary metabolites . In contrast, dihydrodiol and 1-naphthol are no longer broken down in the microsomes.

safety instructions

Naphthalene causes severe irritation and dermatitis on the skin . Naphthalene can damage red blood cells. Inhalation can cause irritation of the mucous membranes, headache and nausea, vomiting and confusion. If ingested, it leads to gastrointestinal disorders, respiratory paralysis , cramps and tremors . Despite its low solubility in water, it is highly hazardous to water (WGK 3). Damage to the cornea, liver and kidneys is possible. It forms explosive mixtures between an air volume fraction of 0.9 to 5.9%. A carcinogenic effect is suspected.

In Germany, the occupational exposure limit for naphthalene was reduced by a factor of 100 to 0.5 mg / m ³ in 2011 .

In 2014, naphthalene was included in the EU's ongoing action plan ( CoRAP ) in accordance with Regulation (EC) No. 1907/2006 (REACH) as part of substance evaluation . The effects of the substance on human health and the environment are re-evaluated and, if necessary, follow-up measures are initiated. Naphthalene uptake was caused by concerns about worker exposure , high (aggregated) tonnage and high risk characterization ratio (RCR). The re-evaluation started in 2016 and was carried out by the United Kingdom . A final report was then published.

Derivatives

Numbering of the substituent positions in naphthalene

Surname	SumFormula	Molar mass [g / mol]	Melting point. [° C]	Boiling point [° C]	Density [g / cm 3 ]	Refractive index
1-naphthoic acid	C 11 H 8 O 2	172.18	157	300	-	-
2-naphthoic acid	C 11 H 8 O 2	172.18	182	-	1.08	-
1-naphthoic acid chloride	C 11 H 7 ClO	190.63	16-19	190 (35 torr )	1.265	1.6552
1-naphthol	C 10 H 8 O	144.17	94-96	278	1.224	-
1-naphthaldehyde	C 11 H 8 O	156.18	1-2	160 (15 torr)	-	-
1-nitronaphthalene	C 10 H 7 NO 2	173.17	53-57	340	1.22	-
1-fluoronaphthalene	C 10 H 7 F	146.16	−19	215	1.323	1.593
2-fluoronaphthalene	C 10 H 7 F	146.16	61	211.5	-	-
1-chloronaphthalene	C 10 H 7 Cl	162.62	−6	259	1.194	1.632
2-chloronaphthalene	C 10 H 7 Cl	162.62	59.5	256	1.138	-
1-bromonaphthalene	C 10 H 7 Br	207.07	−2	279	1.489	1.670
2-isopropyl naphthalene	C 13 H 14	170.255	14th	268	0.975	-

See also

• naphtha

literature

• BUA - Substance reports 39. Naphthalene . Wiley / VCH, Weinheim 1989, ISBN 3-527-28066-9 .
• Harald Derner: Investigations into the resonance Raman effect on anthracene, naphthalene and p-nitro-p-dimethylamino-azobenzene. Dissertation. Freiburg (Breisgau) 1986, ISBN 3-8107-2217-0 .

Web links

Commons : Naphthalene  - Collection of images, videos, and audio files

• Medical information
• Hazards and Metabolism

Individual evidence

1. ↑ ^{a b c d e f g h i j k l m n} Entry on naphthalene in the GESTIS substance database of the IFA , accessed on April 13, 2019(JavaScript required) .
2. ↑ Entry on naphthalenes in the Classification and Labeling Inventory of the European Chemicals Agency (ECHA), accessed on February 1, 2016. Manufacturers or distributors can expand the harmonized classification and labeling .
3. ↑ Swiss Accident Insurance Fund (Suva): Limit values ​​- current MAK and BAT values (search for 91-20-3 or naphthalene ), accessed on November 2, 2015.
4. ^ JR Partington: History of Chemistry. Volume 4, Macmillan 1972, pp. 75-76.
5. ↑ Ann. Phil. Volume 15, 1920, p. 74. Garden was associated with Friedrich Accum . According to Brian Clegg, Naphthalene, Royal Chemical Society , he had a chemicals shop in London and was a Scot.
6. ↑ J. Gassett, D. Wiesler, A. Baker, D. Osborn, K. Miller, R. Marchinton, M. Novotny: Volatile Compounds from the Forehead Region of Male White-Tailed Deer (Odocoileus virginianus). In: J. Chem. Ecol. 23, 1997, pp. 569-578; doi: 10.1023 / B: JOEC.0000006397.63647.5b .
7. ↑ EJ Corey, Andrew W. Gross: tert-Butyl-tert-octylamine In: Organic Syntheses . 65, 1987, p. 166, doi : 10.15227 / orgsyn.065.0166 ; Coll. Vol. 8, 1993, p. 93 ( PDF ).
8. ^ NN Greenwood, A. Earnshaw: Chemistry of the elements. 1st edition. VCH, Weinheim 1988, ISBN 3-527-26169-9 , p. 102.
9. ^ NG Connelly, WE Geiger: Chemical Redox Agents for Organometallic Chemistry. In: Chem. Rev. 96, 1996, pp. 877-910; doi: 10.1021 / cr940053x .
10. ↑ VDI 3874: 2006-12 Measurement of Emissions; Measuring polycyclic aromatic hydrocarbons (PAH); GC / MS method (Stationary source emissions; Determination of polycyclic aromatic hydrocarbons (PAH); GC / MC method). Beuth Verlag, Berlin, p. 4.
11. ↑ VDI 2464 Part 4 (draft): 2015-06 Measurement of Immissions; Measuring indoor air; Measurement of persistent organic halogen compounds (POP) with GC / HRMS (Ambient air measurement; Indoor air measurement; Measurement of persistent organic pollutants (POPs) with GC / HRMS). Beuth Verlag, Berlin, pp. 4, 8.
12. ↑ VDI 3957 sheet 2: 2016-03 Biological measurement methods for determining and assessing the effects of air pollution on plants (biomonitoring); Method of standardized grass culture (Biological measuring techniques for the determination and assessment of effects of air pollutants on plants (biomonitoring); Method of the standardized grass exposure). Beuth Verlag, Berlin, p. 24.
13. ↑ Gerfried Deschka: The disinfection of small collections of insects according to more recent points of view. In: Steyr Entomologenrunde. No. 21, Steyr 1987, pp. 57-61.
14. ↑ ^{a b} Kirsten Sucker, Wolfgang Zschiesche, Thomas Hummel, Dietmar Breuer, Silke Werner, Claudia Friedrich, Tobias Weiß, Monika Raulf, Dirk Pallapies, Jürgen Bünger, Thomas Brüning: Naphthalene: Chronic exposure at the workplace - relevance for the derivation of limit values ​​- results of the Cross-sectional study of naphthalene exposure in the abrasives industry. In: Hazardous substances - cleanliness. Air . 77, No. 10, 2017, pp. 439–442.
15. ↑ TM Cho, RL Rose, E. Hodgson: In vitro metabolism of naphthalene by human liver microsomal cytochrome P450 enzymes. In: Drug Metab Dispos . 34 (1), Jan 2006, pp. 176-183; PMID 16243959 .
16. ↑ European Chemicals Agency (ECHA): Substance Evaluation Conclusion and Evaluation Report .
17. ↑ Community rolling action plan ( CoRAP ) of the European Chemicals Agency (ECHA): Naphthalene , accessed on March 26, 2019.