Naphthalene

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Naphthalene is an organic compound with the formula C
₁₀ H
₈ . It is the simplest polycyclic aromatic hydrocarbon, and is a white crystalline solid with a characteristic odor that can be detected at concentrations as low as 0.08 ppm mass. As an aromatic hydrocarbon, the naphthalene structure comprises a pair of fused benzene rings. It is best known as the main ingredient of traditional camphor.

Video Naphthalene

Histori

In the early 1820s, two separate reports describe white solids with a strong odor originating from coal tar distillation. In 1821, John Kidd quoted these two disclosures and then described many of the properties of these substances and their means of production. He proposed the name naphthaline , because it came from a kind of naphtha (broad term that includes a mixture of volatile liquid and flammable liquid, including coal tar). The chemical formula of Naphthalene was determined by Michael Faraday in 1826. The structure of the two joining benzene rings was proposed by Emil Erlenmeyer in 1866, and confirmed by Carl GrÃÆ'¤be three years later.

Maps Naphthalene

Structure and reactivity

Naphthalene molecules can be seen as a combination of a pair of benzene rings. (In organic chemistry, the ring integrates if they share two or more atoms.) Thus, naphthalene is classified as benzenoid polycyclic aromatic hydrocarbon (PAH). There are two sets of equivalent hydrogen atoms: the positions of alpha are numbered 1, 4, 5, and 8 (per diagram in the right margin), and position beta , 2, 3, 6, and 7.

Unlike benzene, carbon-carbon bonds in naphthalene do not have the same length. The C1-C2, C3-C4, C5-C6 and C7-C8 bonds are about 1.37 ÃÆ'... (137 pm) long, while the other carbon-carbon bonds are about 1.42 ÃÆ'... (142 pm) long. This difference, formed by X-ray diffraction, is consistent with the valence bond model in naphthalene and in particular, with the cross-conjugation theorem. This theorem describes naphthalene as an aromatic benzene unit attached to a diene but not extensively conjugated (at least in the ground state). Thus, naphthalene has several resonance structures.

Two isomers are possible for mono-substituted naphthalenes, corresponding to substitutions in alpha or beta positions. Bicyclo [6.2.0] decapentaene is a structural isomer with an integrated 4-8 ring system.

Reactions with electrophiles

In electrophilic aromatic substitution reactions, naphthalene is easier to react than benzene. For example, chlorination and bromination of naphthalene products without catalyst to each give 1-chloronaphthalene and 1-bromonaphthalene. Similarly, while both benzene and naphthalene can be alkylated using a Friedel-Crafts reaction, naphthalene may also be readily alkylated by reaction with an alkene or alcohol, using a sulfuric acid or phosphoric acid catalyst.

In regiochemical terms, electrophilic attack occurs in the alpha position. The selectivity for alpha over beta substitution can be rationalized in terms of the intermediate resonance structure: for an intermediate alpha substitution, seven resonance structures can be drawn, in which four retain an aromatic ring. For beta substitutions, the intermediate has only six resonance structures, and only two of them are aromatic. Sulfonation, however, provides a mixture of "alpha" products of 1-naphthalenesulfonic acid and "beta" 2-naphthalenesulfonic acid products, depending on the reaction conditions. The 1-isomer forms mainly at 25 ° C, and 2-isomers at 160 ° C. Sulfonation to give 1- and 2-sulfonic acid occurs easily:

H
₂ SO < span>
₄ C < H
₈ -> C
₁₀ H
₇ -SO
₃ H H
₂ O

Further sulfonation occurs to provide di-, tri-, and tetrasulfonic acids.

Litiation

Analogue with phenyllithium synthesis is a 1-bromonaphthalene conversion to 1-lithionaphthalene, lithium-halogen exchange:

C ₁₀ H ₇ Br BuLi -> C ₁₀ dd>

The resulting litionaphthalene undergoes a second lithiation, in contrast to the phenyllithium behavior. This 1.8-dilithio derivative is a precursor for a number of peri-naphthalene derivatives.

Reduction and oxidation

With an alkali metal, naphthalene forms a dark green-green anion radical salt such as sodium naphthalene, Na C ₁₀ H ^-
₈ . Naphthalenide salts are strong reducing agents.

Naphthalene can be hydrogenated under high pressure in the presence of a metal catalyst to provide 1,2,3,4-tetrahydronaphthalene ( C
₁₀ H
₁₂ ), also known as tetralin. Hydrogenation further produces decahydronaphthalene or decalin ( C
₁₀ H
₁₈ ).

Oksidasi dengan O
₂ di kehadiran katalis vanadium memberikan anhidrida ftalat:

C ₁₀ H ₈ 4,5 O ₂ -> C ₆ H ₄ (CO) ₂ O 2 CO ₂ 2 H ₂ O

This reaction is the principal use of naphthalene. Oxidation may also be affected using conventional stoichiometric chromates or permanganate reactants.

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Production

Most naphthalene comes from coal tar. From the 1960s to the 1990s, significant amounts of naphthalene were also produced from heavy petroleum fractions during petroleum refining, but the naphthalene derived from petroleum represents only a small component of naphthalene production.

Naphthalene is the single most abundant component of coal tar. Although the coal tar composition varies with the coal from which it is produced, the typical coal tar is about 10% naphthalene heavy. In industrial practice, coal tar distillation produces oils containing about 50% naphthalene, along with twelve other aromatic compounds. This oil, after washing with aqueous sodium hydroxide to remove the acid component (especially various phenols), and with sulfuric acid to remove the basic components, undergoes fractional distillation to isolate naphthalene. The raw naphthalene produced from this process is about 95% heavy naphthalene. The main impurities are aromatic compounds of benzothiophene containing sulfur (& lt; 2%), indane (0.2%), indene (& lt; Ã, 2%), and methylnaphthalene (& lt; Ã, 2%). Naphthalene derived from petroleum is usually more pure than that derived from coal tar. If necessary, crude naphthalene can be further purified by recrystallization of various solvents, resulting in 99% naphthalene weight, referred to as 80 ° C (melting point). About 1.3 million tons are produced each year.

In North America, coal tar manufacturers are Koppers Inc., Ruetgers Canada Inc. and Recochem Inc., and major oil producer is Monument Chemical Inc. In Western Europe, renowned producers are Koppers, Ruetgers, and Deza. In Eastern Europe, naphthalene is produced by a variety of integrated metallurgical complexes (Severstal, Evraz, Mechel, MMK) in Russia, a specialized manufacturer of INKOR naphthalene and phenol and Yenakievsky Metallurgy plant in Ukraine, and ArcelorMittal Temirtau in Kazakhstan.

Resources and other events

Aside from coal tar, trace amounts of naphthalene are generated by certain magnolias and deer species, as well as the Formosa underground termites, which may be produced by termites as a repellent to "ants, poisonous mushrooms, and nematode worms". Some strains of endophytic fungus Muscodor albus produce naphthalene among various volatile organic compounds, while Mushodor vitigenus produces naphthalene almost exclusively.

Naphthalene in interstellar medium

Naphthalene has been tentatively detected in the interstellar medium toward the Cernis 52 star in the constellation Perseus. More than 20% of the carbon in the universe may be related to polyaromatic hydrocarbons, including naphthalene.

Protonated cation naphthalene ( C
₁₀ H
₉ ) are source sections of the Unidentified Infrared Emissions (UIRs) spectrum. The protonated naphthalene differs from neutral naphthalene (eg, used in camphor) because it has additional hydrogen atoms. UIRs of "naphthalene cation" ( C
₁₀ H
₉ ) has been observed by astronomers. The research has been published as "camphor in space."

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Usage

Naphthalene is used primarily as a precursor for other chemicals. The largest single naphthalene use is industrial production of phthalic anhydride, although more phthalal anhydrides are made of o-xylene. Many azo dyes are produced from naphthalene, and so are 1-naphthyl- N insecticides -methylcarbamate ( carbaryl ). Other useful agrichemicals include naphtha acids.

Naphthalenesulfonic acid and sulfonate

Many beneficial naphthalenesulfonic and sulfonic acids. Alkyl naphthalene sulphonate is a surfactant, aminonafthaleneulphonic acid, naphthalene substituted with amine and sulfonic acid, is an intermediate in the manufacture of many synthetic dyes. Hydrogenated naphthalene tetrahydronaphthalene (tetralin) and desahydronaphthalene (decalin) are used as low volatility solvents. Naphthalene sulfonic acid is also used in the synthesis of 1-naphthol and 2-naphthol, precursors for various dyestuffs, pigments, rubber processing chemicals and other chemicals and pharmaceuticals.

Naphthalene sulfonic acid is used in the manufacture of naphthalene sulphonate (dispersant) solvent polymers, which are used to produce concrete and plasterboard (wall or drywall). They are also used as dispersants in synthetic and natural rubber, and as tanning agents (syntans) in the leather industry, agricultural formulations (dispersants for pesticides), dyes and as dispersants in lead-acid battery plates.

Naphthalene sulphonate polymer is produced by treating naphthalene sulphonic acid with formaldehyde, followed by neutralization with sodium hydroxide or calcium hydroxide. These products are sold commercially in solution (water) or dry powder.

Laboratory using

Molten naphthalene provides an excellent dissolving medium for soluble aromatic compounds. In many cases, it is more efficient than other high boiling solvents, such as dichlorobenzene, benzonitrile, nitrobenzene and durene. Reaction C ₆₀ with anthracene is conveniently applied to naphthalene reflux to give a 1: 1 Diels-Alder addener. Aromatization hydroporphyrins have been achieved using a DDQ solution in naphthalene.

Wetting agent and surfactant

Alkyl naphthalene sulfonates (ANS) are used in many industrial applications as nondetergen wetting agents that effectively dissolve the colloidal system in aqueous media. Its main commercial application is the agricultural chemical industry, which uses ANS for wettable powder and dry-flowable drying formulations, and textile and fabric industries, utilizing wetting and removing foam properties from ANS for bleaching and dipping operations.

As a fumigant

Naphthalene has been used as a household fumigant. It was once the main ingredient in camphor, although its use has largely been replaced in favor of alternatives such as 1,4-dichlorobenzene. In a sealed container containing naphthalene pellets, naphthalene vapor accumulates toxicity to the adult and larval forms of many moths that attack textiles. Other uses of naphthalene include use in soil as fumigant pesticides, in attic chambers to expel animals and insects, and in storage drawers and museum cabinets to protect contents from insect pests.

Naphthalene is a repellent for oposum.

Other Use

It is used in special effects of pyrotechnics such as the generation of black smoke and simulated explosions. It is used to make artificial pores in the manufacture of high porosity grinding wheels. In the past, naphthalene was given orally to kill parasitic worms in farm animals. Naphthalene and its alkyl homologues are the main constituents of creosote. Naphthalene is used in a technique for studying heat transfer using mass sublimation.

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Health effects

Exposure to large amounts of naphthalene can damage or destroy red blood cells, most often in people with inherited conditions known as lack of glucose-6-phosphate dehydrogenase (G6PD), which more than 400 million people suffer. Humans, especially children, have developed a condition known as haemolytic anemia, after swallowing camphor or deodorant blocks containing naphthalene. Symptoms include fatigue, lack of appetite, anxiety, and pale skin. Large amounts of naphthalene exposure can cause confusion, nausea, vomiting, diarrhea, blood in urine, and jaundice (yellowing of the skin due to liver dysfunction).

When the US National Toxicology Program (NTP) exposed male and female mice and rats to naphthalene vapors on weekdays for two years, male and female rats showed evidence of carcinogenesis with increased incidence of adenoma and neuroblastoma in the nose, female rats showed some evidence of carcinogenesis based on increased incidence alveolar adenoma and bronchiolar lung, and male rats did not show evidence of carcinogenesis.

The International Agency for Research on Cancer (IARC) classifies naphthalene as a possible carcinogenic in humans and animals (Group 2B). The IARC also shows that acute exposure causes cataracts in humans, rats, rabbits, and rats; and that hemolytic anemia (described above) can occur in children and infants after oral exposure or inhalation or after maternal exposure during pregnancy. Under California's Proposition 65, naphthalene is listed as "Unknown State causing cancer". Possible mechanisms for carcinogenic effects of camphor and certain types of air fresheners containing naphthalene have been identified.

Rule

US government agencies have set limits on occupational exposure to naphthalene exposure. The Occupational Health and Safety Administration has set a permitted exposure limit of 10 ppm (50 mg/m ³ ) for 8 hours of a time-weighted average. The National Institute for Occupational Safety and Health has set a recommended exposure limit of 10 ppm (50 mg/m ³ ) for 8 hours of time-weighted averages, as well as short-term exposure limits at 15 ppm (75 mg/m ³ ).

Cottons and other products containing naphthalene have been banned in the European Union since 2008.

In China, the use of naphthalene in mothballs is prohibited. Dangers to human health and the common use of natural camphor are referred to as the reason for the ban.

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Neththene <

The partial list of naphthalene derivatives includes the following compounds:

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See also

• Camphor
• Dialin, Tetralin, Decalin
• List of interstellar molecules and star states
• Mothballs
• 1-Naphthol, 2-Naphthol
• Sodium naphthalenide
• Wagner-Jauregg's reaction (classic naphthalene synthesis)

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References

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External links

• Naphthalene - National Pesticide Information Center
• Naphthalene - EPA Air Toxics Website
• Naphthalene (PIM 363) - mostly on naphthalene toxicity
• Naphthalene - CDCÃ, - NIOSH Pocket Guide to Chemical Hazards
• Naphthalene in the Pesticide Property DataBase (PPDB)

Source of the article : Wikipedia