නැෆ්තලීන්

නැප්තලීන් සුදු පැහැයෙන් යුත්, ස්ඵටිකරූපී, ඇරෝමැටික, ඝන හයිඩ්‍රොකාබනයකි. එය නප්තලයින්, නැප්තීන්, තාර කැම්පර්, සුදු තාර, ඇල්බෝකාබන් , ඇන්ටිමයිට් ආදී නම් වලින් හැඳින්වුවද සමඟ පටලවා නොගත යුතුය. Naphthalene (not to be confused with ), also known as naphthalin, naphthaline, napthene, tar camphor, white tar, albocarbon, or antimite is a crystalline, , white, solid , best known as the traditional, primary ingredient of . It is volatile, forming a flammable , and readily at room temperature, producing a characteristic odor that is detectable at concentrations as low as 0.08 .

Naphthalene

Names
bicyclo[4.4.0]deca-1,3,5,7,9-pentene
වෙනත් නාම Tar Camphor, White Tar, Moth Flakes, albocarbon, naphthaline, naphthalin, antimite
Identifiers
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3D model ()	Interactive image
	CHEBI:{{{value}}}
	100.001.863
	202-049-5
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(EPA)	DTXSID8020913
Properties
Molecular formula	C10H8
	128.17052 g/mol
Appearance	White solid crystals/flakes, strong odor of coal tar
	1.14 g/cm³
	80.26 °C, 353 K, 176 °F
	218 °C, 491 K, 424 °F
in water	Approximately 30 mg/L
Hazards
(OHS/OSH):
Main hazards	, , possible . Dust can form mixtures with
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Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).  Y   (verify)

History

In 1819–1820, at least two chemists reported a white solid with a pungent odor derived from the distillation of coal tar. In 1821, 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 (a broad term encompassing any volatile, flammable liquid hydrocarbon mixture, including coal tar). Naphthaline's chemical formula was determined by Michael Faraday in 1826. The structure of two fused benzene rings was proposed by in 1866, and confirmed by 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 (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 , such as , 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 , and is consistent with the model of bonding in napthalene which involves three (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.

Like benzene, naphthalene can undergo . 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 or catalyst, naphthalene and chlorine can react to form 1-chloronaphthalene even without a catalyst. Similarly, while both benzene and naphthalene can be alkylated using , naphthalene can also be alkylated by reaction with or , with or as the catalyst.

Two 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 forms predominantly at 25 °C, and the 2-isomer at 160 °C.

Naphthalene can be under high pressure with metal to give 1,2,3,4-tetrahydronaphthalene or (C₁₀H₁₂). Further hydrogenation yields or decalin (C₁₀H₁₈). with or , or catalytic oxidation with O₂ and a , gives .

Uses

Naphthalene's most familiar use is as a household , such as in (although (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 that attack textiles. Other fumigant uses of naphthalene include use in soil as a fumigant pesticide, in 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 ^[], such as the use of moth balls in a tool box.

Naphthalene and its alkyl are the major constituents of .

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 (although more phthalic anhydride is made from than from naphthalene). Other naphthalene-derived chemicals include alkyl naphthalene sulfonate , and the . Naphthalenes substituted with combinations of strongly electron-donating , such as and , and strongly electron-withdrawing groups, especially , are intermediates in the preparation of many synthetic . The hydrogenated naphthalenes (tetralin) and (decalin) are used as low-volatility .

Naphthalene sulfonic acids are used in the manufacture of naphthalene sulfonate polymer which are used to produce and ( or ). They are also used as in synthetic and natural rubbers, and as 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 , and of miscellaneous chemicals and pharmaceuticals.

See also

• (the fully saturated analog of naphthalene)
• Classic naphthalene synthesis: the

References

1. Amoore J E and Hautala E (1983). "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". J Appl Toxicology. 3 (6): 272–290. doi:10.1002/jat.2550030603.
2. John Kidd (1821). "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". Philosophical Transactions. 111: 209–221. doi:10.1098/rstl.1821.0017.
3. Emil Erlenmeyer (1866). "Studien über die s. g. aromatischen Säuren". . 137 (3): 327–359. doi:10.1002/jlac.18661370309.

CRC Handbook of Chemistry and Physics 87th edition

External links

• National Pesticide Information Center - Mothballs Case Profile 2010-06-22 at the Wayback Machine
• Naphthalene - EPA Air Toxics Web Site
• Naphthalene (PIM 363) - mostly on toxicity of naphthalene
• Koppers Inc.[1]
• Recochem Inc.[2]
• Advanced Aromatics, L.P.[3] 2008-12-10 at the Wayback Machine