Pyrene

Chemical compound From Wikipedia, the free encyclopedia

Pyrene is a polycyclic aromatic hydrocarbon (PAH) with the formula C16H10. Consisting of four fused benzene rings, it in a flat aromatic compound. This colorless compound is the smallest peri-fused PAH (one where the rings are fused through more than one face). Pyrene forms during incomplete combustion of organic compounds.[10]

Quick facts Names, Identifiers ...
Pyrene
Structural formula of pyrene
Ball-and-stick model of the pyrene molecule
Names
Preferred IUPAC name
Pyrene[1]
Other names
Benzo[def]phenanthrene
Identifiers
3D model (JSmol)
1307225
ChEBI
ChEMBL
ChemSpider
ECHA InfoCard 100.004.481 Edit this at Wikidata
84203
KEGG
RTECS number
  • UR2450000
UNII
  • InChI=1S/C16H10/c1-3-11-7-9-13-5-2-6-14-10-8-12(4-1)15(11)16(13)14/h1-10H checkY
    Key: BBEAQIROQSPTKN-UHFFFAOYSA-N checkY
  • InChI=1/C16H10/c1-3-11-7-9-13-5-2-6-14-10-8-12(4-1)15(11)16(13)14/h1-10H
    Key: BBEAQIROQSPTKN-UHFFFAOYAB
  • c1cc2cccc3c2c4c1cccc4cc3
Properties
C16H10
Molar mass 202.256 g·mol−1
Appearance colorless solid

(yellow impurities are often found at trace levels in many samples).

Density 1.271 g/cm3[2]
Melting point 150.62 °C (303.12 °F; 423.77 K)[2]
Boiling point 394 °C (741 °F; 667 K)[2]
0.049 mg/L (0 °C)
0.139 mg/L (25 °C)
2.31 mg/L (75 °C)[3]
log P 5.08[4]
Band gap 2.02 eV[5]
−147·10−6 cm3/mol[6]
Structure[7]
Monoclinic
P21/a
a = 13.64 Å, b = 9.25 Å, c = 8.47 Å
α = 90°, β = 100.28°, γ = 90°
4
Thermochemistry[8]
229.7 J/(K·mol)
224.9 J·mol−1·K−1
125.5 kJ·mol−1
Enthalpy of fusion (ΔfH⦵fus)
 17.36 kJ·mol−1
Hazards
Occupational safety and health (OHS/OSH):
Main hazards
 irritant
GHS labelling:[9]
GHS07: Exclamation markGHS09: Environmental hazard
Warning
H315, H319, H335, H410
P261, P264, P271, P273, P280, P302+P352, P304+P340, P305+P351+P338, P312, P321, P332+P313, P337+P313, P362, P391, P403+P233, P405, P501
NFPA 704 (fire diamond)
NFPA 704 four-colored diamondHealth 2: Intense or continued but not chronic exposure could cause temporary incapacitation or possible residual injury. E.g. chloroformFlammability 1: Must be pre-heated before ignition can occur. Flash point over 93 °C (200 °F). E.g. canola oilInstability 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no code
2
1
0
Flash point non-flammable
Related compounds
Related PAHs
 benzopyrene
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Occurrence and properties

Pyrene was first isolated from coal tar, where it occurs up to 2% by weight. As a peri-fused PAH, pyrene is much more resonance-stabilized than its five-member-ring containing isomer fluoranthene. Therefore, it is produced in a wide range of combustion conditions. For example, automobiles produce about 1 μg/km.[11]

Reactions

Pyrene contains two kinds of ring subunits: two a-rings with three CH bonds and two b-rings with two CH bonds.[12] The a-rings are more susceptible to reactions with electrophiles and oxidants. The b-rings can be partially hydrogenated to give tetrahydropyrene. Similarly the b-rings can be oxygenated to give the quinone-like derivative C16H8O2[13]

Oxidation with chromate affords perinaphthenone and then naphthalene-1,4,5,8-tetracarboxylic acid. Pyrene undergoes a series of hydrogenation reactions and is susceptible to halogenation, Diels-Alder additions, and nitration, all with varying degrees of selectivity.[11] Bromination occurs at one of the 1-positions.[14][15]

Reduction with sodium affords the radical anion. From this anion, a variety of pi-arene complexes can be prepared.[16]

Pyrene and its derivatives are used commercially to make dyes and dye precursors, for example pyranine and naphthalene-1,4,5,8-tetracarboxylic acid.

Photophysics

Pyrene has been described as "one of the most studied organic molecules in terms of its photophysical properties ..., by far, the most frequently applied dye in fluorescence labeled polymers". It is an electron donor in some donor-acceptor systems.[17] Its potential as a photocatalyst has also been heavily investigated.[18]

Pyrene was the first molecule for which excimer behavior was discovered.[19] Such excimer appears around 450 nm. Theodor Förster reported this in 1954.[20]

STM image of self-assembled Br4Py molecules on Au(111) surface (top) and its model (bottom; pink spheres are Br atoms).[21]

Pyrene's fluorescence emission spectrum is very sensitive to solvent polarityt.

Diagram showing the numbering and ring fusion locations of pyrene according to IUPAC nomenclature of organic chemistry.

Safety and environmental factors

Although it is not as problematic as benzopyrene, animal studies have shown pyrene is toxic to the kidneys and liver. It is now known that pyrene affects several living functions in fish and algae.[22]

Its biodegradation has been heavily examined. The process commences with dihydroxylation at each of two kinds of CH=CH linkages.[23] Experiments in pigs show that urinary 1-hydroxypyrene is a metabolite of pyrene, when given orally.[24]

See also

References

Cited sources

Further reading

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