Pyrene
IUPAC name pyrene
Other names benzo[def]phenanthrene
Identifiers
CAS number	129-00-0 Y
PubChem	31423
ChemSpider	29153 Y
KEGG	C14335 Y
ChEBI	CHEBI:39106 Y
ChEMBL	CHEMBL279564 Y
RTECS number	UR2450000
Jmol-3D images	Image 1
SMILES c1cc2ccc3cccc4c3c2c(c1)cc4
InChI 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 Y Key: BBEAQIROQSPTKN-UHFFFAOYSA-N Y 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
Properties
Molecular formula	C16H10
Molar mass	202.25 g/mol
Appearance	colorless solid (yellow impurities are often found at trace levels in many samples).
Density	1.271 g/ml
Melting point	145-148 °C (418-421 K)
Boiling point	404 °C (677 K)
Solubility in water	0.135 mg/l
Hazards
MSDS	External MSDS
R-phrases	36/37/38-45-53
S-phrases	24/25-26-36
Main hazards	irritant
NFPA 704	1 2 0
Flash point	non-flammable
Related compounds
Related PAHs	benzopyrene
Supplementary data page
Structure and properties	n, εr, etc.
Thermodynamic data	Phase behaviour Solid, liquid, gas
Spectral data	UV, IR, NMR, MS
Y (verify) (what is: Y/N?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

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

Pyrene is a polycyclic aromatic hydrocarbon (PAH) consisting of four fused benzene rings, resulting in a flat aromatic system. The chemical formula is C₁₆H₁₀. This colourless solid 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.

Occurrence and reactivity [link]

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.^[1]

Oxidation with chromate affords perinaphthenone and then naphthalene-1,4,5,8-tetracarboxylic acid. It undergoes a series of hydrogenation reactions, and it is susceptible to halogenation, Diels-Alder additions, and nitration, all with varying degrees of selectivity.^[1]

Applications [link]

Pyrene and its derivatives are used commercially to make dyes and dye precursors, for example pyranine and naphthalene-1,4,5,8-tetracarboxylic acid. Its derivatives are also valuable molecular probes via fluorescence spectroscopy, having a high quantum yield and lifetime (0.65 and 410 nanoseconds, respectively, in ethanol at 293 K). Its fluorescence emission spectrum is very sensitive to solvent polarity, so pyrene has been used as a probe to determine solvent environments. This is due to its excited state having a different, non-planar structure than the ground state. Certain emission bands are unaffected, but others vary in intensity due to the strength of interaction with a solvent.

Safety [link]

Although it is not as problematic as benzopyrene, animal studies have shown pyrene is toxic to the kidneys and the liver.

See also [link]

• Perhydropyrene

References [link]

1. ^ ^{a b} Selim Senkan and Marco Castaldi "Combustion" in Ullmann's Encyclopedia of Industrial Chemistry, 2003 Wiley-VCH, Weinheim. Article Online Posting Date: March 15, 2003.

• Birks, J. B. (1969). Photophysics of Aromatic Molecules. London: Wiley. 
• Valeur, B. (2002). Molecular Fluorescence: Principles and Applications. New York: Wiley-VCH. 
• Birks, J.B. (1975). Eximers. london: Reports on Progress in Physics. 
• Fetzer, J. C. (2000). The Chemistry and Analysis of the Large Polycyclic Aromatic Hydrocarbons. New York: Wiley. 

External links [link]

• Pyrene