pyrene

Pyrene
IUPAC name	pyrene
Other names	benzo(d,e,f)phenanthrene
Identifiers
CAS number	129-00-0 Y
RTECS number	UR2450000
SMILES	C12=CC=C3C=CC=C4 C=CC(C2=C34)=CC=C1
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
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 (what is this?)  (verify) 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. This colourless solid is the smallest peri-fused polycyclic aromatic hydrocarbon - one where the rings are fused through more than one face. Pyrene forms during incomplete combustion of organic compounds.

Occurrence and reactivity

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. Thus, 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 is susceptible to halogenation, Diels-Alder additions, and nitration, all with varying degrees of selectivity.^[1]

Applications

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 nanosecond, respectively, in ethanol at 293K). Its fluorescence emission spectrum is very sensitive to the solvent's 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

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

References

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

• Pyrene