Policiklični aromatični ugljovodonik

Standard line-angle schematic representation of an important PAH, benzo[a]pyrene, where carbon atoms are represented by the vertices of the hexagons, and hydrogens are inferred as projecting out at 120° angles to fill the fourth carbon valence (as necessary)

Policiklični aromatični ugljovodonici (PAH, poliaromatični ugljovodonici) su ugljovodonična—organska jedinjenja koja sadrže samo ugljenik i vodonik — koja se sastoje od višestrukih aromatičnih prstenova (organski prstenovi u kojima su elektroni delokalizovani). Formalno, the class is further defined as lacking further branching substituents on these ring structures. Polynuclear aromatic hydrocarbons (PNAs) are a subset of PAHs that have fused aromatic rings, that is, rings that share one or more sides. The simplest such chemicals are naphthalene, having two aromatic rings, and the three-ring compounds anthracene and phenanthrene.

PAHs are neutral, nonpolar molecules found in coal and in tar deposits. They are produced as well by incomplete combustion of organic matter (e.g., in engines and incinerators, when biomass burns in forest fires, etc.).

PAHs may also be abundant in the universe, and are conjectured to have formed as early as the first couple of billion years after the Big Bang, in association with formation of new stars and exoplanets. Some studies suggest that PAHs account for a significant percentage of all carbon in the universe, and PAHs are discussed as possible starting materials for abiologic syntheses of materials required by the earliest forms of life.

Nomenklatura, struktura, osobine

Nomenklatura i struktura

The tricyclic species phenanthrene and anthracene represent the starting members of the PAHs. Smaller molecules, such as benzene, are not PAHs, and PAHs are not generally considered to contain heteroatoms or carry substituents.

PAHs with five or six-membered rings are most common. Those composed only of six-membered rings are called alternant PAHs, which include benzenoid PAHs. The following are examples of PAHs that vary in the number and arrangement of their rings:

• Examples of PAH compounds
• 
  Anthracene
• 
  Phenanthrene
• Tetracene
  Tetracene
• 
  Chrysene
• 
  Triphenylene
• 
  Pyrene
• 
  Pentacene
• 
  Benzo[a]pyrene
• 
  Corannulene
• 
  Benzo[ghi]perylene
• 
  Coronene
• 
  Ovalene
• 
  Benzo[c]fluorene

Vidi još

• Pletena žica (hemija)
• Grafen

Vanjske veze

• ATSDR - Toxicity of Polycyclic Aromatic Hydrocarbons (PAHs) U.S. Department of Health and Human Services
• Fused Ring and Bridged Fused Ring Nomenclature
• Database of PAH structures
• Cagliari PAH Theoretical Database
• NASA Ames PAH IR Spectroscopic Database
• National Pollutant Inventory: Polycyclic Aromatic Hydrocarbon Fact Sheet
• Understanding Polycyclic Aromatic Hydrocarbons NASA Spitzer Space Telescope
• Astrobiology magazine Aromatic World An interview with Professor Pascale Ehrenfreund on PAH origin of life. Accessed June 2006
• Oregon State University Superfund Research Center focused on new technologies and emerging health risks of Polycyclic Aromatic Hydrocarbons (PAHs)
• Polycyclic Aromatic Hydrocarbons (PAHs)--EPA Fact Sheet. U.S. Environmental Protection Agency, Office of Solid Waste, January 2008.