PAHS

PAHS may refer to:

Schools

See also

Polycyclic aromatic hydrocarbon

Polycyclic aromatic hydrocarbons (PAHs, also polyaromatic hydrocarbons) are hydrocarbons—organic compounds containing only carbon and hydrogen—that are composed of multiple aromatic rings (organic rings in which the electrons are delocalized). Formally, the class is further defined as lacking further branching substituents off of 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. Though poly- in these cases literally means "many", there is precedence in nomenclature for beginning this class and subclass with the two ring cases, where naphthalene would therefore be considered a simple example; beginning at three rings, examples include anthracene and phenanthrene.

PAHs are neutral, nonpolar molecules; they are found in fossil fuels (oil and coal) and in tar deposits, and are produced, generally, when insufficient oxygen or other factors result in incomplete combustion of organic matter (e.g., in engines and incinerators, when biomass burns in forest fires, etc.). PAHs can also be found at high levels in cooked foods, e.g., in meat cooked at high temperatures over open flame. Benzo[a]pyrene is a well-researched example of a coal tar PAH (see image) whose metabolites are mutagenic and highly carcinogenic; as a class, benzopyrenes, a ring fusion between monocyclic benzene and tetracyclic pyrene rings, result from incomplete combustion at temperatures between 300 °C (572 °F) and 600 °C (1,112 °F).