• structurally
  • They are structurally similar to other halogenated hydrocarbons such as polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs), and polychlorinated biphenyls (PCBs). (wikipedia.org)
  • occurs
  • Benzopyrene is a component of pitch and occurs together with other related pentacyclic aromatic species such as picene, benzofluoranthenes, and perylene. (wikipedia.org)
  • rings
  • Many simple aromatic rings have trivial names. (wikipedia.org)
  • The nitrogen (N)-containing aromatic rings can be separated into basic aromatic rings that are easily protonated, and form aromatic cations and salts (e.g., pyridinium), and non-basic aromatic rings. (wikipedia.org)
  • Examples of basic aromatic rings are pyridine or quinoline. (wikipedia.org)
  • Examples of non-basic nitrogen-containing aromatic rings are pyrrole and indole. (wikipedia.org)
  • In the oxygen- and sulfur-containing aromatic rings, one of the electron pairs of the heteroatoms contributes to the aromatic system (similar to the non-basic nitrogen-containing rings), whereas the second lone pair extends in the plane of the ring (similar to the basic nitrogen-containing rings). (wikipedia.org)