• occurs
  • Benzopyrene is a component of pitch and occurs together with other related pentacyclic aromatic species such as picene, benzofluoranthenes, and perylene. (wikipedia.org)
  • sulfur
  • 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)
  • structurally
  • They are structurally similar to other halogenated hydrocarbons such as polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs), and polychlorinated biphenyls (PCBs). (wikipedia.org)
  • main
  • The two main types are electrophilic aromatic substitution when the active reagent is an electrophile and nucleophilic aromatic substitution when the reagent is a nucleophile. (wikipedia.org)
  • Food
  • The EU-RL for polycyclic aromatic hydrocarbons in Feed and Food as laid down in Regulation (EC) No 882/2004 and Directive 96/23/EC contributes to the implementation of high quality implementation and uniform results. (wur.nl)