FGROUP by class
Carbon Carbon skeleton Hydrocarbon ring N-heterocyclic O-heterocyclic S-heterocyclic Mixed-heterocyclic Oxygen Nitrogen Sulfur Sulfonium (F530000) Tri-alkyl sulfonium (F531000) Di-alkyl aryl sulfonium (F532000) Phosphorus Halogen Boron Magnesium Silicon Iron Cobalt Asenic Selenium Tin