FGROUP by class
Carbon Carbon skeleton Hydrocarbon ring N-heterocyclic O-heterocyclic S-heterocyclic Mixed-heterocyclic Oxygen Nitrogen Nitro (F441000) Nitro alkyl (F441100) Nitro allyl (F441200) Nitro aryl (F441400) Sulfur Phosphorus Halogen Boron Magnesium Silicon Iron Cobalt Asenic Selenium Tin