FGROUP by class
Carbon Carbon skeleton Hydrocarbon ring Monocyclic 6-membered Aromatic Benzene (F211630) Phenyl (F211631) Benzoquinone (F211632) N-heterocyclic O-heterocyclic S-heterocyclic Mixed-heterocyclic Oxygen Nitrogen Sulfur Phosphorus Halogen Boron Magnesium Silicon Iron Cobalt Asenic Selenium Tin