FGROUP by class
Carbon Carbon skeleton Hydrocarbon ring N-heterocyclic Monocyclic 3-membered Saturated Aziridine (F221311) Ethyleneimine (F221311) O-heterocyclic S-heterocyclic Mixed-heterocyclic Oxygen Nitrogen Sulfur Phosphorus Halogen Boron Magnesium Silicon Iron Cobalt Asenic Selenium Tin