FGROUP by class
Carbon Carbon skeleton Hydrocarbon ring N-heterocyclic O-heterocyclic S-heterocyclic Mixed-heterocyclic Oxygen Ether (F320000) Hemiacetal Ether (F321400) Acetal (F321400) Open acetal (F321410) Cyclic acetal (F321420) Nitrogen Sulfur Phosphorus Halogen Boron Magnesium Silicon Iron Cobalt Asenic Selenium Tin