FGROUP by class
Carbon Carbon skeleton 1 carbon Saturated Methyl N-methyl (F101111) O-methyl (F101112) S-methyl (F101113) P-methyl (F101114) Hydrocarbon ring N-heterocyclic O-heterocyclic S-heterocyclic Mixed-heterocyclic Oxygen Nitrogen Sulfur Phosphorus Halogen Boron Magnesium Silicon Iron Cobalt Asenic Selenium Tin