FGROUP by class
 Carbon
 Carbon skeleton
 Hydrocarbon ring
 N-heterocyclic
 O-heterocyclic
 S-heterocyclic
 Mixed-heterocyclic
 Oxygen
 Nitrogen
 Sulfur
	Mercaptan (F510000)
	Thiol (F510000)
	Thioacid (F516000)
	Thioether (F521000)
	Sulfide (F521000)
	Disulfide (F522000)
	Trisulfide (F523000)
	Tetrasulfide (F524000)
	Sulfonium (F530000)
	Acyl thioester (F540000)
	Thioester (F540000)
	Thiocarbonyl (F550000)
	Sulfoxide (F561000)
	S-oxide (F561000)
	Sulfone (F562000)
	Sulfonyl (F562000)
	Sulfenate (F571000)
	Sulfite (F572000)
	Sulfonate (F573000)
	Sulfate (F574000)
	Thiosulfate (F575000)
	Sulfamate (F581000)
	Sulfenamide (F582000)
	Sulfonamide (F583000)
 Phosphorus
 Halogen
 Boron
 Magnesium
 Silicon
 Iron
 Cobalt
 Asenic
 Selenium
 Tin