FGROUP by class
 Carbon
 Carbon skeleton
 Hydrocarbon ring
 N-heterocyclic
 O-heterocyclic
 S-heterocyclic
 Mixed-heterocyclic
 Oxygen
 Nitrogen
 Sulfur
	Thioether (F521000)
	Sulfide (F521000)
		Di-alkyl sulfide (F521100)
		Alkyl aryl sulfide (F521200)
		Di-aryl sulfide (F521300)
		Alkyl allyl sulfide (F521400)
		Allyl aryl sulfide (F521500)
		Di-allyl sulfide (F521600)
		Alkyl acetylene sulfide (F521700)
		Allyl acetylene sulfide (F521800)
		Thioacetal (F521900)
		Hemiacetal thiol ether (F521900)
 Phosphorus
 Halogen
 Boron
 Magnesium
 Silicon
 Iron
 Cobalt
 Asenic
 Selenium
 Tin