Chemistry:Sulfur oxoacid

Short description: Acid containing sulfur, oxygen, and hydrogen

Sulfur oxoacids are chemical compounds that contain sulfur, oxygen, and hydrogen. The best known and most important industrially used is sulfuric acid. Sulfur has several oxoacids; however, some of these are known only from their salts (these are shown in italics in the table below). The acids that have been characterised contain a variety of structural features, for example:

• tetrahedral sulfur when coordinated to oxygen
• terminal and bridging oxygen atoms
• terminal peroxo groups
• terminal S=S
• chains of (−S−)_n

Acid	Formula	Formal oxidation number	Structure	Related anions	Notes
Sulfuric acid	H2SO4	+6		Sulfate, SO2−4 and hydrogen sulfate commonly known as bisulfate, HSO−4	Best known and industrially significant.
Polysulfuric acids including disulfuric acid (pyrosulfuric acid)	H2SO4·nSO3	+6		Disulfate (commonly known as pyrosulfate), S2O2−7 and trisulfate, S3O2−10	Pure disulfuric acid melts at 36 °C. Present in fuming sulfuric acid, oleum. Examples known for n = 1 and n = 2.
Peroxymonosulfuric acid	H2SO5	+6		Peroxomonosulfate, OOSO2−3	"Caro's acid", a solid melting at 45 °C
Peroxydisulfuric acid	H2S2O8	+6		Peroxydisulfate, O3SOOSO2−3	"Marshall's acid", a solid melting at 65 °C.
Dithionic acid	H2S2O6	+5		Dithionate, O3SSO2−3	Not isolated in pure form, only concentrated solutions have been prepared
Thiosulfuric acid	H2S2O3	0 (for the terminal sulfur), +4 (for the central atom)		Thiosulfate, S2O2−3 Hydrogenthiosulfate HS2O−3 (ammonium salt prepared in anhydrous methanol at −80 °C)	Aqueous solutions decompose.
Disulfurous acid or pyrosulfurous acid	H2S2O5	+5 (of the sulfur atom bonded to 3 oxygen atoms), +3 (of other sulfur atom)		Disulfite commonly known as metabisulfite, S2O2−5	Not known.
Sulfurous acid	H2SO3	+4		Bisulfite, HSO−3 and sulfite, SO2−3	Not known.
Dithionous acid	H2S2O4	+3		Dithionite, O2SSO2−2	Not known.
Sulfoxylic acid	H2SO2	+2		Sulfoxylate, SO2−2	Free acid not known
Polythionic acid	H2SxO6	0 (for the bridging S atoms), +5 (for the terminal central S atoms)		Polythionates, O3S(Sx−2)SO2−3. Example trithionate, tetrathionate, pentathionate, hexathionate, heptathionate, octathionate, nonathionate, decathionate, undecathionate, dodecathionate, tridecathionate, and tetradecathionate.	Examples known with x = 3, 4, 5, 6, 7, 8, 10, 12, 14.
Thiosulfurous acid	H2S2O2	−1 (for the exterior sulfur atom ), +3 (for the central atom)		Thiosulfites	Not known
Dihydroxydisulfane	H2S2O2	+1			Acid known

See also

• Chlorosulfuric acid
• Fluorosulfuric acid
• Nitrosylsulfuric acid
• Peroxydisulfuric acid
• Sulfinic acids
• Sulfonic acids

External links

• Sulfur+Acids at the US National Library of Medicine Medical Subject Headings (MeSH) Sulfur oxoacids along with other acids containing sulfur