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{{short description|Chemical compound}}
{{confused|Sulfuric acid}} {{chembox
{{distinguish|Sulfuric acid}}
| Verifiedfields = changed
{{chembox
| verifiedrevid = 417930064
| verifiedrevid = 470482579
| Name = Sulfurous acid
| Name = Sulfurous acid
| ImageFile_Ref = {{chemboximage|correct|??}} | ImageFile_Ref = {{chemboximage|correct|??}}
| ImageFile = Sulfurous-acid-2D-pyramidal.png | ImageFile = Sulfurous-acid-2D-pyramidal.png
| ImageSize = 150px | ImageSize = 150px
| ImageName = Sulfurous acid | ImageName = Sulfuric(IV) acid
| ImageFile1 = Sulfurous-acid-3D-balls.png | ImageFile1 = Sulfurous-acid-3D-balls.png
| ImageName1 = Ball-and-stick model of sulfurous acid
| ImageSize1 = 200px
| OtherNames = Sulfuric(IV) acid<br/>Thionic acid<br/>Sulfinic acid
| ImageName1 = Ball-and-stick model of sulfurous acid
| IUPACName = Sulfurous acid | IUPACName = Sulfurous acid
| SystematicName =
| Section1 = {{Chembox Identifiers
| Section1 = {{Chembox Identifiers
| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
| CASNo = 7782-99-2
| CASNo_Ref = {{cascite|correct|CAS}}
| ChEBI_Ref = {{ebicite|correct|EBI}}
| ChEBI = 48854
| ChEMBL_Ref = {{ebicite|correct|EBI}}
| ChEMBL = 1161699
| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
| ChemSpiderID = 1069 | ChemSpiderID = 1069
| EC_number = 231-973-1
| Gmelin = 1458
| PubChem = 1100 | PubChem = 1100
| UNII_Ref = {{fdacite|correct|FDA}} | UNII_Ref = {{fdacite|correct|FDA}}
Line 22: Line 31:
| InChI = 1/H2O3S/c1-4(2)3/h(H2,1,2,3) | InChI = 1/H2O3S/c1-4(2)3/h(H2,1,2,3)
| InChIKey = LSNNMFCWUKXFEE-UHFFFAOYAJ | InChIKey = LSNNMFCWUKXFEE-UHFFFAOYAJ
| SMILES = O(=O)O
| ChEBI_Ref = {{ebicite|changed|EBI}}
| ChEBI = 48854 | SMILES1 = O(O)
| SMILES1_Comment = Tautomer
| SMILES = O=S(O)O
| ChEMBL_Ref = {{ebicite|correct|EBI}}
| ChEMBL = 1161699
| StdInChI_Ref = {{stdinchicite|correct|chemspider}} | StdInChI_Ref = {{stdinchicite|correct|chemspider}}
| StdInChI = 1S/H2O3S/c1-4(2)3/h(H2,1,2,3) | StdInChI = 1S/H2O3S/c1-4(2)3/h(H2,1,2,3)
| StdInChIKey_Ref = {{stdinchicite|correct|chemspider}} | StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}
| StdInChIKey = LSNNMFCWUKXFEE-UHFFFAOYSA-N | StdInChIKey = LSNNMFCWUKXFEE-UHFFFAOYSA-N
| CASNo = 7782-99-2
| CASNo_Ref = {{cascite|correct|CAS}}
}} }}
| Section2 = {{Chembox Properties | Section2 = {{Chembox Properties
| Formula = H<sub>2</sub>SO<sub>3</sub> | Formula = {{chem2|H2SO3}}
| MolarMass = 82.07 g/mol | MolarMass = 82.07 g/mol
| ConjugateBase = ]
| pKa = 1.857, 7.172
| pKa = 1.857, 7.172<ref name=P82db>{{cite book|title=Ionisation Constants of Inorganic Acids and Bases in Aqueous Solution|editor-first=D.&nbsp;D.|editor-last=Perrin|edition=2nd|series=] Chemical Data|issue=29|publisher=Pergamon|location=Oxford|year=1982|publication-date=1984|orig-date=1969|lccn=82-16524|isbn=0-08-029214-3|at=Entry&nbsp;217}}</ref>
}} }}
| Section3 =
| Section7 = {{Chembox Hazards
| Section4 =
| ExternalMSDS =
| Section5 =
| EUIndex = 016-011-00-9
| Section6 =
| EUClass = Corrosive ('''C''')
| RPhrases = {{R20}}, {{R34}} | Section7 = {{Chembox Hazards
| ExternalSDS =
| SPhrases = {{S1/2}}, {{S9}}, {{S26}}, {{S36/37/39}}, {{S45}}
| GHSPictograms = {{GHS05}}{{GHS07}}
| FlashPt = Non-flammable
| GHSSignalWord = Danger
| HPhrases = {{H-phrases|314|332}}
| PPhrases = {{P-phrases|260|261|264|271|280|301+330+331|303+361+353|304+312|304+340|305+351+338|310|312|321|363|405|501}}
| FlashPt = Non-flammable
}} }}
| Section8 = {{Chembox Related | Section8 = {{Chembox Related
| OtherCpds = ]<br/>] | OtherCompounds = ]<br/>]<br/>]
}} }}
}} }}


'''Sulfuric(IV) acid''' (] spelling: '''sulphuric(IV) acid'''), also known as '''sulfurous''' (UK:&nbsp;'''sulphurous''') '''acid''' and '''thionic acid''',{{citation needed|date=July 2023}} is the ] with the ] {{chem2|H2SO3}}.
'''Sulfurous acid'''
(British English: '''sulphurous acid''') is the ] with the ] H<sub>2</sub>SO<sub>3</sub>. There is no evidence that sulfurous acid exists in solution, but the molecule has been detected in the gas phase.<ref>{{cite journal | author = D. Sülzle, M. Verhoeven, J. K. Terlouw, H. Schwarz | title = Generation and Characterization of Sulfurous Acid (H<sub>2</sub>SO<sub>3</sub>) and of Its Radical Cation as Stable Species in the Gas Phase | journal = ] | volume = 27 | pages = 1533–4 | year = 1988 | doi = 10.1002/anie.198815331 | issue = 11}}</ref> The conjugate bases of this elusive acid are, however, common anions, ] (or hydrogensulfite) and ].


] of solutions of ] in water show only signals due to the SO<sub>2</sub> molecule and the bisulfite ion, HSO<sub>3</sub><sup>&minus;</sup>.<ref>{{Jolly2nd}}</ref> The intensities of the signals are consistent with the following ]: ] of solutions of ] in water show only signals due to the {{chem2|SO2}} molecule and the bisulfite ion, {{chem2|HSO3−}}.<ref>{{Jolly2nd}}</ref> The intensities of the signals are consistent with the following ]:


::SO<sub>2</sub> + H<sub>2</sub>O {{eqm}} HSO<sub>3</sub><sup>&minus;</sup> + H<sup>+</sup> {{block indent|1={{chem2|SO2 + H2O ⇌ HSO3− + H+}}{{spaces|10}}''K''<sub>a</sub> = 1.54{{e|−2}}; p''K''<sub>a</sub> = 1.81.}}
:::''K''<sub>a</sub> = 1.54{{e|&minus;2}}; p''K''<sub>a</sub> = 1.81.


<sup>17</sup>O ] provided evidence that solutions of sulfurous acid and protonated sulfites contain a mixture of isomers, which is in equilibrium:<ref name="InorgChem">{{cite book
Aqueous solutions of sulfur dioxide, which sometimes are referred to as sulfurous acid are used as ] and as disinfectants, as are solutions of bisulfite and sulfite salts. They are also mild ]es, and are used for materials which may be damaged by ]-containing bleaches.
| title = Inorganic Chemistry, 3rd Edition
| chapter = Chapter 16: The group 16 elements
| author1 = Catherine E. Housecroft
| author2 = Alan G. Sharpe
| publisher = Pearson
| year = 2008
| isbn = 978-0-13-175553-6
| page = 520
}}</ref>


{{block indent|{{chem2|− ⇌ −}}}}
==References==

<references/>
Attempts to concentrate the solutions of sulfurous acid simply reverses the equilibrium, producing sulfur dioxide and water vapor. A ] with the formula {{chem2|4SO2*23H2O}} has been crystallised. It decomposes above 7&nbsp;°C.

==History and production==
Sulfurous acid is commonly known to not exist in its free state, and due to this, it is stated in textbooks that it cannot be isolated in the water-free form.<ref>{{Greenwood&Earnshaw2nd|page=719}}</ref> However, the molecule has been detected in the gas phase in 1988 by the dissociative ionization of ].<ref>{{cite journal |author1=D. Sülzle |author2=M. Verhoeven |author3=J. K. Terlouw |author4=H. Schwarz | title = Generation and Characterization of Sulfurous Acid (H<sub>2</sub>SO<sub>3</sub>) and of Its Radical Cation as Stable Species in the Gas Phase | journal = ] | volume = 27 | pages = 1533–4 | year = 1988 | doi = 10.1002/anie.198815331 | issue = 11}}</ref> The conjugate bases of this elusive acid are, however, common anions, ] (or hydrogen sulfite) and ]. Sulfurous acid is an intermediate species in the formation of ] from sulfur dioxide.<ref>{{cite book|last1=McQuarrie |last2= Rock |date=1987 |title=General Chemistry |edition=2nd |publisher=W.H. Freeman and Company |location=New York |page=243 |ISBN=0-7167-1806-5}}</ref>

==Uses==
Aqueous solutions of sulfur dioxide, which sometimes are referred to as sulfurous acid, are used as ]s and as disinfectants, as are solutions of ] and ] salts. They are ]d to ] or ] by accepting another ] atom.<ref>L. Kolditz, ''Anorganische Chemie'', VEB Deutscher Verlag der Wissenschaften, Berlin 1983, S. 476.</ref>


==See also== ==See also==
*] * ]
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==References==
{{reflist}}


{{Hydrogen compounds}} {{Hydrogen compounds}}
{{Sulfites}}
{{Authority control}}


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Latest revision as of 23:24, 9 January 2025

Chemical compound Not to be confused with Sulfuric acid.
Sulfurous acid
Sulfuric(IV) acid
Sulfuric(IV) acid
Ball-and-stick model of sulfurous acid
Ball-and-stick model of sulfurous acid
Names
IUPAC name Sulfurous acid
Other names Sulfuric(IV) acid
Thionic acid
Sulfinic acid
Identifiers
CAS Number
3D model (JSmol)
ChEBI
ChEMBL
ChemSpider
ECHA InfoCard 100.029.066 Edit this at Wikidata
EC Number
  • 231-973-1
Gmelin Reference 1458
KEGG
PubChem CID
UNII
CompTox Dashboard (EPA)
InChI
  • InChI=1S/H2O3S/c1-4(2)3/h(H2,1,2,3)Key: LSNNMFCWUKXFEE-UHFFFAOYSA-N
  • InChI=1/H2O3S/c1-4(2)3/h(H2,1,2,3)Key: LSNNMFCWUKXFEE-UHFFFAOYAJ
SMILES
  • O(=O)O
  • Tautomer: O(O)
Properties
Chemical formula H2SO3
Molar mass 82.07 g/mol
Acidity (pKa) 1.857, 7.172
Conjugate base Bisulfite
Hazards
GHS labelling:
Pictograms GHS05: CorrosiveGHS07: Exclamation mark
Signal word Danger
Hazard statements H314, H332
Precautionary statements P260, P261, P264, P271, P280, P301+P330+P331, P303+P361+P353, P304+P312, P304+P340, P305+P351+P338, P310, P312, P321, P363, P405, P501
Flash point Non-flammable
Safety data sheet (SDS) ICSC 0074
Related compounds
Related compounds Sulfur dioxide
Sulfuric acid
Selenous acid
Except where otherwise noted, data are given for materials in their standard state (at 25 °C , 100 kPa). checkY verify (what is  ?) Infobox references
Chemical compound

Sulfuric(IV) acid (United Kingdom spelling: sulphuric(IV) acid), also known as sulfurous (UK: sulphurous) acid and thionic acid, is the chemical compound with the formula H2SO3.

Raman spectra of solutions of sulfur dioxide in water show only signals due to the SO2 molecule and the bisulfite ion, HSO−3. The intensities of the signals are consistent with the following equilibrium:

SO2 + H2O ⇌ HSO−3 + H          Ka = 1.54×10; pKa = 1.81.

O NMR spectroscopy provided evidence that solutions of sulfurous acid and protonated sulfites contain a mixture of isomers, which is in equilibrium:

[H−OSO2] ⇌ [H−SO3]

Attempts to concentrate the solutions of sulfurous acid simply reverses the equilibrium, producing sulfur dioxide and water vapor. A clathrate with the formula 4SO2·23H2O has been crystallised. It decomposes above 7 °C.

History and production

Sulfurous acid is commonly known to not exist in its free state, and due to this, it is stated in textbooks that it cannot be isolated in the water-free form. However, the molecule has been detected in the gas phase in 1988 by the dissociative ionization of diethyl sulfite. The conjugate bases of this elusive acid are, however, common anions, bisulfite (or hydrogen sulfite) and sulfite. Sulfurous acid is an intermediate species in the formation of acid rain from sulfur dioxide.

Uses

Aqueous solutions of sulfur dioxide, which sometimes are referred to as sulfurous acid, are used as reducing agents and as disinfectants, as are solutions of bisulfite and sulfite salts. They are oxidised to sulfuric acid or sulfate by accepting another oxygen atom.

See also

References

  1. Perrin, D. D., ed. (1982) . Ionisation Constants of Inorganic Acids and Bases in Aqueous Solution. IUPAC Chemical Data (2nd ed.). Oxford: Pergamon (published 1984). Entry 217. ISBN 0-08-029214-3. LCCN 82-16524.
  2. Jolly, William L. (1991). Modern Inorganic Chemistry (2nd ed.). New York: McGraw-Hill. ISBN 0-07-032768-8.
  3. Catherine E. Housecroft; Alan G. Sharpe (2008). "Chapter 16: The group 16 elements". Inorganic Chemistry, 3rd Edition. Pearson. p. 520. ISBN 978-0-13-175553-6.
  4. Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. p. 719. ISBN 978-0-08-037941-8.
  5. D. Sülzle; M. Verhoeven; J. K. Terlouw; H. Schwarz (1988). "Generation and Characterization of Sulfurous Acid (H2SO3) and of Its Radical Cation as Stable Species in the Gas Phase". Angew. Chem. Int. Ed. Engl. 27 (11): 1533–4. doi:10.1002/anie.198815331.
  6. McQuarrie; Rock (1987). General Chemistry (2nd ed.). New York: W.H. Freeman and Company. p. 243. ISBN 0-7167-1806-5.
  7. L. Kolditz, Anorganische Chemie, VEB Deutscher Verlag der Wissenschaften, Berlin 1983, S. 476.
Hydrogen compounds
Compounds containing the sulfite group (SO2−3)
H2SO3 He
Li2SO3 Be B C (NH4)2SO3
NSO−2 		O SO2F Ne
Na2SO3 MgSO3·x(H2O) Al Si P +SO4 +Cl Ar
K2SO3 CaSO3·x(H2O) Sc Ti V Cr Mn Fe Co Ni CuSO3·Cu2SO3·x(H2O) Zn Ga Ge As Se Br Kr
Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag2SO3 Cd In Sn Sb Te I Xe
Cs BaSO3 * Lu Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn
Fr Ra ** Lr Rf Db Sg Bh Hs Mt Ds Rg Cn Nh Fl Mc Lv Ts Og
 
* La Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb
** Ac Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No
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