Selenous Acid - Wikipedia

Selenous acid[1]

Names
IUPAC names Selenous acidSelenic(IV) acid
Other names Selenious acid
Identifiers
CAS Number	7783-00-8 Y
3D model (JSmol)	Interactive image
ChEBI	CHEBI:26642 Y
ChEMBL	ChEMBL2009089
ChemSpider	1060 Y
DrugBank	DB11127
ECHA InfoCard	100.029.067
EC Number	231-974-7
KEGG	D05814 Y
PubChem CID	1091
RTECS number	VS7175000
UNII	F6A27P4Q4R Y
UN number	3283 2630
CompTox Dashboard (EPA)	DTXSID9024300
InChI InChI=1S/H2O3Se/c1-4(2)3/h(H2,1,2,3) YKey: MCAHWIHFGHIESP-UHFFFAOYSA-N Y InChI=1/H2O3Se/c1-4(2)3/h(H2,1,2,3)Key: MCAHWIHFGHIESP-UHFFFAOYAW
SMILES O[Se+]([O-])O
Properties
Chemical formula	H2SeO3
Molar mass	128.984 g·mol−1
Appearance	white hygroscopic crystals
Density	3.0 g/cm3
Melting point	decomposes at 70 °C
Solubility in water	very soluble
Solubility	soluble in ethanol
Acidity (pKa)	pKa1 = 2.46pKa2 = 7.3[2]
Conjugate base	Hydrogenselenite
Magnetic susceptibility (χ)	−45.4·10−6 cm3/mol
Pharmacology
Routes ofadministration	Intravenous infusion
Legal status	US: ℞-only
Hazards
GHS labelling:
Pictograms
Signal word	Danger
Hazard statements	H301, H331, H373, H410
Precautionary statements	P260, P261, P264, P270, P271, P273, P301+P310, P304+P340, P311, P314, P321, P330, P391, P403+P233, P405, P501
Related compounds
Other anions	Selenic acidHydrogen selenide
Other cations	Sodium selenite
Related compounds	Sulfurous acid Tellurous acid Polonous acid
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Y verify (what is YN ?) Infobox references

Chemical compound Pharmaceutical compound Selenious Acid

Clinical data
AHFS/Drugs.com	Monograph
License data	US DailyMed: Selenious_acid
Identifiers
DrugBank	DB11127
CompTox Dashboard (EPA)	DTXSID9024300
ECHA InfoCard	100.029.067

Selenous acid (or selenious acid) is the chemical compound with the formula H2SeO3. Structurally, it is more accurately described by O=Se(OH)2. It is the principal oxoacid of selenium; the other being selenic acid.

Formation and properties

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Selenous acid is analogous to sulfurous acid, but it is more readily isolated. Selenous acid is easily formed upon the addition of selenium dioxide to water. As a crystalline solid, the compound can be seen as pyramidal molecules that are interconnected with hydrogen bonds. In solution it is a diprotic acid:[3]

H2SeO3 ⇌ H+ + HSeO−3  (pKa = 2.62) HSeO−3 ⇌ H+ + SeO2−3  (pKa = 8.32)

It is moderately oxidizing in nature, but kinetically slow. In 1 M H+:

H2SeO3 + 4 H+ + 4 e− ⇌ Se + 3 H2O  (Eo = +0.74 V)

In 1 M OH−:

SeO2−3 + 4 e− + 3 H2O ⇌ Se + 6 OH−  (Eo = −0.37 V)

Selenous acid is hygroscopic.[4][5]

Uses

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The major use is in protecting and changing the color of steel, especially steel parts on firearms.[6] The so-called cold-bluing process uses selenous acid, copper(II) nitrate, and nitric acid to change the color of the steel from silver-grey to blue-grey or black. Alternative procedures use copper sulfate and phosphoric acid instead. This process deposits a coating of copper selenide and is fundamentally different from other bluing processes which generate black iron oxide. Some older razor blades were also made of blued steel.[6]

Another use for selenious acid is the chemical darkening and patination of copper, brass and bronze, producing a rich dark brown color that can be further enhanced with mechanical abrasion.[citation needed]

It is used in organic synthesis as an oxidizing agent for the synthesis of 1,2-dicarbonyl compounds, e.g. in laboratory preparation of glyoxal (oxaldehyde) from acetaldehyde.[7]

Selenious acid is a key component of the Mecke reagent used for drug checking.[8][9]

Medical

[edit]

Selenous acid can supply the trace element indicated in people as a source of selenium.[10][11]

Health effects

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Like many selenium compounds, selenous acid is highly toxic in excessive quantities, and ingestion of any significant quantity of selenous acid is usually fatal, however it is an approved dietary source in proper amounts. Symptoms of selenium poisoning can occur several hours after exposure, and may include stupor, nausea, severe hypotension and death.

References

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1. ^ Lide DR (1998). Handbook of Chemistry and Physics (87 ed.). Boca Raton, Florida: CRC Press. pp. 4–81. ISBN 0-8493-0594-2.
2. ^ Ka and pKa for Polyprotic Acids. ucdsb.on.ca
3. ^ Holleman AF, Wiberg E (2001). Inorganic Chemistry. San Diego: Academic Press. ISBN 0-12-352651-5.
4. ^ Lide DR, ed. (1995). CRC Handbook of Chemistry and Physics (76th ed.). Boca Raton, FL: CRC Press Inc. pp. 4–82.
5. ^ "Selenious acid". PubChem. Retrieved 2020-01-17.
6. ^ a b Scarlato EA, Higa J (28 June 1990). "SELENIUM (PIM483)". Retrieved 29 December 2010.
7. ^ "Glyoxal Bisulfite", Organic Syntheses, Collected Volume 3, p.438 (1955).
8. ^ "Colour Test Reagents-Kits for Preliminary Identification of Drugs of Abuse" (PDF). National Institute of Justice. 2000-07-01. Retrieved 2012-01-26.
9. ^ "Material Safety Data Sheet - Product Name: Reagent for Special Opiates" (PDF). Sirchie Finger Print Laboratories, Inc. May 12, 2006. Archived from the original (PDF) on October 18, 2006.
10. ^ "Selenious acid injection, solution". DailyMed. 1 May 2020. Retrieved 22 October 2020.
11. ^ "Drug Approval Package: Selenious Acid Injection". U.S. Food and Drug Administration (FDA). Retrieved 22 October 2020.

External links

[edit]

• "Selenious acid". Drug Information Portal. U.S. National Library of Medicine. Archived from the original on August 29, 2021.

v t e Hydrogen compounds

H3AsO3 H3AsO4 HArF HAt HSO3F H[BF4] HBr HBrO HBrO2 HBrO3 HBrO4 HCl HClO HClO2 HClO3 HClO4 HCN HCNO H2CrO4/H2Cr2O7 H2CO3 H2CS3 HF HFO HI HIO HIO2 HIO3 HIO4 HMnO4 H2MnO4 H2MoO4 HNC NaHCO3 HNCO HNO HNO2 HNO3 H2N2O2 HNO5S H3NSO3 H2O H2O2 H2O3 H2O4 H2O5 H3PO2 H3PO3 H3PO4 H4P2O7 H5P3O10 H[AuCl4] H2[PtCl6] H2OsCl6 H2S H2S2 H2Se H2SeO3 H2SeO4 H4SiO4 H2[SiF6] HSCN HNCS H2SO3 H2SO4 H2SO5 H2S2O3 H3O H2S2O6 H2S2O7 H2S2O8 CF3SO3H H2Te H2TeO3 H6TeO6 H4TiO4 H2Po H[Co(CO)4]

v t e Selenium compounds
Se(−II)	Se2− H2Se Al2Se3 Sb2Se3 As2Se3 Bi2Se3 CdSe CaSe CSe2 OCSe CrSe CoSe CuSe (CH3)2Se GaSe Ga2Se3 GeSe In2Se3 FeSe PbSe MgSe MnSe MnSe2 HgSe MoSe2 NiSe NbSe2 NbSe3 PxSey PuSe ReSe2 Sm2Se3 Ag2Se Na2Se SnSe TiSe2 WSe2 USe2 ZnSe
Se(0,I)	Se3S5
Se(I)	Se2S6 Se2Cl2 C3H7NO2Se
Se(II)	SeBr2 SeCl2 SeS2
Se(III)	Se4N4
Se(IV)	SeO2−3 SeBr4 SeCl4 SeF4 SeO2 SeS2 SeOF2 SeOCl2 SeOBr2 H2SeO3
Se(VI)	SeO2−4 SeF6 SeO3 SeO2F2 H2SeO4
Se(IV,VI)	SeO2−4 + SeO2−3

v t e Salts and covalent derivatives of the selenite ion

H2SeO3 He Li Be BxSexOx C +NO3 O +F Ne Na2SeO3 Mg Al Si P +SO4 Cl Ar K Ca Sc Ti V Cr MnSeO3 Fe2(SeO3)3 Co Ni CuSeO3Cu2OSeO3 ZnSeO3 Ga Ge As +SeO4 Br Kr RbHSeO3 Sr Y Zr Nb Mo Tc Ru Rh Pd Ag2SeO3 Cd In Sn Sb Te I Xe CsHSeO3 Ba * 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 Ce2(SeO3)3 Pr2(SeO3)3 Nd2(SeO3)3 Pm Sm2(SeO3)3 Eu Gd Tb Dy Ho Er Tm Yb ** Ac Th(SeO3)2 Pa U Np Pu Am Cm Bk Cf Es Fm Md No

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