Selenous acid

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Selenous acid [1]
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Names
IUPAC names
Selenous acid
Selenic(IV) acid
Other names
Selenious acid
Identifiers
3D model (JSmol)
ChEBI
ChEMBL
ChemSpider
DrugBank
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EC Number
  • 231-974-7
KEGG
PubChem CID
RTECS number
  • VS7175000
UNII
UN number 3283 2630
  • InChI=1S/H2O3Se/c1-4(2)3/h(H2,1,2,3) Yes check.svgY
    Key: MCAHWIHFGHIESP-UHFFFAOYSA-N Yes check.svgY
  • InChI=1/H2O3Se/c1-4(2)3/h(H2,1,2,3)
    Key: MCAHWIHFGHIESP-UHFFFAOYAW
  • O[Se+]([O-])O
Properties
H2SeO3
Molar mass 128.984 g·mol−1
Appearancewhite hygroscopic crystals
Density 3.0 g/cm3
Melting point decomposes at 70 °C
very soluble
Solubility soluble in ethanol
Acidity (pKa)pKa1 = 2.46
pKa2 = 7.3 [2]
Conjugate base Hydrogenselenite
−45.4·10−6 cm3/mol
Pharmacology
Intravenous infusion
Legal status
Hazards
GHS labelling:
GHS-pictogram-skull.svg GHS-pictogram-silhouette.svg GHS-pictogram-pollu.svg
Danger
H301, H331, H373, H410
P260, P261, P264, P270, P271, P273, P301+P310, P304+P340, P311, P314, P321, P330, P391, P403+P233, P405, P501
Related compounds
Other anions
Selenic acid
Hydrogen selenide
Other cations
Sodium selenite
Related compounds
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Selenious Acid
Clinical data
AHFS/Drugs.com Monograph
License data
Identifiers
DrugBank
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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.

Contents

Formation and properties

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

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

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

Health effects

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.

Related Research Articles

<span class="mw-page-title-main">Selenium</span> Chemical element with atomic number 34 (Se)

Selenium is a chemical element; it has the symbol Se and atomic number 34. It has various physical appearances, including a brick-red powder, a vitreous black solid, and a grey metallic-looking form. It seldom occurs in this elemental state or as pure ore compounds in Earth's crust. Selenium was discovered in 1817 by Jöns Jacob Berzelius, who noted the similarity of the new element to the previously discovered tellurium.

A selenide is a chemical compound containing a selenium with oxidation number of −2. Similar to sulfide, selenides occur both as inorganic compounds and as organic derivatives, which are called organoselenium compound.

<span class="mw-page-title-main">Hydrogen selenide</span> Chemical compound

Hydrogen selenide is an inorganic compound with the formula H2Se. This hydrogen chalcogenide is the simplest and most commonly encountered hydride of selenium. H2Se is a colorless, flammable gas under standard conditions. It is the most toxic selenium compound with an exposure limit of 0.05 ppm over an 8-hour period. Even at extremely low concentrations, this compound has a very irritating smell resembling that of decayed horseradish or "leaking gas", but smells of rotten eggs at higher concentrations.

Selenic acid is the inorganic compound with the formula H2SeO4. It is an oxoacid of selenium, and its structure is more accurately described as O2Se(OH)2. It is a colorless compound. Although it has few uses, one of its salts, sodium selenate is used in the production of glass and animal feeds.

<span class="mw-page-title-main">Telluric acid</span> Chemical compound (Te(OH)6)

Telluric acid, or more accurately orthotelluric acid, is a chemical compound with the formula Te(OH)6, often written as H6TeO6. It is a white crystalline solid made up of octahedral Te(OH)6 molecules which persist in aqueous solution. In the solid state, there are two forms, rhombohedral and monoclinic, and both contain octahedral Te(OH)6 molecules, containing one hexavalent tellurium (Te) atom in the +6 oxidation state, attached to six hydroxyl (–OH) groups, thus, it can be called tellurium(VI) hydroxide. Telluric acid is a weak acid which is dibasic, forming tellurate salts with strong bases and hydrogen tellurate salts with weaker bases or upon hydrolysis of tellurates in water. It is used as tellurium-source in the synthesis of oxidation catalysts.

<span class="mw-page-title-main">Selenium dioxide</span> Chemical compound

Selenium dioxide is the chemical compound with the formula SeO2. This colorless solid is one of the most frequently encountered compounds of selenium. It is used in making specialized glasses as well as a reagent in organic chemistry.

<span class="mw-page-title-main">Selenite (ion)</span> Anion composed of selenium and oxygen

Selenite refers to the anion with the chemical formula SeO2−3. It is the oxyanion of selenium. It is the selenium analog of the sulfite ion, SO2−3. Thus selenite is pyramidal and selenium is assigned oxidation state +4. Selenite also refers to compounds that contains this ion, for example sodium selenite Na2SeO3 which is a common source of selenite. Selenite also refers to the esters of selenous acid, for example dimethyl selenite (CH3)2SeO3.

<span class="mw-page-title-main">Sodium selenite</span> Chemical compound

Sodium selenite is the inorganic compound with the formula Na2SeO3. This salt is a colourless solid. The pink coloured pentahydrate Na2SeO3(H2O)5 is the most common water-soluble selenium compound.

<span class="mw-page-title-main">Sodium tellurite</span> Chemical compound

Sodium tellurite is an inorganic tellurium compound with formula Na2TeO3. It is a water-soluble white solid and a weak reducing agent. Sodium tellurite is an intermediate in the extraction of the element, tellurium; it is a product obtained from anode slimes and is a precursor to tellurium.

<span class="mw-page-title-main">Selenol</span> Class of chemical compounds

Selenols are organic compounds that contain the functional group with the connectivity C−Se−H. Selenols are sometimes also called selenomercaptans and selenothiols. Selenols are one of the principal classes of organoselenium compounds. A well-known selenol is the amino acid selenocysteine.

<span class="mw-page-title-main">Hydrogen telluride</span> Chemical compound

Hydrogen telluride is the inorganic compound with the formula H2Te. A hydrogen chalcogenide and the simplest hydride of tellurium, it is a colorless gas. Although unstable in ambient air, the gas can exist long enough to be readily detected by the odour of rotting garlic at extremely low concentrations; or by the revolting odour of rotting leeks at somewhat higher concentrations. Most compounds with Te–H bonds (tellurols) are unstable with respect to loss of H2. H2Te is chemically and structurally similar to hydrogen selenide, both are acidic. The H–Te–H angle is about 90°. Volatile tellurium compounds often have unpleasant odours, reminiscent of decayed leeks or garlic.

<span class="mw-page-title-main">Aluminium selenide</span> Chemical compound

Aluminium selenide is the inorganic compound with the formula Al2Se3.

<span class="mw-page-title-main">Selenium oxydichloride</span> Chemical compound

Selenium oxydichloride is the inorganic compound with the formula SeOCl2. It is a colorless liquid. With a high dielectric constant (55) and high specific conductance, it is an attractive solvent. Structurally, it is a close chemical relative of thionyl chloride SOCl2, being a pyramidal molecule.

Selenium trioxide is the inorganic compound with the formula SeO3. It is white, hygroscopic solid. It is also an oxidizing agent and a Lewis acid. It is of academic interest as a precursor to Se(VI) compounds.

<span class="mw-page-title-main">Selenium oxybromide</span> Chemical compound

Selenium oxybromide (SeOBr2) is a selenium oxohalide chemical compound.

<span class="mw-page-title-main">Selenium compounds</span> Chemical compounds containing selenium

Selenium compounds are compounds containing the element selenium (Se). Among these compounds, selenium has various oxidation states, the most common ones being −2, +4, and +6. Selenium compounds exist in nature in the form of various minerals, such as clausthalite, guanajuatite, tiemannite, crookesite etc., and can also coexist with sulfide minerals such as pyrite and chalcopyrite. For many mammals, selenium compounds are essential. For example, selenomethionine and selenocysteine are selenium-containing amino acids present in the human body. Selenomethionine participates in the synthesis of selenoproteins. The reduction potential and pKa (5.47) of selenocysteine are lower than those of cysteine, making some proteins have antioxidant activity. Selenium compounds have important applications in semiconductors, glass and ceramic industries, medicine, metallurgy and other fields.

<span class="mw-page-title-main">Sodium selenate</span> Chemical compound

Sodium selenate is the inorganic compound with the formula Na
2SeO
4. It exists as the anhydrous salt, the heptahydrate, and the decahydrate. These are white, water-soluble solids. The decahydrate is a common ingredient in multivitamins and livestock feed as a source of selenium. The anhydrous salt is used in the production of some glass. Although the selenates are much more toxic, many physical properties of sodium selenate and sodium sulfate are similar.

<span class="mw-page-title-main">Rhenium(IV) oxide</span> Chemical compound

Rhenium(IV) oxide or rhenium dioxide is the inorganic compound with the formula ReO2. This gray to black crystalline solid is a laboratory reagent that can be used as a catalyst. It adopts the rutile structure.

<span class="mw-page-title-main">Selenium tetrachloride</span> Chemical compound

Selenium tetrachloride is the inorganic compound composed with the formula SeCl4. This compound exists as yellow to white volatile solid. It is one of two commonly available selenium chlorides, the other example being selenium monochloride, Se2Cl2. SeCl4 is used in the synthesis of other selenium compounds.

<span class="mw-page-title-main">Sodium selenide</span> Chemical compound

Sodium selenide is an inorganic compound of sodium and selenium with the chemical formula Na2Se.

References

  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. 1 2 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.
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