imported>OAbot: Open access bot: url-access updated in citation with #oabot.

2025-05-27T03:42:02Z

Open access bot: url-access updated in citation with #oabot.

New page

{{Short description|Chemical compounds containing selenium}}
{{See also|Category:Selenium compounds|organoselenium chemistry}}

[[File:Selenium dioxide sample.jpg|thumb|right|Selenium dioxide]]
'''Selenium compounds''' are compounds containing the element [[selenium]] (Se). Among these compounds, selenium has various [[oxidation state]]s, 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.<ref>{{Citation |title="无上"文明古国：郭实猎笔下的大英 |date=Mar 2015 |url=http://dx.doi.org/10.1142/9789814667227 |pages=1–268 |access-date=2023-12-01 |publisher=UniSIM Centre for Chinese Studies, SIM University|doi=10.1142/9789814667227 |isbn=978-981-4667-21-0 |url-access=subscription }}</ref> For many mammals, selenium compounds are essential. For example, [[selenomethionine]] and [[selenocysteine]] are selenium-containing [[amino acid]]s present in the human body. Selenomethionine participates in the synthesis of [[selenoprotein]]s.<ref>{{Cite journal |last1=Block |first1=Eric |last2=Birringer |first2=Marc |last3=Jiang |first3=Weiqin |last4=Nakahodo |first4=Tsukasa |last5=Thompson |first5=Henry J. |last6=Toscano |first6=Paul J. |last7=Uzar |first7=Horst |last8=Zhang |first8=Xing |last9=Zhu |first9=Zongjian |date=2001-01-01 |title=Allium Chemistry: Synthesis, Natural Occurrence, Biological Activity, and Chemistry of Se -Alk(en)ylselenocysteines and Their γ-Glutamyl Derivatives and Oxidation Products |url=https://pubs.acs.org/doi/10.1021/jf001097b |journal=Journal of Agricultural and Food Chemistry |language=en |volume=49 |issue=1 |pages=458–470 |doi=10.1021/jf001097b |pmid=11305255 |bibcode=2001JAFC...49..458B |issn=0021-8561|url-access=subscription }}</ref> The reduction potential and pKa (5.47) of selenocysteine are lower than those of [[cysteine]], making some proteins have antioxidant activity.<ref>{{Cite journal |last1=Byun |first1=Byung Jin |last2=Kang |first2=Young Kee |date=May 2011 |title=Conformational preferences and p K a value of selenocysteine residue |url=https://onlinelibrary.wiley.com/doi/10.1002/bip.21581 |journal=Biopolymers |language=en |volume=95 |issue=5 |pages=345–353 |doi=10.1002/bip.21581 |pmid=21213257 |issn=0006-3525|url-access=subscription }}</ref> Selenium compounds have important applications in [[semiconductor]]s, glass and ceramic industries, medicine, [[metallurgy]] and other fields.<ref>{{Citation |title="无上"文明古国：郭实猎笔下的大英 |date=Mar 2015 |url=http://dx.doi.org/10.1142/9789814667227 |pages=1–268 |access-date=2023-12-01 |publisher=UniSIM Centre for Chinese Studies, SIM University|doi=10.1142/9789814667227 |isbn=978-981-4667-21-0 |url-access=subscription }}</ref>

==Chalcogen compounds and oxyacids==
[[File:Selenium-dioxide-chain-3D-balls.png|thumb|Structure of the polymer SeO2: The (pyramidal) Se atoms are yellow.]]
Selenium forms two [[oxide]]s: [[selenium dioxide]] (SeO2) and [[selenium trioxide]] (SeO3). Selenium dioxide is formed by the reaction of elemental selenium with oxygen:<ref name="house2008">{{cite book |title=Inorganic chemistry |first=James E. |last=House |publisher=Academic Press |year=2008 |isbn=978-0-12-356786-4 |page=524}}</ref>
:<chem>Se8 + 8 O2 -> 8 SeO2</chem>
It is a [[polymer]]ic solid that forms monomeric SeO2 molecules in the gas phase. It dissolves in water to form [[selenous acid]], H2SeO3. Selenous acid can also be made directly by oxidizing elemental selenium with [[nitric acid]]:<ref name="wiberg_holleman">{{cite book |title=Inorganic chemistry |last1=Wiberg |first1=Egon |last2=Wiberg |first2=Nils |last3=Holleman |first3=Arnold Frederick |publisher=Academic Press |year=2001 |location=San Diego |isbn=978-0-12-352651-9 |page=583}}</ref>

:<chem>3 Se + 4 HNO3 + H2O -> 3 H2SeO3 + 4 NO</chem>
Unlike sulfur, which forms a stable [[sulfur trioxide|trioxide]], selenium trioxide is thermodynamically unstable and decomposes to the dioxide above 185 °C:<ref name="house2008" /><ref name="wiberg_holleman" />

:<chem>2 SeO3 -> 2 SeO2 + O2</chem> (ΔH = −54 kJ/mol)
Selenium trioxide is produced in the laboratory by the reaction of [[anhydrous]] [[potassium selenate]] (K2SeO4) and sulfur trioxide (SO3).<ref>{{Greenwood&Earnshaw|page=780}}</ref>

[[Salt (chemistry)|Salts]] of selenous acid are called selenites. These include [[silver selenite]] (Ag2SeO3) and [[sodium selenite]] (Na2SeO3).

[[Hydrogen sulfide]] reacts with aqueous selenous acid to produce [[selenium disulfide]]:
:<chem>H2SeO3 + 2 H2S -> SeS2 + 3 H2O</chem>

Selenium disulfide consists of 8-membered rings. It has an approximate composition of SeS2, with individual rings varying in composition, such as Se4S4 and Se2S6. Selenium disulfide has been used in shampoo as an anti[[dandruff]] agent, an inhibitor in polymer chemistry, a glass dye, and a reducing agent in [[fireworks]].<ref name="wiberg_holleman" />

Selenium trioxide may be synthesized by dehydrating [[selenic acid]], H2SeO4, which is itself produced by the oxidation of selenium dioxide with [[hydrogen peroxide]]:<ref>{{Cite book |doi=10.1002/9780470132517.ch9 |last1=Seppelt |first1=K. |last2=Desmarteau |first2=Darryl D. |chapter=Selenonyl Difluoride |title=Inorganic Syntheses |year=1980 |volume=20 |pages=36–38 |isbn=978-0-471-07715-2 }} The report describes the synthesis of selenic acid.</ref>
:<chem>SeO2 + H2O2 -> H2SeO4</chem>

Hot, concentrated selenic acid can react with gold to form gold(III) selenate.<ref>{{Cite journal |last1=Lenher |first1=V. |date=April 1902 |title=Action of selenic acid on gold |journal=Journal of the American Chemical Society |volume=24 |issue=4 |pages=354–355 |doi=10.1021/ja02018a005 |bibcode=1902JAChS..24..354L |url=https://zenodo.org/record/1428902}}</ref>

==Halogen compounds==
[[Iodide]]s of selenium are not well known. The only stable [[chloride]] is [[selenium monochloride]] (Se2Cl2), which might be better known as selenium(I) chloride; the corresponding [[bromide]] is also known. These species are structurally analogous to the corresponding [[disulfur dichloride]]. Selenium dichloride is an important reagent in the preparation of selenium compounds (e.g. the preparation of Se7). It is prepared by treating selenium with [[sulfuryl chloride]] (SO2Cl2).<ref>{{cite book
|title=Handbook of chalcogen chemistry: new perspectives in sulfur, selenium and tellurium |author=Xu, Zhengtao |editor=Devillanova, Francesco A. |publisher=Royal Society of Chemistry |year=2007 |isbn=978-0-85404-366-8 |page=460}}</ref> Selenium reacts with [[fluorine]] to form [[selenium hexafluoride]]:
:<chem>Se8 + 24 F2 -> 8 SeF6</chem>

In comparison with its sulfur counterpart ([[sulfur hexafluoride]]), [[selenium hexafluoride]] (SeF6) is more reactive and is a toxic [[pulmonary]] irritant.<ref>{{cite book |title=Proctor and Hughes' chemical hazards of the workplace |first1=Nick H. |last1=Proctor |first2=Gloria J. |last2=Hathaway |editor=Hughes, James P. |edition=5th |publisher=Wiley-IEEE |year=2004 |isbn=978-0-471-26883-3 |page=625}}</ref>
Some of the selenium oxyhalides, such as [[selenium oxyfluoride]] (SeOF2) and [[selenium oxychloride]] (SeOCl2) have been used as specialty solvents.<ref name="house2008" />

==Selenides==
Analogous to the behavior of other chalcogens, selenium forms [[hydrogen selenide]], H2Se. It is a strongly [[wikt:odiferous|odiferous]], toxic, and colorless gas. It is more acidic than H2S. In solution it ionizes to HSe−. The selenide dianion Se2− forms a variety of compounds, including the minerals from which selenium is obtained commercially. Illustrative selenides include [[mercury selenide]] (HgSe), [[lead selenide]] (PbSe), [[zinc selenide]] (ZnSe), and [[copper indium gallium diselenide]] (Cu(Ga,In)Se2). These materials are [[semiconductor]]s. With highly electropositive metals, such as [[aluminium]], these selenides are prone to hydrolysis:<ref name="house2008" />
:<chem>Al2Se3 + 3 H2O -> Al2O3 + 3 H2Se</chem>
Alkali metal selenides react with selenium to form polyselenides, {{chem|Se|n|2-}}, which exist as chains.

==Other compounds==
Tetraselenium tetranitride, Se4N4, is an explosive orange compound analogous to [[tetrasulfur tetranitride]] (S4N4).<ref name="house2008" /><ref>{{cite journal |last1=Woollins |first1=Derek |title=The Reactivity of Se4N4 in Liquid Ammonia |journal=[[Polyhedron (journal)|Polyhedron]] |year=1993 |volume=12 |pages=1129–1133 |doi=10.1016/S0277-5387(00)88201-7 |issue=10 |last2=Kelly |first2=Paul F.}}</ref><ref>{{cite journal |last1=Kelly |first1=P.F. |last2=Slawin |first2=A.M.Z. |last3=Soriano-Rama |first3=A. |title=Use of Se4N4 and Se(NSO)2 in the preparation of palladium adducts of diselenium dinitride, Se2N2; crystal structure of {{chem|[PPh|4|]|2|[Pd|2|Br|6|(Se|2|N|2|)|]}} |journal=[[Dalton Transactions]] |date=1997 |pages=559–562 |doi=10.1039/a606311j |issue=4}}</ref> It can be synthesized by the reaction of [[selenium tetrachloride]] (SeCl4) with [[Metal bis(trimethylsilyl)amides|{{chem|[((CH|3|)|3|Si)|2|N]|2|Se}}]].<ref>{{cite journal |doi=10.1021/ic00060a031 |title=A simple, efficient synthesis of tetraselenium tetranitride |year=1993 |last1=Siivari |first1=Jari |last2=Chivers |first2=Tristram |last3=Laitinen |first3=Risto S. |journal=Inorganic Chemistry |volume=32 |issue=8 |pages=1519–1520}}</ref>

Selenium reacts with [[cyanide]]s to yield [[Potassium selenocyanate|selenocyanates]]:<ref name="house2008" />
:<chem>8 KCN + Se8 -> 8 KSeCN</chem>

==Organoselenium compounds==
{{Main|Organoselenium chemistry}}
Selenium, especially in the II oxidation state, forms stable bonds to [[carbon]], which are structurally analogous to the corresponding [[organosulfur compounds]]. Especially common are selenides (R2Se, analogues of [[thioether]]s), diselenides (R2Se2, analogues of [[disulfide]]s), and [[selenol]]s (RSeH, analogues of [[thiol]]s). Representatives of selenides, diselenides, and selenols include respectively [[selenomethionine]], [[diphenyldiselenide]], and [[benzeneselenol]]. The [[sulfoxide]] in sulfur chemistry is represented in selenium chemistry by the selenoxides (formula RSe(O)R), which are intermediates in organic synthesis, as illustrated by the [[selenoxide elimination]] reaction. Consistent with trends indicated by the [[double bond rule]], selenoketones, R(C=Se)R, and selenaldehydes, R(C=Se)H, are rarely observed.<ref>{{cite journal |last1=Erker |first1=G. |last2=Hock |last3=Krüger |last4=Werner |last5=Klärner |last6=Artschwager-Perl |title=Synthesis and Cycloadditions of Monomeric Selenobenzophenone |journal=Angewandte Chemie International Edition in English |volume=29 |issue=9 |pages=1067–1068 |year=1990 |doi=10.1002/anie.199010671 |first2=R. |first3=C. |first4=S. |first5=F.G. |first6=U.}}</ref>

==See also==
* [[Arsenic compounds]]
* [[Bromine compounds]]

==References==
{{Reflist}}

{{Selenium compounds}}
{{Authority control}}

[[Category:Selenium]]
[[Category:Selenium compounds]]
[[Category:Chemical compounds by element]]

Selenium compounds - Revision history

imported>OAbot: Open access bot: url-access updated in citation with #oabot.