Seleninic acid
{{Short description|Class of chemical compounds}}
{{distinguish|selenenic acid}}
File:Methaneseleninic acid.svg]]
A seleninic acid is an organoselenium compound and an oxoacid with the general formula {{chem2|RSeO2H}}, where R ≠ H. Its structure is {{chem2|R\sSe(\dO)\sOH}}. It is a member of the family of organoselenium oxoacids, which also includes selenenic acids and selenonic acids, which are {{chem2|R\sSe\sOH}} and {{chem2|R\sSe(\dO)2\sOH}}, respectively. The parent member of this family of compounds is methaneseleninic acid ({{chem2|CH3\sSe(\dO)\sOH}}), also known as methylseleninic acid or "MSA".
Reactions and applications in synthesis
Seleninic acids (particularly areneseleninic acids) are useful catalysts for hydrogen peroxide epoxidations, Baeyer–Villiger oxidations, oxidations of thioethers, etc.; peroxyseleninic acids ({{chem2|R\sSe(\dO)\sOOH}}) are thought to be the active oxidants.{{cite journal | doi = 10.1039/b008198l| title = Selenium catalysed oxidations with aqueous hydrogen peroxide. Part I: Epoxidation reactions in homogeneous solution| date = 2001| last1 = Ten Brink| first1 = Gerd-Jan| last2 = Fernandes| first2 = Bruno C. M.| last3 = Van Vliet| first3 = Michiel C. A.| last4 = Arends| first4 = Isabel W. C. E.| last5 = Sheldon| first5 = Roger A.| journal = Journal of the Chemical Society, Perkin Transactions 1| issue = 3| pages = 224–228}}{{cite journal | doi = 10.1021/jo0057710| title = Selenium-Catalyzed Oxidations with Aqueous Hydrogen Peroxide. 2. Baeyer−Villiger Reactions in Homogeneous Solution1| date = 2001| last1 = Ten Brink| first1 = Gerd-Jan| last2 = Vis| first2 = Jan-Martijn| last3 = Arends| first3 = Isabel W. C. E.| last4 = Sheldon| first4 = Roger A.| journal = The Journal of Organic Chemistry| volume = 66| issue = 7| pages = 2429–2433| pmid = 11281784}}{{cite journal | doi = 10.1021/jo300313v| title = Cyclic Seleninate Esters as Catalysts for the Oxidation of Sulfides to Sulfoxides, Epoxidation of Alkenes, and Conversion of Enamines to α-Hydroxyketones| date = 2012| last1 = Mercier| first1 = Eric A.| last2 = Smith| first2 = Chris D.| last3 = Parvez| first3 = Masood| last4 = Back| first4 = Thomas G.| journal = The Journal of Organic Chemistry| volume = 77| issue = 7| pages = 3508–3517| pmid = 22432805}}
Structure, bonding, properties
Methaneseleninic acid has been characterized by X-ray crystallography.{{cite journal | doi = 10.1021/jf001097b| title = Allium Chemistry: Synthesis, Natural Occurrence, Biological Activity, and Chemistry of Se -Alk(en)ylselenocysteines and Their γ-Glutamyl Derivatives and Oxidation Products| date = 2001| 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| journal = Journal of Agricultural and Food Chemistry| volume = 49| issue = 1| pages = 458–470| pmid = 11305255}} The configuration about the selenium atom is pyramidal, with Se-C = 1.925(8) Å, Se-O = 1.672(7) Å, Se-OH = 1.756(7) Å, the angle OSeO = 103.0(3)°, the angle HO-Se-C = 93.5(3)°, and the angle OSeC = 101.4(3)°. The structure is isomorphous to that of methanesulfinic acid Seff, K.; Heidner, E. G.; Meyers, M.; Trueblood, K. N. "The crystal and molecular structure of methanesulfinic acid." Acta Crystallographica Section B 1969, 25, 350–354.
Benzeneseleninic acid ({{chem2|C6H5\sSe(\dO)\sOH}}) had been previously characterized by X-ray methods{{cite journal | doi = 10.1107/S0365110X54002551| title = The crystal structure of benzeneseleninic acid| date = 1954| last1 = Bryden| first1 = J. H.| last2 = McCullough| first2 = J. D.| journal = Acta Crystallographica| volume = 7| issue = 12| pages = 833–838| bibcode = 1954AcCry...7..833B}} and its optical resolution reported.{{cite journal | doi = 10.1002/1521-3773(20010702)40:13<2460::AID-ANIE2460>3.0.CO;2-Q| title = Optically Active Seleninic Acids: Optical Resolution and Stability| date = 2001| last1 = Shimizu| first1 = Toshio| last2 = Watanabe| first2 = Itaru| last3 = Kamigata| first3 = Nobumasa| journal = Angewandte Chemie International Edition| volume = 40| issue = 13| pages = 2460–2462| pmid = 11443664}}