- Sulfoxide
A sulfoxide is a
chemical compound containing a sulfinylfunctional group attached to two carbon atoms. Sulfoxides can be considered as oxidized sulfides. (The use of the alternative spelling sulphoxide is discouraged byIUPAC .) An example of a sulfoxide occurring in nature isalliin .Nature of the bond
Sulfoxides are generally represented with the structural formula R-S(=O)-R', where R and R' are organic groups. The bond between the
sulfur andoxygen atoms differs from the conventional double bond between carbon and oxygen in, say, ketones. The S-O interaction has anelectrostatic aspect, resulting in significant dipolar character, with negative charge centered on oxygen. The bonding is similar to that in tertiary phosphine oxides, R3P=O.A
lone pair of electrons resides on the sulfur atom giving ittetrahedral molecular geometry as for sp³ carbon. When the two organic residues are dissimilar, the sulfur is a chiral center, for example, methylphenylsulfoxide.The energy required to invert this
stereocenter is sufficiently high that sulfoxides are optically stable, that is, the rate ofracemization is slow at room temperature. Chiral sulfoxides find application in certain drugs such asesomeprazole andArmodafinil , and they are also employed as chiral auxiliaries. ["Oxidation of sulfides to chiral sulfoxides using Schiff base-vanadium (IV) complexes" Ángeles Gama, Lucía Z. Flores-López, Gerardo Aguirre, Miguel Parra-Hake, Lars H. Hellberg, and Ratnasamy SomanathanArkivoc MX-789E 2003 [http://www.arkat-usa.org/ark/journal/2003/I11_Mexico/MX-789E/789E.asp Online article] ] Many chiral sulfoxides are prepared fromasymmetric catalytic oxidation of achiral sulfides with atransition metal and a chiral ligand.Reactions
Sulfide s are the usual starting materials to sulfoxides byorganic oxidation . For example,dimethyl sulfide withoxidation state of -2 is oxidized todimethyl sulfoxide with oxidation state 0. Further oxidation converts the compound to dimethyl sulfone wherein sulfur has the oxidation state +2.Sulfoxides, such as DMSO, have basic character, being are excellent
ligand s and readily alkylated. Alkyl sulfoxides are susceptible to deprotonation by strong bases, such assodium hydride . [Iwai, I.; Ide, J. "2,3-Diphenyl-1,3-Butadiene" Organic Syntheses, Collected Volume 6, p.531 (1988). http://www.orgsyn.org/orgsyn/orgsyn/prepContent.asp?prep=CV6P0531.pdf.]References
External links
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