A sulfoxide is a chemical compound containing a sulfinyl functional group attached to two carbon atoms. Sulfoxides are the thio equivalents of ketones. (The use of the alternative name sulphoxide is discouraged by IUPAC.)

Nature of the bond

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The structural formula of a sulfoxide is generally represented as R-S(=O)-R' where R and R' are the organic groups. The bond between the sulfur and oxygen atoms is not a normal double bond (with overlap of π bonds between p orbitals of adjacent atoms), and it is believed that electrostatic interaction between a negatively charged oxygen and positively charged sulfur accounts for most of the bonding.

Not drawn is the electron lone pair on sulfur and the geometry around sulfur is actually tetrahedral as with carbon. When the two organic residues are dissimilar sulfoxides can be chiral. Chiral sulfoxides find application in certain drugs such as esomeprazole and they are also employed as chiral auxiliary . Many chiral sulfoxides are prepared from asymmetric oxidation of achiral sulfides with a transition metal and a chiral ligand.

Reactions

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Sulfides are often the starting materials for sulfones by organic oxidation. For example, dimethyl sulfide with oxidation state of -2 is oxidized to dimethyl sulfoxide with oxidation state 0. Further oxidation takes the compound to dimethyl sulfone with oxidation state +2.

Methyl sulfoxides (like DMSO) have an acidic character, because the sulfoxide group stabilizes the anion that results from loss of a methyl hydrogen.

References

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1. 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 Somanathan Arkivoc MX-789E 2003 Online article

External links

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Functional groups | Organosulfur compounds

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