Stereospecificity

In chemistry, stereospecificity is the property of a chemical reaction that yields different stereoisomeric reaction products from two stereoisomeric reactants depending on the reaction conditions. Stereospecificity differs from stereoselectivity in that stereospecificity describes a reaction that necessarily yields a given stereoisomer because of the mechanism of the reaction, while stereoselectivity describes a reaction where the mechanism allows for the formation of both products, but the formation of one of the products is favored. Stereospecificity always yields 100% of a particular stereoisomer, while stereoselectivity does not necessarily give 100% of the favored isomer (although 100% stereoselectivity is possible).

For example, the addition of dibromocarbene to cis-2-butene yields cis-2,3-dimethyl-1,1-dibromocyclopropane whereas addition of dibromocarbene to the trans isomer exclusively yields the trans cyclopropane.

Chiral synthesis is built on stereospecific reactions where also the optical activity of a chemical compound is preserved.

Another example is disrotatory ring closing reaction trans-cis-trans-2,4,6-octatriene to cis-dimethylcyclohexadiene.

See also

* Stereoselectivity
* Dynamic stereochemistry

References

* Skell, P.S. and Garner, A.Y. "Journal of the American Chemical Society". 78, 3409 (1956)