Epoxide

  An epoxide is a cyclic functional group epoxides obtain the epoxy prefix such as in the compound 1,2-epoxycycloheptane which can also be called cycloheptene epoxide.

A polyethylene glycol, also known as polyethylene oxide.

Synthesis

Epoxides are usually created by one of the following reactions:

• Olefin Peroxidation involves the oxidation of an nucleophile, although they both operate in that capacity, and the reaction is considered to be concerted (the numbers in the mechanism below are for simplification).

• Enantioselective alkene epoxidations can be found in the Sharpless epoxidation, the Jacobsen epoxidation and the Shi epoxidation.
• Intramolecular S_N2 substitution. This method is a variant of the halide are right next to each other in the same molecule (such compounds are generically called halohydrins), which makes this a simple ring closure reaction.
• In the carbonyl groups and sulfonium ylides.

Reactions

Typical epoxide reactions are listed below.

• Nucleophilic addition to an epoxide can be base or acid catalyzed.

• Under acidic conditions, the nucleophile attacks the carbon that will form the most stable carbocation, i.e. the most substituted carbon (similar to a halonium ion). Under basic conditions, the nucleophile attacks the least substituted carbon, in accordance with standard S_N2 nuclephilic addition reaction process.

• acidic conditions.
• lithium aluminium hydride and water generates an alcohol. This reduction process can be considered to be the nucleophilic addition of hydride (H-) to the epoxide under basic conditions.

• Reduction with alkene. This reaction in effect is a de-epoxidation ^[2]:

See also

• polyethers

References

1. ^ Bartlett Rec. Chem. Prog 1950, 11 47.
2. ^ Lower valent tungsten halides. New class of reagents for deoxygenation of organic molecules K. Barry Sharpless, Martha A. Umbreit, Marjorie T. Nieh, Thomas C. Flood J. Am. Chem. Soc.; 1972; 94(18); 6538-6540. Abstract