Which way does an epoxide open?

After deprotonation to reform the acid catalyst a 1,2-diol product is formed. If the epoxide is asymmetric, the incoming water nucleophile will preferably attack the more substituted epoxide carbon. The epoxide ring is opened by an SN2 like mechanism so the two -OH groups will be trans to each other in the product.

Which side of an epoxide is attacked under acidic conditions?

Under acidic conditions, epoxides open in an “SN1 like” fashion with the nucleophile attacking the more substituted end.

What is epoxide ring opening?

In aqueous solution, base catalyzed epoxide ring opening occurs by SN2 attack of a hydroxide ion at the less hindered carbon. Acid-catalyzed ring opening involves protonation of the epoxide oxygen atom, followed by an SN1-like carbocation formation at the more substituted carbon.

Are epoxide reactions racemic?

If an achiral epoxide is the starting material, then a racemic mixture of enantiomers is formed because the two carbons of the epoxide ring are equivalent and attacked by the nucleophile at the same rate.

Can h2o open an epoxide?

One possibility is that the hydrogen-bonding formation between epoxide oxygen and water may activate epoxides based on the reports, showing that the hydrogen bond between alcohol (or phenol) and epoxide can accelerate their ring-opening reactions.

What do you mean by acid-catalyzed ring opening?

The acid-catalyzed ring-opening reaction of epoxides follows a mechanism with S N2 features (inversion of stereochemistry, no carbocation rearrangements), the mechanism is not strictly a S N2 mechanism.

What reagent makes an epoxide?

Treating an alkene with a “peroxyacid” (that’s a carboxylic acid containing an extra oxygen) leads to direct formation of an epoxide. A popular peroxyacid for this purpose is m-CPBA [m-chloroperoxybenzoic acid], although other peroxyacids of the general form RCO3H also find use.