Reactions of Epoxides
Epoxides, also known as oxiranes, are very reactive compounds with a cyclical ethergroup consisting of three atoms. This ring has a lot of tension, which explains the reactivity of the epoxides. In this lesson we go over some of the reactions of these compounds, but since the software is still in development at the time of writing we can't show all possible reactions (yet).
Synthesis of epoxides
Epoxides can be created from alkenes using a peroxide (such as mCPBA) or from a simple reaction of ethene with oxygen.
Nucleophilic substitution of epoxides
The oxygen of the epoxide can take on a proton in acidic conditions, leaving behind a nucleophile. This nucleophile will then preferentially attack the most substituted carbon of the epoxide group, which will force the generated OH+ group onto the other carbon. It is therefore possible to sometimes create two reaction products. See for example the reaction below (the first reaction product is the major product).
In neutral or basic conditions a nucleophile can directly attack the epoxide group. This leaves a negative oxygen which then just takes a proton from the solvent. Because the nucleophile attacks directly it is the extent of sterical hindrance that determines the main product. Therefore, in these conditions the nucleophile is added to the least substituted carbon. See for example the reaction below (closely watch the main product).
Synthesis of alcohols through epoxides from alkenes
Note that it is possible to create alcohols from alkanes without carbokation rearrangements by first forming an epoxide. See the following consecutive reactions.
Practice