Epoxidation
Epoxidation
An epoxide is a three-membered ring of two carbon atoms and one oxygen atom.
Epoxides can be synthesized from alkenes by the addition of a peroxyacid, also called a peracid. A peroxyacid looks much like a carboxylic acid, but it contains three oxygen atoms instead of two. Any time a compound is encountered with “extra” oxygen atoms in it, that compound is probably an oxidizer.
The epoxidation reaction is usually run in an inert, non-nucleophilic solvent in order to avoid an unwanted side reaction. Chlorinated solvents like carbon tetrachloride, CCl4, or methylene chloride, CH2Cl2 are good solvents for this reaction. Often, MCPBA is the peroxyacid used in an epoxidation reaction. With its chloro group, it is quite soluble in the needed chlorinated solvents.
Epoxidation Example:
Anti-hydroxylation - a triangle reaction
Before we get into this, if you do not remember the triangle reaction analogy, review it here.
If instead of using MCPBA in a chlorinated solvent, a peroxyacid in water is used, the epoxide formed can further react. This is a triangle reaction. In this reaction an acid (the peroxyacid) is present. Once the epoxide is formed, the peroxyacid can protonate the epoxide. The epoxide is holding a sign overhead announcing it has positive money. Water, a weak nucleophile, can backside attack the more substituted carbon atom resulting in a glycol with anti-stereochemistry.
6. Draw the products of the following reactions.
a)
b)
c)
d)
Answers
6.
a)
b)
c)
d)
