Learn everything about Epoxidation and Catalytic Air Oxidation of Alkenes — mechanism, catalysts, examples, and simplified Class 12 Chemistry notes. Perfect for board exams and NEET preparation.
Epoxidation/ Catalytic Air Oxidation of Alkene
Definition of epoxidation
The catalytic addition of oxygen to the
double bond of an alkene to form an epoxide (oxirane) is called epoxidation.
Product of epoxidation
The product of epoxidation is epoxide (IUPAC: oxirane) which is a three
membered cyclic ether with an oxygen atom in a ring. The
epoxidation of an alkene is clearly an oxidation, since an oxygen atom is
added. The simplest epoxide is epoxyethane (ethylene oxide). Epoxide belongs to
a class of chemicals called heterocyclic compounds having cyclic
structures in which one (or more) of the ring atoms is a hetero atom (i.e.
an atom of an element other than carbon).
Reagent for Epoxidation/Epoxidation Reagent
The epoxidation reaction of an
alkene is carried out with an epoxidation
reagent, usually a peroxyacid or peracids, a carboxylic
acid that has an extra oxygen atom in a -O-O- (peroxy) linkage to
give an oxygen-containing three-membered ring called
an epoxide or oxirane. (Another way
to say it is epoxidation is the electrophilic
addition of oxygen to the double
bond of the alkene).
peroxyacid or peracids
Peroxyacids are derivatives of
carboxylic acids that contain an additional O-O bond. The peroxyacid reagent
forms an acid as by-product, while the epoxide is formed. Peroxyacids are highly selective oxidizing agents.
There are several types of
commonly used peroxyacid such as peroxy
trifluoroacetic acid, peroxyacetic
acid, hydrogen peroxide,
and mCPBA. The most common peroxyacid
used for the epoxidation of alkenes (like propene) is meta-chloroperoxybenzoic acid, or mCPBA.
Some simple peroxyacids and their
corresponding carboxylic acids are shown next.
A peroxyacid epoxidizes an alkene
by a concerted electrophilic reaction where several bonds are broken and several are
formed at the same time. Starting with the alkene and the peroxyacid, a
one-step reaction gives the epoxide and the acid directly, without any
intermediates.
General Reaction
Examples
Book Reaction
