How do you name epoxides and ethers?

1 Answer
Jun 15, 2016

There are several accepted ways of naming ethers and epoxides.


Ethers have two types of names.

1. Substitutive names

The compound is named as an alkane with an alkoxyalkane.

For example, #("CH"_3)_2"CH-O-CH"_3# is 2-methoxypropane.

2. Functional class names

#"R-O-R'"# is named with the names of #"R"# and #"R'"# in alphabetical order, followed by the class name "ether"

For example, #("CH"_3)_2"CH-O-CH"_3# is ethyl isopropyl ether.


Epoxides have four types of names.

1. Substitutive names

The compound is named as an alkene with an epoxy substituent.

For example, 1,2-epoxybutane.

2. Functional class names

The compound is named as an epoxide of the corresponding alkene.

For example, 1,2-epoxybutane is also named as but-1-ene epoxide.

3. The Hantzsch-Widman name

The ring is named as a cyclopropane in which the #"O"# atom replaces a #"CH"_2# group (indicated by the prefix "oxa") — with the "a" being dropped when followed by a vowel.

The three-membered saturated ring is indicated by the prefix "ir" ("tri" backwards without the "t") followed by the suffix "ane".

Thus, 1,2-epoxybutane is called ethyloxirane.

The O atom is automatically number 1, so the ethyl group is on C-2.

No locating number is necessary, because there is no such compound as 3-ethyloxirane.

4. As an oxide of the corresponding alkene (common name)

Examples are ethylene oxide and propylene oxide.

The first three methods are accepted by IUPAC.

The fourth is used only for simple alkenes such as ethylene, propylene, and butylene.