Naming Ethers, Epoxides, Sulfides
Introduction
The ether functional group is singly bonded carbon-to-oxygen-to-carbon. The oxygen atom is sp3 hybridized because it contains two single bonds and two lone pairs of electrons.
Ethers are common solvents in the chemistry lab. Two of the more common ether solvents are ethyl ether (also called diethyl ether or ether) and THF (tetrahydrofuran). Ethers are good at dissolving both polar and nonpolar compounds. Because there is no hydrogen atom on the oxygen atom, ether molecules do not hydrogen bond to each other. Therefore, they have fairly low boiling points. This makes a good solvent because when the reaction is complete, the ether solvent can be easily removed by distillation. DME and dioxane are water soluble. They are good solvents because they can be removed from an organic product at the conclusion of a reaction by simply washing with water.
Ether solvents
Ethers are also used as anesthetics. In 1846, Boston dentist William Morton demonstrated that ethyl ether can be used to painlessly extract the teeth of patients. Ethyl ether is also very flammable, which caused quite a problem in the days before electric lights! Ethyl ether also made patients quite nauseous. Today, halogenated ethers are commonly used as general anesthetics.
Ethers as general anesthetics
Methyl tert-butyl ether, MTBE, is used as an oxygenate in gasoline fuel. It increases the octane rating of the fuel and works as an anti-knocking agent. MTBE is now banned in gasoline by many states because it has found its way into drinking water.
Methyl tert-butyl ether, MTBE
Crown ethers
Crown ethers are cyclic ethers. They are a special subset of ethers. The many oxygen atoms with their lone pairs of electrons make crown ethers especially good at binding to positive cations.
18-crown-6 crown ether binding to potassium cation
Nomenclature
Ether Nomenclature
IUPAC Nomenclature
Ethers are named by naming ether substituents as alkoxy groups attached to the base chain. Their names take the form alkoxy alkane.
IUPAC named ethers
Common names
Ethers are commonly named by naming the two alkyl groups, usually in alphabetical order, followed by the word “ether” in the form of alkyl alkyl ether. The common name takes the form alkyl alkyl ether.
Commonly named ethers
Ether rings have some common names as well. Furan is a five-membered ether ring with two double bonds in it. If four hydrogen atoms are added to furan turning the double bonds into single bonds, the solvent tetrahydrofuran, THF, is made. To locate the substituents on these rings, the numbering of the ring starts at the oxygen atom.
Ether rings
Epoxide nomenclature
Epoxides, or oxiranes in old school language, are three-membered ether rings. Epoxides are commonly made from the oxidation of an alkene using a peroxyacid. Epoxides are named by stating the alkene from which the epoxide was formed followed by the suffix “oxide”.
Another way to name epoxides is to name them as a substituent on a more important part of a molecule. In that case, they are named using the prefix “epoxy” and given a location using the numbers of the two carbons to which the oxygen atom is attached.
An older, common method to name epoxides is to use the old-school name oxirane. The simplest epoxide, ethylene oxide, is also called oxirane. One common naming method is to name the substituents on the oxirane followed by the suffix, oxirane.
Sulfide nomenclature
Since oxygen and sulfur are in the same column of the periodic table, there is a sulfur analogue of ethers. Sulfides, also called thioethers, are the sulfur analogue of ethers.
IUPAC
Sulfides are named by naming an alkylthio group as an attachment on a base chain. It takes the form as alkylthio alkane.
Common
The common name for sulfides is much like the common name for ethers, but the suffix “sulfide” is used instead of “ether”.
Sulfide ring
One common sulfide ring that you should know is thiophene. Notice that thiophene is analogous to furan. To identify where substituents are, the numbering of the thiophene ring begins at the sulfur atom and works its way around the ring. The nitrogen ring analog of furan and thiophene is called pyrrole.
1. Name the following compounds.
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b)
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f)
g)
Answers
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a)
b)
c)
d)
e)
f)
g)
