Naming Ethers

In this article we will learn Naming of Ethers in organic chemistry. Ethers are the colorless, pleasant smelling and highly volatile organic compounds. Ethers are oxygen containing chemical compounds which are considered as derivatives of alcohols or water. 

Key words: Ether, Epoxide, Common Names of Ethers, IUPAC Names of Ethers.

What are Ethers?

In olden days ether is used as anesthesia during surgeries. Also ether is widely used as a solvent in industrial processes. Like alcohols, ethers are considered as derivatives of water, where both hydrogen atoms are replaced by alkyl / aryl groups.

Basically there are two types are ethers: Symmetrical ethers where two alkyl / aryl groups are identical and Unsymmetrical ether where alkyl / aryl groups are different. Another category is Cyclic ethers where the oxygen atom is present in the cyclic ring. Three member cyclic ethers are very common. They are known as epoxides or oxiranes.

Ethers are having similar bent structure like water. They have low boiling points as compared to alcohols. Also ether dissolves wide range of non-polar and polar compounds. Therefore ethers are used as a solvent for many organic reactions in laboratories and industries.

Common Names of Ethers

Ethers are named by two alkyl / aryl groups bonded to oxygen atom and adding suffix “ether”. The unsymmetrical ether is named by writing alkyl / aryl groups in alphabetical order followed by addition of word ether.  The symmetrical ether is named by writing prefix “di” followed by alkyl / aryl ether. 

For example, consider following molecule which has “methyl” and “phenyl” groups bonded to the oxygen atom. Therefore common name of the compound is “methyl phenyl ether”. Here the groups attached are written in alphabetical order.

Consider another example, where “tert-butyl” and “methyl” groups are bonded to the oxygen atom. In this example “butyl” comes before “methyl” by alphabetical order. The prefixes like “tertiary” or “secondary” are not considered for writing alphabetical order. Therefore name of the compound is “tert-butyl methyl ether”.

The symmetrical ethers are named in the format “di alkyl / aryl ether”. For example, consider following molecule where two ethyl groups are bonded to the oxygen atom. Therefore name of the compound is “diethyl ether”. 

Let’s see another molecule where two phenyl groups are bonded to oxygen atom. Therefore name of the compound is “diphenyl ether”.

IUPAC Names of Ethers

According to IUPAC nomenclature system, ethers are named as “alkoxy alkane”. The smaller group is considered as “alkoxy group” and larger group is named as parent alkane. Therefore ethyl methyl ether is named as methoxyethane.

Consider the example of n-butyl ethyl ether, here ethyl group is smaller group and n-butyl group is large. So parent alkane is butane and ethoxy group is present at carbon number 1. Therefore name of the ether compound is “1-ethoxybutane”.

Cyclic Ethers

Cyclic ethers are heterocyclic compounds and oxygen atom is numbered 1 for numbering the atoms present in the ring. Three membered cyclic ethers are very common, they are called as epoxides. The common name of epoxide is given form name of the alkene from which the derived by oxidation reaction. For example an epoxide derived from ethylene is called “ethylene oxide”. And the epoxide derived from cyclopentene is called as “cyclopenten oxide”.

The four membered cyclic ethers are known as oxetanes. For example, four membered cyclic ether in which “methyl” group is present at carbon number 2 is called as 2-methyl oxetane.

The five membered saturated ethers are known as tetrahydrofurans because they derived from aromatic compound furan. For example, a five membered saturated cyclic ether in which “methyl” group present at carbon number 3 is known as “3-methyltetrahydrofuran”.

The six membered cyclic ethers are named as derivatives of aromatic compound pyran. For example, six member and saturated cyclic ether is known as tetrahydropyran. If the “methyl” substituent present at carbon number 4, then name of the compound is 4-methyltetrahydropyran. 

Dioxanes are the cyclic ether which consists of two oxygen atoms in the ring. In general six member dioxanes are common. They are named based upon the position of the oxygen atoms. For example: 1,2-dioxane ; 1,3-dioxane and 1,4-dioxane.

IUPAC Names of Cyclic Ethers

According to IUPAC naming system cyclic ethers are named based upon the size of the ring. The root names of cyclic ethers are shown in table. According to this naming system, epoxide is named as “oxirane”. The tetrahydropyrane is named as “oxane”.

Ring size	Root name of ether
3	oxirane
4	oxetane
5	oxolane
6	oxane
7	oxepane
8	oxocane
9	oxonane
10	oxecane

Polyethers

Polyethers are the polymers of which consist of several ether linkages. The polymers are name based upon their monomers. If end groups of the polymer are hydroxyl groups then the term glycol is used for nomenclature. For example; polyethylene glycol (PEG) has monomer ethylene glycol. The polypropylene glycol (PPG) has propylene glycol monomer.

Crown Ethers

Crown ethers are cyclic ethers containing several oxygen atoms in the ring. The oxygen atoms present in the ring forms complexes with cations and outer surface of the ring is hydrophobic. Due to this property of crown ethers, cation becomes soluble in non-polar solvents. Therefore crown ethers are widely used in phase transfer catalysis. 

Common Names of Crown Ethers

The crown ethers are named by writing two numbers which specify the ring size and number of oxygen atoms present in the ring.  For example, the name 12-Crown-4 indicates that crown ether has 12 member ring and there are four oxygen atoms present in the ring. Similarly, 15-Crown-5 shows that there is 15 member ring and 5 oxygen atoms present in the molecule. 

IUPAC Names of Crown Ethers

According to IUPAC naming system crown ethers are considered as derivative of cycloalkanes. The prefix “oxa” is written for the oxygen atoms. The positions of oxygen atoms are denoted by numbers. And prefixes like “tetra”, “penta” or “hexa” are written to indicate number of oxygen atoms present in the ring. The oxygen atom is given position 1 then remaining atoms are numbered in ascending manner. For example, 12-crown-4 has IUPAC name “1,4,7,10-tetraoxacyclododecane” because it have 12 member ring so the root name is “cyclododecane” and there are four oxygen present at position 1,4,7 and 10.

15-crown-5 is named as “1,4,7,10,13-pentaoxacyclopentadecane”. The molecule has 15 member cyclic ring so the root name is “cyclopentadecane”. There are five oxygen atoms present at 1,4,7,10 and13. Hence the correct name of the compound is “1,4,7,10,13-pentaoxacyclopentadecane.

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