11.1: Structure and Nomenclature of Ethers
Structure and Bonding
Ethers are organic compounds with an ether functional group which is characterized by an oxygen atom connected to two — identical or different — alkyl, aryl, or vinyl groups. The C–O–C linkage in dimethyl ether — the simplest ether — has an approximately tetrahedral bond angle of 110.3 degrees. The oxygen atom is sp3- hybridized, with the C–O distance being about 140 pm.
Classification of Ethers
Based on their attached substituent groups, ethers can be classified into two categories — symmetrical and unsymmetrical. Symmetrical ethers have two identical groups attached to either side of an oxygen atom — for example, dipropyl ether, diphenyl ether, and more. Unsymmetrical ethers have two different groups attached to either side of an oxygen atom — for example, ethyl methyl ether, butyl methyl ether, and more.
Rules Underlying the Nomenclature of Ethers
For common names, the different alkyl groups attached to the oxygen atom are arranged in alphabetical order, and the word ‘ether’ is added at the end — for example, benzyl phenyl ether. If both the alkyl groups are the same, then the prefix ‘di’ is used — for example, diethyl ether.
For IUPAC names, the larger group name becomes the root word, and the smaller group part is named alkoxy. For example, methoxypropane.
Cyclic Ethers: Heterocyclic Compounds
Cyclic ethers are heterocyclic compounds with an oxygen atom in a saturated ring. The IUPAC nomenclature for cyclic ethers uses the prefix ‘ox’ followed by the suffix ‘irane,’ ‘etane,’ ‘olane,’ ‘ane’ to indicate the number of carbon atoms in the three-membered, four-membered, five-membered, and six-membered ring systems, respectively. The number priority of the atoms of the ring begins with the oxygen atom.