Module 6: Structure and Nomenclature of Alcohols and Ethers

A primary alcohol has at least two hydrogens attached to the alcohol carbon (R–CH₂–OH); a secondary alcohol has only one hydrogen attached to the alcohol carbon (R₂CH–OH); a tertiary alcohol has no hydrogens attached to the alcohol carbon (R₃C–OH).

The simpler alcohols are commonly known by their trivial (common) names obtained by adding the word alcohol to the name of the alkyl radical; for example:

By the I.U.C. method, the longest carbon chain containing the –OH group is chosen as the base. The suffix of the hydrocarbon name is changed from –ane to –anol and when necessary the position is indicated by number preceding the letters –ol. Polyhydroxy compounds are named as diols, triols, and so forth.

In more complex molecules where the parent name is not that of an alcohol, the –OH group and its position are indicated by a prefixed number and the radical name hydroxy; or the suffix –ol; for example:

Compounds containing two alcohol radicals are known as diols (or glycols); those containing three radicals are known as triols. Some common names are:

Ethers (R–O–R) are named in two ways. Ethers containing symmetrical or simple alkyl radicals are named by giving the alkyl radical names and adding the word ether; for example:

By the I.U.C. system the ether is considered as a hydrocarbon group with a single hydrogen replaced by an alkoxy group. The name of the longest chain hydrocarbon is prefixed with the numbered position and name of the alkoxy group. The alkoxy group is named as the hydrocarbon radical name by changing the suffix from –yl to –oxy.

Epoxides are compounds containing the ring –C–O–C–. The simplest is ethylene oxide (named as the alkene precursor + oxide). In more complex compounds the group is given prefix numbers and the name epoxy.