- Ethers, sulfides and halides are lower priority functional groups than hydrocarbon
- Ether, sulfide and halide functional groups on hydrocarbons are named as substituents at the front of the name
A few select functional groups, such as ethers, sulfides, and halides, are low priority, meaning that they are given lower priority than the main hydrocarbon root/suffix. As a consequence, they are given the same nomenclature priority as alkyl substituents and are listed as branching substituents.
The following tables show the appropriate format when they are listed before the root of the hydrocarbon.
Expand this section to review functional group structures
In the first example below, there is a bromine substituent at the 4-position. This molecule is named according to the standard IUPAC hydrocarbon nomenclature rules using “bromo” as the substituent name. The molecule is called 4-bromo-3-methylheptane. In the second example, there is an ether substituent at the 3-position of the root chain. The oxygen is connected to one carbon, making the entire substituent a “methoxy” group. If the carbon chain on the ether were to extend by one, as in the next example, the substituent would be an “ethoxy” group.
Sulfide nomenclature is directly analogous to ether nomenclature. In the first example below, there is a sulfide functional group attached to the main hydrocarbon. This group is treated as a substituent and called a methylthio group. If the sulfide chain is extended to three carbons, it is called a “propylthio” substitutent
Interactive: