One or more carbons may be attached to the longest continuous chain as branches. The branch is located by a position number. Carbons are numbered so that the functional group has the lowest number. If there is no functional group present, then the first branch should have the lowest number.
The branch is named by dropping the "-ane" ending of the root then adding the "-yl" ending. The branch names precedes the main chain root name. Examples: One carbon: methane = methyl Two carbons: ethane = ethyl Three carbons: propane = propyl
Example top left - Branched Alkane: At carbon 3 there is a one carbon branch = methyl. At carbon 4 there is a two carbon branch = ethyl.
Example lower left - Branched Pentene: At carbon 2 there is a one carbon branch = methyl. At carbon 4 there are two separate one carbon branches = methyl