| carbon number | stem | carbon number | stem |
| 1 | meth | 5 | pent |
| 2 | eth | 6 | hex |
| 3 | prop | 7 | hept |
| 4 | but | 8 | oct |
prefix + stem + suffix
For an alkane the suffix is ane.
The stem indicates the number of carbons in the longest chain.
Various stems are given in the table.
The prefix indicates the nature of the branch and the position of the branch on the main carbon chain.
Nature of branch:
The prefix for a saturated hydrocarbon branch is the stem (indicating the number of carbons) with an -yl ending.
The prefix for a saturated hydrocarbon branch is the stem (indicating the number of carbons) with an -yl ending.
CH3– methyl
CH3CH2– ethyl
Position of branch:
The carbons in the longest (stem) chain are each given a number.
Carbon number 1 is the carbon at the end of the chain closest to any substitutents.
For compounds having multiple branches that are identical, the positions of the branches are indicated by numbers separated by commas.
CH3CH2– ethyl
If a molecule contains more than one branch of the same composition, the prefix is preceded di, tri, tetra as appropriate to indicate how many of that chain is present.
There is no space (or dash) in this part of the name (dimethyl, for example or trimethyl in the compound below).
There is no space (or dash) in this part of the name (dimethyl, for example or trimethyl in the compound below).
Position of branch:
The carbons in the longest (stem) chain are each given a number.
Carbon number 1 is the carbon at the end of the chain closest to any substitutents.
For the compound above, carbon number 1 is at the right-hand end of the chain.
For compounds having multiple branches that are identical, the positions of the branches are indicated by numbers separated by commas.
Thus the name of the compound above is 2,4,5-trimethylheptane.