Branched alkanes have four part names:
locator + prefix + stem + suffix
For branched alkanes having 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).
For compounds having multiple branches that are identical, the positions of the branches are indicated by numbers separated by commas.
locator + prefix + stem + suffix
For branched alkanes having 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).
The compound below has trimethyl in its name.
The carbon at the end of the chain closest to any branches is given the number 1. 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.