Naming Branched Molecules


To name a branched molecule, first determine the longest continuous chain possible - see example below - this may mean not trusting the obvious way to interpret the drawn structure.

Next, start from the end of that chain that is closest to a branch. Count the carbons as you go along - if there is a one carbon branch off the second carbon of the chain, that's a "2-methyl" group; a three carbon branch off the eighth carbon of the chain is a "8-propyl" group. If the branch itself is branched, we use brackets - e.g., 2-(2-ethylhexyl)

1. Determine the longest chain - six carbons, "hexane"

2. Start naming from the end closest to a branch; 2-methyl, 3-methyl, 3-ethyl (not 4-ethyl, 4-methyl 5-methyl)

3. Collect like branches together and put in alphabetical orders; 3-ethyl-2,3-dimethylhexane

The molecule 3-ethyl-2,3-dimethylhexane