 In this video, we'll go through some worked examples of how to name branched hydrocarbons. So I'm going to start by suggesting you try to name these two molecules for yourself. Pause the video, draw out the condensed structural formula if you need to, to get a good idea of what the molecules look like, and then try to name each one. Okay, so here are the condensed structural formulae, and now to name them. First, find the longest chain in the molecule. This one has seven carbons, and they're all single bonds, so we know that the base of the name is going to be heptane. There's one branch, and the branch has two carbons, so the name of the branch is ethyl. Now if we number the main chain, the branch is attached right in the middle, so it doesn't actually matter which direction we number in. And it turns out that the branch is on the fourth carbon. So the final name for this molecule is for ethyl heptane. Again, remember the hyphen to separate numbers and letters. Now for this one, first find the longest chain in the molecule. Did you spot the trick here? The longest chain is not always the one that runs straight across the page. Here is the longest chain, and it has eight carbons in it. So this molecule is based on octane. There's one substituent of one carbon, so that's a methyl, and when we number the main chain, we'll start at this end because the branch is closer to that end, and we'll find that the branch is on the third carbon. So the final name for this molecule is three-methyl octane. A quick word on numbering the main chain. Remember the aim in the numbering is to get the lowest possible number in the name of the molecule. In the second molecule, if you were to start numbering from the left, the branch would be on carbon number six, but if we start at the right-hand end, closer to the substituent, the methyl group is on carbon number three. In the interests of efficiency and clear naming, we go for the lowest possible number.