 final group to look at are functional group isomers. Now functional group isomers have the same basic molecular formula and a similar arrangement of the carbon skeleton. The difference is that there is now a change in the functional group. So something that we were naming previously, we've changed that name now. So let us have a look at something like one hexane and cyclohexane. So this is a new kind of a compound that we haven't looked at before. So let's have a look and see how this particular one would come together. So hexane has six carbons. One, two, three, four, five, six. So hexane has six carbons and it has three, four, five, six, seven, eight, nine, ten, eleven, twelve hydrogens. So the formula for one hexane, so you can see the double bond is on the end carbon. So I'm going to just slightly change the name here to hexoneene. And when I draw it, I'm drawing it like this, three, four, five, six. For saving of a little bit of time, I won't put the hydrogens in, but every time I have a bond that's not actually already showing that it's bonded to a particular type of atom, they're all going to be hydrogens. So this is my hexoneene molecule. Now what I want to do is I want to create an isomer. So to create an isomer, I can't add or subtract any atoms, but I also want to change the functional group. Now this time the functional group is a double bond. One of the simplest ways to turn an alkene into an alkyne is to actually break this bond. And when we break this bond, we can create a cyclic structure. So what I'm going to do is in breaking that bond, I need another hydrogen in one place. And I just connect that. So it's now a ring structure. So you can see I now have a ring structure, which is a slightly different structure. It's also got no double bonds. So it's no longer an alkene. The fact that it's in this kind of circle type arrangement, it looks more a little bit like a hexagon the way that I've constructed it. But the fact that it's in this ring means we use the prefix cyclo.