Naming two isobutyl groups systematically | Organic chemistry | Khan Academy

In the last video, we named this molecule using the common names for this group right over here, and I thought it would be fun to also use to do the same thing, but use the systematic name. So, in the last video, we called this isobu, but if we wanted to do it systematically, we would look at this group.

We would start at where it is attached to the main backbone, and we would think about the longest chain of carbons from there. So if we start there, we can get one, two, three carbons. So if we're dealing with three carbons, then this is going to be a propy group, and we would number it one, two, three.

And we see on the two carbon of the propy group, the two carbon of the propy group, we have a one carbon group right over here. So this is a methyl group branching off of the two carbon of the propy group. So we could call this; we could call this thing the systematic name. Instead of calling it isobu, we could call it two methyl. That's the methyl group right over there.

So let me write this down: two, two methyl propy, two methyl propyl, two methyl propy, and so this is the systematic name. And of course, there's two of them. This is a two methyl propyl right over here. Instead of an isobu, we'll call it two methyl propyl, and this is another two methyl propyl.

So instead of writing the 57 di-isob here, we can instead substitute that with the systematic name. So let's do that. Let me copy and paste everything else that comes before it. So let me copy, copy, and paste it. Whoops, whoops, I'm in the wrong layer of my program.

Let me go one layer down, so let me copy and paste it again. Copy and paste. There we go. So I got that part, but now I'm going to write this part differently. So we still have stuff. It's still on the five carbon and the seven carbon of our main chain, so five, seven.

And we have two of them, but when we're doing systematic naming, we won't say di this thing. Instead, we say bis. So five, five, seven B. That says that, hey, we got two of what I'm about to say, B this thing.

So let me copy. That's in a different layer. Let me copy and let me paste that B this stuff right over here. And then, of course, we have cyclo-octane, and then, of course, we have cyclo-octane, and we are done. We have named it systematically as well.