Naming Bicyclic Compounds - Video Tutorials & Practice Problems
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Bicyclic rings possess multi-ring systems within the same molecule.
Types of Bicyclic Molecules
Basically there two general categories of bicyclics:
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concept
The two types of bicyclic molecules
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as we talked about before. Bicycle. It's basically come into different categories. There's what I call the normal by cyclists. And what that would be is just on one structure with two rings that are attached by one bonk. All right, so I could say this is ring number one. This is ring number two. This would be a normal bys. I click. Then we have the other type of bi cycle called the Bridge by psy clicks, and these actually have three rings total. Okay? And I know it can be difficult to visualize, but basically imagine that you have one ring down here that is basically the bottom the base, and then you'd have a second ring formed on this side, and then you have your last during your third ring formed on that side. Okay? And what that means is that you have three rings that are all in this compound structure, and they're all connected by what this is called the bridgehead atoms. And remember that the bridgehead atoms are simply these right here. Okay, so we call. That was bridgehead. Okay, Now, it can be difficult to visualize this, but it turns out that both of these structures. Both the three d one that I drew here and this one over here are both the same thing. OK, they're just two different ways to represent the same molecule. Basically the bottom part down here. That's cyclo. That's actually a cyclo hexane that I have drawn right here. So that would be that blue part right there. And then the bridge, which is the part that comes over the top that I'm drawing in red would be right here. Okay, so this is basically the to date, the two d way to represent it or plainer. Okay, on this would be the three D way to represent it. Okay, But in either case, they're both the same thing. Sounds go on and figure out how to name these guys. It turns out that by cyclists, because of their added complexity of multiple rings, are gonna be named completely differently, as as model cyclo al canes
Bridged Bicyclic Nomenclature (Three Rings)
The bridgehead atom (one of the circled ones) must always be in the “1” position
The name is formatted as bicyclo[ringsize1.ringsize2.ringsize3]alkane
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concept
How to name a bridged bicyclic
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So we're gonna have thio kind of figure out what this normal creature is. The first step is we have to figure out which Adam gets the one position, and it turns out that the bridgehead Adam must always be in the one position. Now, there are two different bridgehead Adams in all of these molecules. So the one you would pick would depend on maybe how close it is to a substitue int. Okay, but regardless, you're always gonna give your one position toe one of the bridgeheads. Okay, so let's go ahead and look at this compound. The bridgehead would be either this one or this one. In this case, there are no substantial in, so it doesn't matter which one I pick, but one of those would have to get the one position. Okay, so let's just give the back one with one position, then the next thing we do is we look at the actual format of the of the name and what you'll notice is that a few things have changed. First of all, the prefix used to be cyclo if it was one ring, but now we're gonna exchange that for bi cycle by cycle just stands for the fact that it's a bicycle, it compound. So any time you have bridgehead Adams, anytime you have two rings or more conjoined together, that's going to be bi cycle. Okay, then notice that the end, okay? Or the functional group would just be an al cane. And what's interesting about this is that we're gonna some all of the carbons together to get the name of this al cane, meaning that I'm going to count up how many carbons are in this entire structure. And that's gonna be the name of my al cane. Okay, so if we wanted to, we could go ahead and just used these first few steps on this compound. We could say, Well, this is a bicycle. Oh, compound. Because the fact that bridgehead Adams, it also is gonna be an octane, because I have carbons. Now, is that the correct numbering? Absolutely not. Don't take that as me saying that's the way to number of the Al Cane. I'm just saying that they're eight total. I was just counting. Okay, so that means it is definitely gonna be a by cyclone octane. But now let's talk about these funky numbers in the middle because I know you're already thinking. How do I do that? Basically, what we do is we figure out how Maney carbons are inside of these rings. That air, not bridgehead, Adams. Okay, so what I would do is, I would say, in this case, there's three rings. Remember? I taught you guys that in a bridge compound, there's three rings. So you would say Okay. How? Maney non bridgehead atoms are in ring number one. Ring number two and ring number three. Then you put them together using periods. Okay? And we list them from largest two. Smallest. Okay, So would start off with my largest ring here. End off with my smallest ring size there. And you might guess that the middle one would be in the middle at ring, too. Okay, let's go ahead and look at the structure. Now, what I see is that I have my bridgeheads that all label right here, bridgeheads. And then what I've got is a few different rings. I've got the bigger ring, which is right here. So I called up one number one and what will notice is that I have 123 carbons that are not bridgehead atoms on that ring. So that means the ring size of this would be equal to three. Okay, then let's go to the next one. The next one will be over on this side on this side. I would have 12 atoms that are not bridgehead Adams on that side. So that means the size of this ring would be to and then finally at the top, notice that I only have one carbon in between my bridgehead atoms. So I'm looking for is how many different carbons are in between these bridgehead atoms. In this case, I would only have one, so that would have a ring size of one. Okay, now, what I do is, I go ahead and I put them together in order of largest to smallest. And that indicates that all right, we've got an eight member structure. Two carbons are bridgehead, Adams, because you always have to bridgehead Adams. And then three carbons are in one ring. Two carbons, Aaron, another ring, and one carbon is in the last string. And that's what this color coding has to do it. So three would be here. Two would be here and then lastly, one would be up here. All right, so now what I've done is I've just taught you guys how to basically name in UN substituted, um, by cyclic. But what if we actually need to number it in terms of substitutes? How about if I have a metal group coming off this location right here? What location does that method get? Is it a wine? Is it a two? Is it an eight?
Fused Bicyclic Nomenclature (Two Rings)
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How to name a fused bicyclic
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Well, the way we figure that out is by using the next rules. Let's scroll down a little bit. The next rule states that we're gonna number when it comes to substitue INTs. If we have to number the locations of substantial INTs, we're gonna number from the largest ring to the smallest ring. Okay, And remember that your bridgehead, Adam always gets the one position. So what that means is that if we were to go ahead and number these carbons up here Okay, let's go ahead and number all eight. The first one, the one that would get the number one position would be one of these bridgehead Adams. Okay, I'm just gonna put it on the back. But if you put it on the front, that would be equally acceptable. Okay, then. Which Adam should get my to should be the other bridgehead. Actually, no, I should go around the largest ring first, so that means it's gonna be 234 five. Okay, so those are the numbers so far. Okay, Now, what I need to do is I need to go around my second largest ring, so my second largest ring would be the blue one. So then this would be six and seven. And then finally I would go to my least my smallest ring, and that would be eight up here. OK, so it's a little bit unusual, but it makes sense if you just think we're going from the largest to the smallest. Okay, so in this case, if we were to start numbering this carbon, the very first one would be here. Okay? And then, as I've drawn in this diagram, we would go to the largest ring, which is this to carbon one. And then to the smaller rings will be 234 and then to the smaller ring, which would be five. Okay, even though notice that I have a substitution in the five position, but it's okay like that. Still, that wouldn't get the two position. Why? Because I have to be consistent. I always have to start off from the biggest ring and work to the smallest one now. Ah, questioning eyes might be wondering is Okay, now I know how to do this for a bridge compound, but what about a normal bys? I click like this one. Notice that this one doesn't have three rings. It only has to. It only has this to carbon ring on one side. And then if you go around these your bridgeheads, right? If you go around, it only has one carbon on the other. Okay, that's actually part of the ring. The metal group is a substitution. It doesn't count towards the ring size. So then what you're thinking is what happened to the third ring? Remember? I always have to have three rings. Well, it turns out that that only happens when you have a bridge. If you have a bridge, then you're gonna have three rings. What if you don't have a bridge? Well, if you don't have the bridge, then the third ring is just gonna count as zero. Okay? What? You're basically telling the reader there is if you put a zero in the third position, that means this is not a bridge structure. This is a normal bys. I click where I only have two rings. Okay, So as you can see in this case, the way we numbered this was that we had five metal because it was a method in the five position, then by cycle, because I have two rings conjoined by one bond and then where What that means is that I have one ring has two carbons that are not bridgehead. Another ring that has one carbon that is not bridgehead. And then I'm missing the third ring. Why am I missing the third ring? Because there's no bridge at all. Okay, so I'm just gonna right here once again that zero means no bridge. Okay? And then finally we call this the heck sane because the fact that there's six carbons total in the structure
*Error: The name of this molecule was misstated in the video. Please refer to the name below (pentane)!
Awesome job! These are some of the hardest molecules to name, so if you got them, you’re ahead of the curve.