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- So when we name organic molecules,
- the core of what we think about
- is just how many carbons form the chain or
- form the ring that we're looking at?
- So let's say I have something like this.
- And hopefully, you're reasonably familiar
- with what this represents.
- And I'll review it a little bit.
- So let's say I have something like this.
- That is the molecular structure right there.
- And so the first question you should be asking is
- how many carbons are there there?
- And some of you might say, wait,
- how is that even a molecule?
- And just as a review, the end point of every line
- represents a carbon.
- So that's a carbon, that's a carbon, that's a carbon,
- that's a carbon, that's a carbon, that's a carbon.
- And we have one, two, three, four, five, six carbons
- and we have no double bonds.
- So if you have all of that information
- you're ready to name this molecule.
- And before I actually name it, let me just kind of give you
- all of the different prefixes.
- So if you have one carbon, the prefix is meth-.
- If you have two carbons, the prefix is eth-.
- And it's good to memorize at least up to about 10.
- And actually it kind of repeats after that.
- If you have three carbons, the prefix is prop-.
- Prop- like propane, and you've heard of ethane and methane.
- So you'll see all of that soon.
- Four, you're talking about but-.
- Five, and after five it kind of becomes the traditional
- prefixes that we associate with a lot of these numbers.
- So at five, it's pent-, like pentagon.
- Six, it's hex- like hexagon.
- Seven is hept-.
- Eight is oct-, like octagon.
- Nine is non-.
- Ten is dec-.
- And then after that,
- it kind of starts to have a pattern here and
- you're not going to really deal with things much beyond
- the teens, but I'll just write them down here
- just out of interest.
- Eleven is undec-.
- And for those of you who know French,
- I'm not one of them, but I know that
- one in French is une, or in Spanish, uno.
- So it's 1 and 10: 11.
- Twelve is dodec-.
- Do or dos, if you're speaking Spanish, for 2.
- Dec for 10, 2 and 10, that's 12.
- Thirteen, you could imagine what it's going to be.
- It is tridec-.
- Fourteen is tetradec-.
- A tetrapod is something with four legs.
- And after that it, becomes very systematic.
- At fifteen is pentadec-.
- Notice pent-, 5 and 10.
- Sixteen is hexadec-.
- Seventeen is heptadec-.
- So it just goes on and on and on.
- I don't think I've got to go-- it's hexadec-, heptadec-,
- octodec- is eighteen,
- nineteen is nonadec-,
- and then twenty is actually iso-.
- But we won't even go into that.
- This'll probably serve our purposes.
- I mean, I could go up to sixteen is hexadec-.
- So this is just how many carbons are
- in our longest chain.
- What I drew here is just one chain.
- So we could immediately--let's try to name it.
- Well, how many carbons do we have here?
- Well, we have one, two, three, four, five, six carbons.
- So we'll be dealing with hex- as a prefix.
- And then to get, I guess, the post-fix on this prefix, or
- the kind of the root, you look to see if there are
- any double bonds here.
- And there are no double bonds here.
- And if we have no double bonds in this carbon chain,
- we're dealing with an alkane.
- This is called an alkane,
- which is a general term for all of the chains of carbons
- that have no double bonds on them
- or no triple bonds: all single bonds.
- So in this situation, you take hex- for six,
- so this is hex-.
- And then, because it's an alkane, it gets
- the -ane from alkane.
- So this is hex- this is hexane.
- Let's do another one.
- Let's say I have this thing right here.
- I'll draw-- let's make it even longer.
- So let's say I have that thing right there.
- So how many carbons do we have?
- We have 1-2-3-4-5-6-7 carbons.
- They're all single bonds, so it's an alkane.
- So this will be seven carbons.
- It is heptane because we have all single bonds.
- Now, if things form a chain, or if things form a ring,
- I should say, we put the prefix cyclo- in front of it.
- So if I have-- let me show you what I'm talking about.
- So if I just have five carbons, one, two, three,
- four, so one, two, three, four, five.
- OK, so that's five right there.
- I have one, two, three, four, five carbons in a chain.
- If I just have five carbons in a chain like this,
- this would be pentane.
- But if I have five carbons and they form a ring,
- so let me draw it.
- So it's one, two, three, four, five carbons
- and it forms a ring.
- Let me make the drawing a little bit better.
- So it's really, I'm just drawing a pentagon.
- But notice, this has five carbons on it.
- I can draw the carbons here.
- Carbon, carbon, carbon, carbon, carbon.
- And just as a review, what you don't see is the hydrogens
- they're bonded to.
- Each of these guys have two bonds,
- so they must have two bonds with something else
- and those are going to be with hydrogens.
- And I'll draw it here just as a bit of a review, but you
- notice very quickly, the drawing gets extremely messy
- when you draw the two hydrogens
- on each of these carbons.
- So it's a little bit over-- maybe
- I shouldn't be doing that.
- But there you go.
- So it becomes very messy when you draw the hydrogens, so
- it's better to just assume that they're there.
- If we don't draw all four bonds of the carbon, the other
- two bonds are going to be with hydrogen.
- So here, you might say, OK, this is an alkane,
- because I don't have any double bonds here.
- All of these are single bonds with the carbon.
- I have five carbons, so you might say this is pentane, but
- you have to think about one more thing.
- It's in a ring, so we add the prefix cyclo- to it.
- So this is, because it's a ring, we write cyclopentane.
- Cyclopentane.
- So let me just break that apart.
- This tells us that we're dealing with a ring.
- You see that this is a ring right there.
- This tells us that we're dealing with five carbons,
- and then this tells us right here,
- the -ane part, that tells us
- that they are all single bonds.
- All carbon-carbon single bonds.
- No double or triple bonds.
- All single bonds.
- So let's go the other way.
- Let's start with the word and let's see if we can figure out
- what the actual structure would look like.
- Let's say I have cyclononane.
- So what is this telling me?
- This tells me I'm dealing with a ring.
- That is a ring.
- It's going to have a ring structure.
- It's going to have nine carbons, nine C's, and then
- it's an alkane, so they're all going to be single bonds.
- Single bonds
- So if I want to draw it, I want to draw nine carbons in a ring
- it's not a trivial thing to draw.
- I'll try my best, so let's see, that's one, two, three,
- four, five, six, seven, eight.
- Let's see, let me draw it.
- I'll try a little a better shot at it.
- Let's see, I've one, two, three, four, five, six,
- seven, eight, and then nine.
- And then you can connect the last. So let me make sure that
- this is-- and obviously, I could have drawn it better
- than that, but hopefully, you can see all of the edges here.
- So I have one, two, three, four, five, six, seven, eight,
- nine carbons.
- It's in a cycle, it's in a ring.
- I have nine carbons.
- They're all single bonded, so this is cyclononane.
- Although, there's probably better ways to draw that ring right there.
- So if someone were to tell you: octane,
- and that word might feel familiar to you from the gas station.
- They are literally talking about the molecule octane.
- And now you know, or at least you have a sense of what
- they're talking about.
- The oct- tells you that you have eight carbons.
- There's no cyclo- in front of it, so it's not a cyclo.
- It's just going to be a chain.
- And then the -ane part tells you that they're all single bonds,
- so it's just going to be eight carbons in a chain.
- One, two, three, four, five, six, seven, eight.
- It's just going to look like that.
- One, two, three, four, five, six, seven, eight.
- In the next few videos, we'll add more to these molecules
- and make the names even more complex.