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- We've already touched on ethers in several videos.
- They've been our useful aprotic solvent in several of
- our reactions.
- But I thought it was about time that we actually devoted
- a video or two to ethers.
- And like all things that we've done in organic chemistry, a
- good way to familiarize ourselves with the molecules
- and how they look, is to actually name them.
- So let's do a couple.
- And the first few you've seen already.
- So let's say we have this molecule right here.
- What I'm going to do is I'm going to teach you two
- ways to name it.
- The common name, and that's probably the more important
- one, especially with ethers.
- Because, as you could imagine, that is the more common name.
- That is what people say.
- And then I'll also show you how to name it
- using the IUPAC name.
- So let me write this down.
- IUPAC name, which is the International Union of Pure
- and Applied Chemistry.
- And they've come up with kind of the official naming
- protocols for all of these organic molecules.
- This is actually the convention that we used
- earlier when we did the alkanes and the alkenes.
- But in the case of ethers, the common name is more common.
- So the common name for this molecule right here.
- You look at the two carbon groups here.
- So let's see.
- You have this one right here.
- That is an ethyl group.
- That's an ethyl group right there.
- You have one, two carbons.
- And then you look at the other carbon group right over there.
- That's also an ethyl group.
- You have one, two carbons.
- So you call this-- let me just write this down-- that is also
- an ethyl group.
- So the common name for this is just diethyl ether.
- And the ether tells you, this part tells you, that you have
- an oxygen in between your two ethyl groups.
- This is the common name.
- Now the International Union of Pure and Applied Chemistry
- official name for it.
- You kind of do something similar to how we named other
- things before.
- You look for the longest chain.
- Let me redraw it.
- So maybe on the left hand side I'll do the common names.
- On the right hand side I'll do the IUPAC names.
- So let me redraw what the common name
- of the diethyl ether.
- You look for the longest chain.
- In this case, there's two longest chains.
- There's this one that has one, two carbons.
- And then you have this one, that has one, two carbons.
- So you can pick either one.
- I'll just pick this one as the main chain right over there.
- It has two carbons, no double bonds.
- It is an ethane.
- And then you say, OK, I have this alkoxy group.
- We put the oxy at the end of it because it has this oxygen
- right here.
- But it's the alk part of it has two carbons, one, two.
- So we call this right here, we call this ethoxy.
- So one other way to name this, we have this ethoxy group
- attached to the one carbon.
- We're just going to start numbering on this side of the
- ethane, just because that's where the group is, attached
- to the one carbon.
- So we call this 1-ethoxyethane.
- You'll almost never see it actually named this way, even
- though this is the official name.
- You're much more likely to see this as diethyl ether.
- And at least in my brain, this resonates a lot more.
- You just say what are the two groups.
- And you throw the ether at end.
- You know that there's an oxygen in between.
- Let's do a couple more of these.
- So let's say I have this molecule right here.
- I have this molecule right over here.
- The common way is you look at the two groups on either side
- of the oxygen.
- So this right here-- let me do this in a different color--
- this group on the left right here, we have
- one, two, three carbons.
- It's a propyl group, but we're attached
- to that middle carbon.
- So this is an isopropyl group.
- And on the right hand side right here, we
- just have one carbon.
- So this is right here-- I keep using that blue-- this right
- here, this is a methyl group.
- So the common way of naming it, you just list both of
- these groups and then you write ether.
- And you list them in alphabetical order.
- I comes before m.
- So this is, the common name is isopropyl methyl ether.
- Now if we were to do the IUPAC naming, we look for the
- longest carbon chain.
- Let me redraw the molecule itself.
- So let me redraw the same thing right there.
- So what's the longest carbon chain here?
- Well we have one, two, three carbons right there.
- We only have one carbon right there.
- So this thing right here is our longest carbon chain.
- It has three carbons on it, and it had no double bonds.
- So eth, meth, prop, propyl, or it's actually propane.
- So this is our longest. So we write propane right there,
- because we're using the IUPAC naming mechanism.
- And then we look at this methoxy group right here.
- And I call this a methoxy group, because I have the o.
- That gives us the oxy.
- And I just have a methyl group right here.
- So this is methoxy.
- You remember that meth is the prefix for just having only
- one carbon.
- We add the oxy because that oxygen is there.
- And it's attached to the two carbons on the propane chain,
- no matter what direction you start naming from, or
- numbering from.
- One, two, three.
- So this is 2-methoxypropane.
- Let's do another one.
- Let's do one more.
- And I think you'll get the gist of at least the
- reasonably simple ethers to name.
- So let's put a ring over there.
- And then that's attached to an oxygen.
- And then we have another carbon chain right here.
- And then we have another carbon chain right there.
- Let me just copy and paste that so that I don't
- have to redraw it.
- So let me copy and paste.
- All right.
- So let's do the common name first. That always tends to be
- a little bit more fun.
- So on this side, we have one, two, three, four, five, six
- carbons in a cycle.
- This right here on the left hand side is
- a cyclohexyl group.
- This on the right hand side, we have one, two, three.
- This is just a straight-up propyl group.
- And so when you name the ether, you just put these two
- groups in alphabetical order, and you add an
- ether at the end.
- So it's cyclohexyl.
- C comes before p.
- So it's cyclohexyl propyl.
- Let me get that shade of yellow right.
- Cyclohexyl propyl ether.
- Now let's do the IUPAC way to name it.
- So you look for the longest carbon chain here.
- In this case, it's going to be the cyclohexane right here.
- We have one, two, three, four, five, six carbons there.
- We only have one, two, three there.
- So this is kind of our backbone.
- So we write down cyclohexane.
- No double bonds, so it's a hexane.
- So that's the cyclohexane right there.
- If you just had these three carbons, it would be a propyl.
- But this is not just three carbons.
- It's three carbons and then an oxygen.
- So we would call it a propoxy.
- So this is propoxy group.
- And you don't have to number it because it can just be
- attached to any of these carbons.
- It would essentially be the same molecule.
- So you can just call this propoxy cyclohexane.
- Let me make it a little bit closer to the cyclohexane.
- Propoxy cyclohexane.
- But once again the common name is what you're
- more likely to see.
- Now that we've named a few of them, let's think a little bit
- about their properties.
- What we've seen already is that-- and we've used it
- several times, especially in our Sn2 reactions and things
- like that-- places where we didn't want
- protons floating around.
- We used actually diethyl ether.
- And in general ethers do make for good solvents.
- They tend to be fairly unreactive.
- So good solvents.
- Especially when you're looking for an aprotic solvent.
- Remember, aprotic means you don't have hydrogens that can
- kind of lose their electron to maybe an electronegative atom
- like an oxygen.
- And then the proton just floats around, and then can go
- and react with other things.
- This does not have any hydrogens directly bonded to
- an oxygen in any of these cases.
- So it is an aprotic solvent.
- And because it doesn't have any hydrogens bonded to the
- oxygen, you also have no hydrogen bonding.
- And just as a bit of a review, you know that in water you
- have the situation-- let me draw some water molecules-- in
- water you have the situation where the
- oxygen hogs the electrons.
- So it has a partial negative charge.
- Hydrogen gets its electrons hogged or taken away, or it
- spends less time with them.
- So it has a partial positive charge.
- So this oxygen will have a partial negative charge.
- And so the hydrogens with the partial positive charge are
- attracted to the oxygens with the partial negative charge.
- And you have this hydrogen bonding.
- And this hydrogen bonding makes water.
- It pulls the molecules together.
- So you need to put more energy into it for it to either melt,
- or for it to actually boil.
- And for the molecules to kind of get ripped
- away from each other.
- And that's also true with alcohols.
- Alcohols only have one hydrogen to each oxygen, but
- they still have the hydrogen bonding going on.
- In the case of ethers, there is no hydrogen bonding.
- I'll represent each of the carbon chains
- with an R and an R.
- I'll write R prime right here to show that it could be a
- different carbon chain than this right here.
- And the R stands for radical.
- Not to be confused with free radical.
- Completely different things.
- This R just means really a carbon chain
- attached to this oxygen.
- But here there's no hydrogen getting its electrons hogged
- by oxygens with partial positive and
- partial negative charges.
- So you're not going to have that type of hydrogen bonding.
- And because of that, ethers have much lower melting and
- boiling points.
- It's much easier.
- You have to put less heat into the system for these molecules
- to break away from each other, because they aren't attracted
- to each other as much.