Okay, so this is part B of lecture three for organic chemistry two. And in the first part, we looked at alcohols. And in this lecture, we're going to be looking at ethers. So this is essentially just a brief overview of the naming and classification and properties and a little exploration of diethyl ether. So what is an ether?
An ether is a compound and where you have an oxygen atom. that is bound to two alkyl or possibly aryl species. Aryls are like aromatic species, and we'll get into that later. So you have an oxygen and you have two other groups on it.
So those R groups can be the same, so that means you've got a symmetrical ether, or they can be different. So we could have a methyl on one side and an ethyl on the other side, so asymmetrical ethers. So how do you name them? Well, we've got the IUPAC system.
So you name the ether as if the alkane were substituted. Okay, so it will be alkoxy plus alkane. So if this is your ether, you've got your alkoxy.
Remember your alkoxides that we found from our alcohols? Alkoxy, alkane. That's the IUPAC system. So alkoxy group alkane. If you have a number before the alkoxy, it shows you where the position of the OR group is situated on that parent carbon chain.
So normally you look at your long chain, you draw in the plane the longest chain you have, and then that... alkoxy group, the number on it will tell you where on the chain it is sitting. So I love this one, just to me, it looks like a seagull.
So we look at this one, and I see we have an alkoxy group, 1, 2 carbon, so that's ethyl, so ethoxy, and that's 1, 2, and that is ethane, so ethoxy ethane. Now there's common names where the alkyl groups are written in alphabetical order, and then you add the word ether to the end. So you could have an alkyl group, an aryl group, and that's like an aromatic group. So you would say, let's see, if you have a methyl group and an ethyl group, you put it in alphabetical order.
So it'd be ethyl, methyl, ether. I hope I have that right. If I know my alphabet. Okay, so if we're going to do the common name for an ether, we have an ethyl, and we have another ethyl group.
So you wouldn't say ethyl, ethyl ether. You have diethyl ether, because there's two ethyls, diethyl ether. And then, of course, we've got historical names, because people were doing chemistry before they decided to try to systematically name things.
So this is just called ether because this is one of the first ones they were using quite commonly, or ethyl ether. So let's look at this one. Is this a symmetrical ether?
Well, to me, it looks like it's different. We've got a different alkyl group to a different alkyl group there. So how are we going to do it? Well, we look at the alkoxy group on there, and that's a methyl group, so methoxy.
And then the rest of it is... one, two, three propane. So one methoxy, because that methoxy group is on the one of the propane, one methoxy propane.
Or we have a methyl group and we have one, two, three, we have a propyl group. What's M comes before P, so it would be methyl propyl ether. And remember, we're talking about potentially having aryl groups, that that's like an aromatic group here.
Well, clearly this isn't a symmetrical ether, so we have a methoxy group, so we would call this methoxybenzene, or we have methylphenylether. Oh, shoot. Oh, fiddlesticks.
Don't know what I just did there. Sorry, guys. Oh, that was fun.
Sorry, Bear with, bear with, bear with. Okay, so we have methylphenyl ether, and the historic name is anisole. Oh, I'm just quite overcome with excitement. I don't know what I did there. So what are the properties of ethers?
Well, the interesting thing about ether is they're quite inert, which means they're inactive. So they're used as solvents for organic reactions, because it's good to use a solvent that's not reacting with your... what you're trying to get to react, so that's quite useful. So if we look here, here's a compound, diethyl ether, okay, the molecular mass of this is 74, and the boiling port is 35 in centigrade, so it's got quite a low boiling point.
Let's compare it to alkane, see it looks quite similar, here's pentane, sort of the same shape without the oxygen, The molecular mass of that is 72, and the boiling point is 36. So it's got a pretty similar boiling point. It's quite low. Let's look at alcohol. 1, 2, 3, 4. Butan-1-ol, butanol.
It's got a very similar sort of shape and size. The molecular mass is 74, but the boiling point of this is 118 degrees. So you can see ethers have... a very low boiling point compared to alcohols or you could say alcohols have a very high boiling point compared to these two and just to remind you why do alcohols have a high boiling point it's because of hydrogen bonding so just to remind you electronegative oxygen dipole being push created here through the the electrons being pulled towards that electronegative oxygen and it's happening as well through this bond where the electrons are being pulled away from that hydrogen there towards that oxygen, which means overall we have a partially negative charge over the oxygen and we have a partial positive charge over that hydrogen. So that means we end up with hydrogen bonding.
And here is that example I showed you. Here's ethanol here. The red is the oxygen. Here's ethanol and other ethanol.
There's oxygen and there's hydrogen. That hydrogen there, which has a positive charge, a partial positive charge, and the oxygen has a partial negative. So you can see how it sort of self-assembles, holds together through this hydrogen bonding.
And the impact of that is a very high boiling point, whereas ether has a very low boiling point, which makes it very easy to work with in the lab. So here we go. Here's a use of diethyl ether. And we've just explored that it has a low boiling point.
So what's really good about ethers is that they're very good solvents. Things dissolve generally quite well with them. They have this low boiling point, which I've just emphasized.
They're not very reactive, hardly reactive at all. You'd have to really, really work on it, which is great when you're doing it. It helps prevent all these side reactions happening. And it... It doesn't mix with water.
So you can use ether to extract other organic materials from water. You can actually pull it into another layer. So that's really super and very, very helpful.
But there are some bad things about using ethers because one is it's very flammable. So you have to be very careful if you're working close to heating units, okay? And it also can...
form these things called peroxides. See those two alkoxy groups that are bound to each other? These are explosive. So there are some bad things to use in ether, but there are positives.
And one of the positives is it was discovered in 1846 that you could use ether as an anesthetic. You would inhale this ether so that when you actually had surgery... formed on you, you weren't aware of it. So this is an interesting painting of the first public demonstration of surgery using ether as an anesthetic.
And what's interesting is they mention the name of all of these people here. This fellow in the middle hasn't been mentioned, so I don't know how things turned out for him, but it's a nice portrait of him one way or the other. So Dr. Morton...
demonstrated this use. This was his ether inhaler and this was used safely and effectively for over 100 years for an anesthetic for surgery. So, that's pretty impressive. The only thing is you just cannot be around heat sources and, you know, hopefully as a surgeon you wouldn't be smoking, but, you know, I don't know what they did 100 years ago. So, anyway, that's the upshot of ether.
We've learned how to name it. We've learned why it's got a low boiling point compared to an alcohol. And we've learned that it's useful in labs because it's not reactive. it's miscible, we can actually, miscible, we can extract compounds with it, but there is a danger of being flammable and forming peroxide.
And that was it, that was a short one, wasn't it? By the way, just to let you know, there's another wee video that I've made on curly arrows and different arrows, just so you can recognize them. I was asked to do this a few years ago, so I'm just putting it out there just for information in case you're curious.