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Current time:0:00Total duration:10:59

Video transcript

we've already touched on ethers in several videos they've been are useful a protic solvents 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 you you've seen already so let's say we have this molecule right here 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 also show you how to name it using the IUPAC name so let me let me write this down I you P a cname which is the International Union of pure and applied chemistry and they come up with kind of the official the official naming protocols for all of these organic molecules and these 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 the common name for this is just diethyl ether die-die ethyl 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 this is the common name comma 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 you look 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's let me redraw what the common name of the diethyl ether 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 could 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 it is an ethane it is ethane and then you say okay I have this I have this alkoxy group and we call that we put the oxy at the end of it because it has this oxygen right here but it's it's the the alkyl part of it has two carbons one two so we call this right here we call this ethoxy ethoxy so one other way to name this we have this ethoxide 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 one ethoxy ethane so this is one foxy foxy ethane 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 what are the two groups and you throw the ether at the 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 I so I so propyl 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 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 I so robell methyl isopropyl methyl ether 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 that 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 so it is and had no double bonds so f meth probe the propyl or it's actually a 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 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 methoxy you remember that meth is the prefix for just having only one carbon we have the oxy because that oxygen is there and it's attached to the two carbon on the propane chain no matter what direction you start naming from or numbering from one two three so this is two methoxy propane two methoxy two methoxy propane let's do another one let's do one more and I think you'll get the the gist of at least the reasonably simple ethers to name so let's put a let's put a 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 alright so let's do the common name first that's always tends to be a little bit more fun so on this side we have 1 2 3 4 5 6 carbons in a cycle this right here on the left hand side is a cyclohexyl group cyclo cyclo heck little group this on the right hand side we have one two three this is just a straight-up propyl group propyl 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 cyclo cyclohexyl propyl get that shade of yellow right cyclohexyl propyl ether 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 cyclo hexane no double bonds so it's a hexane so that's the cyclohexane right there if you just had 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 pro poxy so this is pro epoxy group pro epoxy 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 could just call this pro poxy cyclohexane pro epoxy let me make it a little bit closer to the cyclohexane pro epoxy pro poxy 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 so 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 need it where we didn't want protons floating around we use actually diethyl ether and in general ethers do make for good solvents they tend to be fairly unreactive so good good solvents especially when you're looking for an a protic solvent remember a protic means you don't have hydrogen's that can kind of lose their electron - maybe electoral 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 hydrogen's directly bonded to an oxygen in any of these cases so it is an a protic solvent and because it doesn't have any hydrogen's bonded to the oxygen you also have no hydrogen bonding and just as a bit of review you know that in water you have the situation let me draw some water molecules in water you have this situation where the oxygen hogs the electron so it has a partial negative charge hydrogen gets it's its electrons hogged or taken away or it spends less time with them so it's a partial positive charge so this oxygen will have a partial negative charge and so the hydrogen's 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 a height one hydrogen to each oxygen but they still have the hydrogen bonding going on in the case 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 there's no 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