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Current time:0:00Total duration:8:35

Video transcript

it's possible have ethers in a ring system and there many different types of ring systems that you can have with ethers in them the one that studied most of the time would be the epoxides due to their reactivity here we have the simplest Epoque side and one name for this would be ethylene oxide because this molecule is made from ethylene and that's where you get your two carbons from like that so you could call this ethylene oxide or you could give this an IU pack name and since there are two carbons in it for the IU pack name we start with ethane as our parent name and we know that the epoxy ID forms between carbons one and two so we can go ahead and write one two epoxy ethane for the IU pack name let's do another one here so let's put some more some more carbons on here so we'll put a few extra carbons and we'll name this using IU PAC nomenclature so once again find your longest carbon chain alright so we can go ahead and find how many carbons in our longest carbon chain that would be one two three and four like that so we can go ahead and write butane for our parent name so we go ahead and put butane in here I want to next number my carbon chain to give the lowest number possible to these substituents so in this case it makes more sense to number from the left so I get one two three and four to give my substituents the lowest number possible I can see now that my my epoxide forms between carbons 2 & 3 so I'm going to write 2 3 epoxy butane like that and I know that I also have a methyl group coming off of carbon 2 so to complete the name all I have to do is write 2 methyl on the front here so now I have two methyl 2 3 epoxy butane for my IU PAC name so how do we make a POC sides we've already seen one way to do it and an earlier video we started with our alkene and to the alkene we add a peroxy acid and a peroxy acid looks a lot like a carboxylic acid except it has an extra oxygen in there like that and in the mechanism for the epoxidation of alkenes we saw was a con certain mechanism where one of those oxygens was added in here to form our a pox I'd like that so check out the earlier video to see the mechanism for epoxidation of alkenes so in this video we're going to cover another way to make epoxides and that is using halo hydrants so to make a halo hydron you also start out with an alkene and we also saw this mechanism in an earlier video and you add a halogen and water and we're going to add bromine and water and we end up adding the O H and an one bromine across our double bond so we ended up getting an anti addition of an OHA and a bromine okay so they're going to add on opposite sides from each other like that okay so this this molecule is called a halo hydrant and again check out an earlier video for the mechanism to form a halo hydron once you form a halo hydrogen you can use that halo hydrogen to form an epoxide alright so let's let's go ahead and take that halo hydrant and let's see the mechanism of how we can form an epoxy from that so I'm going to redraw that halo hydron so I'm going to go ahead and put in the Oh H here like that put my lone pairs of electrons and then I have my my bromine over here and I'll go ahead and put in my lone pairs of electrons on bromine as well and for right now we can say anything could be attached to this and we'll go in to go into stereochemistry in the next video so what we need to do is add a base so something like sodium hydroxide will work so we're going to add in sodium hydroxide na plus o H - right so the hydroxide anion is going to function as a base all right so a lone pair of electrons on the oxygen are going to take this proton on our alcohol and these electrons in here are going to kick off onto our oxygen so let's go ahead and draw the result of that acid-base reaction all right so what we what do we make from that well now we have our oxygen with three lone pairs of electrons around it like that which give this oxygen it gives the oxygen a negative-one formal charge and we still have our bromine here like that and then we still have these other groups attached to our carbon so in the next step the next step we need to think about again the polarization in the in the bonds between carbon and our halogen right our halogen is more electronegative so the halogen is going to take a little bit of this electron density in the bond between carbon and bromine and therefore give the bromine a partial negative charge all right this carbon is going to lose a little bit electron density so this carbon is actually partially positive and so the alkoxide that we forms when the alcohol is deprotonated has a negative charge it's going to function as a nucleophile the partially positive carbon wants electrons it's going to function as an electrophile and we're going to get a a nucleophilic attack by our alkoxide anion on our partially positive carbon so it is actually an intramolecular williamson ether synthesis so if you think about it right if these electrons in here are going to attack this carbon right that would kick these electrons off onto your bromine like that and it's an intramolecular williamson ether synthesis where your alkoxide is the nucleophile in an sn2 type mechanism so if we go ahead and draw the product right now this oxygen was bonded to the carbon on the right now it's also bonded to the carbon on the left and the bromine left that was our leaving group and so we can see that we're going to end up forming an epoxide with this mechanism so let's let's go ahead and do a quick problem here where we're we're forming an epoxide from an alkene and we'll we'll start with cyclohexene so here is our cyclohexane molecule and we'll make an epoxy two-ways right so in the first way we'll add a peroxy acid and that there are several that you could use one of the most common ones would be peroxy acetic acid so peroxy acetic acid alright looks very similar to acetic acid except you have an extra oxygen in there like that so it's epoxidation of an alkene and when we draw our product alright so let's go ahead and draw our product we form an epoxide and I'm going to go ahead and draw the product with a with a wedge here alright so there's an oxygen coming out relative to that plane and if we go ahead and name our product alright so the parent name would be cyclohexane and our epoxide but form between carbons 1 & 2 so we could go ahead and name this as 1 2 epoxy cyclo hexane like that let's go ahead and and let's go ahead and to cyclohexene let's do another reaction let's start with cyclohexane and this time in the first step we'll add some bromine and some water and that will form our halo hydron and in the second step we'll add sodium hydroxide to act as our base and we get an intramolecular Williamson ether synthesis and so we're going to end up with the same product so we're going to end up with the same product here we're going to end up with one two epoxies cyclohexane now for this reaction we don't have to worry about stereochemistry okay so if you think about the oxygen adding from the other side of the Ring we don't have we're we're we're not cool we don't have to worry about stereochemistry for our products because if the if the oxygen added from the other side of the Ring that would actually be the exact same molecule one two epoxy cyclohexane so we'll save stereochemistry for the next video where we can focus in on what happens when you're adding an oxygen to different sides of a plane