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Hydroxyl Group |
Same reagents as oxymercuration, except with alcohol as the nucleophile instead of water.
Concept #1: The Mechanism of Alkoxymercuation.
Transcript
Another way that we can synthesize Ether is through a reaction called alkoxymercuration and you might immediately notice that the sounds a lot like another reaction that you're supposed to know by now and that's oxymercuration so it turns out this is going to be the same exact mechanism as oxymercuration or Oxymerc except that in the top reagent in the oxymercuration step we're going to use alcohol as our nucleophile instead of water, OK? So what you can see is that the biggest difference here is this right here, I have alcohol in place of the water and that's going to make an ether instead of alcohol, OK? So let me just walk you guys through this mechanism really quick, so remember that we get is HG-OAC-OAC......Opps it came out weird OAC and in the first step what we do is the double bond attacks the mercury kicks out one of the OACs and the Mercury attacks back so what we wind up making is a bridge, an Ion bridge so what that's going to look like is like this where now I have a dotted partial bond to HG it's only attached to 1 OAC now, dotted partial and a positive chart, OK? And there should be actually a dotted partial bond here too and a positive charge, OK? So now we've got our intermediate, notice that we can't get any shifts because there's no carbocation and now this is the part that typically water would come in and attack which side do you remember? In this case I have a Markovnikov site here and I have an anti-Markovnikov site there which one would it attack? Markovnikov because that's going to be the one with the most positive character but instead of water what's actually going to attack is in this case ethanol, OK? So my water attacks......I'm sorry my ethanol attacks kicks out the HG And what I wind up getting is something looks like this and I'm going to try to fit in here where now let's say that the alcohol attacked from the bottom then I would draw that the HG the mercury attacks from top or not attacks but is now placed in the top, OK? Cool? Awesome stuff the end of the Oxymerc step, OK? In this case alkoxymerc because I used ethanol, OK? Then remember that we have a reduction step, the reduction step is just NaBH4 and OH negative and you don't need to know the mechanism for this so I'm just going to say don't need to know mechanism, OK? But what we do need to know that happens is that well number there is a positive charge in that O actually, OK? And what's going to happen is that I'm going to wind up reducing the mercury just to an H so this is going to become H, OK? And I'm going to wind up deprotonating my oxygen so now look what that turns into, it turns into ether, OK? Because now what I have is RoR, it's a weird looking ether but it is an ether so I get an ether as my product and that's it's the same as OxyMerc except that you have to just now you have to be aware every time you see an Oxymerc make sure that you look to see whether it's water or alcohol that's attacking because that will make a world of difference in terms of what your product looks like, alright? So I hope that made sense same as I did before we're just using alcohol instead, alright? So let's go ahead and move on.
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