12. Alcohols, Ethers, Epoxides and Thiols
Williamson Ether Synthesis
There are 4 major methods to create ethers. Most of these should look familiar in some way since they are variations of reactions we have used before.
Williamson Ether Synthesis
The name given for the SN2 substitution of an oxide with an alkyl halide.
- Only works with 0°, 1° alkyl halides since 2° and 3° alkyl halides will favor E2.
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The Mechanism of Williamson Ether Synthesis.
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Now I want to talk about ethers. And it turns out that in organic chemistry one you're gonna be responsible to know four different methods to synthesize them. Some of these methods are gonna be stuff that you already know from prior chapters. And some of it is gonna be really related to other reactions you've learned. It's just gonna be tweaked a little bit. Okay, So, overall, this isn't so hard. You just have to keep track of the four reactions to make ethers. So let's start off with the simplest one, which is called Williamson Ether Synthesis, Which sounds complicated. You're thinking, Oh, man, another name that have to memorize. But really, this is an easy reaction. All this is gonna be is an s and two reaction off a primary or a methyl alcohol. Hey, lied with an oxide base. Okay, Now, there's just a typical s into that we would use the flow chart for, so I'd be wondering. Well, Johnny, why does it have the funky name? Well, Williams and ether synthesis is just the name for that specific route that you take on the flow chart. Cool. So even if you forgot the name of this reaction, you would still know what to do just by using the flow chart. So let's go ahead and talk about s and two for a second. Remember that what does s and to really require Ah, good backside. Right. So that's why primary and methyl alcohol Hey, Allied's are awesome at Williamson ether synthesis because they have a really good backside. Well, what happens if I try to use Ah, secondary or tertiary ocular? Hey, light instead? Okay. Lets say that I'm like, Hey, screw the primary alcohol. It I want to start with my tertiary. Can we do that? No, we can't. Because remember that secondary and tertiary alcohol highlights arsed Erik Lee hindered in the back. So what that means is that they're actually gonna favor e to not s into. Okay, So now that I've kind of explained the re agents, let's just draw the mechanism. So as you can see what kind of alcohol it and my starting off with this would be primary. What kind of nuclear file do I have? Is it neutral or is it negatively charged? Well, in this case, this is negatively charged because it's going to disassociate into O E T negative. Okay. So even if you didn't know what this was, we could just use the flow chart. So according to the flow chart, the first question is Is my nuclear file negative or neutral? It's negative. Two. Is it one of my bulky bases? No. Three. Um, what kind of alcohol highlight do I have? Primary alcohol? Hey, lied. Does that always favor a certain reaction? Yes, it favors S and two. So even if you didn't remember this Williamson ether synthesis, it's fine because you could just use the flow chart to figure it out. Okay, so now we just have to draw the mechanism. The mechanism would be a backside attack. My o A T would kick out the br and look what I get. I went up getting a carbon with an O and then in Ethel Group on the other side. Ok, now I'm just replacing the Ethel Group. This is the thing that was e. T before. I'm just drawing it out. Okay, but notice that Look what functional group? I haven't the end. I haven't either. Okay, so I was able to use a ness and to reaction just from the flow chart to make an ether. And this is your first and probably most common form to make ethers in this chapter. Okay, good. So far, let's go ahead and move on to the second way to make ethers.

Additional resources for Williamson Ether Synthesis
PRACTICE PROBLEMS AND ACTIVITIES (7)
- c. Give two sets of reactants (each set including an alkyl halide and a nucleophile) that could be used to syn...
- What is the best way to prepare the following ethers using an alkyl halide and an alkoxide ion? a. b.
- Which of following ethers cannot be made by a Williamson ether synthesis?
- (a) Show how ethanol and cyclohexanol may be used to synthesize cyclohexyl ethyl ether (tosylation followed ...
- A good Williamson synthesis of ethyl methyl ether would be < of reaction> What is wrong with the followi...
- Show how the following ethers might be synthesized using (1) alkoxymercuration– demercuration and (2) the Wi...
- Propose a mechanism for each of the following reactions: b.