12. Alcohols, Ethers, Epoxides and Thiols
Leaving Group Conversions - Sulfonyl Chlorides
Now that we’ve covered alkyl halides, sulfonyl chlorides can be used to convert alcohols into another great leaving group: sulfonate esters.
Learning the mechanism of Sulfonyl Chlorides.
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alcohol's air. Really bad leaving groups. So we're often in the position where we want to convert the alcohol toe, a better leaving group. And one of the options that we can use is so funny. Esther's. So it turns out that Sultani esters are really the ultimate leaving groups of organic chemistry because they're so extremely stable after they leave, they do an amazing job balancing out that negative charge and d localizing it. Okay, so how do we turn an alcohol into a softening Esther? All we do is we just use the chloride of that cell phone, Esther. So we're gonna use a soul final chloride to convert the alcohol into a sulfa Esther, and I'll show you guys how to do that in just a second. So first of all, what is a sulfa? Nay, Esther. Well, if you guys remember, the general structure was just that you had, um, basically an ass with two double bonds owes. Okay, so I'm just gonna draw a line here, and then you had in our group. Okay, So, so funny. Esther would have basically an o on this side on over the C. L is, um then an s the two dough one owes. And then you're our group. Now, the identity of the our group is just going to change the name of the soul. Funny, Esther. In general, all these all of these different molecules can be categorized of self me esters. But they do get individual names. So, for example, the easiest situation would just be, What if it's just a metal group? Well, then, that's called a missile, okay. Or a missile eight. So funny, eh, Strom? Easily. Okay. How about if it's a benzene ring with a metal group? Well, then that's called a tosel. Okay, So basically, if they are is a benzene and a ch three, then that's a tosel e. And then finally, if it's a c f three. So I just replaced three inches with efs. That's called a trifle e. Okay, So really easy. I don't even expect us to memorize all three of these just to be aware that these air all softening esters and they all react almost identically. Okay, so that's what is so funny. Esther is What's the sulfur chloride? Well, so folklore, it just means hey, remove the oh and put a chlorine right there. Okay, so how is this gonna work? So, basically, just you guys know this general structure stands for any of these three. It could be my tosel chloride, my missile chloride or my trifle chloride. Okay, so in this case, let's just start off with the first step of the mechanism. What's gonna happen? Well, my oxygen once again on the alcohol is gonna be considered my nuclear file because it's got extra electrons, not extra. But it just got electrons that air freely able to donate. If I were to attack one of the atoms on this, soften it. Chlorine. I'm sorry. Self softener chloride. Which of them is the most likely to be attacked by a negative charge? In other words, which one is the one with the partial positive? Which one is the one that's the most Electra Filic? And if you draw die, polls were quick to find that the partial positive has to once again rest on the central atom or the sulfur. So what that means is that my arrow is going to do this now. Sulfur can either a four bonds or six bonds in this case, add six. But it can't have seven. So if I make a bond, I do have to break a bond. Okay, On the way that's gonna break is well, I'm just gonna move these electrons up to the oath. Okay? So what that's gonna do is it's gonna make a structure that looks like this where my always still in the front still attached to an H. But now that's gonna be a touch to s O negative. It's all about oh, CEO everyone following that. All the formal charges in No, I do have to draw a positive charge right there. Cool. So can you guys predict what the next step might be? Do I have any good leaving groups present? I do. I have a c L. So what I could do is I could just reform the dull bon and kick out the C l. And what that's going to give me now is same stereo chemistry. I'm still in the front, still having each But now what I have is a molecule. It looks like this. Okay? And I'm missing the our group. I never drew it. Wow. Okay, so just second, there's an our group here. I'm wondering Johnny what happened to the argued before it was there? I just never drew it. Okay, so please draw that into your notes. You should have single bond. Oh, dull bond. O C l R. And then the other. Oh, and that should add up to six. Okay, if you want, you can count it up. It does add up to six. And this also adds up to six. Alright, so I have that. Plus I have the cl leaving group. Perfect. Okay? And then I have a positive charge here. So now the interesting part is that this molecule right here is actually pretty stable. This is my cell phone, E Esther. Okay, so that's really it. I'm not gonna keep going to another step. I'm just gonna keep it like this. This is myself in a Esther, and later on, I can react with it. Okay. Now, the Sultan Esther should be the neutral compound. So what's gonna happen is that my cl or whatever It's usually a c l. My Whatever my anti on in is is going to take away that h so eventually what? I should get it. The end is a neutral self. Iniesta it looks like this O s till 1010 r. And the reason this is so stable is because I mean, basically, there are no formal charges anymore. So I can keep this self iniesta around as long as I want. Just like an alcohol Hey, light, I can keep in alcohol light around And then when I finally want to react with it, I could introduce a nuclear file. Let's just use general n you negative and then I could do a backside attack. Okay, But it's cool that we could just keep the self Iniesta around. Now we just converted alcohol toe a really good leaving group. Okay, which is the sole funny Esther. So up here there was a blank that I skipped earlier and it's actually really important, basically because this reaction all takes place on the oh and notice that the oh never gets attacked during the entire mechanism for softening Esther. This reaction is going to proceed with retention of configuration. Okay, because I'm never doing a backside attack during the course of the reaction. I'm always just ending at the softening Esther, and then I'll figure out what to do with it. later. Later on. Could I do a backside attack? Sure, but that's a different reaction during this reaction to get from here down to here. Okay. From the O. H to the Sultani. Esther noticed that the oh never moved. The O is still in the same exact place it was before. So we call that retention of configuration. Okay, once again, this topic, this section is all about stereo chemistry. So you need to remember that softening Esther's proceed with retention of configuration, whereas vinyl chloride and phosphorus bromide are gonna have proceed with backside attack or inversion of configuration. Okay, so that's it for this. Now, what I want to do is I just want to quickly show you guys a summary of everything that we just learned.
This conversion proceeds without the use of SN2, meaning that we expect retention of configuration.
Yes we know, there is an extra methyl in the original molecule in the video. However, we decided to remove it completely from the problem.
This allows for a backside attack to successfully take place in the last step (seen by the blue Nu-).
Additional resources for Leaving Group Conversions - Sulfonyl Chlorides
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