Lecture 24. Electrophilic Aromatic Substitution


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Lecture 24. Electrophilic Aromatic Substitution
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Vranken, David Van
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This is the second quarter of the organic chemistry series. Topics covered include: Fundamental concepts relating to carbon compounds with emphasis on structural theory and the nature of chemical bonding, stereochemistry, reaction mechanisms, and spectroscopic, physical, and chemical properties of the principal classes of carbon compounds. This video is part of a 26-lecture undergraduate-level course titled "Organic Chemistry" taught at UC Irvine by Professor David Van Vranken. Index of Topics: 00:36- Natural Does Not Mean Safe 01:43- Molecular structure of allantoin CHAPTER 18-Electrophilic Aromatic Substitution=E.A.S. 04:00- Chapter 18 Introduction 08:51- 18.1: Five Important Electrophilic Aromatic Substitution Reactions 14:39- 18.2: Two-Step Mechanism for E.A.S. 22:33- 18.3: Dalogenation with FeX3 and X2 31:05- 18.4: Nitration with HNO3 and H2S04 39:48- 18.4: Sulfation with SO3 and H2SO4 45:56- 18.5: Friedel-Crafts Acylation with RCOCl and AlCl3
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and thank you for making here and it is that daylight savings time this weekend and shift clocks forward and lose an hour of sleep I used to hate that I still do a little bit but maybe it doesn't cost me my much job
finishing up those problems that on on-line sampling works last nite I was just trying to clear the slate so that were
already for Chapter 18 this is our last chapter in the course I saw a news article on the on the Google News website but it was the standard kind of diatribe against natural herbal remedies basically the problem with natural herbal remedies is that nobody is checking to see whether effective or whether they're safe ,comma and you hear this complaint over and over again and it's a real complaint from they mentioned in this article toward the end of the article they mentioned some common herbal remedies have been taken through great efforts taken off the market and you have to really show that that they're truly harming people in some way in order to get the FDA to act honorable the call supplements and mentioned some common problems ,comma that ephedra which is basically an amphetamine derivative Arista logic acid but this 1 I never heard of comfrey and never heard of comparable for maybe all 4 of them are unfamiliar to you and so I wanted to find out more about this Comfrey herbal supplement because I'd never heard of what that is but before and so on so let's let's talk about what I found their kind of an
amazingly small-molecule This is the concrete plans and the reason why people believe that this is helpful or beneficial of course if you're selling an herbal supplement you can't make actual health claims you have to sort of using window to get people to buy your product but if you extract the leaves of this plan to contain the product called Elliott to wind up as a chemist when I look at land when I immediately recognize this is a derivative of the area so this is the small-molecule urea it's the 1st organic compounds ever synthesized by chemist ,comma was the start of the field of guests of organic chemistry and when I look at when I can tell immediately it's actually a condensation product spontaneous condensation product from these 3 molecules to molecules of urea and 1 molecule of glial Otselic acid which is a metabolite that you find all kinds of organisms of what's interesting to me is that it's also why would people believe that this is any way helpful to you it's been shown in laboratory tests on thickness this compound Olanta when can promote political proliferation of mammalian cells so if you worried about the aging of your skin some people believe that maybe it'll keep your skin cells growing and and dividing I don't know anything about that I am somewhat skeptical what was surprising to me is the urea is a common component of urine that secure excreting when you when you use the bathroom Armenians they sell maybe in a slightly different form they sell the same compound late into 1 urine you can buy in India I'm not sure whether the therapeutic or users after Cal urine but every leader of cow urine contains 2 grams of Orlando and so if you like a more readily available source of a Europe of overland to and but you might wanna consider using cow urine instead of the comfrey plant extracts OK it's
mentioned some stuff about the class you give an example 1 week from today at 8 AM in this room and so the clock is ticking I hope you spent this weekend studying that wasn't really valuable time even know was standing outside a very seductive probably made you wanna go outside but I hope you spend some time with your book The working problems every problem you can get your hand on I'm just like my exams will be composed of problems that you've never seen before election to expose yourself to problems you've never seen before and worked them until you always get the answers right you need to practice on problems you've never seen before and do so many of them that you always get the answers right that's how to do well in my exams so exam to build the 1 blessings and we took his I just received those of those files electronic files on Friday nite uploaded them I want to go back and look at your scanned versions the integrated version of exam to and double-check that why you miss the problems if you feel like there is a mistake on the grading than e-mail there's instructions when you when you download your version of the instructions about what you must do if you'd like me to look at her really great and the deadline for the greatest today at 5 o'clock PM so optimistic a look at picture prior examined try to learn from them with extra office hours this week since this is the last week before finals so please take advantage of those in the times for those are posted on a website on OK let's get started with the last chapter here in New York in can 51 B and its Chapter 18 million in the gorge ski Smith textbook and I want to start off by contrasting everything that you've learned up until this point in time and I were totally going to pull the rug out from under you fit in organic chemistry and so what you've been doing up until this point in time for the past 17 chapters everything you've been doing his being based on finding some sort of a leading group using your eyes to detect the leading group like chloride bromide iodide or toss a late and then having some nucleophile and replacing that in some kind of a substitution reactions he'd been doing substitution reactions by looking for lecture negative nuclear files and began the what what's been really hammered into you buy the book is these 2 processes of S 1 innocent too and at the same time that you've been doing that what we told you is that we will never do SN 1 2 reactions on substrates like this and all I have to do is just move this leading group over on the substrate and that never does that to never does this and 1 even if you attach a leading group to a benzene ring it doesn't matter how good that leading group is you never do 1 arrests 2 so so here these are 2 substrates that never do on substitution so as in Wana where's you've been trained to look for substrates thickened USN 1 2 substitutions so we're going to change in this chapter were going to change that Starting now from Chapter 18 when you do substitution reactions or make carbon-carbon bonds are make bonds you're not going to be using into anymore biology doesn't work that way that's not the way DNA synthesized it's not the way on a besides that's not the way protein the synthesized that's not the way you do Google Genesis of the Krebs cycle a amino acid biosynthesis so from now on as into 2 reactions are not going to be the be all and end all found of bond formation for you let me show you were doing in this chapter in this chapter were taking those benzene rings that we set ourselves super stable all those double bonds are part of an aromatic price system they'll never react with anything but what we're going to do is we're going to show you some magical recipes in this chapter they create a lecture files that are so powerful E-Plus is my symbol for Electra that just means something that really wants electrons that's my symbol for electrified and we're going to show you how to do substitution reaction than benzene even I told you benzene .period and all Liu and later on what those that Group B that's kind of a generic symbol is a generic symbol OK so what you're not seeing is that this is a substitution reaction not a nucleophilic substitution it's not 7 1 it's not to and the reason why it's so hard to see that this is a substitution reaction you know you spend all this time trying to learn how to recognize substitution reactions but now because we don't draw the same there it's hard for you to see that something was substituted and what that substituted was a hydrogen was a proton specifically so get ready everything's going to change now in organic chemistry and if you get stuck on a sand to because we because the book did it to you on it given have a hard time making it and can 51 C and in this chapter organ find a zillion ways to substitute a chat but not as in remission you 5 ways to replace that a channel for something that's useful useful for synthesizing gloves useful for understanding biology just really useful the stick of a look at the 5 reactions I'm going to ask you know in this chapter if you can just memorize these 5 transformations here you're halfway there I'm going to show you these 5 reactions in this chapter and then I'm going to show you a bunch of exceptions which is really what creates all the work it's the exceptions the Creole and then I'll show you a few functional group transformations something you can do with the side chains on the make that use for me to make sure this is focused your story OK here's our 5 reactions is your main challenge get out of here today and make you memorize these reactions today they're not that hard but let's take a look at Caltech a little preview here over secret recipes and after I show you these will walk through each 1 of them 1 at a time so you can see how these reactions work again so I'm going to start off with this brominated reaction by simply treated of a
benzene ring with br 2 told you nothing happens you brominated crossed the double bonds of benzene rings around reactive but I can have a special catalyst to this reaction and the catalyst is FEB 3 you've never seen that before it's a Lewis
acid it's going to activate bromine and turn it into a super aggressive electrified and it still doesn't have bromine across the doubled on the benzene ring it substitutes that hydrogen atoms and no 1 on my examine my be so kind as to draw that hydrogen atoms for you I expect you to recognize that there hydrogen atoms attached benzene rings and is doing that on the slightest you can see more clearly that something was substituted and it's not an elected negative leaving OK here's our next recipe the next recipes to use nitrogen acid H N O 3 that's nature gasses 1009 to guess it is actually a strong acid kind of scary because it's a strong acid and its oxidizing it's still not strong enough so they had an acid catalysts to this something even more powerful than nitric acid they had sulfuric acid so that's the two-part recipe you need in order to nitrate of benzene ring so this is what you do OK so our next Oct 3rd reaction this list is to take a functional group that you haven't seen before but you're going to see a lot of edits :colon acid chloride sodium chloride here you can kind of tell it's going to be a leading so it looks kind of like a carboxyl again acid except where there used to be an OH there's a chloride so this is a new functional group for you and you were going to use acid chlorides very heavily in 51 that's going to be your money reagent and 51 seats and were giving you sort of a preview of how useful it region can be and once again we need a Lewis acid and the losers would use is not his iron Lewis acid it's aluminum try chloride sole aluminum is also a very powerful Lewis acid that's going to initiate the reaction so acid chloride was aluminum tray chloride and that allows you to substitute hydrogen atoms with carbon-carbon bonds very powerful stuff OK so this 4th reaction reaction number 4 will undertake sulfur trioxide you might have heard this term acid rain and animal that such a common term if you burn coal that has sulfur in it the skies filled with sulfur trioxide and when it rankings that turns into sulphuric acid so that's not very convenient of course causes buildings made of stone is slowly degrade on acid rain is a big problem here we use the sulfur trioxide region in combination with sulfuric acid and that's a powerful way for making carbon sulfur bonds to look at all the different Hadow Adams up here I show you how to make carbon header carbon halogen bonds did in reaction to actually carbon nitrogen bonds In reaction 3 I should you have carbon-carbon bonds in reaction for actually have a carbon sulfur bonds and the fish that reaction here is to take a different kind of lied and it doesn't really matter what the he'll ideas of the take art and directly attach it to an Al-Qaeda not a carbon group adjusted helping Ethel I supra Opel cycle Texel so no carbon attached to him and can be a chloride if you want will talk more about this on and once again we use the same Lewis acid aluminum try chloride many bothers it's not aluminum try bromide that would work to it's just that's a more expensive reagent OK here's our 5 reactions Melanie be straight with you here they're not all equally useful it's 3 reactions here that are going to be much more useful for the camp 51 series and that's reactions 1 3 3 so these are the most useful of these transformations what you'll find is that carbon sulfur bonds that reaction number for while in others it is not that many things that show that we're going to show you how to do with that I turned out to be important historically and there's there's some important aspects to that but on this just not as many important things you can do with that and this last reaction reaction number 5 has so many exceptions to it on exception number 1 little talk about later is that you have to use this in excess here's my symbol for access and I'm gonna show you all kinds of reasons why that's got exceptions to the reaction and only works in a special case and the it's not really efficient and so you will be be kind of tired of that reaction from the because of all the problems with the OK get out of here and go memorize 5 transformation I promise you some combinations of these will be on every single final exam can 51 B in every section this quarter but these are important transformations for organic synthesis a good stock about the mechanisms for all 5 of these reactions fall go through the same mechanism all of them go through the same mechanism and so I'm going to give you this mechanism and it's a two-step mechanism that never there's no way to replace the chairman of benzene ring through 1 step mechanism so they good start off my my mechanism and I'm going to use this generic symbol once again E plus as a way to symbolize but some sort of an electoral filed it's really really hungry for electron density that's much more Elektra Philippine anything you saw back in Chapter 10 or 11 were elected filets and to work Lorena each Boraine so you were coming ashore these 5 secret recipes for arms and it's it's kind of bothering me someone would draw the Sajad presented to keep my eye on any channel are going to substitute just to remind myself that even if I didn't draw that there is an atom that's being replaced for replacing nature but they did the arrow pushing involves the pie electrons of benzene at these away less reactive than a regular pipeline follows pilot from there so happy they're part of the 6 electron aromatic ring system but if you're electrify was aggressive enough they can react with 1 of the pipe in the benzene ring so I'm going to show that pylon attacking this is very slow this is the slow step in the mechanism because you disrupt their and so when I draw this intermediate it's going to be a cargo cat eyes so I'll go and draw this H. Adams just poised right there and you have to draw that each of you every time you're going to use that each item in the next step we don't always John H. Adams in organic chemistry when we use these structural drawings here's my Koble Carolina took electrons away from that ,comma so it looks kind of like a secondary ,comma can on but it's not a secondary cargo can I'm really it's a little it's got all this resonance stabilization in and we have a special name for this kind of Cobble cat and that arises from edition of electric poles to benzene rings we have a six-member during like this and a cargo cat in those double bonds we call these intermediates in these electrical like aromatic substitution we call these Renea mine so this class of of aromatic rings substrates we call Aryans sold benzene ring is what I would call an airy knits and aromatic on designed as an area near Miami so really that's not plural so forget the plural they're looking at an area near Miami so every single 1 of those 5 recipes that I showed you is occurring under acidic conditions so there's acidic reagents in there and that means there's also counter Ryan's floating around that have long pairs things with minus charges that aren't really very basic many draw this this is my symbol is a minus is my symbol for the conjugate base derived from some sort of an acid and you don't need anything basic to pluck this Proton Aussie that Proton that got dangling out there saying Hey grabbed me on this Proton wants to leave because as soon as we put this Proton on anything can pull that Proton off so we get back here and to Oh my God this is so good it just feels so good analysis than those all frustrated here gets to be really happy because now it's back to an aromatic ring system so limited City is a huge driving force In these selective Billick aromatic substitution they make it very hard to do the 1st step in this reaction might this 1st step is slow because you lose their images city and others rates slow here but the 2nd step is really fast because it wants to regain and that was really pissed off there when he was in Armenia mind and we got to fix that OK so I wanna talk about residents in this area I hope you can see there's going to be all kinds of resonance structures that we can draw here and so I would take the time to draw out in this 1 case here in this very general case all of the different residents structures that we can draw for this uranium and you need to get ready to be to be drawing bunches of resonant structures for the new mines this chapter is going to be filled with that this is exactly the kind of stuff that they ask you 1 standardized exams for engines to professional schools that they really seem to harp on this meaning mind business on the job this positive charge here and the 1st thing that I want you to do it is I want you to resist the temptation and you will have a huge temptation because this harkens back to your understanding of all the stuff that we've covered in the previous chapters I want you to not do this don't take your A-minus or anything negatively charged and attacked the ,comma right she sure doesn't look like it wants to be attacked I thought Koble Caroline's buildings all the time can know if you attack the complicated you'll never get
back Eramet cities do not use a minus to add to the Carla O'Connell I don't take beyond and had there and if you add H X across a double bond of the benzene when you've lost their intensity you've lost 36 kcal per mole aromatic resin stabilization OK talk about resonance stabilization in this cargo can I'm but I'm going to use I'm going to draw 1 of the residents structures I'm going to swing this pie bond over here In and move that double bond to satisfy the cargo can iron and when I do that this next resonance structure that I draw I will have the cargo can I'm in a different place so John Major might be in the same place in here I just shifted that double bond over news that other pie bond it's still there and now my cargo is there and of course fighter substituent at that position that stabilizes cobbled guidelines that would be pretty sweet that residents structure and of course I don't have a substituent at that center now and I don't have a substitute Gagnon the cargo can find this structure OK now it's swinging over this other pie bond another resident structure here's marked my 3rd uranium mine residents structure and you need to be good at seeing a resolution arches in depicting them by drawing and I fully expect you to be good at drawing uranium mines because of practice focus cities are 3 uranium mines residents structures and at a minimum that I can draw there may be other residents structures that have got substituent next to the Carbol care and so on and avoid the temptation to make nuclear files but attack every new my hands to make a single bonds on that never happens A-minus nothing will ever attacked the cargo can I'm the only thing that happens in these cases on is that it is that something will pluck the proton off to help regain to against all 5 of those reactions that I showed you ruminations but Friedel cracks a salacious than the 1 reformer carbon-carbon bond nitrogen reactions solvation they all go through this two-step mechanism you added a lecture file on that adds to a benzene ring you lose their rotisserie and make this frustrated Iranian mine and something plucks the proton off to regenerate affirmative city and the only thing that's going to change these 3 mechanisms is what's that electrified so I'm getting ready to show you all these recipes how you generate super powerful electoral files and then it goes to the same Tuesday mechanism so it's staff with halogen edition OK so this is the halogen nation recipe that I showed you and as I'm indicating up here but you could do the same reaction with at the seal 3 and chlorine too if you do if you don't like having carbon roaming money could make a carbon chlorine Montana benzene ring on enough I ask you how to put a chlorine on the benzene ring just rates seal to enter the seal 3 and reaction will work the same way equally efficiently on now if you doing synthesis there's no reason why carbon roaming bonds on abandoning her better than carbon claim Bonds y learning this reaction you can do as into reactions with Errol bromides a carbon bromine Mountain product akin to ascend to you came to S 1 why on earth would the book show you this and why would I tell you that this is a useful reactions and the reason why this reaction is going to be useful won't be apparent until can 51 seats In Chapter 20 I'm going to show you well somebody will show you a secret reaction in intend 51 see that converts that carbon bromine bond into a super powerful nuclear file more powerful than any nuclear file you have ever seen more powerful than Allcock side nuclear files more powerful than than al-Qaida Lanai nuclear files are more powerful than any minds that bond right there is a super nucleophile and really that's the essence of canned 51 states that I just go off the side there's the media OK so that's why I'm showing you this and it's not going to be that useful until you do have to wait until can 51 saying it should be using up all over the place everywhere you put a carbon roaming nonrecurring column and you're going to be able convert those bonds and a nucleophilic bonds go from leading group to nuclear with that super-secret reaction it's not exceed yet magnesium too but whatever OK so but he does talk about the mechanism I said they all all of these things and all the same to step mechanism and the only thing that changes here's how we generate the and that's what makes these mechanisms look on intimidating and complex let's start off with this but struggle draw molecular bromine that's 1 of the region's that is going to draw 1 of the lone pairs I'm not going to fill in all the lone pairs on the halogen atoms you can't do that later what I wanna do I want a focus on what's the role of this FEB your 3 it's a Lewis acid the iron is very unhappy that iron has selected negative Adams all over it we draw those years 1 of the elected negative Adams is the other elected negative Adams is the other Elektra negative Adam and running out of room but that bromine on top for that I am really would love another pair of electrons if only there were some place where I could find another pair of electrons to some place she where can you find all look at that this is what surprises I don't know if you've ever seen anything using oxygen atoms with lone pairs good interactive Lewis acids zinc chloride activated oxygen here on Wednesday and seal to converted arranged to chloride so this is something that it's new to you that this Lewis acid concept with halogen and we're going to see that targets 3 times where fire reactions to show you the 3 of them and all this kind of Lewis acid activation focus and now we have this very weird looking where this is really going to freak you out because you've never seen anything like this before but what is about to bonds to bromine before it seems that we had psychic Ramon mines and three-member brings whenever you have to bonds to a halogen you have to have a positive charge knowledge but you can't just have to bonds to halogen on without having the charge to look at the positive charged and Iniesta's lone pairs on the bromine but that's the all the rest is so we can see how things fill out OK have brought bromine still has 3 lone peers who cares about that that bromine areas has to long pairs but it's cut this positive charge and uses iron and if I put a positive Georgia and bromine have given negative charge someone I molecule and the negative charge appears here it's the iron that carries the negative charge I would call that bearing the meeting with the negative charges and 8 ending answer would be called a fair each species the point here is that by binding Ironton bromine I've converted this bromine into a super Leading Group this whole thing when circle this entire thing about Bob right here this thing is now super powerful leaving leaving groups more powerful than anything you've seen before super fantastically powerful it's going to make it exceptionally easy for anything 2 attackers bromine and displays that whole the whole FEB work piece of junk OK so let's daughter two-step elective hillock aromatic substitution reaction I told you they all involve the same mechanism all were changing is the electoral file and so now I've shown you the secret Electra filed this at the R and I'm not going to redraw the structure and it's going to write that the br three-year -minus charge there but I'm going to get the charges right that's essential so here's my FEB br for leading get on with those for bromine senators really happy with that and so now going to take my pie electrons in the benzene ring and I'm going to do and SN to like reaction on that bromine atom and I'm going to break this car this bromine growing Bond noted that this super fantastic leading Group even a pathetic pie bonding benzene ring it is good enough to attack the bromine and displaced this year that's how good that Leading Group is even up even a benzene ring can displace that knowledge struck the next intermediate you know mechanism I'm going to have a carbon bromine bond In my next intermediate and there was a hydrogen atom here that I didn't for right if you if you draw this cargo cat I miss Renea mind intermediate like this you're screwed the it is the most important thing you can do on your subject is to draw well the was boarding as you can see the hydrogen atoms that are not drawn but you're not good at seeing things drawn then draw that man because you need that hydrogen atom here you need that Proton you're going to pluck that often step 2 In every 1 of these mechanisms for the 5 reactions we learned in this chapter so you need to know that that hide that Proton is there because we're getting ready to pull that off now so anything can pull that that Adam off I'm going to redraw this this being this this varied species it's got lone pairs on on on all the bromine atoms and I'm just going to draw 1 of the lone pairs on 1
bromine and and this is going to seem weird to you basically tell news anything with a lone pair could pull that off now but this is the of the species that are floating around in your solution this is the species it's most likely on Tupolev protocol that longer plucks off the protons now we're aromatic again that's what better Renea mind wanted was to become and I'm not going to draw the Resona structures here I'm not that there may be cases where you have to draw those residents structures that really mind to understand that the chemical reactivity and look at that we made this this fantastically useful carbon bromine bonds now not useful this quarter but useful next quarter If you hues that over and over and over in 51 C total money reaction there the idea that you can put a bromine atom or chlorine atoms on a benzene ring OK so it's just a two-step mechanism and it looks really complex of all this Ironman bromine on but if you could just focus in on this idea that it's 2 steps every time on and I think it will make things a lot easier let's talk about forming carbon nitrogen violence nitrogen reactions so I remember are two-step recipe and this I used to find it's really hard to keep straight when I was an undergraduate site Niger guess the passive matrix acid sulfuric acid what arson is doing what the reagent is nitrogen acid there are some Ben types of benzene rings not just simple benzene that so reactive you don't need an extra assets but in most cases you would you should always add sulfuric acid when you write this recipe of just assume you have to add a super-duper Dupre powerful acid like sulfuric acid sulfuric acid is way more powerful as a as a proton donors the nitrate gasses epistles include these regions so we want to put in nitro group and benzene ring so on to draw the complete resonance structure for this nitro group it's got all these lone pairs on the oxygen there's another resident structure I could drop puts the 0 minus on top of not going to draw that OK why would you care about this that there is no reason to have a nitro .period a benzene ring the only reason people but nitro groups and benzene rings is so they can reduce them to a meeting of the that's the only reason so nitro groups are useless and and later in this chapter show you a secret reaction yet another secret reaction that converts nite shows which are useless into something useful into enemy Nova so this is a mandolin Indiana lenses super important if you go look at the top 20 billion dollar selling drug list for pharmaceuticals the United States over half of them will have on islands in the so this type of carbonates run that nitro groups but hinterlands so and the secret recipe is this I'll just tell you hydrogen plating on carbon it's the same thing recipe you use the hydrogenated double bonds who would have thought that I would have thought that the conditions used to hydrogenated double bonds can burn off all oxygen is and leave you with an image to group on all and that is a very powerful sequence the sequence retake where you nitrate and reduce OK so that's why I'm showing output nitro groups on there is so I can tell you can convert them to amino groups and in Chapter 25 which is the chapter on a means you're going to come back and use this reaction over and over and over the book is gambling on the fact that you're going to forget this two-step sequence on but I think you're going to remember when Chapter 25 rolls around OK let's talk about the mechanism for this reaction and I'm going to start up by symbolizing my sulfuric acid as HEA although backwards there so that's the sulfuric acid this is that you need a powerful acid catalyst we need duties nitrogen reactions when draw the Lewis structure for nature acid here it is so the and has a positive charge when area for bonds to nitrogen it's going to be a positive charge you just have 1 bond oxygen school never negative charge OK in a million years I would never have guessed this and I don't think he would be the 1st step in this mechanism is hard to figure out if you have not practiced this you will be able to figure this out because you will irresistibly be drawn to use the lone pairs on this oxygen to pull off a proton from your answers by right all minus that should be pulling the proton the acid after that happens 99 times out of 100 this all minus lone pair pulls off the program from the acid but that 1 time out of 100 wins this lone pair pulls off the protons from the acid it converts the OH into waters leaving so you're not crazy if you think the lone pairs on the 0 minus will pull off the Proton but is just couldn't get pulled right back off the oxygen so it'll probe made all miners back and forth back and forth and eventually this OH oxygen will get permeated and Alex take a look at that leading group there's the water leaving group you can see that's now leaving group you've seen that before water leaving groups years the rest of this molecule and In the middle of a lone pair here and that oxygen and about 3 months the oxygen that has to have a positive charge now this looks truly ugly having to positive don't ever do this again don't ever again draw structure in organic chemistry you will never again in organic chemistry CIA structure where the 2 positive charges next to each other on Lewis structure this is the only case the next time you're thinking Oh I've seen applicable try to duplicate this on any other mechanism because all say all your crazy for putting 2 charges positive charges next to each other if you do a quick calculation was cool loans Law you figure out that this is all action there's other residents structures that will help you understand why this is a special case but I just don't want to be comfortable drawing to positive charges next to each other on neighboring atoms or what I want you to see here is that this Leading Group is now so fantastic that you can now push out the leading group water and there you go you've lost water and what it will give you is this intermediate that you've never seen before I'm not going to draw the water leaving group wouldn't under job for you is this spectacularly electron deficient Elektra file called Nitro only in Miami so this is a nitro only mind you've never seen it before I hope you can see all my gosh that nitrogen and everything negative Dole fighting each other unsuccessfully they're fighting each other to see who gets the electrons see never seems naturally in mind before the new stuff and super aggressive electrified and so reacted with nitrate your mom I've she crawled into this reaction very very reactive electrified the amount of the reaction the store this nature only my hand here we go so you know it's going to happen and that's the same Tuesday mechanism that kind of boring but they were going to take this pilot tried OK we got our electoral file which sometimes symbolizes the following is a red pen here because I just like use red pens for my hero pushing got this this pipeline is going to attack a electrify 1 of 5th bond in iTunes Web better break 1 of these bonds all arbitrarily break the bond on the bottom so there we made our carbon nitrogen bonds in we've generated are a reunion mine intermediate we've disrupted aromatase city so we made the nitrogen happy but the benzene ring is kind of sad because it lost electricity and Our nitro group on there now there it is there's always a positive charge if there's war bonds to nitrogen is my home minus and I'm so smart I'm not going to forget to draw that Proton in remember if you do that you're in trouble if you forget to drop in on the fact I like to join in on the stock mutual just to make sure I don't forget to draw in on the uranium mine intermediate that I don't have to go and understand it has helped me make sure I don't forget when I reached this stage but they say this uranium cat I'm positive charge so we lost city very stressed out and anything can pose pro turned off the water can pull the proton off nitrate in irons Campbell was Proton off this going to symbolizes in ionic species here by drawing a minus we don't need to be particular about what what species is pulling the proton often this reaction so Proton of the electrons go back to the benzene ring and regain geneticist step 2 .period so really the only difference here is just the power generated my electrified in the previous reaction was this very weird looking at the BDR for attached to bromine here are electrified Alice is a nitro only a minor 1 and I'm not going to draw the structure for that that's substitute of destroy a note to a case so well and that's nitrogen that's forming carbon nitrogen bonds in on benzene rings and so I
told you that there were 3 more useful reactions and 2 of them that were less useful and I'm going to cover these in order the book covers that 185 reactions 1 2 3 4 5 and I'm going to skip ahead now the reaction number 5 so just to be clear I don't think this is the most useful reaction I can't imagine you're going to see this reaction after Chapter 18 but probably not but fish but here's why use a couple of reasons why it's important starkly what you mean you may or may not remember that we were using we talked about the use of toluene sulfide gas TSO wage or sometimes abbreviated PTS await pair toluene Salonika acid on canvas that when they want a solid acids sulfuric acid is inconvenient because you have to weigh out of yet to measure out a liquid it's not easy to jury to my group to weigh up to my crew leaders of of liquid but tell himself on a gas it is kind of like an organic version of sulfuric acid on and it's a solid you can we have a couple of crystals that it's very convenient and this is how you make it you do this secret recipe for reforming carbon sulfur bonds sulfur trioxide that's the stuff from acid rain on and you use once again were using sulfuric acid is a catalyst for this reaction just like we sulfuric acid as a catalyst for nitrogen why would people that's why do so many textbooks talk about salvation because the 1st class of synthetic antibiotics that wherever produced by organic chemists had these types of softening groups and they were called sold the drugs they were very popular so penicillin was developed and people wanted organic chemist wanted to synthesizer own powerful drugs and they realize that all these dire molecules red dye number 2 red dye number 4 from often tend to bind selectively to 1 kind of selling out another so they tried modifying those and they found that when they put these functional groups on there but that these words kills bacteria faster than they killed human cells and those drugs recalled sulfur bugs and that's why textbooks 88 80 years later a still emphasizing this reaction ,comma and it's it's got some importance but it's not the important cities 50 years ago let's talk about how you generate plus it's in the same kind of two-step mechanism and again with very serious how we generate plus 2 years sulfur trioxide it's a planar molecule actually pleasingly plainer and symmetrical beauty it that the geometry doesn't matter but I'd mention that and when you put this in the presence of sulfuric acid I'm going to symbolize the sulfuric acid like this by age and we we're going to use were going to programming sulfur trioxide it will go from being a powerful Electra filed to being really powerful electrified no I could draw probe nation of alone here and what I'm instead going to do is I'm going to show this pie bond attacking the proton gives you the exact same intermediate of just scandal resident structure of what you would have gotten if you use the lone pair when I use the pipe bombs to attack the protons and the Proton will go on oxygen you can more clearly see White Sulphur becomes such a powerful electrified remember the sulfur is not a 2nd row out there's no architect was sulfur right you can easily have as sulfur trioxide you can easily have 6 bonds to sulfur that's actually pretty common on so don't worry about the factors 6 sponsors sulfur it's not a 2nd row elements a third-row atoms OK so here's this big impregnated sulfur trioxide and that is now a really aggressive electrified and I think the rest of this is pretty obvious it's that same two-step mechanism OK we have inspired bonds that are part of the benzene ring me and I'm not going to redraw this whole structure because in the garden of room soldiers symbolizes like this but you can see why electrify might want to attack that for if I ask you to draw the mechanism I would expect you to draw that this whole Lewis structure here there we go the Reforma carbon sulfur bonds since no 1 draw this intermediate it's that same type of uranium ions but straw that Iranian mine and here it is and I mean this time I'll drop that whole sulfur Neil symphonic acetate group the magazine didn't mention that this class of compounds is called the sole finding gas you may not remember the TSO which stands for prepared toluene Silvana gas on but that's the name of that functional group assault against OK so been all this time drawing this off on gas residue down here but it's exhausting all but if you forget if you're so exhausted that you forget to draw a proton you're going to be in trouble because you need that now you need to show how you're ever going to regain error to and I can't resist drawing this Proton the starting chokers that helps me keep an eye on what substituted don't have to that I like that and then something present in your solution and we don't have to be particular about what polls this Proton off and allows the system to read a narrative there we go now we're back to an aromatic ring system and there's ourself ionic acid product steadily make carbon sulfur bonds then again this is reaction number 4 it's not as powerful as reactions number 1 through 3 but the book covers that sort of 3rd in this sequence of
reactions it covers but let's step back and talk about reaction number 3 the 3rd reaction that I showed you on very powerful reaction and and 1 of the most useful of those of those 5 reactions that showed you because it makes carbon carbon bonds and every organic chemist myself professor Freeman professor Kane professor 1 we'd love to make carbon-carbon bonds so here's a recipe remember that this is that recipe I showed you take some sort of a benzene ring you take this species called an acid chloride which I said you're going to see a lot of this in can 51 that's the acid chloride here it is and then you take this Lewis acid aluminum try chloride looks a little bit like FEB at B 3 and impacted does the same kind of stuff and so it's going to draw out the summer this mechanism is limiting the acid chloride and although the lone pairs on chlorine not their lone pairs on oxygen every fiber of my being wants to use the oxygen long pairs to attack aluminum track because I know that aluminum tranquilized loves oxygen I know that aluminum oxygen in general and in fact the lone pairs oxygen do tackled aluminum but they come right back off oxygen attacks aluminum pots back off oxygen attacks aluminum pots back off every once in a while this chlorine lone pair will attack aluminum and what it does it converts that chlorine into a super powerful Leading Group similarly draw this species this very angry looking species here here's all these bonds look how confusing and complex it is now fact that 2 bonds to to a halogen I have to have a positive charge and there's a limit on positive charge there is I have never negative charge somewhat religious added more electrons to aluminum that could set the negative charge so I would call that a and eliminate if somebody said What's that thing idle at illuminate until you aluminum with a negative charge the point here is that we've just created a very powerful leaving groups see this whole thing here at a leading group had super powerful and is such a powerful leading group that these lone pairs over here on on on oxygen can now bend over and push out this Tetra coral illuminating and and when we do that we generate our key electrified In silly mine and this is called silly minor and you've never seen anything like that before and just put a little labor leaders see that thing right there but that's an easily among the qualified is that what on earth is this silly mind thing what is that about the drug alone I know that's really freaky to and the lone pair with the Texas for illuminate just so we can see here's aluminum stature he drove the guy had enough room to show that that's the contract could study sillier in any sillier mine is more stable than anti-people cobble cow you're totally familiar withdrawing tertiary Koble Caroline's this a silly mine is more stable than a treasure ,comma comments and the reason is both oxygen and carbon have filled up architects that's intrinsically more stable than it than TV will cobble path so it may look freaky to you because I do a resonant structure with a with a positive charge on oxygen but at least oxygen as electrons and carbon has electrons so don't get too freaked out by that psyllium Miami OK that's how we generate an electrified this is called a Friedel crafts reaction on In the early days this is 1 of the most powerful reactions from making benzene ring derivatives and we now have a new set in organic synthesis I don't think we'll have a chance to teach you about those in the camp 51 series we now have a new set of reactions from making bonds to on to benzene rings and but for decades this was the only reaction we have so I'm going to draw the Sicilia mine and is very electrical even those more stable at ,comma cookbook and I'm on it's still very electrical and sewer lecture fileted simple benzene rings will attack at the could draw standard mechanism we attack something of course I'm not going to attack the oxygen atom who would who would attack the atom with the positive charge will be attacked carbon and if you want to understand why you attack carbon draw the resonant structure of any sillier OK so here's our intermediate and Renea mine and that has now lost their matches sitting we now have a key tone group on here while that's convenient can 51 C will focus on carbonyl groups just like biology focuses on carbonyl groups OK and we're not notice I didn't forget to join them that Proton on my mine is my positive charge and so non-elastic some sort of Lewis acid it's actually this tactical or eliminate but we don't have to be really particular about that anything can collect Proton off it is so easy to pluck their Proton off look at that 0 yeah I just feel so good and so now we've regained images city in reform the carbon-carbon bond OK so
that's good war borrower all of our fire reactions that words that were learning about electrical like aromatic substitution so when we come back I'm going to show you how to do this 5th version it's actually another Fieldcrest a reaction not quite as useful ,comma just talk about a whole lot of exceptions to these reactions so get out of here and practice those 5 reactions and will be working on those in discussions action this week


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