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Lecture 21. Conjugation, Resonance, Diels-Alder Reactions, Part 1

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so of this weekend I was
sitting with my daughter and my five-year-old daughter at some sort of sandwich restaurant eating a sandwich and some chips and we were basically fighting over who gets which it's hard to explain to five-year-old and it's going to wonder why the things so addictively delicious and it dawned on me may be 1
reason is that they're so brightly colored you have an unnatural orange color to them that looks more intense than any natural food order look like and so when you turn around the packaging look on the back side you can see there's there's a lot of stuff in here that doesn't look like on but in particular here you get to this section called artificial colors and is as yellow 6 yellow flies Red 40 and those words sound so simple cargo imagine what those could be Yukon obviously those are chemicals of some kind but you can't say anything about what the structure of those molecules are just based on those names and so I got interested in what it was that I was a eating yes is what it may be infected as alluring as you may know that appeared but none of those names mean anything to me and chemists I want the structures or are you pack means that I can derive stuff out of sorts talk about what the structures of those molecules might be there on
secures the structures of those chemical compounds on there was something called the U.S. Food Drug and Cosmetic Act standardize the names of chemical dyes the appropriate used in human food and so there's a long list of chemical dyes are approved and so sometimes the names the other shortened to FD in Cecil Food and Drug and Cosmetic Act yellow 6 FD C red 40 FT yellow 5 and I think that that's not a lot more appetizing than Value Pack named fight to the proxy fight noble Silvana finally resulted not only softening on and I'm not afraid chemical compounds the synthetic but I'd like to know what those compounds are so I wish they would put the long names on the package instead these mysterious short names all draw your attention to the structures here that are making these these chips such a bright warned it's obviously it's not just 1 color compound is a mixture of 3 different colored compounds to get just the right coloration there so here's a yellow compound and in particular here well draw your attention to his is this functional group :colon Heizo linkage and you haven't seen that before namely look very mysterious but by the time you get to the chapter on a means Chapter 25 we will show you how to make these compounds and a and the size of the there's another compound this FTA red 40 it again it's gotten Heizo linkage between 2 benzene rings so in Chapter 18 were going to be all about benzene rings and teaching you how to make bombs to benzene rings just like this bond right here will will show you how to make that bond and again the 3rd ,comma was also has a nasal linkage it's a little bit more fancy but it's basically this like a benzene ring off within a so in Chapter 18 will show you how to make bombs to benzene rings and then Chapter 25 will specifically show you how to make this kind of carbon nitrogen bond you can see how these types of colored compounds are made and Yum Yum next time you open up a bag of chips you have a clear idea of what's making those so delicious looking I can't wait to look at the Cheetos bag to see what's on their next time I grab 1 of those OK so what course we decided exam on Friday and did
fantastic it was out of 128 sweep also posted the scorers on III and we when we initially posted those costs we accidentally left the default out of 100 the exam was not out of 100 out 128 and your score that's posted on III is out of 128 multiple people made perfect scorers 28 out of 128 great job but the meeting was 88 was standard deviation of 23 Great job guys did great and keep working hard we got about 2 weeks left before the exam and remember my advice he was derived by business and so it's not the week before the exam is going to matter it's what you're doing today and tomorrow and the next day and this weekend so you need to be on the material this week and studying like the exam is on next Monday you know it's not on this is the time when we need to really be bearing down on the material OK so we're going to step into a new chapter we just finished this chapter on radicals and there wasn't a whole lot to cover in the chapter on radicals and likewise there's not a huge number of concepts in Chapter 16 who were going to take today's lecture and a little bit of Wednesday's lecture and and cover Chapter 16 which covers Diogenes poly means residents on basically things that have to do a double bonds connected to things and Cisco's step into Chapter 16 in the grievance he Smith textbook by and see what that's all about so 1 of the major themes in Chapter 16 is this idea of conjugation and so let's talk about conjugation what does that mean that I think the best way for me to explain conjugation is to join a molecule that has this property of conjugation and 2 here's a 5 carbon molecule is not contained this is painted dying it's a 5 carbon chain with 2 AL teams in annual notice that the 2 outings are right next to each other and they're separated by a single carbon-carbon single bond there so this is an example of a molecule that is conjugated I would refer to this broadly of heritages .period over there I would refer to this as a conjugated dying and I would contrast that from what some sort of a dying with a tune double bonds away apart from each other in different parts of the molecules that help you see what I out why I described it as a kind conjugated dying when contrast that with some diocese where the double bonds are not conjugated to each other to knowledge or longer molecule this time will draw 6 carbon chain and another Elkins summer way over here on the other side of the molecule that's not conjugated that's a great example of a molecule at a dying there's 2 outings in there as a great example of a dying in which the double bonds are not conjugated to not all diaries of are conjugated let me take an even simpler example of 5 carbon chain so you can better contrast this with the 5 carbon chain over here here's a 5 carbon dying and that's also not conjugated so we refer to these dying means we describe that relationship between a double bonds is that those double bonds are isolated so these are definitely Diogenes but these are isolated dying and media having a hard time seeing on that those double bonds are connected it might help you fight drew the C H 2 between seeking more clearly seen all those double bonds are not connected to each other in any way a base of 2 types of diamonds for 2 classes are 2 ways to think about the depth of the relationship between the double once conjugated 1st isolated and obviously are making a big deal about this because there must be something special about 1 of these it's the conjugated dining or try or painting means it's when you conjugate double bonds that you give molecules special properties OK let's go and talk about not a double bond next to a double bond on will talk about a double bond next to a cat and so I'm going to talk about the prototype of a system in which there is residents in which there is is a property that is that is a little bit related to conjugation actually draw sees on here I think this might help us to see what's attached an 1 more CH in the middle so this is a 3 carbon alloy wheels system we've talked about a little ecology nation this is an aloe can and let me draw another resident structure this so we can see that in fact that positive charge that lack of an object is shared on 2 different carbon atoms and 1 use Errol pushing to help me see how to get to the other residents structure so there's another resident structure and well they will take this pipe bomb that I will swing it over here like this this is the way you depict this with their pushing to show them and creating a new double bond over here if you move the double bond over an attack that Koble can I not that that would be equally good depiction just as long as your precise on drawing double bond shifting over make a new double bond on the other side another words I'm taking electrons away from the carbon it's on the left-hand side of the draw out that's that residents structure when we draw resident structures we always use these two-headed resonance heroes don't draw equilibrium this is not an equilibrium between 2 structures and these are the same molecule and just showing you 2 different ways to depicted these are 2 different depictions of exactly the same molecules so what this picture predicts for me Is that that cobbled Kanye and there's 50 % Koble Caroline character on the left carbon and there's 50 % cargo can I'm on the right carbon and 1 of these residents structures is not better than the other watchlist practice residents there Aero pushing this year as instructed by going back to the other resident structural take this double bond now shifted over and I will precisely and on that cc single but sets an example of how to use error pushing to depict residents and so once again these are not too structures equilibrating they're just 2 different depictions of a single structure so that you already taught about residents back in Chapter 1 so if you want to review that you go back to section 1 . 5 about what residents here is all about on the starting right now we're going to see a lot of resin in Chapter 16 were going to see a lot of residents in our cat lines in Chapter 18 you are going to be drawing will type cat ions and and residents stabilize cat islands and over and over and over and over and over and over and over and over again so I'm so it's good to to have an introduction in this chapter OK so residents I like al-Qaida irons and conjugated dines that's a big theme in this chapter that
world about this let's talk about residents if things don't have to be allocated lines but they can be remedied use embody show you some types of nite mostly chemical reactions here that lead to residents stabilized systems so all start off with this hello bromide here the Select cycle Eckstein all bromide and you learned how to make that you're free radical rumination and promotes accelerated in the last chapter and use light or peroxide or some sort of initiated to get that going on you learn about and how to make these types of look bromides but if you put this into a polar solvent it will stabilize Koble Caroline formation seeking get S 1 reactions out of this and so would draw out the intermediate the Carbol can I'm intermediate that you would get out of this type of 1 ionization and all start off by drawing this resonance structure here but the Carbol can I'm right there with the bromide left so the bromide and I'm leaves me the Carbol cat but there's another resident structural control that's equally good I would see the full picture here this picture makes me want to attack this cobbled cat on the right-hand side but there's an equally good resonance depiction that I should drop because it will help me see that there is an equally good probability that the nuclear file attack on the left-hand side and by drawing those to resonate structures it helps me to see those 2 choices on with great clarity so I urge you when you can't draw to residents structures to residents depictions of the same molecule because it will help you see those choices and reactivity not everything has to be a car can I'm a stake example of arms and acid-base reaction so this is a carboxyl a gasoline demand an an entire chapter and carboxyl gas Chapter 19 immigration sky Smith textbook of I expose a carboxyl ACC acid to Web-based well that's a massive and this is the basis and symbolizing the base with the letter B you should probably expect that that base is going to abstract a protons to pull off a proton and leave negatively charged carboxyl late and I again this is Chapter 19 all over Clijsters can have an entire chapter on this on making carboxyl 89 so let me draw not all of those belong on that oxygen so there's an old mine that you generate but there's an equally good resonance depiction for this molecule in draw that other residents structure and I'll use resonant 0 pushing here to help me see how I get back and forth undertaken that too many electrons here so I'll take this oxygen known pair 1 of these 3 reaction known pairs bring it down to make a C O double bond but I don't have 5 bonds to the central ,comma low-carbon so pick up 1 of those pie bonds and I'll give it to oxygen that helps me see on how I should depict this other resonant structure that's equally good so here is my other residents structure in a bid to equally good residents structures and the 2 equally good resonance depictions maybe it's bothering me that I didn't put the 2 lone pairs on the carbonyl oxygen sold do that here there we go that's satisfying but that that is OK so the 2 equally did not deny the these 2 residents depictions is better than the other they're both equally good residents depictions for carboxyl 89 and this is another example of residents that helpless to explain why carboxyl again acids are acids where they solicited it's because this is an iron is resonant stabilize the negative charges distributed on 2 Electra negative Adams and not just on stuck on 1 election but there is an example of another type of reaction on and this would be an example geologic red like he did everything else but here tributaries over that and is an example of probably the best type of less than 1 reaction you'll ever see better than any S N 1 reaction he saw Chapter 8 as 1 reaction decent chap were lousy and if this is the kind of S 1 reaction that you'll see when you get to Chapter 22 were 21 on and I'll show you why this 1 is special it's because the can I need you generate in this process is better than any other kind of complicated you had ever seen before but strong can and maybe that doesn't look very spectacular to you I guess it doesn't look spectacular to me either on but if I drop lone pairs here it reminds me that those oxygen lone pairs can donate over into the cargo can and depicted that by making former pie here and this is an extraordinary resonance structure I love this it's so satisfying I there's another long period draw that it's not really for the important part here Is it when I draw this other residents depiction every 2nd row Adam has an architect electron I have that's a good cat I'd better than T Beutel or anything else you've ever seen before better than bends OK so the last example is not a chemical reaction I'm just going to remind you that Kerviel groups any carbonyl group we can depict with another resident structure that every time hydrocarbon yoga but have to remember that oxygen is a lecturer negative and so it just makes me want to pick up those electrons that pipeline and given the oxygen if oxygen is selected negative she shouldn't shouldn't this molecule behave like the oxygen has more electrons straw that residents structure here we go Oh yeah In other words ,comma behave like Koble Kanye nuclear files and want to attack the cardinal carving in the camp 51 LB led you get a reaction were so the moral high ground attack ,comma low-carbon and that residents structure explains why OK so let me label these several different systems because he's the kind of the point of Chapter 16 most of the 1st half 80 per cent of Chapter 16 I had a good hour for good or bad has to do with our little cat lines so that's an example of an elixir cat iron and how low can here I have to oxygen negative charge when you deep-rooted a carboxyl aghast said generate a carboxyl late in Iron Works I'm running out of room in the conceded carboxyl you can have Al-Alam and irons that is not very common and you're not going to see them anywhere in the camp 51 series are not going to draw for this is a more common form of an ionic residents the carboxyl again this species right here they have 2 different names for these 2 different resonance structures not so for example over here I would call this that the technical name that you've never heard of is going to some really weird and fancy don't worry about this I don't expect you to know this but this is called a Knoxville Cobby neon ion this resonance structure this resonance depiction is called toxic copying an iron residents the picture and you don't need to know that I don't write it down just trying to impress you I guess this 1 over here you do know the name for that oxygen with 3 bonds there's a bond hearing the methyl oxygen with rebounders Golden Sonia minds this residents depiction is not so and I am residents depiction oxygen with 3 bundles as a positive charge and you've seen the oxygen with 3 bonds before but at age 3 0 plus a hegemony in mind that's not something on bananas lesson and we don't really have a name for this just a resonant structure for carving over OK so these are examples of residents and how we can use 0 pushing to go back and forth from 1 resident structure to the other and I'll expect you to be good at that so practice doing that and it's it's important and it helps us to see how how residents can stabilize cargo can irons residents to stabilize irons and was a major themes for this chapter the booking 1 of Gatlin's keep this picture here and I want draw these attention to these on to the structures here and ask when you got to possible resins structures How do you decide which of those 2 resident structures is better which 1 should you draw the paper which 1 will help you to predict reactivity about these 2 resonate structures for for acetone you've been drawing the structural rigor on the left-hand side but when I draw this these other 2 residents structures with and Oxo car and depiction purses and aunt Sonia mine depiction which 1 should you be paying attention to what truth you should be paying attention to both on but let's let me give you a spare of tools and it's only tools you need to apply you decide which of these 2 residents structures on In the what is most important and maybe it depends on watches what you're trying to see if this is what will decide what's most important
to so here's to rules I'm going to give me that will help you to rank resident structures what's the 1st best resonant structure and what's the second-best resonant structure the most stirred by drawing the species that a little bit ahead of our time here but on this is a resident structural it's going to come up in a big way but in Chapter 22 In Chapter 20 OK so here I'm going to this very weird species that should look a little bit to you like the carbonyl group but it's not a group because there's a double bonds to nitrogen and whenever I have for bonds to nitrogen there has to be a positive charge that will be more plain to you when you get to Chapter 25 economies but from now on maybe it's not so obvious to you but it is true it's helpful OK for bonds to nature in there must be a positive charge there there's another
residents depiction I can draw for this this species is called in and many Miami and you'll see a lot of this in Chapter 20 so let me draw residents depiction for this it's just a different way of depicting his molecule handle start by giving electrons here to the Electra negative Adam that's nitrogen nitrogen is more lecturer negative and carbon and we haven't done a lot of nitrogen chemistry and that you will and so on I draw this other residents depiction it's kind of like that carbonyl group presidents depiction I'm going to have I'm going to draw this is the cobble cannot and so and when I draw this now the positive charge on carbon so 2 different resonance depictions and how I would decide which of these is a better residents depiction rule number 1 whenever you look at 2 residents structures and it's a very simple is the best resonance structure has the most bonds what is simple men don't draw extra bonds that don't belong and violate the act at will but I've got to resident structures on the both valid Lewis structures and when I look over here the many online depiction has more bonds than this other
Koble Caroline depiction and so that's the best resonance structure the way the 1 with most bonds this 1 away with firebombs rank this is this is the number 1 best resonant structure and this would be number 2 and why would I care about but about which residents structure is is the number 1 resident structure whenever I draw some box my exam Isere draw the product in the box I expect you to draw a stable form of a molecule here typically you've been you have been drawing the number 1 resident structure of carbon Neil groups will draw on many the other real reason why should care about this best of all residents structure is the best resonance structure explains the hybridization and shape In other words if I look at number 2 residential here I might think that this nitrogen with 4 different substituent 1 of them was a longer might be pyramidal but that's not true many minds of flat this is the resonance structure that depicts for me but that nitrogen is sp 2 hybridized in flat it's the best resonance structure that predicts the shape of this molecule in the hybridization of nitrogen so look at the best resonant structure if you want to predict the shape of a molecule in the hybridization of the atom you look at the best and that's typically what you been drawn even drawing the best present structure take an example of another pair of structures on understand what all those all taken out the but I'm going to put a substituent on itself he not the ah that's not very exciting I'm going to put in Alcock site online substituent on this molecule and the should look very strange what is that Cox II and iron Dexia deep-rooted needed all if you're going to have an entire spirit chapters on this chapters 20 To win 23 in the book will be all about this type of the structure until help you draw a resonance structure for this will join other residents depiction and to help me see what how to get to that of the residents depiction I will start by taking these electrons on oxygen and pushing them downward to make I volunteer for all I don't have 5 bonds to this carbon so I have to break something I'll break that pipeline and give the other electrons together carbon so this is called an e-mail late and again you can have 2 chapters on undulates over and over and over again you know waits until 2nd drawing late where else until you loving lakes because that's how biology works so you by other residents depiction inside that 2 different ways to depict the same molecule 2 different ways to try to give me some clues about what's the shape of this molecule and how does it react so when I rule number 2 is which were well it's review rule number 1 rule number 1 is which residents structure has the most bonds and if I count that I count how many bonds this carbon hazard as 1 2 3 4 and then I look over here ,comma bonds the carbon hazard as 1 2 3 4 if you add up all the bonds in these 2 residents depictions they be identical to same number of bonds you can use number of bonds to predict which of those residents structures is better if you go by rule number 1 they're equally good but Rule number 2 says after you satisfied the bond deal then you look at did you give the electrons to the more Elektra negative ad so here in each case 1 of these Adams 1 of the 2nd Adams has too many electrons has an online as a negative charge over here it's oxygen on the left over here on the right in this residence depiction its carbon that has the negative charge and I hope you know oxygen is more electric negative the nature the carbon oxygen is more Lecter negative and carbon based on that I like this resonant structure better and over here I like this resin structure not quite as much but here's what's ironic and and also powerful if you care about chemical reactivity if you care about forming bonds and of course I care about chemical reactivity I care about foreign bonds and I care about predicting reactivity it's the second-best resonance structure that explains chemical reactivity isn't that ironic when I looked down over here it's with the second-best resonant structure on top does it predicts for me that nuclear files won't attack nitrogen nuclear files will attack carbon it's the second-best resonant structure that predicts that if I want that I really care about chemical reactivity all draw out the 2nd as resonant structure and predicts that nuclear files attack there if I really care about which 2 ends of this system the 0 minus ended a C-minus and is more reactive when this reacts with Electra files it reacts faster on carbon and I'm just going to abbreviate Electra with plus here so we pay attention to the 1st best resonance structure and the second-best resins structure and its second-best written structure that has the most predictive power for you on so many just show you 1 of them have very little room you're trying to squeeze the sand and sometimes as in the case of the carboxyl 89 dropped 2 different paradigms for you is an aloe cat iron there's 1 resonance depiction foreign Al-Qaeda iron and we draw the other residents structure but the Carbol cabin and on the bottom builder to residents depictions they had the same number of bonds In each case the the cargo can find is on a carbon atoms so there's no difference there those of equally good there is no difference you can't look at that and decide 1 is better than the other on so if you were trying to rank the useful you can't rank them they're both ranked as number 1 they both have the same number of bonds they both
satisfied or dissatisfied electorate negativity so sometimes the 2 resident structures equivalent in terms of which 1 is better which 1 is worse and still does have to drop them both and pay attention right this this picture here predicts for me that nuclear files will attack either end with equal ease of that apparent system OK so whether you never noticed it or not I've I've been in my mind throughout this entire quarter so for thinking about the 2nd as resonant structure and use that as a guide for for predicting the activities In OK select so start to think about hybridization I regret I regret talking about this in this chapter because you're not really going to use this this piece of information and continue until the next chapter but we need to introduce this idea here of how residents effects hybridization sheets of molecules you'll use this in the next chapter not in this chapter so its good start about talking about this I'm going to talk about something that I hope is totally obvious onto you and it's just so it'll help us see why this next part might be a little bit confusing so pneumonia them in a drawer several different second-row Adams who in ways that lone pairs on them so the draw carbon with a lone pair on the carbon atoms and I'll simply remind you that when I do this when I draw like that the carbon is going to have a negative charge it's going to be a car on but the important point is that this will prefer to to be sp 3 hybridized so way back in general chemistry you probably learned something like valence shell electron pair repulsion theory or maybe there's some new name fancy name nowadays but it simply British view the molecules like methyl an iron ore is homologs was with nitrogen In other words ammonia In some set of rules that allowed you to predict the pneumonia would perverted would prefer to be pyramidal not flat match regional plainer but parental so in all of these cases that the the central Avenue here ,comma ' S P 3 hybridized and pyramidal as P-3 3 hybridized and criminal that's the preferred shape that molecule monitored his last 1 over here all dropped from a water molecule just so I can march across the periodic table carbon nitrogen oxygen and others to lone pairs on him and again that's P 3 hybridized and parental that's the the preferred hybridization for all of these 3 systems did in doesn't matter were therefore hydrogen is on carbon and methane it's S P 3 other guys and planning OK but let's contrasted what happens if I have a Caribbean island and there's a double bonds next door your predictions will change and that's what strange your predictions the carbon islands are always pyramidal will no longer be accurate so in other words when I come over here and I put From a double bond on the carbon and I think I left off a negative charge when had negative charge of my car there we go looks a little bit thick there but that's a minus charge to go along with the command now we once we put a double bond there it's not the same situation we once again have to decide what kind of orbital Is that longer going to be and is it going to be S P 3 hybridized sp to hybridize or in appear orbital and and what kind of shape is that molecule going to adopt that the shake strictly correlates with privatization is that carbon with the longer going to be pyramidal or flat and so really there's too extreme depictions of this on the agenda to extreme depictions are 1 would be to have that lone pair exist in a P type and that's totally different from what's above pairs above Ernest baubles but you could draw it with the long period of P type the same the otherworldly for cargo can or you could draw that that lone pair Internet 3 hybridized orbital the way we did above those of the 2 choices and in order to to understand the shape of this molecule you have to ask yourself if you really want this lone pair to interact with either pyre pies .period next door with a double bond next door then you'd really want because pipelines have equal density on the top of the bottom you really want orbital that this longer isn't to have equal size on the top and the bottom right over here by hybridize this lone-parent appear orbital worried as equal size on the top and bottom of albeit equally good interactions with top of higher priced and equally good interactions with the bottom of higher-priced and so you know why am I saying prior pies .period depends on whether Worthington about a radical or alone pair or cobble Cat but it's all the same idea but the fact is you want this war but to be hybridized like this with and with the P word all there if you want to maximize interactions with neighboring double bonds and if you try to do the opposite if you try to cram analyze that and put those electrons into an S P 3 orbital you'll get great interactions here look at his biggest P-3 low but they're all look at that higher star right there the interaction but then you look at the bottom and it's like this week pathetic interaction it's totally losing out so there's 2 choices here if you want to have effective interactions between either a radical or lone pair where cobble can I'm next door to a double bond if you really want effective overlap that would be this case over here what's that supposed to say overlap you get effective overlap with hybridizing with pure bolivars Asian you get effective overlap on both the top and the bottom 2 of the pie systems but if you try to
hybridize it sp 3 because they don't have a good word so-called pathetic overlap on the bottom yet great overlap on the topic but that doesn't make up for the fact the overlap is pathetic so the timeline if he got a double bond and then right next door you have a cargo Cat iron on an iron ore or radical the that Koble Carolina and a radical is going to be an appeal at and that carbon atom will be flat inter-regional plenary because it's sp to hybridized and again we're not going to use that in this chapter yet to hold on to that idea until we get to Chapter 17 next after annual use them to sold on the idea that set of chemistry and some chemical reactions like this we're not quite ready to talk about chemistry and chemical reactions and try to get you ready for this OK I and when I come back to this idea of dying conjugated dying systems in which there's double bonds directly next next to each other and I want to draw up a dying in 2 different conformations To molecules 6 carbons and I just attached this funny way and when I draw like this at the important thing here is to recognize that you can rotate about this central single bond here I can rotate about that bond is free rotation there's nothing stopping upon rotation so when I draw that that will Amir that that different shape of this molecule and this is not a resident structural more because I'm literally moving items that would be totally inaccurate for me to call this a resident structure because I'm literally taking the seat serenely moving those Adams over here there's this there's a rotation that occurring have to draw equilibrium errors at Adams moved places In a resident structure they had do not move so this can be a residence depiction she's just an equilibrium between 2 road honors in both of these molecules are flat if you want to have effective interaction between 1 double bond in the other we call it conjugation then the molecule has to be flat molecule has to be playing and here's 2 completely different player confirmations that equally plain all I've done is afflicted double bond on 1 side of of the molecule versus the other side that they're both planar confirmations and we need some way to describe these 2 different confirmation because they will behave differently when we do chemical reactions and it's important that you recognize these 2 different conformations there's a signal bond between the 2 double bonds and so somebody I don't know who invented this system decided we're to call this system with the 2 double bonds opposite sides of the single bond or in the period planar as italics as Idaho draw italics S with a pen here but that's italics as is called the S Trans confirmation S stands for signal a or sigma bond in between they were rotating around a single mom and this confirmation called the S 6 confirmation and again tonight Alex S. right so when you see a typed out of my colleagues so this is confirmation but so too different confirmations and what will find is that 1 of these confirmations ESS confirmation does a very important in particular type of chemical reactions in strands confirmation doesn't do it Okolona contrasted may look to you like all that's in no this is not only in the SSN as trends are completely independent of leniency but the designations of configuration so when I look at this Al-Qaeda on top here these 2 substituent on cause this Al-Qaeda had busy configuration their aims I'd this kind of the mnemonic you can use so that al-Qaeda on top as is the configuration because the high-priority groups on the same side as a double bond this system as is a completely different type of idea the SSN as trans has to do with this single bond between the 2 out keen moieties by looking at the or the relative orientations of those 2 double bonds relative to the signal bonding between I would call this the SCS confirmation so as fearsome as trains are completely different from Yancy don't confuse those with means easy have to do with substituent attached to double bonds were assessed this industry ancestor do with the relative dispositions of 2 AL teams that are conjugated to each other OK so what In Chapter 16 in section 16 . 7 and 16 . 8 there's some fun stuff about interesting dining that you can find in nature or do what it's that's fun reading on or if you want to memorize in bond lengths it's a great place for you to go it's not the type of thing guy life you see my examined problems that that's not the kind of stuff I will ask you about because all you can really do is memorize those structures on or answer some multiple-choice questions so yet this because if you move Adams let me just make it make it more clear Over here I have a page to see you know where I C H 3 and now I look over here that the methyl groups on the opposite side of this carbon is now moved into different positions if you move any added if you move a single Adam it can't be a resident structure when you draw residents depictions no Adam can change places or removed that items have to be in exactly the same place when you draw 2 2 residents depictions so that can't possibly be a resident structure because there's not 3 ages there have to be otherwise they can't be resident structure so Adams were literally moving around 1 molecules change shapes that's not residents and we have to chair forms of cycle exceeded the nite Inter converting the residents there's an actual the reaction with with an energy barrier not involved with that OK so it's a bit that's talk about the arrangements of double bonds on diamonds so so you'll read Section 16 . 8 about fund molecules that have more than 1 outing in them and you can read some cool stuff about bond lengths those details are not necessary for us but you should read them because they're cool things to read about movements I want to give you 2 different dying so that we can talk about them and compare them and I'm going to give you 2 dying said at exactly the same number of Adams exactly the same molecular formula and all were going to do is were going to change the relative positions of the double bonds in these molecules and so we are going draw a six-member Rainwood 2 outings conjugated to each other at the conjugated dining and I'm going to compare and contrast that With the dining which such double bonds are not conjugated they're not directly connected to each other the CH 2 groups between the 2 double bonds on each side of this molecule and the 2 things that I want to pay attention to have to do with the stability of the molecule versus the reactivity of the bite of the pipe bombs so the molecule itself the overall molecule if I were to rank the stability of of these 2 molecules than what I would say Is it is in comparison the molecule in which the double bonds are conjugated is more stable the overall molecule is more stable and when the double bonds saying number of Adams seems six-member ordering all I've done is taken the double bonds out of conjugation in comparison that arrangement is less stable so
conjugation a double bonds makes molecules more stable molecules are more stable than the larger countries severely dilute the molecules more stable but I want to contrast that now with the overall molecule but just the just the individual electrons that high about all kinds of bonds in this molecule about signaled bonds here ch Sigma bonds but I'm just talking about the pipelines is 1 here there's 1 down there and if I just focus my attention on those pipelines what I would find is that the pipe bonds in the conjugated dying more reactive and the pie bonds when they're not conjugated than when they're isolated are less reactive it's like more reactive in what will take any 1 of those reactions you learned back in Chapter 10 additionally HBO are edition of the R to Hydro borage any 1 of those reactions the conjugated dining will react faster than the isolated dying so I understand what I'm talking about in this case appear entered with the whole molecule itself the down below talking about pipelines now the point out why this is not normal business as usual for the 1st 15 chapters of this book book what you learned about 4 Carbol cat irons which you learn about her radicals and which allow for an alliance is that more stable is less reactive so is dining things conjugation thing is the opposite of everything in 1 for 15 chapters Limoges remind you what you learned for 4 Carbol Caroline's what you learn is tertiary Koble cast irons versus primary care about cobbled Ghanaians you learned that the tertiary couple Caroline molecule here is more stable than a primary couple can you knew that but somehow or another if you you learned that Cobble kinds are less reactive when there are more stable he learned the primary Korbel kinds are really unhappy interim more reactive and the same would be true for an online a radical there's this Converse relationship that things are more stable tend to be less reactive and so now I'm Telling You for conjugated 9th it's the opposite now more stable just happens to correspond with more reactive and the waited to understand that once again is that I'm talking about the stability of the overall molecules all the seasonal the H is pursuing tugboat reactivity I just care about the pie electrons so you can have 1 part of the molecule be more reactive even know the overall overall molecules more stable if I take everybody on this side of the class in examining all of your points so far to the rest of the class on average the overall classes more happy even tho this side of the classes very pissed off and very reactive and so on average the whole molecule can be more stable even if just 1 little part of the more reactive OK so what would happen if you if you did some of your chapter 10 reactions on a dying you added R to a dying of B R 2 to a dime take an example that and so there would be an example at you that you already know about that addition of HBO across double bonds this to double bonds there and I'm just going to talk about adding 1 equivalent of you'll get 2 different products out of this reaction and it's not maybe it's not till the obvious to added 18 B R & Company you can all see the or images remind you where the agency can see more clearly there's stage and there's the age and other words I ended up with an al-Qa'eda the bromide added to either end the al-Qa'eda that's good and drawn a mechanism that will help us to more clearly see how that works out so saloon like this old right here the of some sort of error pushing helped me see how you get and how can I am out of sonar used a double bonds the pluck of a proton and the double bond the double bonds going to prove on the end there in order to give us an allocable Kanye intermediate so here that Balakovo campaign that we get and there's a bromide I'm floating around the areas the bromide so I hope you can see that it's kind of obvious here that that you can get this product on top the 1st product by having the bromide attack and we got 2 different products and we a way to describe those whenever you have a dying system you can number those carbon atoms in the dying With with some numbering system and the way we typically do that is 1 too 3 4 and if we if we look at those numbers In this 1st product here the H in the br attached to carbons 1 into we call that the 1 2 edition pride but I went to any organic chemist and elected is dying and I got the 1 2 edition product they would know exactly what I'm talking about fate the and of next to each other the other product that you typically get as part of a mixture has the Proton and the bromine attached that carbons 1 called the 1 for addition product sold so that nomenclature I think is pretty obvious and you typically get mixtures on but how do you explain the formation of this 1 for addition product the way to explain that 1 for addition product is to draw all the other residents depiction when will the double 1 Nova and I had a couple can on on the other hand and when I draw that other residents the picture and I think it should be obvious on how you get that the product I get the 1 2 edition product if the bromide attacks 1 end of the Al system and I get the 1 for additional product of the bromide that attacks the other and analysis so typically when you have dined you at HBO you will get a mixture of 1 2 1 1 4 additional products but and there's this obscure and this is kind of obscure and it's not 100 per cent general but in the case of UN substituted beauty dying with no substituent the 1 2 edition product forms faster if forms 4 times faster than the 1 for addition products you get an a 20 mixture when you take beauty diners no substituent HBO and if you keep the temperature low that's interesting 1 of those products once faster and it turns out to be the major problem but if you read through and you go on you read on that section which realizes that Allah bromides are susceptible to ionization reactions to S N 1 reactions so when you expose this is some sort of polar solvent system that makes it easier for this bromide to leave and generating now will provoke an iron and I'm not going to draw although well here is 1 of the 2 residents structures are not going to double the residents structures so on you'll get an owl cobble Caroline intermediate and then the bromide can attack the other end in order to give you this and then can go backwards the bromide can pop off again and then we had the original position so this equilibrate back and forth and when you allow aloe bromides to equilibrate you you will equilibrate them such that you end up with the isomer there's the more substituted double bonds and this is just a general I isomers with substituted double bonds are more stable so that's why you favor this other product more substituted double bonds peoples more stable this is nothing more than ass in 1 type substitution with nuclear files the same is leaving group so in other words if you allow this particular system to equilibrate farm it's the 1 for your product that is favored and the book seems to make this big deal about that and I'm not sure why it's so important and that they consider that to be an important issue OK I'm in a good stop
there and when we come back we're going to cover really powerful reaction called the deals older reaction it's a super power away from making six-member bringing it will be on my exams audiences something on the wall behind professor Williams even want example the other sections of the law that these
Vimentin
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Adamantan
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Geröll
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Sekundärstruktur
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Substituent
Terminations-Codon
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Elektron <Legierung>
Querprofil
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Setzen <Verfahrenstechnik>
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Katalase
Reaktivität
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Thermoformen
Vancomycin
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Potenz <Homöopathie>

Metadaten

Formale Metadaten

Titel Lecture 21. Conjugation, Resonance, Diels-Alder Reactions, Part 1
Serientitel Chemistry 51B: Organic Chemistry
Teil 21
Anzahl der Teile 26
Autor Vranken, David Van
Lizenz CC-Namensnennung 3.0 Unported:
Sie dürfen das Werk bzw. den Inhalt zu jedem legalen Zweck nutzen, verändern und in unveränderter oder veränderter Form vervielfältigen, verbreiten und öffentlich zugänglich machen, sofern Sie den Namen des Autors/Rechteinhabers in der von ihm festgelegten Weise nennen.
DOI 10.5446/19490
Herausgeber University of California Irvine (UCI)
Erscheinungsjahr 2013
Sprache Englisch

Inhaltliche Metadaten

Fachgebiet Chemie
Abstract 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: 00:31- Doritos Ingredients 01:38- Molecular Structures of Doritos Ingredients CHAPTER 16-Conjugation, Resonance, and Dienes 03:46- 16.1: What is Conjugation? 10:36- 16.3: Common Forms of Resonance 20:07- 16.3, 16.4: Rank Resonance Structures to Predict Properties 29:00- 16.5: Lone pairs must be in p orbitals to interact with pi bonds 35:27- 16.6: Two flat conformers of conjugated dienes 41:12- 16.9: Reactivity of pi bonds vs. stability of the overall molecule 46:06- 16.10-1,2: Addition vs. 1,4-Addition

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