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Lecture 18. NMR Spectroscopy, Part 2


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I wasn't sure what to make of this news article when I 1st saw this the guy
like eating hash with bacon and eggs in the morning like everybody else wasn't clearly why actual oil but I should have anything to do with it ,comma and it was until I started reading it I realize attacked hashish and that that's kind of interesting whatever is going on here that looks of oil maybe there's something related to hashish so it looks from this article that there are problems with people starting fires when they're trying to extract compounds of of hashish which is the form of marijuana and so the idea is the the Philipson process and probably the problem is you know that natural gas smells bad and we talked about this the reason natural gas which is very flammable and a real fire hazards smell so bad as the purposely contaminated the natural gas in the lines that you have a supplier of arms but of course if you go by a follower of of butane at the store but it doesn't have any contaminant in there to tell you when you fill the room with a highly flammable compound so that I got interested in is a guarantee you to look to the couple videos it's kind of fascinating work with
creative people have done so here the idea is that marijuana and hashish containing this compound built 98 tried to Canavan all finds the cannabinoid receptors in the brain and all kinds of stuff and I guess most people don't have access to the times of organic solvents that I have been for every organic chemist has in their laboratory so what do they do they go buy a can of butane which kind of looks like vaccines which is not a gimmick solvent it the advantage of this it's very easy to evaporate so we have very special evaporator is in our laboratory that allows us to evaporate organic solvents here you don't need anything special so it it seems to me that what they're doing you go to your local supplier by a bunch of marijuana hashish and you need some sort of a 2 made of metal it has a big opening here in a small opening 1 end and then you use a rubber band or something to to tighten on some cloth that this sense solar marijuana doesn't fall out universe and then you stick this pain and of of butane right here on the end and inverted and when you do that and open the valve suddenly all these butane starts to spew into here and of course as gasses and other things start to expand cold so even more of the butane experience and say so the butane goes through this tube extracts out all the organic compounds and it leaves behind the water soluble compounds that are going to get you high because all you care about is the greasy ,comma know there are lots of naturally occurring compounds in the 1 all of them come out but if you really like that concentrated THC and then at the bottom of this when you've turned it upside down right at the bottom of this is all the butane is dripping out the bottom you catch it in a glass dish that's sitting in some warm water and the warm water evaporates all butane and so what you're left with is as all the butane evaporates as this waxy honey like substance found that is super-duper Dupre concentrated in teaching so I hope you use organic history for more useful things that it's like curing cancer diseases but I that's a pretty clever use of organic extractions of open and of course security 88 and you've if you're doing this indoors in your entire room is filled with butane vapors on the slightest Park is going to set off on the whole room will detonate complaints all right so let's get back to an arm of the THC is a cool and margin bring that with me but I so we have been talking about
animal our last lecture and we swing decided we were going to focus on carbon and not because it's so simple and because it is simple relative to Proton in market that makes it very useful to you in solving problems and solving spectroscopy problems so my recommendation to use if you're given infrared de proton RNC 13 data go to the sea 13 in data 1st it's easiest to get powerful information out them and I regret in my last lecture I didn't quite have time to get to these chemical shift reagents for carbon and moral really talked about was chemical equivalents and how many people should expect see 13 spectrum so here's the general range for carbon and remember we said we were going to flood in terms of frequency on a lot in terms of parts per million of which sort of normalizes for different Magnus strengths and the advantages of carbon and Mark is that on the some very distinctive arranges for the chemical shifts of common functional groups so if you have an outsider a key molecule in all of tribal abbreviate that like this and I'll put a chill are here but if you have an outsider aikido it's going to show
above 190 parts per million that's the only started shows about 190 parts per million you do not need I are to tell whether you have a car meal in your company is look at the sea 13 and no worthy of a cardinal in your company and moreover you could tell what type of car Belieu you Avenue ,comma pretty reliably with with C 13 of them are OK so below that we have a different type of carbonyl in this region from 155 to about 185 this is where we have carbonyl groups that have federal atoms attached to a kinds of federal Adams for example oxygen the carboxyl gasses acid chloride to talk more about those later in this quarter on it's really have nitrogen attached to the cop he'll sold all of these different types of carboxyl gas derivatives with a carbon Hill has a federal and attached not carbon hydrogen will be in the range now it is down here at 162 110 this is all the CCW bonded carbon these are not carbons with no oxygen attached just carvings that are a part of apply system and it doesn't matter whether it's a benzene ring a simple double bond they show in that region so you could just looking at region see peaks in this region value you gotta see see double bond and salt of tribal here too to draw benzene ring because it doesn't matter whether it's a benzene rings or just a regular CC doubled on eastern regions now there's 1 tiny little sticker here is as chemical shifts and that is if you have an Al-Qaeda is attached to a carbon meal like this this part the beta carbon going circle here in glorious pink that carbon was sometimes appear down in this range it will look like a cop you know it's not a carbon real carbon you will sometimes appearing at Esther and carbon range and that's the only sort of tough part about there is a sort of overlapping area I hate it when I see peaks at around 159 frequency peaks at 1 59 see that said overlapping regions
man-years sort of left with a little bit of uncertainty Jay-Z benzene ring for now is that I on what is that sold gasoline just come back to this beta carbon thing it doesn't always appearing in this region can but it can appear in this in this Esther and region so we just point out that it could appear in either of those regions OK what about things attached to single wants everything else everything else that has just single bonds attached to the carbon that's all below 110 you don't get a whole lot of information you can't count how many chlorine is elected negative Adams attached it's not as simple as that Al kinds also appeared at the upper end of this region but and you won't do it yourself good trying to figure out whether you got out kinds are allocated carbons his counterpart many carvings you have below 110 and that's all the stuff that singly Mondadori and triple ones aren't that ,comma but more Tripoli bond so the Lucita 13 ranges of I give you see 13 anymore more not only can you count the peaks and have a good estimate for how many unique ,comma you have in your sample and you can also look at where those resonances occur what ppm those residences occur and get some information about Gedo either double bond my compound or is it probably a benzene ring and webmaster very powerful stuff OK now you also have additional peaks in your spectrum almost always so in your seat urging on this very tiny little actually there can expand this and this the answer so you also have these other residences in Europe In your Panama still here's a picture of a section of a C 13 a March and notice here at 77 parts per million there's 3 peaks and you will see that in just about every single spectrum it turns out that that's the carbon from Dubreuil chloroform remember that solvent that I showed you in the last lecture it just so happens that it appears 3 equally sized peaks and it is always at 77 . 4 million you have to dissolve your game example in something right to an organic solvents out walls of carbon atoms will always show up onto don't treat that as part of your sample this little peak here From the spectrum I took this from at 75 . 5 that is part of the sample but those 3 as part of all ignore it don't get caught into trying to assign that as part of your sample now we haven't done proton NMR yet but when we do proton NMR you'll see a similar containment type of peak and this is chloroform when you buy a bottle of beer chloroform it's not 100 per cent due to poor form it's 99 . 9 per cent to Wroclaw form and the other . 1 percentage of binding them
brown bottle is just a regular format that is a proton on man and that always shows up here at about 7 . 2 6 parts per million so you should look for the peak at about 7 . 2 6 and don't treat it as part of your sample that's the containers from the solvent and it's there in putting in most of the Panama's because most show you are carried out in the report of a case on 13 look for those repeats 77 and ignore them and in proton NMR look at peak at 7 . 2 6 CPC at ignored because just from the Seoul OK so
where experts now in this chemical shift range business this would see if we can apply this to a sample like a kind of typical problem that you might have to work if you're in the lab This is the way things work so I have redrawn the those chemical shift ranges up above you just wrote that stuff down just putting it here for your convenience until its apology gondola Avenue think Wannamaker meted out of this alcohol and treated with acid 2nd maker Leading group out of the way each Malpensa methanol in there and then you isolate your product and you're not quite sure what you got the go take a common so what is this thing isolated 1 got a carbon anemometer can figure that out well it could couldn't the Anderson 1 reaction like I was hoping for but also could do an essay in a story 1 reaction but the student types to the 1 product you can generate and how can you be sure which 1 you got right you know these these conditions may make that someone ambiguous so this is where you get a chance to spectroscopy to figure this out and here's the sea 13 a marble and I can tell the 13 just by looking at the fact that this goes from 0 to 100 parts per million proton NMR only goes to about 10 parts per million as soon as I see it is accessed going to 200 . 4 million I know it's a seated unanimous spectrum but this so the 1st thing I do is I look at this 1st of all what you use spectroscopy for user to rule out a possible structures so the 1st thing I do is I look at this product is the and I would no double bonds in their but look down here between 120 and 140 . 4 million right there is no way but that's anything because this ETA has no CC doubled there you go gone right I know there's a CC double-blind in this in this ,comma it's another question is OK looks like it was some sort of elimination reactions which of these 2 elimination reactions to waste the Tracy some CC double-blind stuff them singly bonded stuff in my carbon in Amman and so which 1 of these is is so probably the 1st thing that I would do is I would look at and try to predict how many carbon signals what I expect in the sea 13 a so I seek to Al-Qaeda peaks here and those 2 carbons a different 1 carbon atom Apple 1 carbon doesn't soldiers I expect 1 peek into peaks and I see that I am many singly bonded carbon too I have years of metal that has only single bonds years carbon on the other side of that out and that as the single bonds will be a number and this 1 is distinctive number 5 members 6 number 7 so I expect to see 1 2 3 4 or 5 peaks in the singly bonded region or that seems to match there's 5 peaks here in the singly bonded region I'm not going across that everything I see in the spectrum is consistent with this compound but compare this 3rd compound here so here I sit 2 completely different types of Elkin carbons as 1 with 2 majors on 1 2 carbons so those are distinctive 1 too that would also match now I count over here it how many carbons and I would expect to see the singly bonded and this carbon over here number 3 is not distinguishable is indistinguishable from the bottom both of those carbons are attached to an Al-Qaeda both part of a ring so by symmetry I don't expect to see different signals for that and expect to see 1 signal for car industry and 3 and once again over governs 4 1 4 and the carbon at the foreign will will be a tough
signals so innocently bonded region if this were the compound I would expect to see 1 2 3 extra peaks and I see way more than that were done with the problem immediately the Sooners ACS symmetry and I know that there's too many peaks here in this part of the C 13 to be consistent with that so that's a typical approach to carbon and I'm not counting the peaks is actually pretty powerful immediately started with counting the peaks and probably answered because I probably didn't need this to look at that Al-Qaeda region on but this is how you can use those distinctive peaks like in the carbon he'll region and the Al-Qaeda region to give you a leg up on figuring out on what your structures are OK so that's the end of carbon and March you're now ready to take this little chemical shift range chart and work bunches of problems figure out of and to help you rule out plausible structures so now we're going to switch to Proton and it's it's aggravating it's more complex than it is massively more powerful but I love the fact it's way more powerful than you think it's sucks it's way more complex and whatever the fastest the way it works if you are a man of his spends the significant amount of time investing in learning how to to interpret of proton NMR spectrum it's way more powerful seated OK so the 1st and most important thing you can do with a proton NMR spectra just like common tried to predict how many sets of peaks you should see how many sets of types of unique protons you should see and this is the same thing that I had I brought out with carbon 13 animal so when I look at it that these molecules here just redraw my Brummel propane here but I don't expect these 2 protons and propane to be different the both attached to a carbon is a bromine ions they're both attached to another CH 2 groups those 2 protons should end up getting 1 signal so good labor lettuce as a these
protons over here 2 carbons away from the bromine atoms the attached to a methyl group those I would expect to give their own type of signal and finally come out to the end year CD and all 3 of those products in the United States is the same thing about their distances from the bromine and what the attached to so I would expect to see 3 set of signals are there's 3 types of unique protons in this remote propane molecules and so as long as I know that I can very quickly rule out a zillion different types of compounds that would not fit with that spectrum OK so stuff about there's other compound here I see 2 protons ,comma attached to this Al-Qaeda carbon atop at the top and those are indistinguishable each proton assist to a methyl entranced 1 that's all I could say the same thing for for the other 1 so I would not expect these 2 protons to shore up any different and so are label on label 1 and 2 and know wide I chose to label with a with letters here and now that the protons on this methyl group this methyl group over here on the right-hand side is no different from the methyl group on the left-hand side I would expect those the To be non distinguishable so really I would expect to see 2 types of protons in my pro-China Ma spectrum and just from knowing that I could rule out a whole slew of different different spectra OK so here's another compound that an Al-Qaeda and the difference now is that each side of this Al-Qaeda's differentiated on the right-hand side of chlorine atom and on the left-hand side and method so now when I look at the 2 protons in the top I can see 1 of those pretenders sister chlorine and the other is those are different you being sister chlorine is not the same as being Transtar chlorine and so I would expect these 2 protons to be you can't rotate about that SEC double-bond is the CCW unlocks those on the geometry of the current so I would expect to see 3 sets of signals here that the 3 protons in the methyl group on methyl groups the protons always identical OK so here's a cycling compounds of propane rain here and now I see 1 proton it's attached to the car the chlorine that's kind of distinctive there no other Proton like that but now I have these others to CH 2 groups and over here and this this other side of the ring I see that 1 of the protons is on the same face of the rain the top faces the chlorine atom it's always on the top face the same faces the chlorine atoms together Proton down here is on the bottom face away from the chlorine always nothing ever changes that they can bend reflects a tiny bit but the but that relationship is the same so I would I would it's definitely cleared neither of these is like a and they're not like each other so same faces Coronado's faces court and then I look over at the other side this Proton on the top face on the back side there is definitely the same is as B and has the same relationship it's on the top faces chlorine it's 2 carbons away from the chlorine and I'd say the same for the bottom so here I 3 sets of
signals by further I think because there is generally more protons and the protons farther away from the group's interest the all-white idea of identifying in equivalent protons ,comma is a little bit harder with proton NMR it's and that's just the way what you'll find it's could most important skill that you will have to be able to count on how many sets of distinguishable of distinguishable protons there will be In the proton animal just like it's very powerful acceded to no 1 OK but let me give you a sense for why this will become more complex in theory this is a problem that arises with the 13 you just don't see it often wears this is this is going to give you fits but it's going to bring about all that stereo chemistry stuff on that you had to deal with thing back in Chapter 5 the GreenSky Smith textbooks OK so we need to figure out whether protons are are what we call dies during topic for a major topic these it this is a relationship of 2 protons are Dyess scarier topic they will give different signals the end of March both have different chemical shifts don't do stuff to each other and cause some complexity protons The Colony India topic at the relationship of the to top this city will not be distinguishable Indiana model occurred with exactly the same chemical shift on and we need to distinguish whenever we see due protons attached to special attached to the same carbon whether the dire stereotactic bringing it to and I'll show you a way to do history a chemical tests to distinguish them so let's take this example of beauty I could draw this like this that's the simple line drawings structure but here I have shown the 2 h is there on beauty and while I get is are these 2 protons going to be distinguishable by proton along the way you you can reliably determine that is to use something called busy test it requires you to draw a lot of structures than here's the way the test works what you do is you redraw the structure 2 times here it is and here and there's no shortcut became distraught 1 time you have to draw up to and we're going to do is 1 structure were replace 1 of the hydrogen with the fictitious elements eh I just wanted you could use iodine uranium a zirconium reduced but just so we don't get confuse will put a fictitious element there that we could never confuse with the real the real proved now on the other structure I'm going to replace the other Proton with an element of fictitious element z so now I have 2 different molecules and now all we need to do is establish the relationship between these 2 molecules by these 2 molecules and Nancy emerge diced of each other 1 way to do that as you could sign conning Inglewood pray log on priorities entity In hours in our little skiing here you just assume this he has the lowest priority even lower than a proton so far to assign conical prolonged Cardoso would do something like this party 1 2 3 that would be the S configuration and I look over here and I see Priority 1 2 3 but the disease coming for the reverse that as we are these are intimate of each other and what that means is in this original compound these protons are considered to be an NGO topic that's the relationship and on to you Top so that's the relationship between these 2 programs to I would refer to those living in India topics and easy test tells me that and I know this the test is a lot of work but it's reliable so but there still an antidumping protons those would get exactly the same chemical shift in Myanmar spectrum and that's important to the store another 1 down here I've got a die coral butane molecules and as I did before a going start up a drawing butane twice terror got 1 chlorine going up and that the other chlorine going down I'm sure you know what I make that and then I'm going to this is a much more obscure example here and I've got 2 protons and I'm John decided those the same chemical shifted different chemical ship right the both next to chlorine both 1 ,comma away from methyl group but there's something weird going on here and I can tell whether I would expect the same chemical shift yesterday in the both attached to a car with chlorine and both 1 away from methyl group but so what you do is you buy the seat as your place 1 proton and 1 of those 2 protons with this fictitious elements and then the other structural we replace the other Proton with that fictitious element the and then we tried to establish the relationship here so and words what we would do then apply applied this is the test you again you know it if you can't tell if you can flip it over in your mind and tell whether immediately whether those Ameri images are dies gamers you can also fall back on assigning conical priorities I'm simply going to write what you get here you can do that on your own would just take you a little bit of time to do that and because these are remained tumors of each other the student but I think I don't know if you can tell that you might be able to just flip around in your mind and you'd be able to tell that these aren't just like these these 2 molecules of about these these 2 molecules of above bringing tumors and that's why the protons are need to topic these 2 molecules down here also in intimacy each other you could build models of its if that's hard for you to sing and because of that the relationship between these 2 protons is that they are in India topic and that means they will have exactly the same chemical shift they will have a different kind of culture so there's a lot of work right it's a lot of work to do this but you will frequently have to distinguish between topic and it's usually 99 per cent of the time this is caused by having all of us at Cairo's center in your molecule the sterigenics center if you see a sterigenics center that usually going to have to be applying this test to try to figure things out the is 1 more example here is not always an India topic sometimes cases where the user are different and here I see
Cairo centered on March but it doesn't look meso 0 this was applied the testers would I expect these 2 protons Misik here 1 of them is kind of on the same faces chlorine 1 not on the same money but you can rotate about that bond is there somewhere rotated so I start off by drawing lines by molecule twice there a bromine on hand there's a chlorine on this carbon over here now draw of the molecule a 2nd time it's propane use bromine on the hand this chlorine and carbon too now draw my protons in come out of this Proton going in In back here but there is no superimpose wall so at here's what I noticed I noticed that the stereo chemistry the center here is S and it doesn't change between these 2 in between these 2 compound the chlorine is attached to a non-strategic center in both cases by conical prilog but I because others Darius 190 molecules now that's definitely the opposite stereo chemistry in both of those it's a sterigenics center in both of those and so if I were to assign common-law prolonged here would be Austria chemistry in this case and investors chemistry here write those Bell those are not your images it was truly a mirror image every single Orin as would have been inverted those are streamers of each other these 2 molecules with this fictitious z group in and because these dice scary receive each other that means the relationship between these 2 protons at their diets stereotype and they're going to have different chemical shipments different environments and so you have to whenever you see a Cairo Sentinel molecule utilities get ready to and you're trying to interpret the unmarked you need to just get ready to apply this is the test figure out but whether those 2 companies set of signals should the Indiana market whether pairs of methylene protons H is attached to the similar cock carbon atoms are the the same carbon atom our or an injured topic dies stereotype OK so struck about chemical shift ranges for Proton in so he is a proton NMR spectra sure why but it looks like part of my spectrum is missing out sultry continues on Spector usually plotted out at 10 parts per million every once in a while you got stuff down here in past 10 parts per million but that's unusual you'll find so common modest quite up to 200 parts per million seat and Proton and a modest typically only up to 10 parts per million so I can just look at the axis and immediately I know whether I'm looking at a carbon Anwar approach and there's other obvious differences as well so what the chemical shift ranges that you need to know how to interpret these kinds of spectrum so on opened down here passed a parts from millions this is where you see protons and carboxyl gas it's those typically will be shifted the most of any kind of protein and they're in addition to that the typically brawl the pizza variation the gate down here from 8 parts per million down to about 11 that mixed anyone that Rangel find ages attached to carbonyl ripped out the heights in other words so they're all past the personally million as soon as I see a peek past the part and allied on that ,comma so you won't see stuff down that far In the end the proton among all you know somebody pointed out something that I made a mistake on In the previous led many to correct them while while we're talking about this so that they had to do with the explained to this idea of downfield and feel so alone should correct them before we go on well I can't find that so we call this region of the spectrum that's at high parts per million and unfortunately this is totally counterintuitive we call this the downfield area so I would refer to all these protons arrears downfield and protons at low parts per million I would refer to the noses of field but what I told you was that this is referred to as shielded but that's not that was the opposite I had those reverse this is what we refer to as the shielded all these protons occur downfield because their shield and over here the things that are up field Our upfield because their shielded and I don't use the term shielded India shielded quite as often as downfield and upfield but I had those the shielded and shielded reversed and told again and so is go back to this up to a chemical shift ranges here from 6 . 5 to 8 . 0 0 that's protons attached to benzene rings from time the detonators hearings get shifted way downfield into this region as soon as I see stuff in this region from 6 and a half day particularly in I'm thinking benzene ring and I started drawing plausible structures that benzene rings are you might recall that there's usually a single at about 7 . 2 6 4 solvents so don't count that as part benzene rings so that's your chloroform contaminants from this dude rated solvent used OK so from 4 . 5 6 . 5 those of protons attached to al-Hakim's so that there's been seeded armada is not a huge difference in the chemical shift ranges for carbons in benzene rings in carbons and simple double bonds were isn't it so common among those not a big difference between those carbons but in Proton anemometer is a substantial difference in the chemical shifts for protons that are attached to either of benzene rings are simple out so so at and at lower parts per million that's receipts attached to simple now down here from 2 inactive 104 million are the ages attached to carbons and the carbons have some sort of Elektra negative ad on the oxygen most typically is the most typical 1 sometimes chlorine that's not quite as typical of organic molecules more bromine nitrogen you won't see a lot of that stuff until Chapter 25 OK so now instead of having an oxygen attached common if you attach a pipe bomb by the CEC double-entendre carbonyl group you attach a pipe bombs to that carbon the protons on their typically occur in this region one-and-a-half to 2 and half so notices that this is not a proton that's directly attached to the CC don't want over here protons everyone away then finally down here .period 5 1 have personally that you stole the regular sieges and usually this this part of the spectrum is a mess 1st for typical organic molecules because everything shows OK so why CDs groupings like quite new CDs chemical shift ranges on Monday and wounded to list for you the 3 types of effects that are causing these protons to appear in this region where in these various religions so what's the biggest effect that's causing these chemical shift ranges but without question the the biggest effect this is caused by the magnetic field of nearby high electrons so when I looked down here and then ignored this this carboxyl gasses for the moment I let down here this page is sold for our downfield so far at 5 parts per million because it's directly attached to apply system Carbondale system was a poor price system and benzene rings their way down here at high perch familiar there directly attached to a benzene ring by systems and then these dumplings over here directly attached to a simple CC double bond price system so that the things that cause protons to be shifted the high particularly in the most is being attached to some sort of a double bond that's what causes the biggest ship and being attached to an is not the the same I should say double bond electrons it's it's being directly attached to an type were carving on system because that's the biggest effect and then there's a small effect
and the smaller has to do with inductive effects inductive effects of electrode negative Adams so in other words having elected negative ads like oxygen chlorine doesn't do as much that only shifts you down here to the two-and-a-half to foreign appetite for million range many does shift you saw on tour to hire parchment million but the fact is nowhere near as big as being on a carbon it's part of the SEC doubled 1st pursuit and then there's going to be tiny effects that shift protons tiny tiny units and that is the magnetic fields caused by neighboring were nearby protons and this is called splitting and we'll get to that so huge effects if you're attached to a carbon is part of a double bond small effects if you're attached to a carbon that has other federal Adams attached to it and then there's teeny-tiny effects in this splitting the issue OK so the effects are additive so the more oxygen I could attached to a carbon atom water will be shifted from so notice allied it's shifted the farthest over here but maybe not as far as the carboxyl but not only is it attached to a carbon it's part of a double bond but there's also 1 of those Adams and 1 is an oxygen which is electoral negative so that's why it's shifted farther than that the benzene and the last is any age is no wages and for these for the worst most awful things to have a compound if you're interpreting the pro tournament because they can appear all over the place there is no special chemical shift range I can give you please for 4 protons that part an alcohol on an age and I'm simply going to tell you that if you can't find them anywhere want right basically anywhere in most of the spectrum right away cheers on carboxyl gas past 12 which an outpost can be out here at 5 and a half or 3 or 2 1 and I promise you that's going to send you into fits because those see is weird peak on him and you'll be wondering what it is but 1 little trick I can give you is usually but not always those peaks abroad they look broader than than the other peaks so they might look like this where as all the other peaks the show and well-defined so 1 clue that became clear when the fact is that of a in armada belongs to 1 and OH is that often they'll be brought erotic could look at Woodstock about these these effects here no want to talk about this this effective of being attached to a carbon it's part of a pie system so on there there's a device called a annoyed operates the Carlock door here any time you take a wire coiled wire in Iran electricity through it creates a magnetic field right to the wire right to the coil so when every ounce electron circulating around it creates a magnetic field and this points system the benzene ring and it's hard to imagine the simple double bond is also true for simple the belongs is like is like that of a coiled wire this pilot here that when they get put into an alarm magnetic field those electrons starch spin around start to circulate because of the huge magnetic field due to the being in the carbon al-Ahmed and when they start circulating around they create their own magnetic field and magnetic field they create goes in the opposite direction but the Amon magnet I guess on the
inside of the benzene ring there's going in in the opposite direction but on the outside of the benzene ring they're going that magnetic field is going in the same direction as the Yanomami sold fewer proton sitting on the inside of a benzene and there's no way to get a proton hints the benzene and you'd feel smaller magnetic field but if you're proton sitting on the outside edge of benzene ring directly attached to a benzene ring you'll feel of bigger magnetic field and that's what causes protons attached to benzene rings in AL teams to be shifted so far so let's take an example of 2 different compounds here the cycle had seen no private on that all the ages the same month cycle exceed and compared to another sect member and just plain benzene and look at the huge difference so cycle hexane approach under 1 . 4 3 . million benzene the proton 107 . 3 4 2 huge chemical shift there so there a shift away downfield because they see a bigger magnetic field the protons on the outside of the benzene ring and now and some very clever people of designs super huge benzene rings benzene rings anymore where you can fit protons and inside ensure enough those products he shifted to lower marginal pretty amazing stuff OK so typical benzene rings way the heck shifted down to this kind of 6 and a half past 6 enough parts per million that's called magnetic anisotropy anisotropy means basically an uneven magnetic field that's created by the circulated by truck OK so you don't have to be directly attached to a benzene ring to feel that kind of magnetic anisotropy effect trumpet the farther away you get from them the prices system built more diminished those effects are so and so again this magnetic anisotropy those circulating electrons effect and so I think that's typical simple organic molecules like propane here the chemical shifts for this middle ,comma that's 1 . 2 parts per million and methyl groups at the end show 0 . 9 parts per million and I'm not going to keep writing Part million so that's for the protons on the 2 and methyl groups which are the same so that's a typical organic Our molecule no double bonds in their but when I have protons on molecules that a double bonds it depends on how close the protons are to the double bonds so the biggest effect going see is going to be the protons here that are attached to this carbon atoms and turns out those protons will appear at 5 . 3 parts per million so I have a spectrum here of cycle seen that is a double bond in the protons citizenship of the fathers of the protons that are directly attached to the CC Delavan that's the protons here directly attached their directly attached to the car the bitter double bond if I look at these other protons like here these are not any longer directly attached To the station OCC doubled what this is this carbon you're not part of CCW if Europe 1 ,comma away from SEC double-blind defectors is greatly diminished its analysis is only 2 . 0 parts per million EUR still shifted more than just a regular CH 3 group but right it's not like 5 parts per million to now and we look over here these 2 protons were showing only around 2 parts from him and then we get 1 carbon farther away he sold now or even farther away from this from this double bond and now you just regular allocated so far away from the pie system that is really not feeling that magnetic mines after nets 1 part per million so that these protons over here there's there now just 2 carbons away so these protons there are that's this peak over here about 1 . 7 4 cycle as opposed to an apple OK so then again for a benzene ring in matters how how close you are so here's of molecules Eileen to common solvent actually in organic chemistry that boils at a very high temperature and so the protons that shifted the most of the protons that are directly attached to the benzene ring that's this Proton here so that's xylene is to methyl groups opposite sides of the Nanjing so the protons attached directly to the benzene ring from but those vitiated the most out of past 7 parts per per million but for the protons that are attached to the Koblenz that are attached to the benzene ring the 1 carbon away they don't feel as much of that magnetic anisotropy as you can see the those protons appearing here only about 2 . 4 2 . 5 parts per million so that's the protons over there that's those 3 protons in the novel OK so on matters how close you are if you feel magnetic and I started you have to be pretty and pretty pretty close to the pie system because let's talk about shielding the shielding effects that are related to being attached to carbon lecturer negative Adams so protons have an electron clouds surrounding them and I've kind of depicted that here With this orange smudge business and the intend to is to is to try to depict how that electron clouds shields the Proton from the magnetic field of our Proton and got my electron cloud around it's like I can't quite see the magnetic field there's all this electron density there that's getting in my way and so on so you don't feel the whole magnetic field of your typical Proton because of all that electron density around you but electromagnet that that are attached .period will help pull away some of the electron density they will diminish that electron clout they will they will the shield you another would take away some of that electron density inequality shielded so that's the effect of having a lecturer negative Adams close by so here I joined 3 compounds and discomfort over here coral methane that's the top spectrum and the protons and coral methane that resonated 3 . 0 5 parts per million so it a regular allocation would be down here in 1 part per million but that chlorine atom shifts in way over the 3 . 0 5 that's the effect of the chlorine but weapon to chlorine atoms on there now there is an even bigger effect that D shielding effect where you diminish the electron density the proton sees more of the magnetic field and so now those 2 points now it's 5 . 3 parts per million and we are dimension this chloroform here but the the core from solid this is the common contaminant dual-core forms now it's shifted to past 7 parts per million by having 3 core the sisters shielding the shielding is not as powerful of an effect as the anisotropy produced by nearby pine systems but it's still up to a reasonable effect so they can shift things from you know it's not often you have 3 elected negative Adams on a carbon atom that's sort of extraordinary situations OK so what else is powerful this is the mission 1 of the main reasons why pro-China Mars powerful and that is I can look at the area of the peaks and I can tell you how many protons corresponds to each of those peaks you can do this carbon that the area of the peaks tells me how many protons those there are so here is a compound with molecular formula CH Tando and I see 2 peaks in my hand spectrum from 30 years ago they would have had a little you'd really run spectrum in this little market would go across your screen whenever I got to the the the peak would start moving out In correlation with the area of the game so universal integration line here in red and so I can see years my integration lines this 1st because only 1 centimeter high in the integration won for the 2nd Beach is 1 . 5 cm high so that tells me that there's a 50 per cent more protons under this peak now what I don't know from looking at that but I don't know is whether that's why is that 50 per cent it could be this 1st because 2 H and the 2nd pick is 3 age it could be that this 1st because for H In this so I don't really know whether it's to forces 388 trade that would lead to 2 peaks it had this kind of size difference in the integration mind it could be for age and sex age like that would cause the 2nd peak to be 50 per cent higher than the 1st you don't know both the money manager that is you know the molecular formula you can back out it's not the 2 HGH scenario because there's no other protons in the spectra and your protons need to add up to the number of protons and molecular formula you also know that it is not 1 proton and 1 and a half Proton right there is no compound that as
one-and-a-half protons that's completely impossible like all molecules that unit numbers of protons sold its sometimes when you have when you go to the spectroscopy websites will give these integration lines and I'll just give you the heart of the heights of these integration lines in arbitrary units it could be centimeters it could be furlongs it could be microns I mean they could it's totally arbitrary on but that's stupid I am not going to do that for you in the lab for the level often give you peaks in the did tell you integration numbers listed below the peak words like 2 or 3 and I'm not going to do that for you readers I'm simply going to tell you the speakers for H will be his 6 8 all right there next to the peaks but I expect you to work the problems in the book that do that for you and I'll expect you to work the problems on the spectroscopy sites that don't have this question I I think did not an extended 7 deadline of public money in for Kaesong finish up in Amman on Monday
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Formal Metadata

Title Lecture 18. NMR Spectroscopy, Part 2
Title of Series Chemistry 51B: Organic Chemistry
Part Number 18
Number of Parts 26
Author Vranken, David Van
License CC Attribution 3.0 Unported:
You are free to use, adapt and copy, distribute and transmit the work or content in adapted or unchanged form for any legal purpose as long as the work is attributed to the author in the manner specified by the author or licensor.
DOI 10.5446/19487
Publisher University of California Irvine (UCI)
Release Date 2013
Language English

Content Metadata

Subject Area Chemistry
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: 00:13- Hash Oil 01:25- Structure of tetrahydrocannaboil 04:02- 14.11, 14.12: C NMR Chemical Shift Ranges 11:20- 14.11, 14.12: Practice Using C NMR Chemical Shift Ranges 15:40- 14.2: How many signals should I expect in the H spectrum? 20:46- 14.2: Diastereotopic or Enantiotopic Protons? Use the Z-test 27:19- 14.2: Use the Z-test, Slide 2 29:58- 14.3B: H NMR Chemical Shift Ranges 39:27- 14.3A, 14.4: Shielding and Deshielding Effects-anisotropy 42:23- 14.3A, 14.4: Shielding and Deshielding Effects-proximity to the pi system 46:03- 14.3A, 14.4: Sheilding and Deshielding Effects-electronegative atoms 48:32- 14.5: Integration of H NMR Peaks

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