Lecture 21. Using HMBC to Help Solve Structures


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Lecture 21. Using HMBC to Help Solve Structures
"Putting the Pieces Together"
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Lecture 21. Using HMBC to Help Solve Structures
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Nowick, James
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This is a graduate course in organic spectroscopy, focusing on modern methods used in structure determination of organic molecules. Topics include mass spectrometry; ultraviolet, chiroptical, infrared, and nuclear magnetic resonance spectroscopy.
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yes so as you may have noticed this is this is plan your homework and I want to do this is a demonstration regardless Our whether you've already solve this problem in fact I hope that you've solved this problem because what I'd like you to do is to be able to think really deeply about it and show you my perspective on structure solving and in particular were going to be talking about using each BC as Avery focused tool to help solve structures and specifically for the problem of putting the pieces together you've seen on the templates that I've given you have had this tremendous emphasis released I've tried to have this tremendous emphasis and thinking your way through the problem reading the spectrum getting the formula riding out fragments jotting down what you know jotting down what you don't know if possible and then being able pass focused questions H is incredibly data rich technique that also has ambiguities to it because we get to bond and 3 bond couple she got a huge amount of information a huge amount of data and what I'd like us to do today is to to learn how to use it as a focus too so I want is that through the problem from Silverstein at the the beginning and then focus on the agent Peter B. C. angle so this is this is problem 8 . 4 3
from Silverstein and I wanted jot down my yeah worked this problem just like you folks I wanted jump down my my impressions and working the problem so I look at it I look at this problem and I generally start with if I have I mean what's the most useful thing can get molecular formula and functional groups sort most general stuff and it will be able to get molecular formula in just a moment because we'll actually see all the hydrogen isn't all that card and so we basically will get them get the oxygen for so before we start with the animosity vector there looking at the IRA spectrum I see what looks like in all age groups I see what looks like a carbon yelled at 17 28 it's a little high for a typical tone right difficulty tones a little bit lower and might be an Astor had been emphasizing it's very hard in any sort of level of complexity to get CEO single bonds stretches associated with Astor's it's probably hiding right here at 11 88 sort of get a hint it but we'll see in a moment there's some other hints that .period pointing toward Esther we probably haven't l Keenan that's probably in Elkins ch it could be an aromatic will see in a moment it's not that's probably milking book alright mask Beckett's 200 molecular weight and EDI mass spectrum what I'm going to do before we before we actually get the formula so maybe at this point out just jot down sort of a question mark and the IRA spectrum Esther sort of my thing the RAF this point I wanna go and look at the proton NMR look at the carbon Amara and I really really really been emphasizing this notion of keeping the resonance is separate from the Adams in other words we know resonances it's something you can see we're going to be a signing those residences to the structure as reveal the structure and so we have a common language I go ahead and I simply letter the peaks 80 b Todd staring into the light yes the H I check and we number the carbon resonances and I'll go 1 2 3 sir chloroform for 5 6 7 8 9 10 letter I like to do a good job of working in 2 girls my philosophy every particular integral has experimental error associated with it the best way that you can do it if you know the number of hydrogen to the molecule Reno multiple hydrogen is add up a bunch and divide by the number of times if you don't order in a hurry off and you can get it by inspection with these into Rosa will hard to read their starting them right in baseline they're not offset you can use a ruler and draw straight lines you can slap agreed on it I'm just using my ever ever useful grin and if I'm looking I start to see a ratio that just a hair under 6 Herrandez success here under 3 here under 3 here under 3 this one's just just a little bit actually this is just a hair under 6 here under 9 so basically basically we're talking about like 2 . 2 . 8 Our units the 2nd evidence of an inch per hydrogen this guy is interesting he's coming up a little bit this 1 right at 1 . 6 ppm series coming up over . 6 and I'll tell you about that in a 2nd and then we see 1 that just a hair under . 9 and another that's just a here and there .period 9 so you pretty much have by inspections can go ahead and get and again it's really hard staring in here to wage for a to
H B 1 H 4 C 1 each for D 1 1 H for effort you have to wait for a thank you 3 h Fergie now each is an interesting 1 .period successes in chloroform solutions and chloroform water typically shows up at about 1 . 6 parts per million and so you can kind of see the water peak right over here she of this multiplicative reasonably symmetrical and then you have a little bit of water often decide here I would go in if I were at my own spectrometry I'd go in and zoom in and get better better look and see that I think you can see the encourages gives a little extra kick out for the water so H is to wage why is 3 3 h so in other words are molecular formula has a total of aged 20 and now it's certainly possible 5 had pneumonia or something that the median age might not show up on alcohol and so I'm not immediately locking and this is really important to have to be keeping your wits about you secondary Amina nature's aliphatic secondary meaning is a terribly hard to see alcohols can be brought alcohols can be with the water peak carboxyl like acids can be can be brought as well and can be disappeared after particularly furious chloroform verses Dumas Due to exchange if we look at the carbon in Europe's number 1 is that about 170 just a hair down of 170 about 173 ppm where you would expect for an astronaut where you'd expect for a key town we've got a couple of peaks over here if I want to go ahead at this point I'll say 1 is a quiet too was a quiet looking at the depth 3 years a CH June 4 is a quiet 5 is a H 2 6 is CH 2 7 and 8 are all ch Jews and then 9 10 and 11 all ch so basically if we do this we see we have seen 11 age 20 if we have symmetry in the molecule which you've gotten a couple of homework problems this week of course you might end up with account that's lower few if you're carbons aren't all different or you could have overlapping peaks but symmetries typical reasons if you have a point fennel group you're going to see for carbon peaks but you're going to have 6 carbons if you have a ring like a cycle propane ring and there's no serious entering the molecule you may if you have 1 point of attachment have to methylene so that the same but if I look here unsuspecting and alcohol unsuspecting and Astor I have 200 if I take away see 12 s 11 and aged 20 from that I get 0 3 sons reasonably happy at this point I think I have elected a former the next thing I do With the molecular formula is all started certain it's nice that have a score card here so I might for example over here jot down some thoughts Esther alcohol El Chino as some of the some of the groups that we're seeing in the molecule if I want I can calculate degrees of on saturation and another very useful thing member I don't do it by formula just say see 11 would be age 24 I'm at age 20 so we have to do and sent through so I can help keep my wits about me that also tells me if I a Carbondale and I have an Al-Qaeda and I know I have no rings in the molecules are right now the next place while any questions you thoughts at this sport it was doesn't let's see and this is actually good .period checking yourself I have an incredible ability to screw up arithmetic on my feet which with which means go ahead and and double double-checked yourself in the of of the city could indeed be the always so we've got some interesting points here you can already see so if you're reasonably experience under that anything that we have a serious center in the molecule now even tho I haven't measured the coupling constants I could measure the coupling constants varied conveniently give me a still here and you get the printout but very conveniently a typical aliphatic Ch coupling constant is about 7 her a methyl group next to a methylene is really very typical for this fuel and methyl group next to just about anything is going to be about 7 hurt so immediately from eyeballing this even if I don't know about 600 megahertz and I see this trip would here that's obviously a CH 3 2 two-hour CH 3 next to a CH 2 in fact I can write this as 1 on my fragments here because I think we're pretty obvious at that point for this and this year but if I'm looking at that I see OK these guys are leaning into each other we have maybe pattern it's obviously a big coupling constant this separation is at least twice the separation the triplets of cycle 14 15 hurts coupling constant that is very typical for a general couplings on the back of my mind I'm thinking stereo center something with the methylene it's tested that have mysterious center every methylene in the molecule is going to be die history topic but usually the ones that a further from mysterious center behave as if things are points so we look here we have what looks like an group it wouldn't have surprised me to see more complicated coupling patent for the Saffo group but it doesn't necessarily surprise me the CIA coupling constant and Empresas a less complicated coupling pattern just .period
Quartet I'm pretty certain I have an pretty confident I have enough Leicester prefecture looks like an old CH 2 CH 3 off of awful olestra but it could be something else that ship them are at this point it's time to get analytical and where I like to go next is actually the HM QC rather than the coalition as I was saying in discussion the other day the problem is you're drowning in data and in the cozy quite often in and a lot of the data isn't particularly useful you'll have to die exterior topic protons and both coupled to another to die history topic protons or even tho 1 1 proton and you're getting more information than
you need because you'll get the dire history topic protons are coupling with each other OK but will you get that each one's coupling to 1 of the protons are that gives you some new information but that's redundant if you have to die history topic protons coupled to die history topic protons now you've got lots of lots of data points that basically just tells you you have a CH 2 next to associates to so in order to help make sense of the data I go next to the HM QC and I'm very very rigorous about trying to transcribe stuff and I'm not super but I tend to really try to be analytical so I'm going to copy all of my numbers here the today carbon In a copy all of my letters to the proton access it is a and at this point again agreed is extremely useful if you're working on your own spectrometry you might want to do an expansion you might want no 1 to expand this region just so you can get a closer look and see what's lining up but if you're having trouble following with your eye and things aren't completely obvious slapping grid on the spectrum is a very useful way for example to see that this peak at 9 here is actually crossing with single it's so we have to mouthfuls that a right next to each other 1 of those muscles is a single 1 of them is a triplets and so you can very nicely see that 11 is crossing with Karen intended underlying is crossing with J and then we can go and tennis crossing with H I believe and again I'm going to cheat a little bit because tennis crossing with GE can achieve a little bit because it's hard staring in here and it looks like 7 is crossing with H and N F it looks like it's crossing with 8 and that's 6 is crossing with the ending he says 6 of the In 6 meaning unit looks like 5 is crossing would be saying it has no partner and it looks like 3 is crossing would and this information here really becomes mind Rosetta stone it really becomes the key piece of information that I'm going to be using now in building structure because now that's going to give us all of our easy connectivity is and you need to keep your wits about you about chemical shift as well so you know obviously for talking carbon Neil we're probably talking 1 is a carbon if we're talking about an Al-Qaeda we're probably talking about 2 in 3 being the al-Qaeda and it looks like 3 is a quart carbon of an Al-Qaeda and 2 it is a ch children came so it looks like we have a gem Jim Dine natural group here foreign fighter interesting member the region Europe Alkhan-Yurt carbon protons track pretty well With protons scale and if you're next to it not so what's well on halogen nitrogen those tend to be sort of if few next halogen or nitrogen is tend to be here but if you next oxygen usually tend to be somewhere around here in the 50 to 90 range depending on whether it's an old CH 3 at 1 extreme or say carbon it's a quiet with an alcohol other extreme if you're down further than that could be 2 oxygen and carbon recording of data had been OK so it looks like we probably have a a couple of carbons with an oxygen attached to them number 5 is a C H 2 and number 3 as I said was a C H 2 for is acquired 2 was a quiet 1 quartz and other things that are isolated are going to be problems later on so if you look at this spectrum we have 7 age and 9 J yeah don't show there earlier close the single intimacy 7 h is going to come in we have seen that has nothing on it and so we're going to have to have to to deal with you OK now at this point I'm prepared to go to my cozy this particular cozy the way they plotted the book to save space for allow you to give give bigger spectra they I'm they only plotted the axis on 1 engine that's OK because you can just bounce bounce off an over and then opt otherwise I'd just be bouncing off and up that access however you want to do it this is fine alright so now as I said I am ready to attack my cozy and the 1st thing I'm going to to do is again various slavishly transcribed so I have 3 a In 5 b and see and you really don't want to make a mistake this point 6 days 6 ADS the other nice
thing in addition to having it so that we all I can discuss things together the other very nice things about taking this sort of meticulous systematic approach to 2 this annoying J. here the other thing about taking this sort of meticulous systematic approaches it means that you can settle down the problems come back to it later and get your bearings a lot more quickly because it's not just a we've got a lot of stuff it's actually I've got this resonance and I still don't know where it's where it goes alright at this at this point we want 1 sort build up a fragments and I'm going to look at the cozy you can use a grade you can draw a straight line Sunday whatever whatever you like if you want 1 agreed you can do it this way if your fancy and you like to work off the online problems in prevented the command you if you're using a full version mature about the reader command you actually just slaps agreed right on the screen which is useful and you can even the parameters and acrobat said how following agreed but it's helpful with particularly with the book problems were they tend to be less generous with the extension so at this point I tend to go through and just just list all of my cross speak so if I if I'm working out but I only need to work on 1 side of their knowledge should be pretty symmetrical but if you're uncertain whether anything is noise check efforts on both sides of the diagonal if you're working on spectrometer you can go down the level or upper level with the times 2 were divided by 2 were the slider and you're going to get down to a level where you have 2 types of things at the very bottom you'll just have a basement of noise it particularly in data poor experiment but you'll also have artifacts baseline rolled you're facing is very important in the 2 d experiments in terms of not getting a lot of crap off the baseline so you really wanna take time when you're facing to do the job OK so we've got this peaks 3 380 10 Jerry and it looks like we have something of 380 and 8 F here a puddle ?question mark during the complete picture what's going on for some Sherwood's going on but at this point in analyzing the things I'm not sure OK this is kind and nice because you look hearing you say are idea we've got 686 F. but our another on the same carbon it's no big deal thereby history topic protons that are coupled to each other OK I don't need to stress about that alright ATF Cross 7 H and I think that that about a dozen or or so at this point I wanna put together fragments and this is what I'm using that L follow here we go again 5 days right 5 b 211 I absolutely fired B to 11 hide and known as you notice that you're using multiple sorts of tools in thinking about things because on the 1 hand you're recognizing when we just had the 1 the data in front of us you were recognizing the match of patents and coupling constant your recognizing the 3 her by 3 hydrogen Triplette upfield neck and a 2 hydrogen quartet downfield midfield probably went together as an ethyl Lester group because C H 3 splitting into a triple it has to be next to a CH 2 CH 2 slid into a quartet remember didn't have to be a quartet but CH to Split into a quartet probably is next to associate story could be next to a CH 2 and H word had the same day values I don't know for sure but now with this and everything else I think I can be can be pretty sure so let let me started jot down what I think I have at this point for my fragments I think I have always see 5 age to see 11 H 3 on as 1 fragment and I like to use that way of doing it were put the number on the carbon the letter on the hydrogen so means carbon 5 is part of a CH 2 groups with 2 protons B and see 11 as part of the CH 3 regrouped with 3 per tons of alright what else do I have in my in my scorecard here well that's C H H 2 S Cross speak with 67 H 2 Each gives me another fragment the other thing that I like to do in keeping score at this point is I like this show my balances it helps my thinking to say OK I that means I have a valence here this helps me think about where my unfilled valances are all right what else do I have in my scorecard card I have an al-Khaimah and it's seeing 3 h a French a if I were thinking about it I might say maybe these the 2 distinct hydrogen is here if I later went on and I said Oh wait I thought they were of 1 type of hydrogen but there too and this is important to my analysis all I'd need to deal with this .period is say alright were going called 1 of them a and 1 of them a prime and the nice thing is you're not really number you're really lettering your whole spectrum if you suddenly say Oh wait this resonance is really 2 residences if I decided that age was really 2 residences and of course H really are 2 residences because you have
a serious center the methylene standardized Street topic methylene some like the cozy we saw on discussion section the other time where I was going on we're talking about highly differentiated highly and isotropic CH 2 groups but it's the same same sort of deal so if it were important I could say H & H prime FNF prime if I really started to see distinct cross speaks but honestly I don't so this is absolutely fine for the analysis OK so I have seen 3 and then see 3 seems to be bound to see to which is acquired it we have
we have visitors thinks this situation here where we see this nice crossed speak off of 10 g right 10 she is a methyl groups 10 g is kind of at this position of about 1 . 7 November I said I like to keep some numbers in my head in my sort of quick and dirty is a bonanza methyl is too a Mathilde itself to Aqaba Neil is 2 ppm and a Mathilde that's a little like is about 2 ppm and then I said caveat if you really want to keep an extra number in your head keep 1 . 7 4 that elect so this is very typical of an alone-like like manifolds exactly what you'd expect for its position as exactly the sort of thing that you would expect for a little like coupling so 10 H 3 G comes here and in this kind of makes sense of the Cross speaks so right we're seeing worsening this crossed speak here we're seeing this low cross speak with 8 so if you want to will get it from the H NBC if you don't want to do it but if you wanna get at this point it certainly makes a heck of a lot of sense the 3 is crossing with age so I can put this said if there are uncertain about something if you're concerned about a connection put it in with the dash line it's a great tool to remind yourself on your scorecard on working out the problem if you're worried or concerned about something so at this point we need to figure out the rest of our stuff so let me continue continue with our score card we have Carbondale and that's our 1 I hope you can see this from if you're just about just about on the edge of the screen here alright so we have a carbon we have some other we have some other problems here we have R 6 indeed HE and I'll keep filling in my balances to be good about this just to remind us that we have had some issues of valances here and then I have some carbon and there may be redundancy here I have some carbon that's connected to see 19 8 3 J and that carbon has the baby the acquired a hassle because we're isolating that Mathilde Over here and I have some other carbon remember at this carbon for and that carbon forest pretty far downfield in the sea 13 animal spectrum itself it's just that just about 70 parts per million and that's that's gotta be a carbon next to an oxygen alright so at this point that that's kind of my thinking now certainly certainly by brute force you could now assemble case you would basically start to try all different possibilities and eventually the crumbling come up with the right structure I like this molecule because it's a simple enough molecule that you could but what I'd like to show you now is how HM BC really is this makes this into a much more ah systematic let us say process alright so at this point I'm going to pull up the agent BC spectrum and we get a lot of across your textbook as I've railed about his Dr. did say Chan BC spectra so I've literally on doctors the agent basic what the textbook bid which I don't like is it's taken out of the HM QC type of prosperity in the spectrum is no reason to do that you should be able to identify these you're going to see them in real data the HMV we've talked about this notion of delays we've talked about the idea that you're doing that what's basically a series of pulses and delays were here delays are optimized to different things like that coupling constants of we talked about our debts spectra last time I said the problem with the depth spectrum is you choosing you have to to choose AJ value for the depth spectrum you're going to choose a typical day value and that's going to give an optimum performance at that J. value and guess what if your Jay's or at 145 hurts if their lawful 125 hurts 160 hurts you'll be fine but if there are a lot different you'll start to see other things no agent is optimized to small couplings small couplings typically mean on underwater 0 to 20 hertz and the spectrum downstairs is sort of centered at 10 which pretty much catches at all but that doesn't mean you're 1 bond couplings that 125 parts may not sometimes come in and say you could see your 1 bond couplings the pulse sequence remember and adapt how we turned on the proton D couple on the final acquisition In a typical HM BC you're not turning on the proton decouple in the final part of the acquisition which means you're seeing your ch couplings there most of those are 2 bond coupling so most of those on the order of and 2 and 3 bonds so most them or on the order of 10 which means OK when you're seeing something where Europe's troubled bid
wide the pixel that wide because you're seeing the couple but when you're picking up the 1 bond coupling which is not what the experiment supposed to pick up it is extremely obvious you get these sort of vampire bites around the peak and so I just put across the region that ought to help remind me of what's going on right said this is peak number 11 and this is 11 over here is 11 so those 2 vampire bites there the 1 bond coupling it's trivial lets the information that's already in your agent QC spectrum but it's confusing and this data rich experiment selecting go through and now systematically Number 10 9 8 7 6 5 4 3 1 house systematically number my carbon access call once again slavishly right my labels on the proton Axis 3 8 5 B. C 6 D 60 80 F 10 g 7 h I already did 11 and you can pretty much see all of your sort of vampire fights here there happened to be 6 pairs of here so we're getting 1 around 5 that's your HM QC pattern we're getting 1 around 7 catcher Raychem QC pattern were getting 1 around 6 in were getting what 1 around 10 in 1 around Our even without these types of information you were still extremely data the question becomes worried after computer you just go ahead and suck in all the data and fitting the pieces together that way but as a person you've got tremendous strength that we've already seen apparent recognition we saw we could read that I thought secret In the yesterday we could read the dire Styria topic Nathalie and you were seeing that from this whole host of little things with the guy history topic methylene from the big Jay value from the peak stenting into each other it's the same way most of you were able to tackle those coupling problems on the midterm exam and just read and say OK this is this nitrobenzene This is that nitrobenzene This is this methyl parodying because you were starting to recognize the magnitude of the coupling the tending of the peaks and so forth you got some tremendous advantages and yet we've also got this ability to offer this issue of how do we avoid confusion here so usually what I like to do artists start with my problems and in general my problems are going to be the isolated in general is the peaks that are isolated there going to be both the tough ones to put together like 319 HJ because we don't know where it fits inside coupling into anything but they're also going to be the sources of tremendous strength because those isolated ones are then going to link to the other isolated parts so let's start with the carbon the carbon is 5 B 2 6 5 2 2 0 1 and 6 indeed and 6 2 1 is that very very useful the so remember BC can pick up 2 and 3 bonds couple and the problem is you don't necessarily know which is which that's the Wheeling tough thing with this technique later on will talk about inadequate which is a very powerful technique it's like a carbon-carbon cozy but not a very useful technique because of the low natural abundance of C 13 units very very atypical there have to see the team's next to each other and molecule that's incredibly powerful because it means you can assemble your holes carbon skeleton like a cozy process but the problem with h NBC is you've got both to Winfrey's you're always second-guessing yourself so whenever you can avoid second-guessing it's a tremendous breath of fresh air so here the 5 5 B 2 0 carbon 1 is very nice because that provides a linkage that we kind of story knew this wasn't after Leicester but this tells us cruises the 3 bond coupling is going through there so we can't go any further there can't be any intervening Adam this 6 is less clear because it could be directly connected but at this point I can't know there could be an intervening that's still we know that the Sixers isolated we know that D and isolated they're not J. coupled anything else but I don't know about this policy here at this point so at this point I might write a big question mark here alright I'm not going to go ad nauseam through everything because a lot of the information is redundant so for example Pierre were seeing worth seeing that true is crossing with 7 so this is a for us 2 10 G Cross too In 7 8 2 2 and in a way it could say all of that is redundant because I've already reply I've already placed groups on here and so your children you notice that this is a perfect example if I weren't already sure of this a pretty sure Bialik couple I wouldn't necessarily know since to its crossing with both 7 H and a I wouldn't necessarily know which end this is going because it's tool and 3 bond coupling so Court couple either way so the only thing that's really told me this I think by this point I can go ahead and turn this into a stream to us solid line the only thing that really told me that was the cozy but fortunately will get enough other things because
we're going to see in just a moment what attaches over here to said alright so let's focus let's continue to focus on our isolated peaks so if we look at full and we go with 4 we have 98 of we have 7 h 2 4 we have 6 DNA III maybe the better way to do it is 6 D U 2 4 and we have see 2 1 no Art we have and we're pretty sure at this point we're pretty sure we have this alcohol were pretty sure that C is is the alcohol it's isolated I think at this point we really can't say alright here's our C were on 4 now former is going to be a very very important and and I guess the thing that's confounding to me at this point is the fact that we've got knowing J 2 4 but that's not necessarily saying that that isolated methyl was directly attached to were running out of atoms or going to be good in the 2nd we have 7 and therefore we have 6 the need of war they're probably all attached but watch what happens if I now pick up on another isolated once I probably can start to infer things but let's continue with another 1 of our problems children another 1 of our isolated so let's go off of saying we wouldn't be seeing cost peaks off of see if it works changing rapidly if the alcohol and see where not residing on that on that oxygen for you know several 100 server 10th of a 2nd if it were changing rapidly usually the last satirically congestion alcohol the more rapidly it exchanges so usually a primary alcoholics changes rapidly usually sometimes a 2nd secondary is slow sometimes it's fast usually tertiary tends to be slow or just Mauceri congestion harder for molecule water again make exchange Diaz said a fire core form passes through aluminum not sample but just a coffin through flame referred astride aluminum to good way to reduce exchange because you're getting rid of mass in the simple that here we happened beautiful beautiful coupling off of sic and stuff you look at the Cross speaks again we're going use things focused way we have seen no sign of C 7 see sex and so you won't get all of these days crossed the and that that really is nice because remember here you're going to be picking up here to win 3 bond coupling unless you have any intervening coupling through double bond were sometimes you can pick up for bond coupling remember sometimes like a saddle leans we saw how weird the acetylene behave dimensions to bonds and 50 hertz coupling so you can get home Oprah Barger like coupling but here this is pretty nice we've already taken care of up to over so what can the valuable this is as a linchpin every cause speaking now we get is going to help give us our connectivity so we have seen before that's going to connect over To see sex because we're getting that crossed speak here so we know that this is the rebound that's as far as we can go where really lucky at this point now we get this crossed speak over 2 7 and so again that's just sewing this whole molecule together we have this crossed the 10 9 and we said already here remember we had this fragment we weren't able places but it could be redundant because we're running out of carbons we have this cross feet over 10 9 and so there's our seeing H 3 Jay and now this whole molecule is sold out so if you look at our structure right now I'm just it is a guess of brought real small up here so here is here's the whole structure of a molecule we have our 7 and 8 over here a six-year FL Group are isolated methyl Our isolated hydroxy and this this set of course peaks here has really been key now the good news is there are other isolated points in this molecule that can put things together so when I tried to attack the problem gonna start with the isolated ones obviously eventually you want to go back and sort of check yourself and see that everything is consistent but let's take another point of attack here so I'm just run down this track of 9 9 and and see who 9 jails crossing the 7 9 J is crossing with on 7 9 J is crossing with sex and 9 J is crossing with 4 and so you look at that a call OK that's giving me this same information see the ancient BC is reeling screaming out at me through the isolated ones there was a gift that we got 8 state aid saying might not have couple that's an alcohol 8 saying it might have been exchanging rapidly if there was a menace in our sample was a gift that we got it just gave us the whole problem but we get that same gift right off of carbon non-aligned because not language is giving us and so were crossing over to here and again remember your hydrogen Virginia 1 bond from hydrogen J 2 carbon 1 bond from carbon 92 carbon for and so on any other course speak now has to be attached directly to carbon for so we see across the 7 we see across the sex and we see across the 4 that to bond coupling so that's giving us the information I'll take 1 more isolated carbon just for the for the heck of it it's not really completely isolated but it's it's 10 g and so if we go off of 10 JT let's see we have here 10 g with 3 In
changing with 8 over there and so if you look at that that's also giving us some information we had at 10 to 3 Bialik coupling by the proton NMR so that information was nothing new but you don't get a like coupling right through here so so this information here at 10 g to aid is actually useful had we not enabled the plight had we not been able to place 8 directly onto had we not picked up that'll a coupling or had things been more complicated confusing or had we only at that point had this age NBC crossed the between 2 0 0 and 7 and 8 remember I said to its crossing with both of them is crossing with both H F N H H H and we couldn't be the sure about that if I if I wasn't certain at that point then we could have gotten that later on arm from this cross speaks so there's multiple pieces of evidence all pointing in this direction anyway this is how I view each NBC is being
incredibly powerful for putting pieces together I want to show you a couple of glasses things that sort of common features that are kind of kind of cool there are also germane to what to some of the upcoming homework so it's it's worth actually keep in mind 1 thing that's very cool is OK if you have 2 CH 3 days on a mouthful so remember how I said you can get these vampire bites you can get your 1 bond couplings but if you're going ahead and if you have no Styria center in other words if these metals are either not die history topics were the coincidence then you're ancient BC even if you say these vampire tied by type of cost creates fear and even if you say so here's your Mathilde and here's your work your methyl Anderson 13 here's your methyl in the 8 1 even if you see those types of cross thinks this is a relay champion said "quotation mark speak here because the 2 mouthfuls or crossing with each other so that's kind of cool but in this particular cartoon example there magnetically equivalent if they were magnetically in equivalent if their advisory topic then you'd still ch NBC picked by the way the tough thing about agent the state is you're not guaranteed to get across speak because your diet particularly and 3 by so to bond is weird because you YouTube on Jay's end up being all over the map bold usually show up at No 3 bond is weird in a different way it's weird by die here reliable by Acropolis relationship so if you're too old if you're hydrogen so if you have a guy hand-drawn angle that's defined his age CDC's like so if you have good overlap between this hydrogen and this carbon good geometrical overlap meaning in died Perry pointer Austin Perry Point a relationship you typically get a big check it shows up in the region the but if these 2 are at close to 90 degree angles you're not going to get across the typically and so that's the 1st thing about each NBC that's really confused the beauty of methyl groups it With the methyl group no matter what you're always going to have with least you're always going to have protons and good guy he'd reliable so methyl groups isolated methanol methyl groups in general end up being extremely valuable for each NBC but we also see here that the isolated methyl groups are usually the problem children because you don't know where to put them and fortunately there talkative problem children because they will talk to you In the agent so that's a very useful once a couple of other things just to keep in mind carbon deals if you've got like this if you've got something like this whatever you know the problem is you don't know if it's to bond coupling of 3 bond coupling but if you can build up your pieces and say Oh well I've got both of them then you can figure out alright that Cardinals attached to 1 in the other but let's see I guess I don't know if this comes up we already saw and Esther some people upset today although I didn't know that you could get coupling through Harare Adams but coupling occurs through carbon-oxygen bonds through carbon-carbon bonds through carbon nitrogen bonds so for example an animated here like so again near Carbondale can be a real linchpin you can get all different protons coupling with that carbon wheels so they can they can end up telling you lots and lots of information in pieces together but what's nice is carbon often isolate 1 spin system from another spin system and it's those isolated spin systems what I'm calling fragments that are so hard to put together and that's why in BC is so valuable was the focus of our this should give you the skills to attack the problems not for this week's homework said but for the next week's homework set were the molecules are going to get more complicated and we're going to be more dependent on being able to systematically put the pieces together not only that you couldn't tell a great question James is asking Could we tell the steering chemistry of our center no the Rossoneri would have the exact same spectra as the 1 in India anti-America or the other in India where the only way to differentiate them would be to add something cobbled to make on Moesha Astor here for example whether corralled river ties engage in order to use what's called a coveralls shift reagent which I haven't planned a section on 4 costs but it's basically a Lewis acid that spiral that will interact with the 2 any tumors differently so you need carnality to distinguish morality


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