Lecture 28. Some Other Useful NMR Techniques

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Lecture 28. Some Other Useful NMR Techniques
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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.
Setzen <Verfahrenstechnik> March (territory) Singulettzustand Topicity Deep sea Wursthülle River source Multiprotein complex Emission spectrum Toxicity Taxis Spectroscopy Collecting Connective tissue Azo coupling Tool steel Extract
Spectrometer Activity (UML) Diamantähnlicher Kohlenstoff Plant breeding Wursthülle Methylgruppe Chemistry Artifact (archaeology) Molecule Ageing Colourant Tool steel Setzen <Verfahrenstechnik> Selenite Octane rating Carbon (fiber) Hybridisierung <Chemie> Protonation Wine tasting descriptors Emission spectrum Hydrogen Azo coupling Silencer (DNA) Tablet (pharmacy) Chemical compound Aage
Lactose Spectrometer Resonance (chemistry) Binding energy Set (abstract data type) Alpha particle Elf Ice Molecule Lake Electron Naphthalin Transformation <Genetik> Citronensäurezyklus Lye Opium River source Erdrutsch Alcohol Anomalie <Medizin> Dispersion Lone pair Emission spectrum Spectroscopy Acid Camphor Azo coupling Chemical compound Polymer Aage Cobaltoxide Condensation Nahtoderfahrung Sunscreen Organische Verbindungen Methylgruppe Gasverflüssigung Common land Tool steel Ausgangsgestein Beta sheet Mixture Process (computing) Setzen <Verfahrenstechnik> Metal Tumor Alkane Stickstoffatom Glasses Protonation Coordination complex Water Magnetism Functional group Coordination number Chemical structure Recreation Base (chemistry) Separator (milk) Angiotensin-converting enzyme Lambic
Lactose Ruthenium Finings Chloride Ocean current Wursthülle Stereoselektive Synthese Muscle relaxant Quartz Molecule Ausgangsgestein Benzene River mouth Chromium Setzen <Verfahrenstechnik> Potenz <Homöopathie> Tumor Concentrate Glycosaminoglycan Protonation Multiprotein complex Alcohol Wine tasting descriptors Electronic cigarette Emission spectrum Systemic therapy Spectroscopy Magnetism Azo coupling Breed standard Microbial cyst Library (computing) S-Adenosyl methionine Stuffing
Lactose Thermalquelle Benzoic acid Intergranular corrosion Fiscal year Materials International Space Station Experiment Alpha particle Molecule Tidal race Colourant Öl Derivative (chemistry) River Periodate Dye Chemical reaction Alcohol Anomalie <Medizin> Wine tasting descriptors Emission spectrum Acid Spectroscopy Azo coupling Chemical compound Brass Zunderbeständigkeit Lymphangioleiomyomatosis Stuffing Biomolecular structure Stop codon Cyanide Ester Activation energy Species Plant breeding Spawn (biology) Chemical plant Ocean current Carbonate Wursthülle Muscle relaxant Columbia Records Methylgruppe Man page Sample (material) Origin of replication Table wine Human body temperature Common land Amino acid Active site Tool steel Mixture Monoamine oxidase Process (computing) Chemical reactor Area Mixture Tumor Carbon (fiber) Protonation Electronegativity Water Taxis Phenyl acetate Initiation (chemistry) Functional group Medroxyprogesterone Ion channel Carboxylierung S-Adenosyl methionine
Setzen <Verfahrenstechnik> Diamantähnlicher Kohlenstoff Ranbaxy Set (abstract data type) Wursthülle Columbia Records Anomalie <Medizin> Molecule Emission spectrum Azo coupling Macrocycle Auxin Side chain
Tumor Species Human body temperature Pedosphäre Protonation Mixture Biomolecular structure
Ethylene glycol Omega-6-Fettsäuren Propandiole Columbia Records Wine tasting descriptors Emission spectrum Molecule Water Solvent Mixture Song of Songs S-Adenosyl methionine Methanol
Ethylene glycol Peptide Muscle relaxant Methylgruppe Alkaloid Molecule Sample (material) Ageing Protein Mixture Octane rating Elektrolytische Dissoziation Chemist Adamantane Protonation Wine tasting descriptors Water Emission spectrum Ingredient Acid Functional group Rübenzucker Chemical compound Zunderbeständigkeit Base (chemistry) Deuterium Methanol
so what we've been doing in the costs up until now as I've been trying to to presented a very programmatic and systematic approach to spectroscopy but particularly to animal respect trust the I wanted to give us a small collection of tools for a toolbox into teachers how to use those and then on to them and particularly allow us to build an appreciation so we started into Deanna with toxicity and cozy and then we are Ariz and I'm sorry the bees H uh in QC and cozy and we learned how to use those and then we got to appreciate how taxi could help us in certain situations and also how BC could help us put the pieces together in the last lecture produced chimp QC taxi which helps us deal with overlapped we've also in 1 Indiana more we learned a little bit about the theory of the techniques we've learned about coupling we've tried to undress get a deep understanding of coupling we've had a few special topics in their we've talked about dynamic in Amara which I thought was particularly useful and relevant we've talked about the nuclear over house a effectively reintroduce sound some experiments over there now outsize thinking about 2 days lecture and really trying to think what I wanted to do when I wanted to break away from their aware of things that I found useful for the years or think you might find useful that I don't want to introduce a systematic fashion you may not need these in your toolbox you may need them in your toolbox you may find 2 or 3 years from now on your project you have a particular situation that comes up and you reach back into the recesses of your mind or into the handouts and say Oh yeah I recall he mentioned this in class and now I have a problem that I can use so today's lecture is going to be a little different it's going to be more fragmented it's going to be things that I have found important or in the case of the 1st 2 which I haven't used myself think you might find important and I've given you some of my my sources here and I'll give you some more hardship on some stuff from for my own work and somebody sent a couple of handouts over to change that right so worried like where I'd like us to start is with the issue of coupling and we've got we've got really good and analyzing multiple edits and we've also learned how to address making connectivity when you have complex spectrum when multiple its overlap and across the 1 thing that you lose out on wing multiplex overlap is often it's hard to analyze the multiple it's because they end up being overlapped with another multiple it's I wanted to mention to techniques that may be useful to you in your own research you're going to get these on the final To DJ resolved In Amara is 1 technique and the other 1 is Nkosi which stands for exclusive correlation spectroscopy in this that's the capital only cozy which is exclusive he didn't sell well say both of these can help you extract J values from complex multiple and I just took a couple of examples from sources that I like and the source that I like these days for modern NMR experiments to the extent that I have now bought the book 3 times 1st in the 100 and more version and then in the 2nd edition which is 150 more and more at a March permits and now in the 200 and more and more experiments version is is this book here and I'll just show you very briefly the 2 types of 2 types of spectrum here so this
is this is in that book this is an example of the 2 DJ results spectrum and it's of Avery simple compound it's a two-dimensional technique but it's a two-dimensional technique where you have on the F 1 axis you have H and Amara and on the F 2 at I'm sorry in the effort to access and on the F 1 axis you have J and so just say conceded see this for the 1st 1st time what you have here is basically a projection of the peak like this in other words this speech is a quartet and so along this axis we see 1 2 3 4 and if you want of course on the spectrometer you can then go and get this out separately and basically go along this dimension because remember these contour lines are basically piece coming out like this so this is obviously not a complex spectrum this is a very very simple molecule but you can see what it does to the multiplex of for example here we have a Triplette and you see 1 Maine to Maine in 3 main pieces old bit of artifacts here this is the Mathilde you have a double that of doublets you have a doublet of goblets because you've got your coupling from the methyl group to this hydrogen and then you've got a little like coupling over here and so you can see you doublet of double its here for line so that if you pick this up we just be a doublet of doublets here as they said this is a trivial molecule you would have no need to use this technique for such a simple molecule but where you would bring this sound would be in cases where maybe you had a couple of overlapping multiplexing you really wanted to get your J values remember we said J. values can be very useful for dealing with stereo chemistry and so if you want a figure out OK Dravid 10 hurts coupling constant do I have an axial axial interaction driver 3 herds coupling constant this can come out here you have a double that of quartets In another double of cortex that of course is this 1 is of course associated with this this Proton where you've got a big big trends coupling and then about a 7 hurts coupling the manifold and you can see your lines so you go 1 2 3 and 1 quartet In 1 2 rating war is the other Quartet and here you have another tablet of quartets and you can see here for 10 year so put that away in your toolbox for cases you may need it the this experiment isn't too widely used because in cases where you have really bad overlap you're still going
to have this in other words if I had another multiply right on top of this you would still end up experiencing the 2 of them right on top and see unless they were a little bit separated you wouldn't necessarily be able to to solve anything the technique so this right well you have listened in In their yes so this this next 1 is in the cozy and I think that's the 2nd 1 in your your hand out here and I just want to show you how to interpret the technique in part because when you look at the book for the 1st time it's a little bit confusing so they've taken another trivial compound they've taken a slice that's not on the diagonal so here's your diagonal I'm in other words of course what they've done is an expansion of course you could take the entire spectrum they just didn't in this In particular example I just want to show you how to interpret this so what we're looking at is a molecule that has 3 hydrogen several mutually coupled to each other with different coupling constant so and it's also confusing it's not a square it's not a square things on this axis they've taken the region from about 3 at about 3 ppm and here they've taken the region yourself from about 3 . 3 . 4 or 2 . 8 to 3 . 4 here they've taken it from 3 . 3 to 3 . 9 so that encompasses all of the hydrogen C 1 multiplied for the H 3 a another multiplied for H 3 B which is not on this 1 and so it's a double that of double a doublet of doublets and another aged 2 and I just want to show you the cross speaks here because it's from the cross peaks that you can extract the Jays and so did you see this pattern of old squares here is evil square for docks here In 4 dots here this is giving you the "quotation mark active coupling this is giving you the coupling between 3 B and to and sorry to and the distance basically any of the distances in the squares that distance is the J values so of the distance within the square is the J. value and so that's the reader to be here at 3 3 5 2 to 3 days here we have 2 0 2 3 a and initially it's confusing until you look and you say Oh yeah I see 1 square here and 1 square here you see that and again it's the distances in the square it's this distance that's the age for 2 to 3 s this was the Jafar too 2 3 so you can extract very easily the Jays between different protons from this type of experiment and if you're looking and trying to silence some staring chemistry based on this understand it can be it can be a very valuable tool to add on here we see the 3 8 2 3 being coupling and of course this is the 1 this is the 1 that's going to have the the biggest coupling because that has your gentle coupling general couplings are generally bigger not always because they're highly variable based on hybridization but an sp 3 carbons the generally the biggest and so now you see are overlapping squares here I think what I will do is is to highlight the square so we have 1 square here you may well do is get get fancy here pull out pullout in different different color the highlight the others where so from the sides of the squares basically from putting your cursor on this pattern this . you can get from that distance here you can get the Jays 380 Green Bay again maybe not so so important for this very simple molecule but more important for more complex system all
right so that's what I want to say about it about that now the the 1 that we haven't the 1 that we haven't talked a lot about is carnality and using an animal spectroscopy as a tool to analyze and anti-American purity you can cost the thing that I've emphasized in the course is that in empty Amir's have identical specs In the absence of some costs some source of care ality you can't tell and or molecule from an S molecule and yet many times you're doing some synthetic transformation and you want to ask what per cent III did I generate my molecules in where do I have a single anti-American or do I have a mixture of any tumors and this sort of question that needs some source of carnality and someone introduced 2 ideas here will start off with Carol shift reagents and then I'll talk you talk to you about Carroll director ties agents In in order to talk about how so I'll say they're useful for determining an anti-American purity In order to talk about coveralls shift reagents I 1st need to introduce a different concept and that concept is 1 of the nite induced if free-agency related concept an earlier concept and plain old land tonight and do shift reagents have largely fallen out of fashion they were developed that when in a Mars were much lower field an overlap was a much bigger problem when you had a 16 megahertz cinema spectrometer very few of your multiple it's were beautiful multiplex and a lot of spectra were just overlapping he heaps of jobs and the idea behind Lanpher denied India's shift reagents was to add Parham magnetic Lewis acid that would coordinate to Louis-based Adam on your compound buying to wet and Parra magnetism creates its own little magnetic field so you would create extra dispersion of the molecule that would be related to where the Our Louis where the shift reagent was in relation to other Proton and general format for these reagents many of them were based on your opium their land I'd slanted nights have unpaired electrons unpaired f electrons and many all of them were based on Europea and some of them Prasad amendments some of the others and the general format for them was an act that type of Lincoln act act as a single set Hussein act that is in organic chemistry or coordination chemistry of OK so they're all based on an act the lake and with various types of art groups here and so the metal is typically in the plus 3 coordination states you typically have 3 of these and the great thing about land mines they literally make like a little kind of here's your your opium and you've got this this and this and then you have a spot where you Lewis Louis-based can coordinate let the knives will take basically as many Wiggins is you can throw around so 2 of the Nolan Cairo once before we get to the Cairo wants 2 of non Carol ones that are popular and these are by the way this is all in on the other hand out that I've given you so I used to use friable and this is all taken from friable and but I've worked with some of these compounds myself the Franklin book I used to use as a supplemental text required supplemental texts for the course I like it the few really good chapters the dynamic and more chapters pretty good so this 1 which has tutored groups act CAC has to methyl groups at the Siegel a set made this 1 is called DPM DPM is just died table we'll method not 0 and so the reagent is in the the mr 3 another 1 a lot of them have fluorinated groups and particularly the Carol shift reagents and so this 1 here again it's an act act type title again and this 1 has won entered the room group and 1 hexafluoride probable grew and this 1 is called F 0 D and so the reagent is EU F 0 D bring
In so what these reagents is the molecule will bind to it and then they will create a high degree of magnetic anisotropy usually just battles smidgen of the reagents I wanted to show that to you and then talk to you about the Carroll Carroll ship agents so this is really a beautiful example here so this is on page 336 of Europe friable and hand out In so this is a spectrum of Texas and all all is going to look like crap that any field NMR because you've got all of these mad Filene's right you've got the alpha methylene that's going going to be very disperse even at low field and you've got a debate naphthalene it's going to be at Highfield little bit separated but then you've got the Gamma Delta and Epsilon methylene instead Walhi together this was done low fields the bidders on top of and then you've got the map so this is sort of your typical long chain alkyl groups so they add a little bit of UFO DIA UDP and 3 and look at what happens dear factor you end up finding the shift reagent is reversible pseudo even beautiful equivalent of shift reagent goes on and off rapidly on the enema timescale it binds to the oxygen and then your methylene shift down here your beta Europe Bader absurd so your alpha methylene ships down in your beta shifts less far down in your damn near Delta Nu Epsilon and your Mathilde so what's happening is that that both the distance in a geometrical relationship to the shift reagent that's resulting in shifting downfield from the Parra magnetism the further it is from the further the protons are often the paramedics said the the further you on and up but the less you end up with downfield shift and is also an angular relationships are right so that's sort of the background as said these have I think they're are actually useful tool for solving overlap 1 arm but they have largely fallen out of fashion for that but Cairo's shift reagents is still very useful because you can have either of the 2 when India Murray's binding with different binding constants to work coveralls shift reagent water different geometrical Leyshon ships regardless what happens is the protons of the 2 1 and tumors will separated in and so you can see a methylene for 1 and tumor and as methylene for another in Cuba takes care morality to distinguish corollary at Cairo's shift reagent makes makes for not that carnality and that type of interaction so OK so Carol shift reagents I'm sure there are more out there but the ones that are popular the ones that used are based on can basically it's an condensation of campus right so this is the structure of camphor camphor has a key tone over here it has a methyl hearing has a couple of falls on the bridgehead we've seen camphor before and some of the problems it's a very common outcome in Turkey annoyed structure and by doing an algal condensation you get an an attack here I'm not drawing missile destroyed as a single resonance structure rather than a dotted arrow but you get an act that type of link in and then you do an algal condensation and you can do it with try and you don't do it you buy it from Aldridge you can do it with try for methyl less about the height were hacked to floral Mathilde puerile the Hyde captive floral at the Burau the Heights you can have either try for methyl groups or try have the floor poeple group and these respectively call you and so you have 3 of these on opium just like we did with the other type of late in life is just another rack accolade and so you have the regions that are called EU TFC 3 TFC stands for a try methyl camp for Otto the war in the EU HFC 3 for the have the floor the Pro so let me show you 1 of these compounds and will look at this with so did know we've got our shift reagents so before we had the alcohol what will do in the next demonstration His will look at this where a Cairo Lemieux with fennel effort so the nitrogen has a lone parents Louis basic can coordinate and also you 2 slides there continuing in your friable and handout so usually what you do when you work with these is you tight trade in the reagent because you don't
want to watch reagent if you add too much power will shift reagent you just broaden the spectrum and turn at the help because Parra magnetic Parham magnetism induces relaxation and so if you make for a very fast relaxation you wind up with broad alliance remember you have ever Proton stadium 1 spin state for a while for like hundreds of milliseconds in order to have a sharper life if you're if your Proton is flipping spin states on the order of Unit 10 milliseconds heard Her 30 ms your lines going to be very fact member we it deliberately added power magnetic reagent chromium act act when we talked about the inadequate experiment because we deliberately wanted to get those quartz and other problems to relax a little bit faster so you basically tight trading your shift reagents so they start this is pure fun at Fulham and this is a single an anti-American so this is pure I'll say purer single and anti-American and so then they tied trading in increasing amounts of shift reagents so just look at them the following year and your Mefin as you type trade more and more it starts to walk down feel more and more and at the same time now and so you basically want to get it shifted a bit but not so much that it's all completely brought so they did this 1st with material that was an anti-America purer and then they wanted to go ahead and see if you could distinguish to an empty immersed and so in this case they took this is an NGO and rich and so in the end Ontario rich you'll notice that the 2 methylene is for the 2 the tumor fines for the 2 in emerged now so this is center-left Bellamy and so the Mets signs for the Tuen Ng murders nail separated out because you have the spiral shift reagent that interacts differently With the 2 women Ng and so they undergo different shifting and you can integrate them and they're separated here they do the same experiment with the made you see that the peaks are about equal in size so this can be very useful cause if you're working on a project that's asymmetric Atallah cysts and you want to be able to go ahead measure urine tumor peer-review work out the right system to distinguish urine and humorist standards as quick as taking an animal or spectrum really my so the protons in the Cairo shift reagent while are largely blown out of the way by its parent magnetism but as you'll see in this crap particularly in high concentrations this is 1 one-to-one 1 you'll notice here we see I think it's 1 of the mouthfuls of your scholarship reagent here some of the stuff of your so the answer is yes if you do afterward about them but it can be a very nice and very handy technique I feel get multiple binding points and if you had seen alcohol immediate Woodbine primarily to the Amin and if you had like an alcohol and he fried behind primarily to then you would have a defined to all of you that have to see if so any kind Carroll's shift reagents are not what 0 4 and a Carol ship free-agent well it would shift everything around whether or not it would help you resolve things is uncertain 1 of the 1st things I do when I have problems with overlap and I've done this for the class it is I'll throw the thing in the European scene because Duro been seen creates a shift that's a dire magnetic shift from the ring current of the benzene and so very often if I just got a couple of persnickety overlapping protons of very often just blowing thing Europe benzene is enough to shake up the specter basically what you're trying to do is get some change and see what works alright this next next example here and I'm just putting this is pure Q purists self gratuitous and this this is a very little scientific value it happens to be the 1st paper right I published as an undergraduate and it was just using Carol shift reagents in a in a very unusual way with molecules that basic basically was tied and here but it was just terminating the an anti-American ratios in a ruthenium complex and so what was happening was that was done in a in a non coordinating solvent and so the coveralls shift reagent was coordinating through chloride To the ruthenium complex and you could see the various protons of the ring which separated this is the thing and growing brings the actually see the an interviewer's anywhere how long a long-standing love affair with Annamari spectroscopy and maybe now maybe it's part of words alright so
with enough with self-indulgence the American-backed self-indulgence suspected that Brown is precluded by the way self-indulgence aren't so Carrell and is a real is a real problem for animal because as I said in Amara is not inherently able to tell in tumors apart you've got to do something to distinguish among In tumors said the other way and not the way to go and I'll say and other way because there are lots of clever ways including ways and being developed in the region of ski group right now and that have been published out of the 1st group but another way that's been used for a very very long time is Harold River ties in the agency In India murders do not inherently have different Dannemora spectrum but Dyess staring murders do so if you can take your an anti-American and if you can take your India were mixture of Indian tumors and get it to react where they and their deal pure molecule then you make dies embarrassed and you can distinguish the 2 of them and their tons of them out there tons of Carroll the river Tyson agents I'm just going to show you too 1 of them is very popular it's been around for decades links since the sixties this 1 is called plants called most years reagent is what everyone refers to it as in T P A which is in the taxi try Floro methyl phenyl acetic acid this 1 is the ah anti-monopoly poll :colon Moesha is Hasidim O'Shea's reagents in what you do is you simply prepare a carboxyl to prepare an ester animated derivative with the carboxyl against said and what's called is the reagent itself has 2 very nice handles thinking sharp single Indiana more spectral on Mathilda gives the shops England H 1 and more spectrum but even more a try for a manifold that gives a sharp single the flooring and more spectrum so that's 1 popular 1 4 4 reagents that have a nucleophilic side for compounds that have a nucleophilic site for things that have been elected feel excited 1 popular 1 it is out of our alpha methyl benzoate Wise's sign a lease that's 1 way you can describe so you can buy this inanity of pure from old richer from Fluker there's also version with the natural world I so sigh and react with the means to give your readers they react with alcohols to give carbonates and so you can very easily reactor molecules to make an interview appear to make derivatives in which you now have a carnality and there I'm going to show you 1 example from from my own experience just because it happens to be something I can draw on it also introduces some ideas of of carnality I want to race I guess well areas is this was something that worked well and was easy for me and I like it so now we're kind of in 2 stuff that I like that I think scolded that I think your life too if you come to the point your project where you have such a problem alright so mine a particular problem and project was I was taking amino acids and developing a synthetic methods for making I Sociedade derivatives of these and In the problem was I couldn't tell you get Metamora spectrum in the stuff looks great but would you couldn't tell is argue you also getting the unit tumor in other words is the ransom as nation In the reaction stop put a big question mark here so in this case it's kind of the antithesis of the ISO cyanide being in the molecule that of of interest on being in the dramatizing agent here the molecule we were making had nice sigh it so I just a river ties that by reacting it with methyl benzoate me and so as I said you can get methyl benzoate 1 as a single entity where I happened to take the Fiorentina and Duma here so we treated it with that and that the idea was to see if we were forming dire staring murders and so forth you could look at the dire stereo murders by and say OK are we seeing any evidence of dire staring so this is what you get From the compound with the natural started chemistry and so the question is are we getting many of the diverse Terry so when we took an atom spectrum reinstated now the big problem with a negative result of course is you get a negative result that doesn't prove it's not present maybe the dire Asturian was coincidence so the way you have to address this and this would apply to what you're doing Carol H. PLC or anything else cobbled GC is you need to prepare an authentic samples so there's an easy way and a hard way To do that so the hard way To prepare an authentic sample is to now go ahead and take the initiative to Umar of the amino acid and reacted with this summer with the army and the easy way to do this with simple way to go ahead and take the Indian DMR all of the amenities and reacted with the product set fennel groups
this should be our fiscal year channel here and so the point is that these 2 molecules are Aneityum murders and some of the spectrum of this molecule is identical to the spectrum of the dire stereo so now when you go ahead and you take this molecule here and you don't see any died Terry what you do 0 to confirm that there is no dyeing scary America is used by with this stuff here and you can see if it shows up as a separate State and indeed it did them a foxy Of the 2 ends up being separated by 5 . 2 2 candidate . 0 to 2 . 0 3 ppm which example it becomes like an HP PLC trains which was ample to distinguish and in fact with a very small spiked with a spike of just 1 . 5 per cent you see it so that means that we know that the original was greater than 99 per cent the said nor ostentation speaker Pirates so so that's what I want to add about current role carnality and Annamari Hello an American the useful tool and I think what I wanna do at this point is tossed out a couple of other techniques that I found useful over the years and that indeed we we use so technique that all talk about now is called X C which is exchanged spectroscopy and what this is useful for doing this identifying common former reserve other species in moderately slow exchange the situation comes up we'll prepare a compound let's say a carbonate on and on and you'll see other peaks Indiana more spectrum we saw this good and it's we talked about this with them it's where we could see 2 different programmers or we had that very thorny problem where remember we had a series of spectra and we were talking about this being a minor confident 5 .period problems and so the question is yes sure you say you think it's a con former about how you know you're adviser says hey we can't published this year and animal spectrum isn't pure we don't know if it's pure the reviewers are going to say you've made a mess how you establish that Miss really is your company exchange spectroscopy is the same polls sequence as rosier nose knows it In fact it Justin knows euros he C R spectra In the exchange costs peaks are the same size as the diagonal I'll show you what I mean yeah yet so In a nosy spectrum for a small molecule the cross peaks are opposite signed to the diagonal so the facing you have 1 you saw this Sunday when you worked up some your face sensitive spectra new had for the red regional below region right the color color maps this is your exactly it's facing so these will be on the same side as the battle in the nose spectrum of a small molecule that's going to be opposite the cross speaks in a rosy spectrum that'll be opposite the crossed now the trick on this is timing and they're really 2 different timescales for anymore spectroscopy there's the timescale of it we talked about this when he talked about economic animal there's the timescale all the uncertainty principle the timescale of the uncertainty principle is if a proton doesn't stay in a single spin state for more than a few milliseconds you won't be able to see you know you'll walk how can I explain if you have 2 different states you will be able to see them as distinct unless you stay in those different states for sort of 10 milliseconds before for the you have the timescale of relaxation which is Magnum is Asians returning to the z axis T-1 relaxation of dispersing the ex-wife plane teacher relaxation and that timescales on this water of seconds to you at the window you're exchange process so it's faster than tends then you 10 milliseconds sort of timescale but lower than the 2nd time scale I like the ballpark things in my mind so in other words you will have the window that timescale so it is on the order of 100 milliseconds know the words if you have an estimate that rotates very slowly remember we talked about timescale in energy barriers and temperature you have to raise the temperature to get up into that regime of having exchanged now a lifetime of 100 milliseconds means an extra 4 hurts peak with In other words the peak with half height becomes for Hertz wider and that's very good because a typical double it is like 7 8 hurts so you can sort of see a double its normally has to shop 1 you just want a fact now at your peak so that you're doubling your peaks at getting a little bit fact normally in a sharp line Indiana Morris about like 1 hurts 1 . 3 hurt so you want your lines to get just a little bit Fatah so say channels a temperature so that the peaks broaden slightly by a couple of carrots 0 2
examples and see what I do I think they made them as it was yeah I just took when took 2 papers here on he endowed a couple the couple from my experience nothing profound but very very useful arms for us and I think potentially potential waiting for you so 1 of these when you get multiple controversy it is really really a nightmare because new spectra get so so complicated this is a macrocycle that 1 of my students prepared the molecule has fourfold symmetry but the problem is you have a common from in which the molecule has twofold symmetry the 2 varieties to 2 identical degenerate versions of that conference so in other words here see 1 type of residents here you see 2 types of residences but then each of those 2 can swap around and so my students I was trying to establish that these were indeed Inter converting controversy Ranbaxy spectrum he ran In this case stadium a rosy spectrum just the faces of the Cross speaks the same as the diagonal and if you just look here for example in 1 day spectrum using 3 different it's the worst good examples expansion here but I will take this region here in year one-day spectrum you want you see a whole set of peaks associated with the side chain With these
protons here and when you expand it you can see across the corresponding to 1 exchanging with the other so basically this exchanging with this and then whoops with this not only with this and then another Cross speak with this exchanging with With this over here anyway the point is you can see all of those come from Azinger converting which is very useful for establishing that the related he chose a temperature for this
experiment that was just right for 4 in the other the other paper with a similar thing it was in a equilibration among 2 different species where he's looking at home heterodimers and the next 1 in tumor and another in Indian tumor and this is Michael who did this and saw some new very teeny tiny peaks in the mixture so this is wanted in timber the other an anti-American on little tiny peaks and he wanted to establish whether that was a dire steering America heterodimers so how do you do that you can say the new peaks but what are they so you show that there an exchange so again he ran the nose rosy sequence and was able to see to see exchange cost the sphere the show there in exchange any notice he picked this temperature so that his cheeks suggests the peaks are normally shop anymore ended up just a little bit just to make the pixel broad alright I want to conclude with 2
whether 2 other things again justify a long way away in your toolbox the things that I I find useful so 1 of these is called diffusion awarded spectroscopy dozy In what it does is it basically uses the 2nd dimension to us separated us spectrum by diffusion coefficient In Defense molecular weight and the reason you might find it useful is it's useful for mixtures and identifying impurities In I'll just show you what I'm talking about out with an example and this is an example out of that 200 more so this is a dozy spectrum in your 200 more and
more specter of a mixture of 2 different molecules you know all and ADI tried probable I try ethylene glycol in 2 different solvents into what you're doing is using pulsed field gradients to seperate your molecules by diffusion coefficient basically little molecules like water and methanol diffuse rapidly big molecules like propylene glycol don't diffuse a lot so you wind up with 80 With 8 subs spectrum here so here's your mixture and here's the dozy spectrum and you end up with a sub
spectrum at a small diffusion constant for the peaks associated with the try ethylene glycol another sub spectrum and you can extract out all your spectra were you abuse and all of which is smaller and so you can see all the people for you you know all right so in this mixture you've got all these different peaks you don't know what's what and you say Wait a 2nd this methyl group this methylene this methylene here and that methylene there correspond to the view in all and then you have your methanol here and then you have your water here using methanol in
water we just use this in my lab we use this all the time for looking itself Association of molecules because for example Tatra murders have a diffusion constant that's about .period 6 Stat of monomers 12 we just use this in a way that you might use it very recently a student of mine and he had a sample she just couldn't could not purifying we were trying to say is there something wrong with her chemical or is this an impurity she took a dozy spectrum and she saw very clearly that the the odd the unexpected peaks were low molecular weight impurity molecules so she knew OK it really isn't something the matter with the compounds are at last last point I want Arab water suppression mn so the techniques that are involved use gradients or other pulses to eliminate age too now the reason that this is important to eliminate the water it said the reason this is important is that allows observation of some ages so if for example you have let's say an alkaloid that has an animated and age group and 1 of the able to see that I'm at an age group you can take take a spectrum In 19 10 H 2 O D 2 0 0 because on the laboratory timescale that's the 3rd time scale so we have uncertainty principle relaxation laboratory timescale on the laboratory timescale if you dissolve and hammered impure D 2 0 0 the NHS exchange with deuterium as the the all-ages very quickly in fact the NH exchange with deuterium and you can't see them so you can never see protons on a federal Adam indeed to well never on I won't say never but you almost can't see take this spectrum in water with just a little the 2 0 4 the lot but then the problem is you have 50 Moeller by H 2 0 in your sample you have 100 Moeller protons from that and you need to get rid of it and you can't do it by using ingredients to themselves so I will refer you to 2 things 1 is just in your 101 and more and more spectra an example of this they do it on sucrose which is kind of a lame example Kosuke and never observer wages but you're suppressing the region right around the water but the thing that I will do In conclusion is just give you a hand out and 1 1 closing comment here in this handout I find very useful so you're still you're still fighting the uncertainty principle if you're protons are exchanging very rapidly you will not be able to see them because they will be part of the H 2 O P that's expressed that suppressed you have to get the exchange rate down on the order of hundreds of milliseconds or greater and this happens to be a graph for proteins from a book by Goodrich and when he points out is as a function of pH you have your exchange rate here this grandpa's old confusing this is an exchange per minute so the that I've drawn attention to the true is exchange on the order of 100 per minute in other words a lifetime on the order of 500 milliseconds so in this range protons like Emmitt protons and UN-backed backbones can be observed and in this range up here they're not observable what is that that means that you can never observer wage protons peptide and other sorts of hammered protons can be observed in the acidic pH range but in the basic pH range there the exchange rate ,comma goes fast so typically have to tweak with the pH alone alright that's I think all these sort of final bringing down by wanted to give you of things that I've I've found useful or think you'll find useful and idolize Seiyu a week from Saturday if not sooner


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