Lecture 17. Introduction to 2D NMR Spectroscopy


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Lecture 17. Introduction to 2D NMR Spectroscopy
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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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don't move on and start talking about 2 Aymara spectroscopy it and what we're going to do will be using this as a tool very very useful for structures often there is a whole sort of alphabet soup of different techniques but rather than just unleashing a torrent any people do research in this area just like they do research in organic chemistry and so big thing is invented new techniques to sell specialized problems but rather than trying to sort of talked broadly about everything we're going to focus on getting a few tools in our toolbox and see how to use these techniques to address different problems OMB will start out with 2 tools in the toolbox that will be but hm QC and cozy techniques and then will answer more tools and I'll try to try to put them into some some sort of context there were 2 additional lectures that on specifically on Tueday that will come in either possibly next time or the time after that so we'll be talking specifically about the nuclear over Hauser effect which applies to 1 billion Morris well and we'll be talking about dynamic animal on dynamic effects in animal or spectroscopy but we're going to start storing extra work set will start to bring into the United like to to get you familiar with the tools are right fury against start really really simple-minded I think this is actually a good way to think about that so in 1 day we said the basic idea was you polls and then
you observed right that's your 90 degree polls the observer is your FID have you now senior RAF ID on the spectrum the suggesting this the with police quickly co-signed wave with the dying off so this is your FID and of course what you've got here is an amplitude domain and then over here you have time right this is literally your signaled dying off with time and the co-signed wave that corresponds to the period this city of the various nuclei and so the whole idea you know 1 the 48 transformed Is this time domain on the x-axis ends up getting transformed to a frequency domain and that's your parts per million and so your spectrum still has a to if on the vertical axis and it has frequency In the units of ppm on the horizontal dimension and the reason we call this one-dimensional Lattimore spectroscopy is not because this is the 1 the graph it's not you'd say this is a Tuesday press it's because you have 1 time dimension and that its transformed into a frequency which now into Indiana mark you get two-time domains two-time dimensions in the FIG and they get transformed into 2 frequencies so I'm going to give you just as I've given you my simplified version of an animal or spectrometry the end of that and more spectrometry and I are specter of automata and mass spectrometry and so forth I give you my simplified version of the tune the pulse attorney pulsate sequence is going to be pulse Paulson said observed and so what you do when you do this to me is you get to time dimensions because the way it is your waiting for some time and you're going to vary the way and then you observe and so this 1st wave becomes time 1 will call that T 1 and the 2nd wave T 2 these are not to be confused with the capital tees we talked about for relaxation remember we got about capital T 1 is vertical is is spin spin relaxation were the maximization returns to the Zia axes and capital T 2 is spin lattice relaxation were the magnet Asian spreads out the ex-wife .period these a lowercase teams and then turn transformer when you do it to India the they transform 2 2 frequency domains and so you get a spectrum that might look like this where you have 1 of the main here and this is called your efforts to domain and then another domain here and that's called your F 1 that now what is this as your varying team while you understand here of course 72 year collecting a signal when it's dying off with times you understand that basic transformed that if the period city of the signal is 1 cycle per 2nd we get a line at 1 hurts and if the period this city of this this line is 2 cycles per 2nd you get a liner to and if it's a composite of 1 cycle per 2nd into cycles per 2nd and others you get a spectrum consisting of many Watkins now similarly as you very this to what let's say starting with hypothetically a millisecond in the 1st experiment then the next experiment to Ms the next experiment 3 milliseconds the next for another period this city occurs in other words you're FID what you observed in this time also shows variation that occurs in time variation amplitude of periodic variation those variations transformed to the 2nd frequency and so you get a spectrum now that consists of 2 frequency bombings it is of course plotted two-dimensional way but it is really just this is is actually HUD graft this is a graph if you will and typically these days the way we express it is as a topological maps so you'll typically sees series of contours that just like if you've ever seen topographical map of the mountains each contour represents a certain height so Avery told he has many contours and a short peak as you work on tours so it's really dimensions being represented being projected into but again the reason we call this to Indiana is not because there were 2 dimensions in the graph but rather because the two-time actions are and that's what I want to say about sorted the basic mechanics of the experiment there are 2 general types of 2 D NMR experiments 1 of these experiments is 1 of these families the 1 that will be talking mostly about his collation experiments correlation means connectivity it means literally what's connected to what no other way of thinking of this is coupling can be Proton Proton coupling it can be Proton carbon coupling that's what correlation experiments give you information on you've already been using this type of information from coupling patterns and coupling constants when you see a trip triplet here you say all that 7 methyl bromide integrates the 3 hydrogen you say all that some methyl group that's next to a C H 2 groups when you see a quartet here and it integrates I the on 2 2 hydrogen and you say Oh that's a methylene group that's next to 3 hydrogen is maybe it's next to a methyl group and correlations give that same type of information when you see a 17 herds coupling Unitrends Al Qaim you say all that 17 hurts coupling must have a partner somewhere hot here is it's a partner that also has a 17 hurts coupling singer already using connectivity information in helping to deduce your structures to the experiments Prez provide provide that information in a more general terms the other type of 2 the experiment that will be talking about are over Hauser effect experiments we will be
talking more about the nuclear over effect in a couple of lectures those give rise to information on spatial proximity but these can be very useful for information about stereo chemistry and confirmation Art my philosophy on teaching to Dannemora spectroscopy as I said before there's a whole alphabet soup of techniques that their my philosophy is not to bombard us but to give us a small box a small toolbox of what I'll call Claude techniques in other words techniques that if we are good at we can use to solve a variety of problems and then if you're good with those techniques you'll be able to say Oh here's a hole in my tools where I have a very specialized problem that isn't being sold by these tools and you can go and go to fail or go to the end our manual and say all I'm encountering this particular problem with the cozy in a taxi isn't helping me out but I remember him saying something that there was some type of technique called a relay cozy and saying I can add that to my people so OK the 1st 2 tools that will be talking about are cozy which was really the 1st Maine 2 d technique it stands for correlation spectroscopy and so this is typically Proton Proton Alexis a nuclear coupling and then the 2nd technique that we're going to add to the toolbox is a teacher juicy and this is federal nuclear correlation well I I should say something so we're learning about the modern versions of the experiment H & Q C uses something that's called inverse detection that means on the F 2 dimension you're detecting Proton and on the F 1 dimension you're detecting carbon the older less sophisticated version of this experiment was called had I'm going to put in parenthesis but that's not really it's not the same thing can't quarrel with heroin nuclear correlation spectroscopy announcements when you call that's what you would call a chance to say Hank core was an experiment where you would collect carbon date on the F 2 dimensions and proton data on the F 1 dimension was a slower and less efficient experiments so we're gonna start with these 2 techniques as our initial starting point for building our toolbox and will see that there are extremely powerful were then going to added toxicity taxes is out what stands for total correlation at all but then quotes it's like a super cozy that gives cross speaks with all other nuclear scientist dispenses them I'll show it to you today but you won't have the you won't yet have the experience to see where it's useful will bring in some problems later on but I don't want the body with too much and ancient NBC on is sort of a long-range had Koren fact that's the version of the experiment that it used to be and it is basically these 2 experimental conceptually more complicated because initially ran a waterway need them for it gives you a ton of data but when you start to encounter specific problems of overlap in the case of the former and in the case the latter fragments that you can't put together they'll be very helpful so all of these are correlation techniques and then we will also throw into the mix of court techniques nosy and Rosie these are both over Hauser effect experiments they both give rise to information on proximity knows is good for molecules that are smaller molecules that Avery large but there's a hole right in the middle of medium-size molecules that don't work well in it and Roseanne's ends up working well with size I let's start with cozy and HM QC and let me just show you the general GS of the 2 experiments so let's start with cozy and imagine for a moment that you have to open all and so if you think of your H 1 and a more spectrum of proper you'll probably think of something that looks like still see a trip led with a 1 2 2 1 Triplette forwarded this ch students next to the oxygen and you'll see a single lane for the LH typically unless you're very free of acid very free of of water and a single it is going to correspond to the OH that's going to be a changing rapidly and not coupling unless you as a set of various free you'll see something that looks kind of sorta like a sex tapped India in a 1 2 5 2 10 to 10 2 1 ratio I guess that's not the prettiest 6 tents what make my outer pixel smaller and then you'll see something that looks like a triplet In is 1 2 2 2 1 British eh and as I said you already know correlation you know that's when I see this Triplette here downfield it's telling us that I have 86 and 2 hydrogen it's telling us that I have 2 next to his CHG and when I see this Triplette upfield I see I know that I'm having a methyl groups with integral 3 hydrogen I'm having a methyl group and its next to his age and when I have the SEC staff
here you know that I'm having 1 methylene group if it's to hydrogen and by being a sex that I know it's coupling with equal coupling constants defied different hydrogen so for this simple problem you're very good at reading lists and cozy is providing exactly this type of information but in a more systematic action now a similarly if I have a carbon atom spectrum let's say for the same molecules I may have something that looks kind of sort of like this With let's say 3 lines in it and what ancient QC is going to do is it's going to collate the proton signals With the carbon signals in other words it's going to say this Proton signal is connected is coupled with that carbon signal this Proton signal is coupled with this carbon signal this Proton signal isn't coupled with any carbon signals and this protons signal is coupled with the purpose but let me give you a handout that service starts us and all of the quarter correlation techniques both these 2 and the cozy and the taxi and headquarter and let me show you schematically what I'm talking about local GOP hopes plug-in the machine doesn't it and that's that Art said this is not a real spectrum this is a 80 sketch of the cozy spectrum of all and so is my mobile Little Pigeon pigeon sketch of it and so a cozy is going to give us all over copper lines it's going to give us J 3 3 in other words artisanal couple our genital cut out this summer couplings and R. J I urge 83 Zena Jay choose in other words are germinal coupling any Casey of coupling you'll get long-range coupling as well like alone like coupling In general if your coupling constants are small the signals are going to be even weaker so if you have a very small coupling like an overlooked coupling it may not show up as strongly were if you don't go down and that topographical map enough you may not see it later on we'll talk about some tricks to help bring up those signals were right now basically anything that's coupling is going to give you a Peace now remember I talked about our Accies so this is our effort to access this is our F-1 access and he's technically are not part of the spectrum these are actually one-dimensional spectra added for reference so you typically and you'll be doing this will take a 1 the spectrum and you will use it as a projection on the access to the EC lineup now in terms of the anatomy of a cozy spectrum this is what we call the diagonal and the diagonal basically is just the spectrum in other words it's the Mathilde in here the methylene here the away each year the methylene next to the oxygen and these are the peaks that are interesting user called the Crossed pigs the 4 of them here across peaks if you'll notice are symmetrical about the access and what I always like to do in naming my specter of time will be doing this as a convention in class is will identify all the peaks in the 1 the spectra and will letter them starting at the left of the suspects so I will call this PDA this P being this peak and this piece the will do the same over here b see and what the top what the cozy telling us Is that a notice that lines up with the a is crossing with state and so you see this big and so we have this crossed the 4 Cross and you get the same thing over here and then you have another cross speak here and that's see crossing with date and I like to go ahead and basically keep the idea might peaks my cross speaks before reassigning where those peaks on the molecule so course now we know that in this molecule this is ancient B this is a chair this is HC and this is aged 18 and I'll show you as we progressed will learn more and more to systematically extract is from unknown structures but you can see for example that a crosses and so that's corresponding to this coupling this correlation and we can see that's the crosses with the that's corresponding To this coupling this correlation and we can see in this particular simulated spectrum this particular I should say sketch of a spectrum the because it's not just couple isn't coupling to anything if the were a triple if it were jailed coupling then we would expect it to give across the weather and so we see we'd see a separate peek over here associated with the account .period all right so that's that's served cozy spectrum so now let me show us show you are a using up Spector arts so this is your HM QC spectrum you're a general juicy spectrum picks up 1 bond ch couple coupling in picking up 1 1 ch coupling of course now we have no diagonal because we've got on our effort 1 domain we've got see 13 and on our efforts to the we've got our proton spectra and
so there's no diagonal and what instead we have is a series of cost-cutting and again if I transcribed the structure of the molecule and I call this H B B O C H 2 80 sooner or later 2 CDs C H 3 d for the molecule now what we're going to do is to collate these carbon peaks With the proton peaks and again I liked them very very very slavishly label might peaks I'm going to go through every time I encounter a spectrum I'm going to go through started the left go a B C D for each of my peaks and if I started the carbon I'll do 1 2 3 and so forth and 1 of the reasons I'm so dogmatic about this is because when you get a larger molecules it's very easy to start to get confused you'll have 1 expansion here in 1 expansion there if you take the time to do this it will always help you keep track of what's going on particularly when you have many suspects so OK so now we have these cross speaks here 1 8 so in other words I look across 1 aide I look across to see you here and I look across 3 duty and nothing's crossed with B and so I can say OK this is the 1 this is seen to this is the 1st thought Sir questions at this point new universities have upfield Oh yeah this is possible and in fact let's see which way is it typically typically plotted and I think it's typically plotted this way because you could envision picking this up and putting it here so I think I think you will always see downfield down here but I could be wrong it's it's of no consequence let me put it this way it's of no consequence whether we go from 0 ppm to hide ppm or we go from 0 ppm time you will also see being in the textbook you may see a few had cost factor given for some of the compounds in a high-cost spectrum the see 13 is going to be up here and the Proton will be down here other thoughts your
questions I want to throw into the mix I don't yet expect you to assimilated because we're throwing out a lot of information I want to throw yet into the mix the US there are proxy N H amp Q so the big differences in Toxey and I'm sorry each NBC let me again make our little little schematic molecules here OK in our little schematic molecule In a taxi spectrum you still get all the cross speaks of the cozy but now you get new cross pits with it so we get this from speech here and we get the cost Pete corresponding to this coupling here but in the taxi spectrum what you also get is across between these 2 proton and you don't get across with wage if its exchanging because if it's exchanging it's not part of the spin system following get is crossed peaks With all other protons in the spin system and at this point it's hard for you to see why and how you'd want that the cozy already seems very information rich but it's very good for dealing with the overlapped where your cozy can't walk you through and you can break through overlap with the taxi warrior peaks on top of each other and the other thing it's extremely good for is biopolymers lagos actor rides nucleic acid a proteins and peptides because each residue in a biopolymer typically is 1 spin system so I'll give you a quick schematic of the taxi will have a unique I will have a separate lecture this later on but I wanted just introduce you to the to the basic anatomy here part so this isn't the end of our sketches of the spectrum and it looks just like a cozy In other words you have your diagonal Everything this is the same as the coalition you have 5 games ago and slavishly label are Peaks ABC did ABC did you have all the peaks that you would have seen the Cozart you have your a CPA you have your a d pick your CD pig rather but now you get this 1 additional cross speed so you get a 2 D that's unique to the taxi and that's that cost between these 2 here you can do that and you'll find if I do the same thing here I could call this Cedar seat a city and I could call this deed to air and I I can call this D 2 see it's providing no what additional information the only thing that I use this and doesn't matter whether you use this half for that half the thing that I use it for it basically to check if I'm confused if something's a real peak if there's a lot of noise or some artifacts I'll check if it's there both sometimes things will be clearer and more of that's from a nuclear power federal nuclear right you don't have a dad diagonal you don't have say this element of in are it's the last 1 in our schematic now we come to our aid NBC and let me again sort of show you in my in my simple-minded view on the blackboard here so then will come back come back to our molecule H NBC can be drink like drinking from a fire hose there's a ton of information there and like you went up needing to do is used in a very focused fashion because you'll just drown in people so remember ancient QC was someone bond ch couplings in a speech NBC we get to the end 3 bond ch copper lines if not always in a predictable are guaranteed fashion so in other words this hydrogen will be coupling with this carbon this hydrogen will be coupling with this carbon this hydrogen will also be coupling with this carpet this hydrogen will be coupling with this carbon this hydrogen will be coupling with this carbon this hydrogen will also coupling with that Covance you're getting this tremendous amount of the exchanging rapidly it will be coupling with any of them and again right now it's too overwhelming for you at this point to just throw all the Spektr at you and say use them so what I'm going to put it is just like I say this is particularly taxi is particularly good for overlap and biopolymers what I'm going to do is say that ancient NBC is particularly useful for what I'll call putting the pieces together and you know how long the homework I'm telling you to write down fragments things that you know I know this molecule has an FO group I know this molecule has an isolated methyl group when you're getting to that point and you have these fragments and you're saying how and hacked away systematically put them together this is where H BC sun shines where you say all now I can see that this fragment is somehow connected to that fragment where you have these isolated spin systems and you're trying to put together so I'll give you the schematic of the nature NBC right now so are great question James yes you will sometimes see single bond coupling and respected your textbook actually removed it from a few of their problems and I put it back in I basically took out what the reason is what good is it to have specter textbook that a doctor when you then encounter real spectrum to put it another way you encounter researcher the exam which may be on people's mind works and it looks different and you're like What the hell's going on so you can see those and we will we will get used to that we will see that where are they are not rare and usually in the case of strong peaks and you will know because I will refer to them as you will see them as the state's following vampire bites around the peak they are you will see the 168 splitting our itself we again go back to our system here so you notice now we're getting this very rich piece of information here so for example if this is our molecule always H B C
H 2 B C H C H 3 D and we already know these carbons 1 2 and 3 so let's just will just look at 2 of its so this crossed speak here of 1 today and that's telling us that we're seeing and again this is just my sketch that showing us that we're seeing this long range header in nuclear correlation this crossed speak here of 2 that's my scrawl of it too this cross here of 2 2 D is telling us that now we are seeing this correlation over here and you will see how to use this very varied information rich system future yeah and it's not so much how far remember how I said that J 2 Ch the NJ 3 H typically 0 to 20 in their going to depend on higher 0 210 going to depend on hybridization they will have different intensity is based on the jury if you're J. value is very very small you will pick it out up no matter what you gotta J of like 1 heard good luck finding that coupling on so it's and this is the killer on HMV is that you can't tell your J 2 CIA from your J 3 CH is so you get this information but there always this question marks are the direct you know are they next are they neighbors or they are the nearest neighbors are they neighbors 1 down the road but don't worry about this right we're going to spend a weaker to not using to agent pieces what I do want start out now is on an example with HM QC and cozy and show you how beautifully they work together and show you what hell II solve a simple problem and this is a problem from not this week some work but next week's homework so it'll be sort of a demo problem for you if anyone didn't get 1 there's enough to go around now the other thing I would like to to give you a tool that's useful particularly when you get more crowded spectra and that's these grades is very useful in helping you winding things up they're yours to keep and you can print more on transparency film were fewer lab made surrenders of you and steal them you can go ahead and and go ahead and get them all right now it was the pick up so I wonder whether through this Panasonic quickly so OK this is it the spectrum in and we have a mass spectrum we have an eye on spectrum now the reason I've been pushing on you right fragments right pieces of information is it helps you organize your thoughts and it helps me if I go ahead and you get an answer wrong it helps me figure out what you're thinking watched as often as good thinking along it's alright so I look at the Spectrum see carbon Neal I see something at 1743 I work out the formula from the man's 67 aged 14 0 2 works out for the man there's 1 degree of on saturation and it sure looks looks like it's sinister 1743 is about the right position for Ernesta here the happens it's a small molecule very small molecule I happened to see the CEO single bond stretch by looking the proton NMR spectrum I see some downfield peaks that look like it's consistent with the Nester so take it as a given right now that it's honest I go ahead and I look at my peaks and again I really really really like to get in the habit of labeling them and just walking across the spectrum ABC e F g solo confusing here if I looked closely at looks like a CIA double it can you see the pattern of the double it on top of a trip when you see the 1 2 2 2 1 2 so it looks like I have G is probably a double-edged an age that's spray G and that's probably right over here now you really really usually 1 of the diligent about putting a ruler measuring the height of your integral roles I like to be good I like to take this site beside site this site beside the site this site everything I'm sure of divided by the number of protons and get the most accurate height for Proton possible this 1 is pretty obvious the followed by inspections if I'm really feeling lazy I could always just even use migrated as some sort of whom were roller and I say all 1 . 7 1 . 7 5 points looks like about 5 . 3 5 . 4 the 5 . 4 1 . 7 or 1 . 8 I guess I wanna be good about it I will leave even try to line up migrate a little bit better the about 1 . 7 1 . 7 1 . 7 about 2 . down about but see about 10 .period . 6 and 5 work this out I'm getting about 1 . 7 4 hydrogen about 1 . 7 per hydrogen this ruler by the way is graduated and tenths of an inch is the small tech marks on their case and alright itself I think very quickly go through all and say 1 hydrogen 1 hydrogen 3 hydrogen ends 1 hydrogen 1 hydrogen 1 hydrogen and this is looks like 3 and 3 it looks like it's 6 hydrogen similarly I like to to look at the carbon NMR spectrometers and if I have a debt spectrum I'm very happy and again I'll go and number might peaks 1 2 3 4 phone 5 6 7 and I look at my peak and Isaiah looks like 1 is a clot carbon to looks like a methylene and they have to make judgment calls of my dad doesn't completely clean 3 is a Ch Forza CH 2 In 5 through 7 are Ch now we these data alone I'm going to have this isn't the harder and of a molecule cell With just 1 debate as something you can't you could easily puzzle out the structure but I want to show us how to do data is going to help usually at this point I sort of jot some ideas down as fragments ICI ever methyl group to widen or maybe a methyl group it too might be indicative of CH 3 carbon yield might be something I think I have it looks like I have to methyl groups here 1 of them's a triple at 1 of them's they added a double it so I probably have a fund just tallying up fragments I probably have a CH 3 H to fragment and I probably have another CH 3 and honestly if you puzzled around there you could probably put the structure together but I want to show you this way of putting structured together there were going to do here using a gym QC and cozy in the system alright I actually like to start with my agent QC spectrum and the reason I do is that's going to help me 1st of all it's going to avoid having waste a lot of time gets getting stuck on congenital couplings and it's going to give me Avery systematic way of doing things and again I'm going to
be very slavish ADB C D E F G H E F G H and you notice we've left out the carbon year we left out the carbon deal with about 100 allows another thing include me into the 2 Ernesto the Carbondale was at what 170 something ppm typical Lester so it's not a Mathilde tone it's not now the hydride methyl Tito nite expected like 205 2 to 20 and now the height and expect elect 190 200 so I am pretty darn sure this isn't just anyway but we don't need in agent you see it's not going to college anything because it's a quite carbon is not properly so I start my numbering Chu 3 4 madam doing here and staring in the light of 5 6 set in and now I just look at my cross 6 and so too is crossing with a and B. 3 years crossing with D hours crossing with the E and F every time I get 1 of these carbons crossing with 2 methylene Sino it's that guy a serious topic methylene 6 is crossing with Now this is where it's hard to see that if you have trouble particularly in a crowded spectrum just slap agreed on it and you can save 1 crossed picket lines up kind of scented with age the other crossed the lines up with Jay that included an expansion here I believe they have actually forge their data here I think this crossed speak actually should be spread out and they were trying to make it easy for students buy showing at just under here but again what good is that going to do for you when you encounter your own real data and you say Oh it doesn't look like it looked at the problem so here I look and I see all the ITC nicely conceived the grid lines this lines up with GE this lines up with each so OK so we get 60 In 7 H and now I'm going to be very this is going to become my Rosetta stone for the problems I'm just writing all of my numbers here right over the letters to weigh in to be 85 C 3 D for E for effort and 6 g In seven-page here's where all of this work pays off now we go to the cozy spectrum and what I'd do it again I'm very very very mechanical about this I go ahead and I transcribed from my other access to wait to 5 C 3 days for E for the 6 g 7 H and I do if I had another axis up here I would do the same they only gave us 1 inch projection of going to the matter ah I will now also said to but this molecule together Our itself I literally I go through now I identify my diagonal I draw a line through my diagnosis I don't get confused ruler is better than the side of great but if the grid is what I have on me then I use the grid David always comes prepared he has as ruler however now we're ready to look at our cross peaks way crossing with 2 big that's just I'm taking the two-way the 2 be diagonal Agnola crossing with each other normally I go up and over but here because because they're all undecided over and over so OK that tell us something we don't know right that's our that's our C 2 HA H B the only thing I really do know at this point that's the carbon at 70 parts per million so I know that that carbon probably is connected to an oxygen I think I have a history here all right here is where we start to get some new information because 2 A and 2 B each crossed with 3 days CI No and over so that's useful to weigh With 3 D and to be with 3 days OK that's useful because now I know I have seen 3 age do had it's connected and I'm starting to put this thing together In a systematic fashion and I'm just gonna continue to read my spectrum so we go over here and we say all here we get 3 days costs for and 3 days Cross for said also on page that's useful I have this methylene C 4 0 with the and have connected it's gonna connect up c
4 HE HF building up this chain that's a lot harder to put together then a usual coupling we can just read often see what's coupled with what you say Hey this is useful and I look up here
and I say OK I've got this past week maybe I need to slap a agreed on it to help see how things things lined up and I look at my career and I say that looks like that aligns with with 6 jails and so now I say how OK so I have 3 days winding up also crossing with 6 J OK so 3 days also missed cross With C 6 H 3 J and now I have almost the entire chain belt Hi this cost it here does that tell me anything useful what's that crossed the so I go over normally I'd go over but it's for crossed for after all that's fine and dandy but it isn't telling me anything useful for EU cross for F catches the dire serious topic 1 but now I come to the last ones and I get former With 7 8 you notice this one's lining up for the fall and so hurried to 7 h In this one's for F 2 7 8 and that gives me the last of my chain C 7 H 3 h all I have left now it is I have this isolated methyl 5 H 3 cities right he's not correlating with anything here by nature and BCI could put him in systematically I have 1 :colon left that's C 1 which is part of a carbon that was in my other 1 and you can see how it comes together we had to balance on the carbon Hill that needed to be failed we had a valence on 5 age 3 seeing that needed to be filled we had a villains on the oxygen that needed to be filled the only way To put the molecule together was to connect that valence from 5 H 3 C To see 1 and the balance the other violence on C 1 To the balance on oxygen and bingo you have the whole structure systematically work that obviously it's not as easy the 1st time around as I make it look here but this same strategy will start with a simple problem set next week this same strategy of going ahead and working DHM Tuesday and then working the cozy is going to take you very far


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