Questions related to NMR Structure Elucidation
I recently analysed NMR data for one of my pure compounds and there was a singlet peak (1H NMR) integrating for 18H. My supervisor has said that no natural product comes with a t-butyl moiety and my compound may be a contaminant or plasticizer. Is it because having two t-butyl groups would be bulky and is biosynthetically not probable?
For example in case of NMR spectrum n-Propanol in CDCl3 why don't we get the signal of ( -OH) functional group in the absolute right position of the spectra instead the peak appears after the (-CH2) Group as a triplet. What is the possible reason for that?
Usually the proton NMR ,the aromatic,NH2peak appears downfield between 4-6. Is it possible to observe it at even more down field?.Is there a possibility for merger of aromatic NH2 and aromatic ring hydrogens?
When trying to identify an organophosphorus compound, one of the ways to proceed is to compare the phosphorus chemical shift of the compound of interest with those of a standard. However, this comparison is meaningful only when operating in the same conditions. When using deuterated water as a solvent, pH is one of the parameters that must be taken into account. So does pH really influences the 31P chemical shift ? and if so, how strong is this influence ?
How we can predict or determine apparent molecular mass for globular proteins using pulse field gradient -Stimulated Echo NMR experiments. I am looking forward to characterize the presence of different oligomeric forms of protein using Translational Diffusion Coefficient as a parameter Can anyone suggest the references in which similar studies have been discussed
I have isolated a plant compound and characterized usingLC/MS and NMR but the structure elucidation is very much difficult to us. Will you please help in this regard. If accepted, I will send you LCMS and NMR data to you.
What is the minimum amount of sample required for different kinds of NMR analysis (1H, 13C, 2D NMR etc.)? Does the amount will be vary for different NMR instruments depending on the strength (like 500 mhz, 600 mhz etc)?
Can anyone give me a step by step guide to predict a compound structure using NMR results.After the NMR analysis of our samples, we always been provided with PDF file or Image file of a spectrum. with that how can we predict the structure of a molecule. And is it sufficient to have the H and C NMR to find out the structure or we need the 2D NMR.
Valuble suggestions are welcome. I am basically a microbiologist. I do not have any chemistry background. Moreover, I still search for a chemist for collaboration.
Hope some one will guide me to the right path.
Thanks in advance,
Dear plz confirm NMR spectra of enclosed structure with NMR spectra Whether is it correct or not if not then kindly predict correct spectra if possible
Suppose R1CHOHR2 is a chemical reaction in which hydrogen is replacing by fluorine. Where is the chemical shift of R1CHOFR2 in F19 NMR.
I synthesized (HO)2P(O)CH2CH2P(O)(OH)2 and made NMR analysis. 1H and 31P are very good. 13C gives me a strange pattern, though.
There is a publication about the Methylester, they also observed this pattern but gave no further description. (http://dx.doi.org/10.1016/j.tetlet.2016.06.079)
An unsymmetrical bisphosphonate gave two well defined doubletts of a doublett. Thats easy to explain.
But in this case (see attachment) I can not explain how the signals are achieved.
Has any one an explanation?
I have optimized benzene and biphenyl rings separately. how to combine benzene into the 4th position of biphenyl ring.
I need help regarding the DOSY NMR, I have a sample mixture which consists of two components confirmed by 1H NMR and ESI-MS analysis. The two components has a molecular weight difference of nearly 2500 g/mol . But after doing the DOSY NMR It is showing the single diffusion coefficient value for both the components rather than two diffusion coefficient values.What parameters need to be changed in order get the better resolution of diffusion coefficients in DOSY NMR. Any kind of help will be appreciated. Thanks
For 1H and 13C NMR data analysis, I am using Bruker Topspin 3.5. Is there any preliminary actions I should do on the raw spectrum (background substraction, corrections, etc) before analysing the data? . Thanks all for the support.
I have got 2 pure compounds both 0.8mg. One is a white powder-like substance while the other is clear and gooey-like. I had isolated them using HPLC and wanted to know if they can be analysed by NMR even though their masses are quite low. Both are able to dissolve in MeOH.
In aluminoborate glasses, B - Al interactions are preferred over Al - Al or B - B interactions due to tetrahedral avoidance rule. Can anyone comment on the comparison between B - B and B - Al interactions in aluminoborate glasses? Which one of the two is thermodynamically more stable/favorable? Any reference from literature?
I am observing a peak at 0.08 ppm in the 1H NMR spectra CD2Cl2 (I attach a copy of the 1H NMR spectra).
Does anyone had observed this before? Does anyone know what compound gives a signal at 0.08 ppm in the 1H NMR spectra CD2Cl2?
Many thanks for your help
I expected occurrence of two isomers populated at 3% and 97%, but it seems i used diluted sample. can u advise which concn. is suitable for 1D and 2D NMR measurement. I noticed in HNMR and CNMR that the amplitude is very low. iN NOESY and HMQC, i noticed the intensity of cross peaks is fairly good.
I noticed that two carbons have integration of 50, while the other carbons have integration between 110-130. Can i conclude existence of two isomers. Regarding H-NMR, peaks integration are almost identical.
Dear All, Can anyone kindly assist in the interpretation of the attached file containing 13C NMR of a newly isolated compound. I need the assistance of an expert in NMR interpretation and structural elucidation of the file attached to this post.
I would gladly welcome your kind assistance. Thanks. You could also contact me via email@example.com
Dear one and all,
I am working on a metabolite of an organism. I am trying to deduce the structure of that metabolite using spectral analysis. I got the chemical shifts around 60-65 ppm for the methylene moieties connected to the nitrogen atom. And 68-73 ppm chemical shifts for the methylene moieties connetced to carbonyl moiety. The compound is containing an iodine atom as well. In general, the methylene mioeties can not have such higher chemical shifts. Why am I getting such results? Whether, it is due to presence of iodine moiety?
How far the chemical shifts in a NMR spectrum are influenced by presence of iodine moieties in a carbonyl compound? Whether the chemical shifts for the methylene moieties connected to nitrogen atom and/or carbonyl carbons can go around 60-70 ppm in a NMR spectrum.
I need some opinion. I've conducted my research project using bioassay- guided method. Out of three sample crude extract I've used, only two of them showed an activity. I've further fractionated the two of it using packed column. Unfortunately, none of the fraction showed any activity. What I can conclude is that the activity happens because of the synergistic interaction between phytochemical present in crude. Do I still need to isolate those compound? Or should I just proceed to identify what compound contain in each fraction using NMR perhaps? For the information, I did screening those fraction using TLC and in each fraction, there were one or two spots developed under UV 365 nm.
I have isolated Triterpenoids olean type. For structure elucidation I am working on NMR spectral data My peaks for 12-ene in oleanolic acid is different compared to the reported chemical shift. My nmr solvent is chloroform whereas I could fine the data in Pyridine. So how solvent changes the chemical shifts for only 12-ene rest are same?
Pertaining on the title, I would like to know, how do you double check the result to ensure all compound identified is correct. Here I attached the lc-ms result for perusal. I don't have authentic standard to check it. Can I just use Nmr or FTIR to double check the structure and compound. please advise
My protein has two tryptophans. The indole resonance of one disappears while unfolding and then reappears when the protein completely unfolds. What could be the possible reasons?
i am in need of reference NMR data for physcion 1-O-β-gentiobioside. I searched it but could not find. i want to know the change in chemical shift values in proton and carbon NMR data when the glucose is attached to 1 and 8 position of an aglycon, Physcion.
I synthesized iron oxide NPs capped with a branched polyethyleneimine.
But I dont know how many amines are included on iron oxide NPs
and actually I also dont know polyethyleneimine cover the iron oxide NPs
Though I used IR spectrometer to check functional group on surface of iron oxide NPs, I couldn't confirm amine functional group. I think the reason is the color of iron oxide NPs is black.
There have been instances where I observed a new spot in TLC plate and have isolated it via Column Chromatography.But it could not be characterized even after obtaining data for 1H, 13C and DEPT 135.
I am trying to find a way to analyse migration of certain type of organic molecules into polymer tubing. This organic molecule contains basically carbon/hydrogen/oxygen. I've tried to use IR microscopy to detect the molecule in the tubing cross-section, however, the peaks were barely discernible on top of the polymers, given that most peaks overlap, and the quantity of this molecule is very low. I am thinking about using the isotope labeling for the molecule, substituting hydrogen with deuterium. The IR microscopy is one option, since C-D, O-D will all have different peak locations from the C-H, O-H. Considering the low quantity of the molecule, are there more straightforward/sensitive/nondestructive ways to detect D element itself? SEM/EDX is not feasible to light elements, what are other options?
One of my isolated compounds didn't match with any structure on Scifinder data base. Do i have to try other data bases or not? If it is yes which database that I should look through?
Thanks in advance
Respected Researchers, I have isolated Astaxanthin compound and it is in semi-solid phase. Just i have isolated bands by Pre-TLC. Anybody can suggest me how to prepare and send my sample for NMR analysis?
Running a reduction with excess of PhSiH3. In the NMR of my aliphatic product I find a big ugly bulge in aromatic area. It can only be some oligomers or polymers of arylsilanes bound with Si-O or Si-C* bonds. The reaction was quenched by HF in methanol and product isolated by column chromatography (the impurity doesn't show up in TLC), so the sneaky polymer is not so easy kill.
Does anyone have a clue how to destroy or get rid of this thing? My product is rather stable, so, harsh methods can be used.
* At the reaction conditions I can also see the formation of Ph2SiH2 from PhSiH3, so, the formation of new Si-C bonds is definitely possible
I get the fragments of Pulegone, Menthofuran, Sabinene hydrate, Dihydro carvone from GC/MS. So, how can I decide the chemical structure of fragments? Is there any reference paper regarding the fragment structure of those terpenoids?
The use of a combination of natural product/herb and medicine is still difficult to establish the effects produced by them.
Can anyone share about the step in investigating the combination effect of plant and a single compound drug in inhibiting enzyme?
I am wondering, if it is possible to have multiplate and doublet of doublet anomeric protons in polyphenol glycosides? If possible then in what case? Usually, alpha- and beta- configurations of sugar attachments are determined through J-couplingvalue but J value is absent in multiplate anomers whereas there are two J values present for doublet of doublet anomer. So how can we determine the alpha- or beta- configuration of sugar.
I am looking forward its answer with literature references.
Hi, I am performing a cyana str. calculation using automated noe assignments.
The following is my CALC.cya file.
peaks := 13Cnoe,15Nnoe # NOESY peak lists
prot := new # names of chemical shift lists
constraints := new.aco # additional (non-NOE) constraints
tolerance := 0.028,0.028,0.32 # chemical shift tolerances
calibration := # NOE calibration parameters
structures := 200,20 # number of initial, final structures
steps := 10000 # number of torsion angle dynamics steps
rmsdrange := 10..80 # residue range for RMSD calculation
randomseed := 434726 # random number generator seed
noeassign peaks=$peaks prot=$prot autoaco
The problem here is that I have acquired the 13C and 15N edited noesy spectra with slightly different mixing times which is 100 and 120ms respectively. Now how do I ask cyana (OR perform peak calibration) to set slightly upper distance limit to 15N noesy?
Your response is highly appreciated. Thank you for your time.
I am working on Natural products and we search for Novel products and check its NMR prediction online.Before, our university had an access to nmrdata.com but now we don't have an access. I ma not so skilled so that i can directly draw a structure from 13C NMR. as,i have no idea without NMR database.So, please anyone can help me to tell me any website on which i can check my NMR data for free.Thanks.
My compounds are aromatic. The peaks and integration of aromatic region is accordingly, still some extra peaks mainly from 0.7 to 3 ppm, are observed. the peaks from 2 to 3 are usually singlet. The compounds are purified by c.c using DCM or ethyl acetate/n-Hexane. Can you please share your experience??????? Thank You.
Is it possible to assign a noesy spectrum with sparky/nmrfam. If not what other softwares are good for a reliable noesy spectra assignment.
I am willing to analyze this molecule (3,3',4,4'-benzophenone-tetracarboxylic dianhydride, also known as 4,4′-Carbonyldiphthalic anhydride) by NMR spectroscopy (1H).
I cannot find any scientific reference about this analysis, although my guess was CDCl3, but maybe there is a better solvent, such as d6-DMSO ?
Could anyone please explain how and when 195Pt satellites can disappear from 13C NMR spectra in 2JPt-P-C or 3JPt-P-C-C heterocoupled systems? Thanks.
I've got the C9 formula of a lignin sample, and calculated the percentages of each proton type from the 1H NMR spectra. Now how should I calculate the proton numbers per C9 formula? I need the specific calculation method, or the related references.
Hi everyone! I'm currently on my way for structural elucidation and I'm having a hard time getting a useful HMBC data. I'm using a Varian 500 MHz and VNMRJ 3.2 as software to operate the machine. I'm just using the default settings for gHMBCAD because I think they are already optimized(Jnxh=8 Hz etc.). Most of the time, the data that I usually obtained includes several peaks at around from 1- 5 ppm(mostly in the aliphatic region) but lacks signals for aromatic and carbonyl groups. My sample weighs usually at around 1-3 mgs. Usual operations such as finding lock signals, shims seems to be fine, temperature etc. Do you have any thoughts about my problems. I run it mostly more than 12 hours. Thanks in advance.
I have searched through Dictionary of Natural Products and found a reported compound. The structure of my compound was found to be identical with the reported one. However, there are some slight difference in signals for proton NMR which might be due to the use of different solvent. I am using deuterated chloroform while the reported compound was measured using DMSO-d6. Three NH-functional groups were observed with my compound exhibiting signals at 6.39, 8.15, and 10.14 ppm as opposed to the reported signals at 8.14, 10.55 and 10.79 ppm in 1H NMR spectrum. Thus, I would like to figure out the novelty of my compound. Is the use of different solvent for NMR analysis the cause of such difference in signals?
I would greatly appreciate any opinion or suggestions about my question from any professionals and researchers in the field. Thanks in advance
I have extracted oil from a shell and I assume that it is product A is dark brown in colour. I then distilled product A and obtained a colourless product B. I want to combine A and B so that I can find a drug which can be used for cancer. Is it possible? If no, please can you explain why?
I got some active principle say it as an antibiotic. In order to know the exact molecule what are all the validations and methods I should employ to find its structure. Kindly brief each and possible references. Though FTIR , NMR and MALDI can help I wanted to know any thing else is still available new?
While I run H nmr for an isolated cpd using CD3OD as a solvent, the CH3O group which should appear at 3.8 ppm is lost. It only could be detected through HSQC cross peak.
I am trying to record the 2D-NMR of a peptide in DPC. Currently I am having some problems to get the proton NMR signal itself after addition of DPC into the water solution of peptide. Though the proton NMR of peptide in 10% D2O water is very clean. After addition of DPC (generally people start titration with target lipid until observe any micelle effect or chemical shift of peptide H-NMR signal) the H-NMR signal disappears. Does anybody have an idea on how to solve this? Peptide precipitates in SDS micelle.
Some isolated compounds are somehow difficult to detect their masses by electron bombardment MS
I have been trying to alkylate one of my early transition metal-dichloride complexes. The alkylating reagent is benzyl magnesium chloride (as a 2M THF solution). In spite of all my attempts, I am unable to get rid of the free benzyl magnesium chloride peak at 2.75 ppm in my 1H NMR (C6D6 solvent). How does one commonly remove such impurities? Crystallization does not help!
Is their any relation between the J-coupling constant and the geometry of molecules? I have a molecule: 1,3-Oxazepine 4,7-dione derivatives and it has chiral center. I would like to determine if it has R or S configuration and was wondering if I could do so by using the J-coupling constant? If so, how?