Questions related to Nuclear Magnetic Resonance
The elutrap apparatus I need is for electroeluting the RNA from large preparatory polyacrylamide gel for NMR application. The Elutrap is discontinued kindly please let me know if there is an alternative available for india market .
The reviewer asked me "NMR: An external standard should be referred for calibration?" But I did not add external standard (TMS or TSP.) when I made it, may I use heavy water (sample dissolved in heavy water) to locate the residual peak of heavy water solvent (4.71)?
In the structural characterization of polysaccharides, the reviewer asked me a question about nuclear magnetism
“NMR: an external standard should be referred for calibration.？”
what is the meaning of external standard ？
There are some papers using HPLC & NMR for separation and determination, respectively. But I am looking for some other techniques, easy to apply and more available?
Many thanks in advance.
My compounds are not completely soluble in the DMSO-d6, CDCl3, MeOD. I also tried combination of solvents, also I tried 0.1% HCl and heating. Because of the less solubility of compound, the NMR peaks are not as intense as the solvent peaks and I found after heating the compound it is capturing the moisture and showing a sharp peak.
Please help me out to produce the publishable NMR data.
Thank you in advance
I am looking for a good reference for 1-13C NMR peaks for Beta-hmb (beta-hydroxy beta-methylbutyrate), and alpha-HIC (alpha-hydroxyisocaprate). I have not been able to find a single experimental instance of 1 carbon Beta-HMB, or aplha-HIC; however, this experimental data is important for proving a hypothesis in a paper I am working on.
Hi everyone, I am trying to assess the drug loading of a small molecule on PEG. I don't find anything in literature. How can I measure (for dosing purposes) how much of the small molecule is actually attached to PEG? I have read that someone did it with NMR integration but I don't see how since I don't know the exact number of hydrogens in the PEG. Does someone have an idea?
I used a 2 M trifluoroacetic acid solution and hydrolyzed the EPS at 100°C for 2 h. How can I distinguish this method hydrolyzed the samples completely? I don't have access to NMR
Is there an effective way to detect oil/lubricant residuals dissolved in an organic solvent. Both qualitative and quantitative measurements are fine. I am looking for more of a bench top method, quick and easy. I know NMR or HPLC are good for detection.
Is it possible to use UV/VIS spectrophotometer or contact angle measurement??
Any other idea would be highly appreciated.
I would like to ask a question about crude (1H) NMR product yield calculation?
When we assign product integration and internal standard integration for percentage yield calculation does solvent (DMF. EtOAc and DMSO) which is used for reaction and workup affects percentage yield? Should I need to give a high vacuum before the crude 1H NMR?
Thanks in advance.
I am working on seaweed polysaccharides and I conduct proton and C13 NMR analysis for the characterization of these polymers. So is there any good software that can interpret the NMR signals/peaks? Or atleast any experts who can help with this?
Is there any rule to apply in the deconvolution of a MAS V51 NMR curve (in my case, the central transition -1/2 <-> 1/2)? Like limitation of the number of peaks, baseline selection, etc.?
I have used two polymer called PCL and PLGA in 50:50 ratio to make electrospun nanofiber. Are they going be present still in 50:50 ratio in the nanofiber? Is it possible to determine by NMR?
I am working with some molecules having benzotrifluoride and fluorobenzene. In the C13 NMR, some couplings are seen. If you have any good paper on the Carbon-Fluorine coupling and coupling constant, please share it with me. It will be appreciated.
I'm working on metal-organic coordination complexes, I got a wavy and large NMR shifts for some of complexes which I anticipated as paramagnetic.
Can you explain the relation between paramagnetic nature and large shifting in NMR ?
I am using MestReNova software for NMR data processing and plotting, but I am unable to find out an option by which I can show the integration and peak values in the stacked spectrum. stacked spectrum only showing peak, neither peaks values nor integration values. please help me out.
I am conducting long NMR experiments at 30°C on samples that contain some volatile compounds and chloroform-d as lock solvent. In order to avoid the loss of the analytes and the solvent, I would like to flame-seal the NMR tube. I managed to do so by using a torch lighter. However I found in some bibliographical sources that, the tube must be placed under vacuum.
My question is : Is it mandatory to place the NMR tube under vacuum when sealing it by flame ?
Looking for a high-reliability lab that can run plant samples for metabolomic analysis using untargeted approaches byeither NMR or LC-MS with follow up with data analysis (PCA/PLSDA).
If possible ideally also annotate discriminatory compounds
Already came across a few amongst which creative-proteomics/metabolomics in USA although many focus more on biomedical sciences (BioAnalytix Inc, Charles River Laboratories, or KBI Biopharma).
I have learned that there are different methods to study Hydrogen diffusion in metals, like pulsed field gradient (PFG) NMR, and quasi-elastic neutron scattering.
QENS has the advantage of giving the spatial and temporal information.
Are the both methods very effective for all the materials (here restricted in metals and alloys)?
What's the difference between them?
Are there any limits for these two methods? for examples, the covered length scale? or time scale?
I have synthesized a polymer of PAMAM and I see some traces of ethylenediamine (used for the modification) in the NMR. I want to know is there any method I can purify my polymer to get rid of the ethylenediamine? As purification of this polymer is difficult. Both the ethylenediamine and polymer are soluble in the same solvent.
Der NMR colleagues,
- How can one discriminate NH2 from NH3+ reliably by use of solid-state NMR. The difference in 15N chemical shift due to protonation is often smaller compared to changes induced by different crystal-environments.
- Due to technical limitations (spinning speed < 15 kHz) we do not have the possibility to acquired 1H data (not knowing whether this would help!).
- I measured buildup-curves [I5Nsingal(cross-polarization time)] of 15N magnetization, but the results were not very convincing.
Big thanks for any idea!
A sample of water and xerogel was prepared and used. The sample was put in the NMR machine. Then, the sample was inserted in the dryer and then again in the NMR machine several times. The same happened for the second sample which had water, xerogel, and NaCl.
Do you know any software (free would be the best!) to plot first-order simulated NMR spectra (including chemical shift, coupling constants, splitting pattern and integration)?
After NMR calculations with Gaussian 16 (NMR=(GIAO, SPINSPIN)) I obtained my chemical shifts and coupling constants. Unfortunately, Gaussview, as well as Multiwfn are able to plot only chemical shifts without taking account of spin-spin couplings.
I found WebMo seems able to carry out this kind of plot but not sure it is available for free and would prefer a program working stand-alone on my own computer. I also know NMRPlot, implemented with ENSO package for XTB is able to do this, but not sure it could read Gaussian 16 output.
Thank you by advance!
I have a mixture of some unknown chemicals. e.g. Isophthalic acid, terephthalic acid, adipic acid or neopentyl glycol, 1, 6-Hexanediol, ethylene glycol etc.
In these mixture 1 component is measure while the other two are in very small quantity which I am not able to detect in NMR.
Can I find the small quantity via GC-MS? if yes, how to develop the method for the detection?
Solvent suppression or in general selective suppression of NMR signals is well established and known in 1D 1H experiments. But how to perform multiple signal suppression (more than one NMR signal) in 2D experiments ? for example perform a COSY with the suppression of two specific NMR signals.
I am working on a NMR data but I could not open the file format in MNova 14. It is showing unknown fid file format repeatedly. I tried to find out the solution but I could not sort it out. Please leave your valuable suggestions to get me out of this problem.
Hello to you all,
In my lab we are trying to find a substitution for producing amorphous water to our current method (using 50 % glycerol and freezing with liquid nitrogen).
When researching the matter, I couldn't find any physical method that produces any substantial amounts of well-vitrified water.
The closest thing would be high pressure freezing used in EM, but it seems that the degree of crystallisation is still quite high here, at least in areas of the sample.
We are using the glassed sample for dynamic nuclear polarisation experiments. The less well-vitrified our sample is, the less NMR signal we get due to the nonuniform distribution of the radicals needed for signal amplification
In our group, the monofunctional benzoxazine monomer containing both bulky group and reactive group was synthesized, and then copolymerized with main-chain benzoxazine resin to form a series of copolymers. We proposed that increasing free volume and cross-linking density simultaneously in the resin could induce the formation of specific multi-structural networks (relatively dense near reactive group and relatively loose near bulky group). We did not find the evidence of the presence of multi-structural network based on the homogeneous morphologies from FESEM results. Nevertheless, the assumed mechanism could be discussed based on the results of true density and cross-linking density (DMA) results of the copolymers.
Now we just wonder whether solid NMR is available to characterize the formation or presence of the multi structural network.
I performed a Gaussian calculation and get the data of NATURAL LOCALIZED MOLECULAR ORBITAL (NLMO) ANALYSIS.
I'm wondering if it would be possible to get the sum of the contribution of ''Pi NLMO'' to each Cartesian NMR shielding tensor.
What keyword should I use to get all the NLMO that contributions to Atom in different portions(ex: Sigma-zz) using Gaussian and NBO7.0?
I calculated the NLMO by using the keyword ''NMR=GIAO pop=NCSall IOp(6/65=-1)'' in NBO3.0.
But, it does not work for NBO7.0.
I have samples that contain analytes with relatively low concentration (in the order of tens of ppm) in various solvents (aqueous and organic solvents). As the 1H NMR solvents signals are very strong they hinder the observation of the analytes signals (which are present in relatively low quantities), hence, I would like to perform 1H multiple solvent suppression experiments. How should I proceed ? Which pulse program to choose ? (I work on a BRUKER Avance neo spectrometer).
Thank you in advance.
If I were to look at the same Li salt in a series of solvents would I expect to observe a trend in which the 7Li NMR signal shifts up field (becomes more shielded) as the Gutmann donor number of the solvent is increased? What other important characteristics of the solvents should I consider when analyzing the results of said experiment?
Can anyone suggest me how to distinguish between two -NH proton in NMR . my ligand structure consists of two -NH protons. From NMR it was observed one -NH peak resonated at 11.27ppm and another at 10.59ppm. Both the NH protons lie side by side and both of them are attached to carbonyl group on either side. Now I have to ascertain which NH proton posses 11.27 ppm value and 10.59 ppm. Structure is given below. Should I go for D2O exchange NMR.plz help.
I have been making labeling medium for NMR work where I add the following:
K2HPO4 12 g/L
KH2PO4 9 g/L
15NH4Cl 3 g/L
NaCl 2.5 g/L
ISOGRO®-13C,15N, Powder 1 g/L
13C-Glucose 4 g/L
MgSO4 0.5 g/L
H2O 1 L (pH adjusted to ~7.4 with NaOH)
When I adjust the pH to 7.4 I observe a huge precipitation. What is precipitating?
Hoping all you are fine.
I need to know if someone can recommend me how to know if Al extracted from a zeolite is extraframework or of the framework? (Other technique than NMR of Al)
In Colombia it is complicated to perform NMR of solids and we need to know that data.
Open also to collaborations.
Thanks a lot,
With kind regards,
I have tried to quaternise P4VP and the mass residue increases from 0 to 12% at 750oC. I have tried to quaternise by chloroacetamide and confirmed it through FTIR and NMR
Hi everyone, I hope you can help me answer my questions:
1- what is the benefit of terminal hydrogen in nanosheets?
2- I need simple information help me to understand B3LYP, LaNl2DZ, GGA and BSSE in easy way
3- I need simple information help me to understand NLO, UV, IR,NMR, E(thermal), ZPE and Cv and their importance in hydrogen storage
The protein is in phosphate buffer pH 8 and when i try to decrease to ph7 it aggregates.
Is a virus envelope protein with 42 Kda and it is fusogenic. I want to do some NMR experiments with this protein, and i can decrease pH in low concentrations like 5 uM. But when i concentrate to 300 uM it aggregates.
Thank you all!
Our group is trying to synthesize PIM-1 and bought some TFTPN from different companies. However, the TFTPN from different companies showed different colors-from white to yellow. The companies told us that they are the same good and provided us with the NMR spectrum. I am confused about how could the same compound has two colors. Did you encounter the same issue before or have any idea?
I searched the related questions, some people answered that the nitro group will make this carbon missing in the NMR. But I would like to know the principle how does the nitro group affect?
I have functionalised some low viscosity alginate with adipic dihydrazide. I have already carried out FTIR on the polymer, which shows that my synthesis has been successful in modifying the alginate with the ADH. I am now trying to conduct NMR on it to find the degree of functionalisation. However, I cannot get the alginate-ADH to dissolve properly in any of the standard NMR solvents (DMSO, DMF, water). Deuterated water has been the most successful so far, but the alginate will only dissolve at 0.25 wt%, which is too low to get a good spectrum. At the standard 2 wt% it forms a gel, which means I can't do NMR on it. Does anyone have any idea what is causing this problem or what I can do to solve it? Thanks in advance!
These are the papers I used for the synthesis protocol:
They do not mention any solubility issues when it comes to conducting NMR.
In a synthesis, I am trying to react a cationic Re complex (with BF4 as counter anion) with tetrabutylammonium chloride. This gives me a Re-Cl complex and nBu4NBF4 (tetrabutylamonium tetrafluoroborate) in the reaction mixture. For workup, I am washing with pentane and diethylether and extracting the ReCl complex in benzene. But the NMR shows signals for tetrabutylammonium cation. Could anyone suggest me how to clean up the reaction?
P.S.: The Re compound is air and water sensitive. Prepared in glove box.
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?
In Vietnam, there is not any place to test the solid-state CP-MAS C13 NMR spectra at the current time. If you know, please recommend in the details (contact person, reference price, and so on). Thank in advance!
It is known that direction of the ring current in an aromatic molecule is such as to generate a magnetic field that opposes the external field inside the ring (a 'diatropic' current), while the ring current in an antiaromatic molecule flows in the reverse direction ('paratropic'). What is the reason behind this?
Can anyone please explain which type of structure is preferred for a ligand-Receptor docking study? When both the NMR based and X ray crystallography based structures both are available in PDB?
Hi I am relatively new at using Gaussian. I ran an NMR calculation in gaussian09 but when I try to view this it doesn't look anything like the example in the documentation. It doesn't show any splittings or couplings even though I used the SpinSpin module. Also I have fewer plot properties visible. Have I missed something out of my input file? Sorry if this is a silly question and thanks in advance.
I seem to be having issues adding attachments. This is the beginning section on my input file.
#n B3LYP/6-31G(d) NMR = (giao,spinspin)
Sorry I wasn't clear, I was already using GaussView. I've now used another computer to upload pictures and you can see in the NMR I've done its a series of lines rather than a spectra with the splitting patterns and there aren't many properties available to alter.
I want to make Poly(N-Isopropylacrylamide) amine terminated, using Free Radical Polymerization (i use AIBN as initiator and DMF as solvent, reaction temperature is 70˚C) and 2-aminoethanethiol as chain transfer agent.
After polymerization, i concentrate the reaction mixture and precipitate in ether, then filter and vacuum dry to obtain white powder.
I have tried several times but the NMR spectra shows no peak of amino terminated.
Is there any tips or suggestion to make AESH correctly reacted and make sure that my product has amine terminated group at the end of polymer chain?
I am trying to use CB(8) and various gels as a part of my PhD project, and wish to do some NMR on it to confirm inclusion within it. But as it is quite insoluble in many solvents or they become a gel in other solvents, I do not know the best way to go about it. Any suggestions would be appreciated!
I intend to characterize a synthesized polymeric particle, and I've been wondering if the CP-MAS version can provide any additional information about the involved chemical bonds and the material's inherent properties. If it does, is the method of interpretation any different?
It's a Sparky beginner. I wanted to make a nice picture with protein assignment but for all assigned residues I have the name format as ex. L166N-HN and I want to avoid "N-HN". I have found in Sparky manual that:
Display format for assignment labels
The assignment format specifies how to display assignment labels on contoured spectra. The default format is "%a1-%a2" for a 2-D spectrum. The "%a1" means display the full atom name for the w1 assignment. The full atom name includes the group. Then the "-" is just put into the label. Then "%a2" means display the atom name for the w2 assignment. The "%a2" will not display the group if it is the same as the group displayed in the preceding "%a1" part. To force the groups to be displayed use "%A1-%A2". In general, "%a" means display the atom name and leave off the group name if the preceding % format displayed the group, whereas "%A" means always show the full atom name. To show just the group names use "%G1-%G2". To show just the group name for the w2 axis use "%G2".
So I've changed the assignment format for %G2, but nothing changed in my spectrum, although peak list changed. I also tried to save the new peak list and upload it again, but then I have problems with unreadable lines..
I have a question concerning a 2D-1H/1H-NOESY NMR of a two-compound mixture.
The compounds in question are two atropoisomers which are present in a roughly 2:1 ratio (the phenomenon of atropisomerism is known for these compounds:
- Kingo, U. et al., Chemistry Letters 1999, 28 (1), 63-64
- Göstl, R. et al., Chemistry – A European Journal 2012, 18 (45), 14282-14285
- Uchida, K. et al., Journal of Molecular Structure: THEOCHEM 2002, 579(1), 115-120
- Goldberg, A. et al., The Journal of Physical Chemistry A 2003, 107 (25), 4982-4988).
Having examined the corresponding 1H, 13C, COSY, HSQC and HMBC- spectra I could elucidate the connectivites of the major compound present (in CD2Cl2 @ 280 K, concentration roughly 50 mM). To ascertain which of the two possible atropoisomers is the major compound at hand I have recorded a 2D-NOESY spectrum and the result is shown in the attachment. What you see there are the crosspeaks between the aliphatic protons (namely the allylic protons of a 1,2-cyclopentene moiety and the methylene of two attached 2-ethyl-hetar-1-yl systems in 1,2-position of the cyclopentene).
Now the strange thing I noticed are the crosspeaks e.g. between the dublett at 7.81 ppm to the multipletts at 3.05 and 2.90 ppm since HSQC clearly tells me that these latter two multipletts clearly correspond to the minor species. Along those lines, the crosspeaks between the three multipletts at around 7.55 to 7.65 ppm to the multiplett at 3.25 ppm should also not be possible since the former downfield multipletts clearly belong to the minor species (as elucidated by heteronuclear coupling).
The question I have is now the following:
Has anyone of you experienced similar artifacts in 2D-NOESY spectra?
Best regards and I'm looking forward to your ideas
EDIT: Could it be that the mixing time was too long and that this is why I see correlations between the isomers?
I synthesized alginate methacrylate and performed an NMR spectrum. I'm not an expert in organic chemistry and I would like to be sure how to calculate the degree of methacrylation.
Thank you very much for your help
I have a freshly synthesized formyl-CoA but not sure if it really is. Some published articles introduce that they used ToF Mass spectroscopy. But as a matter of money and time, for me it will be difficult to use it.
What other techniques can I use to identify this big molecule formyl-CoA?
Can I use NMR?
A little explanation of how it's possible will be hugely appreciated.
I prepared an in-cell E. coli NMR sample according to the protocol mentioned in :
However, I was not able to lock the sample with 10%D2O. Any help would be highly appreciated. Thank you.
I suspect I have some dissolved methane (and maybe propane) in my aqueous solutions. Please see attached spectrum (for both spectra: number of scans is 256; same receiver gain; same method; water suppression was poorer for my experimental sample). In green is my experimental sample and in red a control one with only pure water (red shows a few peaks which can only be some sort of contamination). If it was a liquid or solid species, I would buy a commercial standard and spike my NMR tube after acquiring the spectrum to see if a new peak(s) appears or the one I saw previously grows (confirming it's the same species).
Is this possible with gases? Should I simply add such gas in the headspace of the NMR tube, shake the contents for a while, and re-analyze?
On top of this, I'm of course performing all sorts of negative controls to make sure these putative gases don't come from a contamination and were indeed synthesised during my experiments (which is what I'm looking for).
I did some reaction of polymer synthesis in which triethylamine was used. I have NMR of the resultant polymer in which I am expecting that triethylamine is converted into diethylamine. Is it possible? Please share some references. Thanks in advance.