Questions tagged [nmr-spectroscopy]

This tag should be applied to all questions about nuclear magnetic resonance, including the underpinning theory and the measurement or interpretation of spectra.

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35 views

$j$-$j$ coupling interaction in Magnetic Resonance Spectroscopy

I am studying Magnetic Resonance Spectroscopy and I have some difficulties in understanding the j-j coupling interaction. What does actually happen from the physical point of view to the electronic ...
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1answer
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19F NMR line spectra

I am trying to figure out the NMR spectra of F3P-BH3 I am solving this out using 2nI+1 rule. IP = 1/2 and IB = 3/2 Hence for this compound, (2nIP+1)(2nIB+1) = (2x1X1/2+1)(2X1X3/2+1) = (2)(4) = 8 ...
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Why would T1 relaxation time change ~20 fold between solvents for the same substance?

I have a simple, completely conjugated pyridinium salt with MW of ~300 g/mol. The molecule consists of regular non-labeled atoms (only C, H, N). If the 1H T1 relaxation time for this molecule is ...
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why the The 15N–{ 1H} spectrum of [Pt(NH3)3 H2O] shows 6 lines instead of 3 if all the NH3 are supposed to be equivalent? [closed]

The 15N spectra for [Pt(NH3)3 H2O] shows 6 lines, I don't understand why because the 3 (NH3) are chemically equivalent and when interacting with Pt will generate a double satellite lines and a middle ...
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1answer
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Identifying the molecular structure of compound with sum formula C8H14O3 formula using NMR and IR spectrometry data

I am looking to identify the molecular structure of a compound with the sum formula $\ce{C8H14O3}$ using the NMR and IR spectrometry data below. I was able to figure out the molecule as My friend ...
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31 views

Volume of sample for quantitative NMR

I’m interested in quantitating lithium via NMR using a Magritek Spinsolve 60MHz bench top NMR spectrometer. Is there any evidence that suggests the volume of the liquid sample used in the NMR tube has ...
6
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2answers
149 views

How can a nonlinear field gradient be generated in NMR?

I am working on the topic of optimal control in NMR, where spins undergo non-unitary evolution caused by gradient field pulses at different time intervals. I am studying the effects of this on the ...
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2answers
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Diastereotopic methylene protons in achiral molecules

Are the protons in methylene groups of achiral molecules such as propane-1,2,3-triol or 3-hydroxypentanedioic acid diastereotopic? Consider propane-1,2,3-triol. To me, replacing one of the protons in ...
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1answer
47 views

Finding the structure based on spectra

I had to identify the structure of a drug based off the spectra I had. I suck at this. I gave it my best go and got some ugly structure, only to check it using a database and find out I was wrong. I ...
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Negative DBE/Degree of Hydrogen Deficiency?

I tried calculating the Index of Hydrogen Deficiency for C6H15SiCl, and I get negative one. I get this value by subtracting the number of chlorine and hydrogen atoms from that of the carbon atoms, and ...
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1answer
51 views

Benchtop NMR spectroscopy parameter explanation; tau and number of points [closed]

I have just carried out an exploration of the effect of different solvents and conditions on the 1H caffeine relaxation by benchtop NMR spectroscopy. When collecting the 1D 1H NMR spectra of the ...
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H NMR signals in 1,4-dichlorobutane spectrum

I have come across H NMR spectrum of 1,4-dichlorobutane and I have noticed that signals there are different to what I would intuitively expect. Instead two triplets there are two multiplets of more ...
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Splitting of ethyl ester proton NMR

I synthesised a dihydropyridine molecule today and recieved my NMR. I am wondering where the complex splitting for the 7 and 22 protons is coming from. My spectrum: 1.26ppm, triplet, 6H 2.33ppm, ...
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2answers
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NMR definition and meaning [closed]

honestly, I have seen a lot of problems with "NMR" spectrums, I looked for this title in Charles Mortimer's general chemistry book, but I didn't see any sort of data, can anyone unfold what ...
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1answer
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Proton NMR splitting in 2-substituted furan

I have recently run proton NMR on 1-(furan-2-yl)ethan-1-ol I synthesised in the lab. My 400 MHz spectrum consists of the following peaks: 7.36 ppm (dd, J = 1.9, 0.9 Hz, 1H) 6.31 ppm (dd, J = 3.3, 1....
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1answer
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13C-NMR of aniline: Why are carbons that are further from the amine group more downfield than carbons that are closer? [closed]

A $\ce{^{13}C}$-NMR of aniline shows that the carbons further from the $\ce{-NH2}$ group are more downfield than the ones near the top of the benzene ring. If electronegative atoms like nitrogen have ...
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How to use NMR readings to determine the molecular structure of a compound? [closed]

A question in my exam came as follows: How is NMR used in the determination of structure of organic compounds? I have studied NMR spectroscopy and I know how to determine values using an NMR ...
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2answers
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Can non-deuterated solvents be used for 13C-NMR (and in fact other nuclei)?

Basically, my question is can you used a non-deuterated solvent for 13C NMR? I'm thinking that there might be some problems with locking?
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Challenges Associated with Earth's field NMR

The ACS recently hosted a virtual conference and there was an interesting talk on NMR experiments using the Earth's magnetic field. What surprised me was the number of molecules studied with Earth's ...
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Proton NMR of tert-amyl alcohol

I just started learning about proton NMR. According to Molbase, the HNMR data for tert-amyl alcohol (2-methylbutan-1-ol) shows four kinds of protons at 0.9 ppm, 1.24 ppm, 1.44, and 3.65 ppm. However, ...
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1answer
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What is the density of sodium trimethylsilylpropanesulfonate (DSS)?

I tried to look for the density of sodium trimethylsilylpropanesulfonate (DSS) online but could not find anything. Perhaps someone here measured it/knows where it may be found?
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1answer
224 views

Why is H in OH group is more shielded than in H in CH2 group (ethanol NMR spectroscopy)?

I am confused with this $\mathrm{^1H}$-$\mathrm{NMR}$ spectroscopy result: Shouldn't $\ce{H}$ in $\ce{OH}$ group the singlet be more towards the left of the $\mathrm{NMR}$ spectrum? It is near the ...
3
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1answer
253 views

Identify the structure of compound with C₉H₁₀ formula using IR and NMR data [closed]

Use IR and NMR data to define the structure of the molecule, the formula of the given structure $\ce{C9H10}.$ On what basis do we conclude that its structure is that (the answer) only? On what points ...
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Distinguishing between different geometries of bromochlorobis(triphenylphosphine)platinum(II) using ¹⁹⁵Pt NMR

Question The question off which I am basing my question assumes that $\ce{[PtClBr(PPh3)2]}$ can exist in either the square-planar or tetrahedral geometry. If one would use $\ce{^{195}Pt}$ NMR ...
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2answers
98 views

Why are excess nuclei required to produce an NMR signal?

In NMR, an excess population of nuclei is required to produce a signal. If saturation is achieved (same number of nuclei in the α and β states) no net signal can be produced. A signal is produced when ...
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1answer
106 views

What happens to the NMR of an alcohol when D2O is added?

What difference you expect in the 1H NMR spectrum of phenol in $\ce{CDCl3}$ after a drop of $\ce{D2O}$ is added to the test tube? 1) Since the $\ce{-OH}$ of the phenol is quite acidic, it undergoes ...
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196 views

Why does sp2 hybridization result in a greater chemical shift in carbon NMR?

Carbon NMR has a very wide chemical shift range. This is attributed to the relative proximity of electron-withdrawing groups (1-2 bonds separation) compared to proton NMR (2-3 bonds separation) along ...
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1answer
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Product operator analysis for CHn groups in HSQC and HMQC

I'm taking and advanced NMR course this semester and we are learning about product operator formalism. I have a homework where I'm supposed to apply this formalism to an HSQC and HMQC experiment. The ...
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Chemical shift difference methyl groups in 4-hydroxy-2,5-dimethyl-3-hexanone

Can someone explain why the NMR Spectrum of 4-hydroxy-2,5-dimethyl-3-hexanone shows a chemical shift difference for the methyl groups at the end? Why aren't the other carbons have a difference? Below ...
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The IR/ H-NMR analysis of benzophenone?

I think I have figured out the IR spectrum for benzophenone. Would it be that the sharp peak in the middle (1700 cm^-1) is for the ketone and the little peaks pass 2900 cm^-1 rang are the sp2/sp3 ...
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Is it possible to estimate the abundance of conformers from J values?

I have a system of two disubstituted cyclohexanes and I want to estimate the abundance/ratio of the two based on the J values and if possible, roughly estimate the difference in free energy. To get ...
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1answer
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The H NMR analysis of the hydrogens in salicylic acid

I am currently working with an unknown and from the IR spectrum I was able to figure out that the compound I am working with is salicylic acid. I am looking at the H NMR, but I am a bit confused on ...
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Explanation of Specific Chemical Shifts on an H-NMR Spectrum

Recently, I've been looking into chemical shifts on H-NMR Spectrums and I came across a graph I didn't quite understand... As you can see from the spectrum attached, the signal emitted from the ...
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HNMR spectroscopy mono-carboxylated acid

During lab, I have done following reaction: I did HNMR of the product, to be certain if the product really was formed. The HNMR gave following results: And looked like this: So my question is: has ...
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1answer
86 views

Sensitivity of Carbon NMR Compared to Proton NMR

I am trying to figure out exactly how much less sensitive carbon NMR is from proton NMR. In a lecture, my professor said that carbon NMR is 1/5800th as sensitive as proton NMR for the following ...
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1answer
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What is diamagnetic in diamagnetic dilution?

I'm reading a paper where the authors study a peptide solution where each peptide may have two spin labels attached to them. They put the peptides on the surface and study them using a diamond sensor. ...
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1answer
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Why do the splittings in mirrored COSY crosspeaks differ?

I have a COSY spectrum of a mixture of butanal and butyl bromide and I don't understand why the cross-peaks have various/different splitting on the other sides of the diagonal. I think it may have ...
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Open resource for spectroscopic raw data

Is anyone aware of reliable resources (ideally public) which allow the user to download the raw spectroscopic data such as infrared spectrum of small organic molecules, or rotational spectrum of HCl/...
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What is the best way to go about matching proton-NMR spectra to molecules?

I've attatched an example question. I have already solved this one, I'm wondering about what, in your experience, is the most time-efficient way of approaching a question like this one. I can solve ...
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Can all NMR spectrometers perform special techniques such as COSY, NOESY, HETCOR,..? [closed]

Do you need special spectrometers for: probing nuclei other than hydrogen or carbon? performing 2D spectroscopy such as COSY, NOESY, HETCOR, HSQC,.. Or are these techniques usually available on ...
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1answer
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Assigning Peaks and Determining J Values for Mata-Disubstituted Benzene

I need to determine as many J values as I can for 3-methoxybenzaldehyde. The peaks overlap a lot, and I don't see the expected ddd or dt pattern that I would expect for the hydrogen on carbon 6. The ...
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1answer
60 views

1H NMR of cyclohexanecarbaldehyde

Can someone please explain how to assign the 1H nmr peaks of substituted cyclohexane group? I am more familiar with interpreting substituted benzene. I get that the signal near 10ppm refers to the ...
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1answer
109 views

1H NMR of 4-Methylanisole

I have been pondering the assignment for the 1H NMR peaks observed. I can't really make sense of the observations from what I know. https://www.chemicalbook.com/SpectrumEN_104-93-8_1HNMR.htm My ...
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1answer
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Why do certain signals in proton NMR experience extensive splitting despite only having 1 neighbour?

I came across the compound 3-methylpentan-2-ol. Looking at its proton NMR spectra, it seems there is a lot of splitting for the signal at 4 ppm. I'm assuming that the 4 ppm represents the proton in ...
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Difference between H-NMR with C$^{13}$ and C$^{13}$- NMR [closed]

I don't know if I am overcomplicating things but I am having trouble understanding the difference between H-NMR with C$^{13}$ sample and C$^{13}$-NMR. For example, if I have the molecule below ...
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2answers
71 views

Coupling in C-NMR

Given the structure below, sketch the $^{13}$C - spectrum in a $^{13}$C marked sample The data given is the chemical shifts (left) and the coupling constants (right) The correct spectrum is given at ...
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309 views

Shoulders of NMR peaks

I want to ask a question about the shoulders of peaks when separating overlapping peaks. I have the following spectrum circled with relevant shoulders: I believe that the spectrum above shows an ...
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1answer
421 views

1H NMR splitting of 3-methyl-1-butanol

I have a question about 1H NMR splitting of 3-methyl-1-butanol. The spectrum looks as the following. The assignment of the NMR spectrum is the following. ...
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1answer
71 views

What exchange timescales are needed to cause decoupling in NMR?

I'll try to explain the source of my confusion as clear as possible: (*) The methyl protons in toluene are decoupled because the C-C bond between the methyl group and benzene allows very fast ...
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1answer
74 views

Software for simulating NMR spectra [duplicate]

I am wondering is there any open source software that predict NMR spectra by giving the chemical shift? Something like Spinach library http://spindynamics.org/group/?page_id=12 (Matlab is not free, ...

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