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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101 views

Elucidating an unknown compound using 1H- and 13C-NMR spectral data [closed]

I am currently struggling with the following NMR spectrum for this compound: I know for sure that we should multiply the integrals of the hydrogen atoms by four, and that the compound contains at ...
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2answers
50 views

Just looking for some help with finding relative ratios of components in a mixture using proton NMR

G'day, I am used to identifying molecular structure in isolation using proton and carbon NMR, but have never worked with a mixture before. The mixture relates to the following spectrum: The spectra ...
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Spectroscopy of phosphite

These images were taken from IChO 2002 prep problems. May I please know why there are 7 peaks for C-H? This indicates that there are 6 hydrogens the H in the C-H is coupled too, but I can only find 5 (...
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Reading materials about Spin 1 Systems in NMR

I am working on spin 1 systems and I came across this book Spin 1 NMR by Chandrakumar and chapter13 of Spin Dynamics. This book is good but i still have doubts pertaining to the system Hamiltonian ...
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1answer
112 views

Can resonance structures account for NMR spectroscopy chemical shifts?

I am unable to understand why the alpha carbon to the carbonyl group is of lower chemical shift compared to the beta carbon based on the effects of electronegativity and hybridisation. Since if ...
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50 views

How to make standard sample for NMR signal-to-noise ratio

I want to make a sample for proton NMR signal-to-noise-ratio measurement. It is conventional to use 1% ethylbenzene in d-chloroform, as specified here. I have two questions: What is meant exactly, by ...
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40 views

Why is the 2-bond (Sn-H) coupling constant larger than the 3-bond Sn-H coupling constant for tetraethyltin?

I was looking at the NMR spectrum of tetraethyltin [$\ce{Sn(CH2CH3)4}$], and found that the $\ce{Sn-H}$ coupling constant between $\ce{Sn}$ and $\ce{CH2}$ is larger than that between $\ce{Sn}$ and $\...
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2answers
163 views

NMR spectrum chemical shift confusion

Recently started on NMR spectrum, and I'm slightly confused about chemical shifts and their connection to the resonance frequency and magnetic field. From what I know, the "new" way of doing ...
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1answer
32 views

Does the amplitude of the RF pulse affect the NMR signal?

I know that the NMR signal depends on the static magnetic field strength $ B_0 $ (by Boltzmann equation) and its gyromagnetic factor. While NMR occurs when the RF pulse frequency matches the equation: ...
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52 views

Which atoms in indole possess the greatest amount of electron density?

Presumably the amine acts as an electron donor, but that would suggest extra electron density of the adjacent carbons, making them more shield, which isn't seen in the results in the image below. ...
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96 views

Why does the addition of heavy water cause OH and NH peaks in NMR spectra to disappear?

When $\ce{D2O}$ is added to a sample, the OH and NH peaks in a $\ce{^1H}$ NMR spectrum disappear. This is the basis of (for example) the $\ce{D2O}$ shake test, and is also the reason why peptide/...
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Find the structural compound from carbon and proton NMR spectrum

The proton and carbon NMR spectrum datas for compound W (201 g/mol) are shown below. Based on Diagram 1 and Diagram 2, draw the structural formula of compound W according to the type of hydrogen and ...
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1answer
55 views

Assignment of the 13C NMR spectrum of 4'-bromoacetophenone

I was doing a 13C NMR prediction of 4'-bromoacetophenone on chemdraw but I can't figure out why positions 5 and 5' appear further downfield than positions 4 and 4'. I know both Br and the carbonyl ...
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1answer
229 views

Is this the NMR spectrum of 3-methyl-1-butanol?

It is a $\ce{^1H}$-NMR spectrum and I think the signal near 3,61 ppm is the CH2 group next to the hydroxy group. But which signal is the hydroxy group and which protons are in the multiplet?
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1answer
51 views

Why would substitution of H with D alter chemical shift?

The $\ce{^{119}Sn}$ chemical shift of the dimeric tin hydride shown below (R=terphenyl) changes on addition of $\ce{D2}$ from a 1:2:1 triplet at $\pu{657.9 ppm}$ (due to coupling between $\ce{Sn}$ and ...
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1answer
397 views

How do you distinguish ferrocene, acetylferrocene and diacetylferrocene in a NMR spectra? [closed]

I made an experiment where I made a Friedel-Crafts acetylation of ferrocene. Now I would like to know if/how I can distinguish ferrocene, acetylferrocene and diacetylferrocene in a NMR spectra? For my ...
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1answer
55 views

The type of H-NMR spectra observed for S=PF2H and other inorganic molecules similar to this

I was hoping to learn more about the types of splitting observed in inorganic molecules such as S=PF2H. I am familiar with the typical splitting patterns associated with the study of organic molecules ...
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Why are 13C CP MAS NMR signals sometimes split by N, and absent in dipolar dephasing?

A past paper question on solid state NMR I was looking at asks why, in $^{13}$C CP MAS NMR, carbons directly bonded to nitrogen are "occasionally" split, and why they're usually absent in ...
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23 views

How do we explain NMR shielding in filled valence shells?

It is universally recognized that NMR measures the shielding of nuclei from magnetic fields by electrons. The electrons move, producing an eddy current that produces an opposing magnetic field. It is ...
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3answers
749 views

How to assign overlapping multiplets in 1H NMR spectra?

In the above $\ce{^1H}$ NMR spectrum ($\pu{400 MHz}$, $\ce{CDCl3}$) the methyl, alkene, and $\ce{CCl3CH2}$ protons are fairly easy to assign however, the protons in the cyclohexene ring show overlap ...
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29 views

Assigning carbon-13 NMR for ethyl 2-oxo-2H-chromen3-carboxylate

I have a molecule and an NMR spectrum, and I need to assign the NMR peaks to each of the carbons to the molecule: I know that the 14.19 ppm and the 61.94 ppm correspond respectively to the carbon 12 ...
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1answer
65 views

Do the αβ and βα states of homonuclear AX system have same energy?

I was studying nuclear Overhauser effect and came across this diagram$^1$: This diagram shows the energy levels of four possible nuclear spin states of homonuclear AX system. The white/grey boxes ...
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36 views

Origin of the NMR shielding

In a paramgnetic material the induced dipole moment of atoms or (molecules) of the material aligns with the external field. I can understand this by Zeeman splitting. A term symbol splits into states ...
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44 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
48 views

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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37 views

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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1answer
42 views

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
638 views

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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1answer
55 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 ...
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2answers
157 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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75 views

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
58 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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84 views

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
59 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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176 views

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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66 views

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
100 views

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
102 views

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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0answers
81 views

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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549 views

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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88 views

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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214 views

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
998 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 ...
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1answer
472 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
172 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
345 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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665 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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