Nuclear Magnetic Resonance. This tag relates to NMR spectroscopy, the experimental technique of measuring the resonance and thus deducing the molecular structure of the given compound.

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absorption radiation in NMR [on hold]

what is the reason of resonant absorption by nuclear spin only with the correct frequency of EM radiation that is applied? why it is not possible for applying arbitrary EM radiation to excite the ...
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Historically, how was the connection between NMR peaks and hydrogen atoms made?

A large part of the basis of this question may be due to the student who didn’t pay attention in the history section of the NMR course (and not during the technical details bit either) but I find the ...
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What would the phosphorus-NMR of trifluorodiphenylphosphorane look like?

I'm fairly new to NMR especially $\ce{^{19}F}$ and $\ce{^{31}P}$ NMR, we've not been formally taught NMR yet but we're expected to know $\ce{^{19}F}/\ce{^{31}P}$ NMR for our exam for basic molecules. ...
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19F MAS NMR chemical shift tensor and the crystal structure

$\ce{^{19}F}$ MAS NMR is measured on fluorine-doped $\ce{TiO2}$. $\ce{F}$ is to substitute $\ce{O}$ and the crystal structure is anatase, which has a tetragonal crystal system with a space group ...
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Relative magnitudes of 2- and 3-bond coupling constants

Why is geminal coupling weaker than 3-bond coupling in complex coupling? It would make more sense that atoms that are closer to each other influence each other more. Take methyl acrylate for example. ...
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Determination of structure by 13C and 1H NMR spectroscopy

I'm trying to interpret a $\ce{^{13}C}$-NMR and $\ce{^1H}$-NMR spectrum. So far, I've decided that $\ce{CH3-C}$, $\ce{CH2-CH3}$ and $\ce{CH-CH}$ exist in the structure. I'm not sure but I guess there ...
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Monitoring H -> D exchange

I was wondering how the exchange of hydrogen by deuterium, like on arenes like benzene could be monitored for a reaction on a scale larger than say 10 g of product. While I know that C6D6 is ...
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1H NMR of Acetylferrocene

I'm trying to analyse the proton NMR of this, and there's one singlet for the H on the non-substituted Cp ring and a singlet for the methyl group, as expected. However, while I was expecting to ...
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Wavy baseline in carbon NMR

I realize anything NMR-related is essentially physics, but I figured this was a better place to ask this. I have this issue fairly regularly (with one instrument in particular) where my baseline ends ...
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Why does Mn(CO)5(CH3) have a 1H NMR peak at -0.21 ppm?

I would have thought that all the pi backdonation from the Mn to the carbonyl would reduce the electron density on the CH3 increasing the chemical shift.
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How to explain two NMR spectra of the (allegedly) same compound with slightly different shifts?

For my synthetic lab work I synthesised a Horner-Wadsworth-Emmons phosphonate; for the sake of the question let’s assume it to be the one presented in the image below. When first synthesising it, I ...
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Why are the ethyl ester methylene protons not diastereotopic in ethyl (+-)-2-methylbutyrate?

In the following compound, there is one chiral center and two methylene groups. Why are the protons on the ethyl ester methylene not diastereotopic?
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Benzene and proton in 1H NMR

The chemical shift in benzene is around 7.27 ppm, which is lower than, for example, aldehydes. However, the magnetic field due to the pi electrons are in line with the applied magnetic field $B_0$, ...
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In NMR Spectroscopy why use absorption and dispersion components of the FID spectrum rather than magnitude and phase?

In chapter 4 of Dr James Keeler's book 'Understanding NMR spectroscopy' (http://www-keeler.ch.cam.ac.uk/lectures/Irvine/chapter4.pdf) he explains how to calculate the expected spectrum of a FID ...
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Identify products of Propiophenone using nmr

I've been analyzing a compound "propiophenone", using NMR and IR, and I can't tell which of the nmr spectrums relates to which isomer of C9H10O2 is which. At first I thought the two isomers ...
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H NMR of 4-chlorochalcone

In an aldol condensation reaction, I synthesized a molecule out of two unknown reactants. These reactants I found to be 4-chlorobenzaldehyde and acetophenone which made 4-chlorochalcone. I was given ...
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Percolation network analysis with 1H MAS solid state NMR

Assume you have a composite rubber that was produced in an extrusion process and it consists of a basic polymer with some additives. One of the additives does not get mixed with the basic resin but ...
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What happens to the shielding of the proton when an alcohol is oxidized?

The full question: For H-NMR, the magnetic field experienced by a hydrogen atom can be externally applied or internally induced or some combination of the two. When the applied and induced ...
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Does this NMR show the carboxy group?

This is the NMR for the molecule shown. I was told that carboxy group will be in the above 10ppm range. Does that tiny signal at about 12.9 ppm indicate the carboxy group though? I dont understand ...
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Book says hydroxyls produce singlets in region 1.5ppm - 5ppm, but I dont see how or why?

For example, the $\ce{CH3OH}$ molecule I've uploaded. The hydroxyl H is within 3 bonds of three other equivalent H's, so this would produce a quartet using n+1 rule, wouldn't it?
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Does diamagnetic anisotropy only apply to a proton bonded to triple bonded carbon?

Lecture tells me that double bond, with the sp^2 bonding will have more s-character, which will hold the electons closer to nucleus, which means a more deshielded proton which means downfield chem ...
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How many total absorptions would appear on proton -NMR spectrum for this molecule?

I count 7 equivalent absorptions total, but answer says 8. I don't see where this eighth absorption comes from? Heres how I'm counting starting on right side of molecule: 1 is Carbox acid H 2 is ...
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Why do NMR spectrums have the higher chem shift values closer to x-axis? [closed]

Im not understanding what the intuition is behind why the graph is represented so that the higher chem shift value is closer to x-axis (shouldnt it be the other way around?) I understand that ...
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Why don't labile protons such as -OH and -NH have a characteristic chemical shift?

Is it simply because the H instantly disassociates so it is a proton with zero shielding?
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Why use TMS in NMR spectroscopy

I get the thing that TMS has a large proton number giving a strong spike in NMR spectrum but apart from that is there any other reason why just TMS is used and not any other molecule, can't it be a ...
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Determining structure using ¹H NMR and IR

I have a homework problem where I'm to draw the structure of a compound of molecular formula $\ce{C10H12O2}$ using the following IR data and $^1$H NMR spectrum: IR absorption at 1718 cm$^{-1}$ ...
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Coupling constant in 1H NMR with phosphorus

I had a doublet with peaks at 5.6336 and 5.5886 ppm with the machine running at 300 MHz, I got a $J_P$$_H$ of 13.5 Hz is this correct for this molecule ( Ethoxycarbonylmethyl(triphenyl)phosphonium ...
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Interchange of axial and equatorial groups in Me2NPF4

The $\ce{^{31}P}$ NMR spectrum of $\ce{Me2NPF4}$ when recorded at room temperature consists of a quintet with intensities $1:4:6:4:1$. However, at $-100~\mathrm{^\circ C}$, the spectrum is as shown ...
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What does radiofrequency really do in NMR & MRI?

In NMR, the protons’ frequencies are affected by the magnet which makes them precess around its magnetic field so now all protons will have different frequencies according to their environment ...
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Why only one peak is observed in NMR spectrum of H2?

Assuming a downward magnetic field is applied and the nuclear spin of two equivalent protons in $\ce{H2}$ are all in ground state $\downarrow\downarrow$ initially. Would the required energy of one of ...
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Diastereoisomer of quinic acid and its proton NMR?

The question is such: Quinic acid, A, has the gross structure shown below: (i) Draw all the possible diastereoisomers of A and indicate which are chiral. (ii) Quinic acid is optically ...
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How to distinguish diastereomers of unsaturated ketones by NMR?

I am synthesising a natural product that contains an α-methylated α,β-unsaturated ketone (see image below). The natural product’s stereochemistry is an (E) configured double bond. I ...
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Interpretation of 1H-NMR spectra for Z-ochtodenol

I'm struggling to understand the 1H-NMR data for this compound. I managed to find the compound using the data I had, but at the end I can't assign the peaks properly. My confusions are: ...
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NMR coupling pattern for hydrocarbon

What does the 1H NMR spectroscopy coupling pattern look like for the hydrogen attached to the carbon that the blue arrow is pointing to? There is a $\ce{CH2}$ attached to ether side of the carbon, ...
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Coupling patter for a methyl-butyl ether [duplicate]

What would the high resolution H-NMR spectroscopy coupling pattern look like for the hydrogen attached to the carbon the arrow is pointing at? I am confused because there is a CH2 connected to either ...
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Explanation for these 1H NMR spectra?

In CDCl3 solution, the different diastereoisomers of 3-amino-2-butanol have different 1H spectra: for one diastereomer, the coupling constant between H atoms on C2 and C3 is 6 Hz, for the other it is ...
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Why are protons in the same position in 1-chloro-4-nitrobenzene magnetically different?

Protons in ortho positions towards the nitro group are said to be magnetically different, even though they're chemically equivalent. Same goes for protons ortho towards the chlorine. Why is that so?
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Deuterated solvents vs. regular solvents

Working on dissolving aspartame and i was wondering if it dissolves well in methanol will this mean that it dissolves well in deuterated methanol ?
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How to isolate and determine an unknown molecule in a known heterogeneous mixture using HNMR

I am currently working on an assignment as part of my second year lab course. Essentially I have to determine the unknown molecule which is present at 5-15 wt% in 1 gram of Aspartame. I am planning ...
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Proton-decoupled phosphorus spectrum of a ruthenium complex

>Regarding the complex $\ce{[RuH2(CO)(PPh3)3]}$ There are three possible ochtahederal stereochemical configurations, a) Draw these isomers indicating which, if any, are chiral and identify ...
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How does one calculate chemical shift in a gauge independent manner?

The literature on ab initio calculations of chemical shift in NMR experiments usually provide Lamb's and Ramsey's formulae as the solution. Yet the expressions explicitly depend on vector potential ...
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How many peaks would there be in H1 NMR of ethene?

Would there be 2 peaks? Since the bonds can't rotate. Likewise, how many peaks would there be in trans-but-2-ene and cis-but-2-ene?
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Shifting of axial and equatorial protons

I know this NMR represents cyclohexanol and I have figured out what each peak represents. If the 3 peaks at 1.9, 1.7,1.5 all represent equatorial protons as they are shifted downfield compared to the ...
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NMR analysis problem

I've been given this NMR along with the IR and Mass Spec and assigned the task of figuring out the unknown compound. I know that it is cyclohexanol and by analysing the NMR I know that the peak at ...
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308 views

Why does DMF (dimethylformamide) have 3 peaks in its 1-H spectrum?

I get that the carbons can't rotate around the nitrogen due to its partial double bond character, but how does this result in the hydrogens being in different environments? As such would this mean all ...
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NMR: Estimate rate of coalescence when coalescing signals are multiplets

The coalescence rate on a 300 MHz spectrometer can be found from $$k_C \approx 2.22 \cdot \Delta \delta * 300 $$ The difference in chemical shift is easy to find when only singlets coalesce, but ...
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Identifying spin system for ethyl butanoate

I am to identify the spin system of ethyl butanoate, but I am confused as to how I should start. Chemically equivalent and not magnetically equivalent: $\ce{AA'A''}$ or $\ce{BB'B''B'''}$, etc ...
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H NMR of 4-chloroacetophenone

For the H NMR of the compound I am wondering why peak (A) is the farthest out of all of them? I think that it is due to the electro negativity of oxygen. Am I correct? If so, why would the presence of ...
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Is there a consensus how to report coupling patterns greater than quartets?

When analysing NMR spectra, every student at one time during their chemistry studies learns about vicinal coupling and that it produces the characteristic signal shapes of proton spectra. The ...
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How to control the purity and quality of fatty acids or their CoA thioesters?

Background: We are looking into getting a series of cis-mono-unsaturated very-long-chain (C20-C32) fatty acids (with different, specific double-bond positions) — and/or the corresponding acyl-Coenzyme ...