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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Why is an alcohol proton so shielded?

Considering how electronegative oxygen is, why is the chemical shift of alcohol protons (1H-NMR) not so high? The chemical shifts of the protons on 3-propanol are about 1.20 for the carbon-1 ...
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Are there any free phosphorus-31 NMR spectral libraries?

I know that there are some sites like Sigma Aldrich and AIST for $\ce{^1H}$ NMR and $\ce{^13C}$ NMR, but was wondering if there were any free sites to compare $\ce{^31P}$ NMR spectra?
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How to compute the NMR shift in Gaussian09 for only one specific atom in a bigger unit cell?

I am trying to compute the NMR shift for a specific atom in the middle of the surrounding crystal unit cell (1 surrounding anion sphere and 1 cation sphere) in Gaussian09. I only need the chemical ...
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hydrogen environments of benzenephenone

The hydrogen in $\ce{C4}$, $\ce{C6}$, $\ce{C10}$ and $\ce{C8}$ belong to same hydrogen environment. The hydrogen in $\ce{C3}$, $\ce{C1}$, $\ce{C11}$ and $\ce{C13}$ belong to the another hydrogen ...
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Why does the transverse magnetization in Fourier Transform NMR consist of Ix+iIy ($\hat{I}_x+i\hat{I}_y$)?

More specifically, the expression for the average expectation value of the transverse magnetization has the following form: $$M^+(t)=N\gamma \hbar \text{Tr}(\hat{\sigma}(t)\hat{F}^+)$$ with ...
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What does the 129Xe NMR spectrum of XeOF4 look like?

What will the $\ce{^129Xe}$ NMR spectrum of $\ce{XeOF4}$ look like? I know that its electron pair geometry is octahedral, and the molecular pair geometry is square pyramidal. I believe that the ...
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66 views

How can I link the data to what I know as correct?

I am currently struggling with an assignment question regarding structural determination using both $\ce{^1H}$ and $\ce{^{13}C}$ NMR data. The first thing I have done is calculate my double bond ...
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42 views

Why are signals of carbon and hydrogen atoms (in NMR spectra) split by coupling to 19F?

Why signals of carbon and hydrogen atoms (in NMR spectra) are split by coupling to $\ce{^{19}F}$? Some spectra books only states that $\ce{^{19}F}$ (natural abundance 100%) has a spin quantum ...
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79 views

Are the circled hydrogens homotopic, enantiotopic, diastereotopic or unrelated?

I'm very confused. According to the answer key, the circled hydrogens are diastereotopic. I thought they were enantiotopic. My thought process is the following. They aren't homotopic because ...
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1answer
30 views

Proton attached to N or O in HNMR spectroscopy [duplicate]

I was wondering why a hydrogen attached to a nitrogen or oxygen is not able to couple with p+ on adjacent carbon atoms and hence why it always appeats as a singlet in HNMR spectroscopy?
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Multiquantum coherences in NMR spectra

Why are multi-quantum coherences unobservable in regular NMR experiments ? This is relevent to the DQ-filter experiment which exploits this property.
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[BrF6]- and it's 19F NMR

$\ce{[BrF6]^-}$ is an octahedral molecule. I think it would have only one fluorine environment due to the rotational symmetry. $\ce{Br}$ has I=3/2 and therefore is unlikely to cause splitting due to ...
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71 views

HNMR identification problem

Heyo, this a repost because my previous post's format was a bit mediocore and hence I though it would be just better to redo the post again. I have been trying to solve this NMR question for about 4 ...
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1answer
58 views

Spins spin coupling on proton NMR for an aldehyde?

On a proton NMR, does the hydrogen in the CHO group cause coupling, or get coupled itself? Specifically, I a considering 2-methylpropanal. I cannot decide whether the H in the aldehyde group would be ...
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32 views

The nuclear Overhauser effect

I am having some trouble with understanding the NOE. The carbon NMR spectra can't be integrated, because the protons attached to the carbon atoms will make primary carbon atom relaxation faster than ...
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1answer
86 views

What happens to chemical shifts of protons close to aromatic systems in ¹H-NMR?

I have two questions regarding chemical shifts on aromatic systems. First, what does being near an aromatic system do to protons? If we look at the spectra of 1-napthalenemethanol and then ...
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46 views

NMR population difference from a pulse of known flip angle

I want to know how a radiofrequency pulse of known flip angle $\beta$ changes the population difference of a set of isolated spin 1/2 nuclei. I know that the equilibrium magnetization is related to ...
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Help me to identify the structure of unknown compound from my 1H NMR , 13C nmr and dept 135

I need help to determine the structure of unknown compound from my 1H NMR , 13C nmr and dept 135 spectrum? I am a student and in my organic chemistry class we each had an unknown chemical from ...
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78 views

How can I deduce the structure of my compound from this NMR spectra?

I have no idea how to determine the substituents on the aromatic ring from this NMR spectra. There is (or ‘might be’) a triplet on my NMR around $7.59 - 7.65\,\mathrm{ppm}$ which has 4 hydrogens ...
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156 views

NMR: Magnetic and chemical equivalence in benzene

According to my textbook, all the protons in $\ce{^{12}C_6{}^{1}H_6}$ are magnetically equivalent, but those in $\ce{^{13}C_6{}^{1}H_6}$ are not. I understand that for two nuclei to be magnetically ...
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Pt[BrCl(PR₃)₂] cis, trans isomer nmr - Which is cis and which is trans?

the question is, The two square planar isomers of $\ce{Pt[BrCl(PR_{3})2]}$ have a different $\ce{^{31}P}$-nmr spectra. One shows single group of lines, the other shows two distinct resonances, each ...
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243 views

1H NMR Broad peaks

Is there any particular reason that peaks in proton NMR can appear with a larger integral ratio than expected, that is to say one specific proton absorption stretches over a wide ppm range? I have a ...
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How to predict the ³¹P NMR spectra?

What can I predict about the $\ce{^{31}P}$ spectra of $\ce{TiP2O7}$? To get the required information about the crystal structure of the compound, here is a screenshot from the ICSD website: Since ...
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90 views

Why do the two methylene protons in ethylbenzene have a chemical shift at 2-2.9?

The data sheet does not have any chemical shifts in this range for compounds containing only carbon and hydrogen
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Why do NMR coupling constants change with temperature?

Why do coupling constants change with temperature in NMR?
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Splitting across a double bond in ¹H NMR

Why do the Hs in the figure below split into doublets instead of staying as a singlet. Wouldn't they be isolated from each other since the double bond does not rotate?
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Spin spin coupling in a proton NMR of an ester?

I am learning about proton NMR and spin-spin coupling, and am confused about whether splitting occurs over an ester bond. Specifically, in the case of ethyl methanoate, HCOOCH2CH3, if I were to number ...
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proton NMR deshielding

The protons alpha to the oxygen in methyl propionate are more shielded than their corresponding protons in ethyl propionate. . We can see from the NMR data that this is the case as well. My ...
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Could I get a hint on the structure of this molecule based on HNMR spectra?

Chemical formula is $\ce{C7H6O3}$. IR spectra has a peak at 3238, which I believe could be an alcohol, phenol, or carboxylic acid. There's an additional peak at 3015, which I believe is either an ...
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1answer
140 views

What does it mean in a Ni(II)complex if the HNMR spectrum appears unbroadened and unshifted & what does this tell you about the coordination geometry?

I am trying to work out the an unknown Ni(II) complex. I don't known the geometry and I have read that broad lines on the nmr spectrum indicate large compounds with symmetric environments. Does this ...
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54 views

NMR and pseudorotation

I think it has something to do with the fact that at high temp it interconverts and so all the coupling constants are the same hence quintet but at lower temps the frequency of the rotation is less ...
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7,7-dichlorobicyclo[4.1.0]heptane NMR solving

i made a synthesis of this material in the lab and now i got the H-NMR specta , and by litreture i know that i got the right product. im having trouble to match the hydrogens to the peaks,i tried to ...
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Interpreting the NMR spectrum of Wittig salt p-carboxybenzyl triphenylphosphonium bromide

I synthesized the Wittig salt p-carboxybenzyltriphenylphosphonium bromide. Below is the proton NMR spectrum I measured. I'm having a little problem of matching the peaks to the hydrogens, especially ...
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116 views

Why is there a doublet instead of a singlet in this Wittig reaction salt configuration NMR?

I did an NMR sample to my salt p-carboxybenzyl triphenylphosphonium bromide. I got a doublet at 5.26, and according to every article it belongs to the $CH_2$ next to $P^+$, but how come I didn't get a ...
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201 views

Suggest possible structures for the compound PF3(Ph)(NMe2) using the NMR data

use these data to suggest the possible structure for the compound PF3(Ph)(NMe2): 19F Spectrum, two signals: a doublet of doublets, J=56 and 819Hz, -39.5ppm, relative intensity 2 a doublet of ...
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1H NMR proton coupling

I had the opportunity to work with a NMR spectrometer and decided to learn some of the theory behind it. After finishing Clayden's chapter on $^{1}\textrm{H}$ NMR (Ch. 11) I'm still left with some ...
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270 views

Assigning 1H NMR spectrum and predicting peak coupling patterns

I have a the proton NMR of this molecule: There are 6 individual hydrogens and none of them are equivalent. In the spectrum I have been given there are only four peaks. I have been able to assign ...
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284 views

Which has the higher chemical shift E/Z alkene?

If you have a simple alkene for example 1-methyl-But-2-ene then you will have two methyl groups on one side of the double bond, which one of these will have the highest. Will the one on the same side ...
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150 views

Assigning Carbon NMR

I have a molecule and I need to assign the carbon NMR to each of the carbons. My molecule is The peaks I have for the carbon NMR are shown below. I have also used the DEPT to work out if it's a ...
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1answer
45 views

Are there some similarities between J-coupling and j,j-coupling?

I'm a bit confused having heard two different terms in different lecture parts: J-coupling There is the J-coupling (= indirect dipole dipole coupling = scalar coupling) which arises from a ...
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How to assign the signals in the H-NMR of Aspirin?

I need to assign the H-NMR of aspirin, below is aspirin with the H's labelled. The peaks I have are: 2.30ppm (I this is a singlet and would be F) 7.07ppm (I think this is E) 7.29ppm ...
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147 views

HNMR Assignment

I have a molecule and i need to assign the hnmr. I have a printed spectrum So far my answer is: chemical shift_______splitting pattern_______coupling constant ...
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290 views

What splitting pattern is this?

I am trying to find the structure of an unknown molecule. What is the splitting pattern of these sets of lines? I think my unknown molecule is butanol and the hydrogens this splitting pattern is ...
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484 views

Proton NMR signals and rings

Does pyridine or furan have the more shielded proton NMR signals? I know that both are aromatic, so both have rather deshielded signals due to ring current combining constructively with the applied ...
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1answer
67 views

Chemdoodle to mestranova

Is it possible to copy my chemdoodle displayed structure into mestranovea? I have tried simple dragging (mac) and all the various copy/paste options... any ideas?
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130 views

13C NMR peak location in butanone

The above is the correct $ ^{13}C $ NMR spectrum of butanone. In the $ ^{13}C $ NMR spectrum of butanone, I figure that the peak locations of the first and third carbons should be switched (27.3, ...
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Relation in the sign (+/-) for gyromagnetic ratio and magnetic susceptibility

Is there a relation (or formula) between the sign of the magnetic susceptibility and the gyromagnetic ratio of a nucleus in NMR?
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465 views

NMR: Most deshielded protons (electron withdrawal)

Of these two molecules, which one would be expected to have the most deshielded signal? First off, I think the wording of this question is wack because neither of these molecules has only one NMR ...
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Using MestReNova: An Introduction

Can anyone help me with a quick question regarding MestReNova 9.0. I have been fiddling with this thing all day and before you ask yes, I have consulted the users guide to no avail. I want to do ...
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Nuclear magnetic resonance : Difference between S and I

In the lecture our professor told us that nuclei with S>1/2 have a quadrupole and are therefore detected with NQR instead of NMR. The majority of all elements have nuclei with S>1/2. I wondered why ...