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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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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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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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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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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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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126 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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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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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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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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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
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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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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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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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T1 spin-lattice relaxation times, deviation from exponential relationship

For longitudinal relaxation, one would think that the magnetic moment obeys this simple relationship $$M_z = M_0\left[1 - 2\exp\left(\frac{-t}{T_1}\right)\right].$$ However there is always a point ...
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Why does peak decoupling occur in H-NMR spectra?

For example, when we analyze the conversion of some chemical compound, certain characteristic areas tend to decrease (ok). However, why can a peak (i.e., one peak) generate smaller peaks (i.e., more ...
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Why does Larmor precession occur in NMR?

Larmor precession is the phenomenon that in NMR the spin (and by default also the magnetic dipole moment) of protons does not line up with the applied magnetic field but rather precesses around this ...
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How far does the delocalisation (resonance) effects for substituents extend for a conjugated system?

Let's say we have a conjugated system like this one: Now, the delocalisation of the benzene electrons with the nitrate system means that the ortho, and para positions on the immediate benzene ring ...
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Why does sensitivity of nmr spectrum improve with increased magnetic field strength

I am struggling to find an equation that illustrates this and a qualitative explanation to go along with it. I presume that the noise remains at the same intensity and somehow the intensity of the ...
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On the angle subtended between the angular momentum vector and the applied field for a single spin

According to Dr James Keeler of Cambridge University in one of his lectures at Queensland University, the angle theta can be any angle, but I struggle to see how this is true. There are only a certain ...
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677 views

NMR magnetically equivalent protons for a 1,4-disubstituted benzene ring

Below I have drawn a molecule with random substituents $\ce{X}$ and $\ce{Y}$: If the distances from $\ce{H_b}$ and $\ce{H_a}$ to $\ce{H_d}$ are considered, they are different - $\ce{H_b}$ is 5 bonds ...
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Interpretation of Carbon-13 NMR Spectra for Chemically Similar Carbon Atoms

I am analyzing the Carbon-13 NMR data from a reaction I will be modifying. There is not NMR data available for the specific compound I am attempting to synthesize; however, the compound I am ...
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NMR splitting of protons in a ring

I was presented with the following compound and asked to comment on the splitting of the proton $\ce{H_a}$ in $\ce{^1H}$ NMR. The question presented today was: What is the chemical shift (below) ...
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NMR Coupling in an aromatic system via π system

I was presented today with the following molecule: and asked the splitting pattern of $\ce{H_a}$ given that up to $\mathrm{^3J}$ and $\mathrm{^4J}$ coupling is allowed. I thought that $\ce{H_a}$ ...
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NMR of a bridging Methyl complex

I was provided with the following structure of an inorganic metal complex: And asked to give information on its NMR spectrum shown below The highfield signal is caused by a singlet with Platinum ($I ...
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NMR in pyridine no meta splitting

Consider the NMR of Brominated Pyridine shown below: When I looked at the NMR data, I was confused because I thought that H2 would also be split in the meta position by H6 but the data says that this ...
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How can the formula of WD-40 remain a trade secret?

Wikipedia says WD-40's formula is a trade secret How can it remain a secret today? Can't mass spectrometers, NMR and other equipment be used to determine the structure of the compounds that go ...
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Why does the nitrile carbon experience more shielding than a carbonyl carbon in CNMR?

In organic chemistry lecture, we were given a chart of approximate signal shift ranges for different carbon types in CNMR spectra. carbonyl carbons (C=O) have a range of about 155-210 ppm, but the ...
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which oxygen atom make intramolecular hydrogen bond in salicyclic acid?

When I googled about intramolecular hydrogen bonding in Salicylic acid, I found that there are two type of hydrogen bonding. Which one is more appropriate? And another question, if there ARE two ...
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What do X-ray diffraction and NMR tell about the Proteins? [closed]

I have gone through a simple idea that proteins have different conformations; it is a dynamic system. Moreover, whenever we do ensemble experiments, so we get an average picture. There are some ...
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Why do the NMR peaks shift when H+ concentration and temperature are varied on the reversible hydrolysis of pyruvic acid to 2,2-dihydroxypropionate? [closed]

We performed two experiments. Each of the peaks are referring to the methyl peaks in both reactant and product of the hydrolysis reaction. We varied $\ce{H+}$ concentration of the reaction and the ...
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AX Spin system ordering

I would like to ask a question about the ordering of the $\ce{X}$ spins on the right hand side of an $\ce{AX2}$ energy diagram. I was given the diagram here below: and asked to evaluate why this ...
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Definition of NMR peak

In NMR a spectrum consists of noise and peaks. While steps, such as repeated scans or smoothing of the spectra can reduce noise some still remains. As such one step usually taken is to bin the data so ...
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Determining structure from C-NMR spectrum, is my answer correct?

Determine the structure of the compound whose spectral data is given below and explain your reasoning (5 marks for structure, 15 marks for reasoning). The peak at 7.27 ppm does not belong to the ...
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Identify the structure of the compound (C3H5NO) given its NMR chemical shifts

I am trying to figure out the structure of the compound $\ce{C3H5NO}$ given just the following data from the 1H NMR spectrum: $\delta 5.8 ~ \text{(singlet, 1H)}; \delta 6.2 ~ \text{(triplet, 2H)}; \...
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H-NMR with 10H integration?

I have the following two spectra (IR and 1H-NMR) see below. The chemical formula is: C16H16O2 Thus DBE = 9 My approach: From the IR, I can see that there's no broad peak around 2500-3300, thus I ...
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Am I using these spectra to identify the compound correctly?

What is the structure of the molecule whose data is shown below? Explain your answer [...] EI mass spectrum: The highest peak observed is $m/z$ 210 and its abundance is low. The only other significant ...
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How to recast Henderson–Hasselbalch when fitting data on a chemical shift vs. pH graph for NMR

I've just been getting into organic and been reading about H-H related to $\mathrm{NMR}$. I've been seeing articles state how recasting of H-H is necessary and want to know how equations like below ...
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Determine structure from NMR

So I've come across this lovely spectrum of a compund where only its chemical formula is given with C5H9NO. I have made the pictures of the spectrum available below. obviously there is some pretty ...
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How do I figure out how many hydrogens my compound actually has using a mass and NMR spectrum?

Question 3: It said $m/z = 122,$ and $m/z = 124$ is in a $3:1$ ratio, so I figured that meant that chlorine is present. Then I thought $m/z$ was the actual compound's molecular mass. So I used ...
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Determining number of unique hydrogens in lactupicrinal 1H NMR

I'm having trouble understanding which hydrogens are magnetically distinct in the following molecule (lactupicrinal): I've counted all the hydrogens (there are 20) and I know that hydrogens in a ...
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How does the splitting in this molecule take place?

Consider the following molecule and data: $$ \begin{align} \mathrm{H_a} &= \pu{1.0 ppm} &\quad J_\mathrm{ab} &= \pu{5.0 Hz}\\ \mathrm{H_b} &= \pu{3.0 ppm} &\quad J_\...
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Identifying Structure based off 1H-NMR & Mass Spectroscopy Data [closed]

I have almost the whole night trying to identify this structure with no avail as there is always one part that does not fit. The determined formula for this structure was $\ce{C13H17BrO}$ from the $m/...
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Radiofrequency transmitter in an NMR experiment: Is there an involvement of (electromagnetic) radio wave?

A student in Chemistry StackExchange asked the effect of radio waves on matter, which led to an interesting set of arguments by some users. It was pointed out that in a proton nuclear magnetic ...
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What are the effects of radio waves on matter?

Different regions of the electromagnetic spectrum interact differently with matter: Microwave radiation can induce molecular rotation. Infrared radiation can induce molecular vibration. Visible and ...
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Why is cis proton coupling larger than trans proton coupling in cyclopropanes?

In Clayden, Greeves, Warren Organic Chemistry Second Edition Page 815, it states: In four- and three-membered rings, cis couplings are larger than trans ... but I did not find an explanation for ...

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