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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How to construct NMR spectra from chemical shift tensors?

If I know the chemical shift tensor (from ab initio methods), $\sigma$, for each atom in my structure, is it possible to construct an NMR spectra for my system? If yes, how and what mathematical ...
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What other nuclei besides hydrogen and carbon 13 could be detected using NMR and is H1-NMR synonymus to NMR?

From my understanding NMR spectroscopy works by analyzing the resonance frequency of each structure around a hydrogen or carbon. Since every structure is unique and has unique resonance frequency it ...
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HNMR - Peak Splitting

If you have $\ce{CH3-\color{\red}{CH2}-CH2Br}$ Then the $\ce{CH2}$ (in red) would have a peak splitting of $12$ because $(n+1)(m+1)$ where $n$ for the $\ce{CH3}$ is $(3+1=4)$ and m for $\ce{CH2}$ is $...
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Can the amount of shielding in proton NMR caused by ring currents be predicted?

My textbook (Organic Chemistry, 2nd Ed. Hornback, Joseph) states that if a hydrogen is located near the center of an aromatic ring it will experience an (often quite sizable) upfield shift, as seen in ...
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Identifying protons in NMR using the J values

When looking over an old organic midterm I came across this question. As you can see I got half of it right, but honestly I'm not sure how I got that one right or how you would answer this in ...
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How many signals would be seen in total in the 13C NMR spectrum

This is NanoBalletDancer. How many different carbon environments are there in NanoBalletDancer – i.e. how many signals would be seen in total in the 13C NMR spectrum? I counted 8 signals from ...
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605 views

Unexplained peak cluster in proton NMR trace?

I am working on a straight-forward NMR graph as part of my test prep. I have a pretty limited understanding of NMR, but I thoroughly read the chapter leading up to this practice question and am having ...
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1H-NMR and deducing structures

here is the data booklet we must refer too: Here is the exam paper solution: I dont understand how they conclude this. Peak areas and the chemical shifts seem to be different for me. For example ...
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Why are NMR typically taken for a power of 2 scans?

Why do we typically take $n^2$ scans, even in the basic NMR experiment? I've heard various explanations, including that it helps the fast Fourier transform, and would like to know the real reason.
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rate determination by 1H NMR spectroscopy

Currently I investigate a reaction where a starting material A reacts with an excess of thiophenol B towards products C and D. As shown by recurrent TLC analysis of the reaction, the formation of D ...
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How do I overlay spectra in an ACD/NMR Processor, version 12.01?

I am having great difficulty getting spectra to overlay (the option doesn't even appear) after setting to new window mode and selecting each spectrum.
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Alcohol irregularities in Hydrogen NMR

We've started learning about NMR in my ochem class and my instructor told us that in Hydrogen NMR an alcohol can have a fairly wide range of possible values - usually from about 2 to 5. He said that ...
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¹¹B NMR in a borosilicate tube

I'm just wondering, if one were to run a $\ce{^{11}B}$ NMR on a boron containing sample in a borosilicate tube, how could we separate the spectra of the tube and the sample? Apart from using a ...
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How to predict a COSY NMR spectra for an AMX spin system?

Does anyone know how to draw (predict) a hypothetical COSY NMR spectra for AMX spin system (the spin of A M X nuclei is 1/2)?
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Is aromaticity of the 4 aromatic amino acids affected by pH?

During a discussion of NMR, my lecturer told me to think about which amino acids contain protons in an aromatic ring, and whether any are likely to be affected by changes in pH. The 4 aromatic amino ...
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Chemical shift value and proton NMR spectroscopy

I am a bit confused about what chemical shift value signifies in proton NMR spectroscopy. If the proton of the standard substance TMS absorbs X Joules of energy to go into resonance, than a substance ...
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Sources for raw 1H-NMR data?

Where can one find examples of raw data for an 1H-NMR spectrum? This may sound as an odd request, so I'll give some context. I have found lots of images of spectra such as this: where you can see ...
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What is the multiplicity of this signal in the ¹H NMR of glutamine in D₂O

The 2 Hydrogens near the carbonyl (the lower 2 $\ce{H}$s are not bonded to the nitrogen) should be the most deshielded so I think they appear as the rightmost peak in the NMR. Are these 2 $\ce{H}$s a ...
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Why are all the phenyl protons in benzyl alcohol equivalent in the ¹H-NMR spectrum?

Below is a $\ce{^1H}$ Nuclear Magnetic Resonance (NMR) spectrum for benzyl alcohol. The hydrogen in the alcohol group gives rise to a unique signal. The two hydrogens in $\ce{CH2}$ give rise to a ...
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Can ammonia be detected by a 1D-1H-NOESY experiment?

I'm not detecting ammonia in my samples while using a NOESY pulse program for a 1H-NMR experiment. Is it possible for ammonia to be detected by a 1D-1H-NOESY experiment?
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What is deuterium-depleted water actually used for?

I noted, flipping through the paperback Alfa Aesar catalogue today, that they sell deuterium-depleted water. Under the usage category, they list 'NMR'. I'm trying to work out what specific use this ...
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Why is the Gaussian Window Function used to enhance resolution in 1D NMR spectra?

In a recent question it was explained that Gaussian window functions are not used in 2D NMR spectra as they can introduce artifacts into the spectrum baseline by truncating the FID. Why then are they ...
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Why is a squared cosine window function commonly used for 2D spectra?

In nearly all default parameter sets for 2D NMR experiments on Bruker spectrometers, the window function is set to a pure squared cosine function for both dimensions (...
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Why do aromatic hydrogen atoms have a higher chemical shift value compared to aliphatic hydrogen atoms?

In Nuclear magnetic resonance (H-NMR) spectroscopy, the chemical shift of aliphatic hydrogen atoms are very much closer to the 1.0 ppm than that of aromatic hydrogen atoms. Aromatic hydrogen atoms ...
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Can a NOESY NMR experiment be halted partway through and give meaningful results?

Some NMR experiments can be halted partway through the acquisition and still give perfectly valid results: The traditional 1H experiment for example. Others, like a Saturation Transfer Difference ...
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238 views

Why is it so difficult to create mock NMR spectra of macromolecules?

From what I understand, if you have a NMR spectra, you can determine the structure of a macromolecule but it is very difficult to determine what the NMR spectra of an expected structure would look ...
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13C NMR spectrum only showing solvent

This is my first time taking a $\ce{{}^{13}C-NMR}$ spectrum and while I'm aware the signal to noise ratio is much lower compared to $\ce{{}^{1}H-NMR}$, I didn't realize it was quite this bad. I took a ...
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Regenerating the imaginary data of a 2D NMR spectrum with a hilbert transform

2D spectrum take up a large amount of hard disk space. At my last lab it was standard practice to delete the imaginary portions of the spectrum with xfb n (We used ...
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What are the differences between the HMQC and HSQC experiments?

This afternoon, I was having some trouble with an HSQC (Heteronuclear Single Quantum Coherence Spectroscopy) spectrum I was trying to acquire, and the spectroscopist recommended I try HMQC (...
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What factors are important for quantitative analysis of a proton 1D-NMR spectrum?

Besides elucidating or verifying a chemical structure, NMR can also be used e.g. for quantifying a mixture of different chemicals. Depending on the quality of the spectrum and the specific substance,...
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What benefits do higher-rated NMR tubes provide?

You can buy NMR tubes in a huge variety of qualities, with an equally huge difference in price between the cheapest and the most expensive NMR tubes. They are usually rated for a specific spectrometer ...
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Splitting of multiplets in ¹H NMR spectra?

I'm currently taking VCE (Victorian Certificate of Education) Chemistry classes, and we're currently studying the interpretation of spectra produced by Hydrogen NMR (Nuclear Magnetic Resonance) ...

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