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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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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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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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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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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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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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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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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Product operator analysis for CHn groups in HSQC and HMQC

I'm taking and advanced NMR course this semester and we are learning about product operator formalism. I have a homework where I'm supposed to apply this formalism to an HSQC and HMQC experiment. The ...
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Chemical shift difference methyl groups in 4-hydroxy-2,5-dimethyl-3-hexanone

Can someone explain why the NMR Spectrum of 4-hydroxy-2,5-dimethyl-3-hexanone shows a chemical shift difference for the methyl groups at the end? Why aren't the other carbons have a difference? Below ...
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The IR/ H-NMR analysis of benzophenone?

I think I have figured out the IR spectrum for benzophenone. Would it be that the sharp peak in the middle (1700 cm^-1) is for the ketone and the little peaks pass 2900 cm^-1 rang are the sp2/sp3 ...
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Is it possible to estimate the abundance of conformers from J values?

I have a system of two disubstituted cyclohexanes and I want to estimate the abundance/ratio of the two based on the J values and if possible, roughly estimate the difference in free energy. To get ...
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The H NMR analysis of the hydrogens in salicylic acid

I am currently working with an unknown and from the IR spectrum I was able to figure out that the compound I am working with is salicylic acid. I am looking at the H NMR, but I am a bit confused on ...
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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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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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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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why is the H-NMR chemical shift of methane lower than that for ethane?

If we replace one hydrogen in methane by a methyl group we arrive at ethane. Now we can say: Carbon is more electronegative, and so it withdraws electrons which leads to deshielding. This is why the ...
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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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On the origin of spin-lattice relaxation

According to P.J. Hore in the Oxford Chemistry Primer "Nuclear Magnetic Resonance" p57, 'the dipolar coupling, modulated by molecular motions, causes nuclear spins to experience time-dependent local ...
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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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