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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predict the no. of signals in NMR spectroscopy for the compound-3-nitro butan-2-ol [closed]

i would like to know the details, such as the triplets or quadruplets as given in the NMR spectroscopy for the compound 3-nitro Butan-2-ol.
Akshaya Devi Vijaya Kumar's user avatar
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Methanol splitting pattern [closed]

for methanol, are the splitting patterns 2 singlets or 1 singlet and 1 doublet. And does OH group in COOH always show a singlet pattern
tbro's user avatar
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1 answer
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Why does epsilon caprolactone not have triplets on 1H NMR?

Looking at the structure of epsilon caprolactone (CL), you'd assume that the methylene protons (CH2) on either side of the ester would give you triplets. However, experimentally those peaks actually ...
CurioChemo's user avatar
7 votes
0 answers
183 views

Difference in 13C NMR spectrum

The tasks proposed in Spectroscopy challenge, I found two structures that are mostly similar in allylic moiety, the contradiction is presented below: Considering two carbons of the alkene bond, it ...
Shira's user avatar
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Carbonyl and thiocarbonyl 13C NMR

According to this paper, the deshielding effect of C=S group is specifically due to the delta(11), which is the least shielded component. However, the conclusion tells me that this component is ...
Seiji's user avatar
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Why do protons in same chemical environment do not exhibit spin-spin coupling?

Reading introductory tutorials on proton NMR for the determination of chemical structure, I was told that protons can exhibit spin-spin coupling, thus creating multiplets on an NMR graph. The coupling ...
ScientiaNatura's user avatar
2 votes
1 answer
102 views

2D NMR of a Funky Disaccharide

Below you'll find the structure of the disaccharide and three 2D NMR spectra - COSY, HSQC, HMBC. I have to match the signals in the spectra to the nuclei that caused them. Answers to any subset of the ...
Dilara's user avatar
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Multiplicity and signals of cis−[(Ph3P)2PtF2] in two NMR spectra

I am interested in the number of the signals and their multiplicities in the $\ce{^{31}P\{^1H\}}$ and $\ce{^{19}F\{^1H}\}$ NMR spectra of $\ce{[\textit{cis-}(Ph3P)2PtF2]}$. It is given that $\ce{Pt}$ ...
MathEnthusiast's user avatar
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Why would 1-ethenyl-2,6-dimethylbicyclo[2.2.0]hexane give off 8 H1 signals?

I am trying to figure out this problem, and can only find seven signals, two from the double bond, one from the single bond attached to the double, there is symmetry, so one signal on the methyl, one ...
Benjamin's user avatar
2 votes
0 answers
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Which group is more ortho/para-directing?

Currently working on assigning the C NMR and H NMR spectra for this molecule (I believe it's called E-E bis(4-methylbenzylidene)acetone ) but I'm a bit confused as to whether the methyl group is more ...
ajk's user avatar
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Why do t-butyl and isopropyl groups deshield the ipso carbon in C13 NMR more than a Me group?

I have a t-butyl group attached to an aromatic ring and I am confused about why it increases the shift of the ipso carbon about 20ppm. I know that C is slightly more electronegative than H, and this ...
Daniel Corcoran's user avatar
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Carbon 13 NMR peaks - ketones

Why the shift of acetophenone's carbonyl carbon at C13 NMR spectrum is larger than the equivalent peak at trifluoroacetophenone ? Particularly , the first one is located at 197.94 ppm whereas the ...
user142167's user avatar
7 votes
1 answer
418 views

What is molecular "tumbling" in NMR?

In NMR textbooks, it is often said that small molecules tumble faster and large molecules tumble slower. What is "tumbling" exactly? When I searched for it, someone says that it is any ...
Krang Lee's user avatar
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1 vote
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Assignment of NMR peaks of polystyrene

I’m having trouble identifying the peak around 3,75 ppm in the 1H-NMR spectrum of polystyrene measured at 400 Hz in CDCl3. Could someone please provide their perspective on it? I see it appear in a ...
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NMR splitting of equivalent, but separated protons

I’ve been trying to understand why equivalent sets of protons that are coupled behave as equivalent to a single coupled pair. For example in the spectrum for Diethyl ether: Both groups of Hb are ...
Mozzd's user avatar
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Predicted H NMR spectrum shows two signals for NH2 group

There are two singlet signals for NH2 group around 2.4 and 3.05 ppm. Spectra is predicted (from MNova), so there was no water present. Why the signal of NH2 group isn't a broad singlet?
Lucia Boldišová's user avatar
-1 votes
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Why are different Aluminium valencies observed from NMR and what logic can be used to normalise molar ratios of different valency atoms?

Question 1: I've observed different chemical shifts in 27Al Nuclear Magnetic Resonance (NMR) spectra of commercial aqueous sodium aluminate, indicating the presence of both trivalent [Al(III)] and ...
Hendrix13's user avatar
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2 votes
1 answer
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How to determine the value of the NOE from the NOESY spectrum?

I have 1D NOESY spectra from which I need to find out the value of the NOE (%). Is it enough to simply measure the intensity of the resulting peaks or is it necessary to subtract it from the ...
Klee's user avatar
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1 answer
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H-NMR Analysis of C15H24O

I was able to figure out that the structure of this compound was a benzene ring with 2 equivalent trimethyl groups to give the 18H singlet. Another non-equivalent methyl group to give the 3H singlet. ...
Mason's user avatar
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31P-13C coupling in bis(diphenylphosphino)methane

In the 13C NMR spectrum of bis(diphenylphosphino)methane (dppm), some of the phenyl carbon signals appear to be split into triplets. It makes sense to me that the center methylene is split into a ...
newbie chemist's user avatar
1 vote
1 answer
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What shifts protons on a benzene ring to lower ppm?

Why do these protons appear at 6.9 and 6.93 ppm, at lower ppm value? I assumed it was due to the anisotropic effect, specifically I thought the circulating (pi) electrons induced a magnetic field ...
ilovecats's user avatar
4 votes
1 answer
426 views

Interpreting NMR: what does it mean when there are two signals when there should be (and looks like) only one, and integration where there is no peak?

A couple of basic questions. So in this spectrum, there seem to be two peaks at 2.38-2.347, but this signal should be a singlet and correspond to the methyl group. So does this mean anything? Another ...
anfjnn's user avatar
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What's the current of an aromatic ring?

Aromatic molecules like benzene have a ring current, created by the movement of electrons around the ring. This is most visible during proton NMR, when the magnetic field of the ring current opposes ...
WaveInPlace's user avatar
3 votes
2 answers
222 views

NMR and dienes to isolate certain isotopes?

I am looking to achieve isotope separation using transition states. In the rxn of dienes with halogens, based on the temperature, the dienes can create a thermodynamic product or a kinetic product. ...
Young Jun Lee's user avatar
2 votes
1 answer
577 views

evaporating DMSO/Ethanol

I'm preparing to do a thiolclick reaction and to get a homogenous phase I found it's best to use DMSO/ethanol as solvent for the -ene and thiol reagents. I need the ethanol specifically for hole-...
Tom Meijer's user avatar
3 votes
0 answers
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What could be the origin of a persisting distorted water NMR signal?

I am currently running some solvent suppression experiment on water samples. I first run a one scan 1H experiment to get the ''O1P'' and then implement it in the solvent suppression experiment (''...
Salem's user avatar
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-2 votes
1 answer
320 views

How to read 1H-NMR- and IR-spectre (for ibuprofen) [closed]

I have read the answers to related/similar questions. They didn't help. I have to read a proton-NMR-spectrum and an IR-spectrum of ibuprofen. The structure formula is given to: I have not been ...
Daniel's user avatar
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3 votes
1 answer
503 views

What's the exact mechanism of spin coupling in NMR?

The most common one that's found nearly in every textbook and site is that splitting occurs due to the alignment of neighboring proton either with or against the external magnetic field so as it's B ...
Amr Ahmed's user avatar
5 votes
1 answer
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Why are fluorine-19 NMR spectra less affected by paramagnetic centers than other common nuclei?

I know that 19F NMR spectra are less sensitive to paramagnetic centers as an empirical fact: it’s my experience and that’s what people in my lab have always been saying. For instance, some of my ...
XChemist's user avatar
2 votes
1 answer
384 views

1H-NMR: How does the oxygen in ethers act as a spin coupling barrier while the oxygen in hydroxy groups doesn't?

It is possible to observe coupling between a hydroxyl proton and other protons. Why does the oxygen atom in ethers prevent any further coupling and act as a sort of barrier between spin systems? Or is ...
hebabla's user avatar
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2 votes
2 answers
1k views

NH protons not appearing in H NMR spectrum of 3,4-dihydropyrimidone derivative (solvent: CDCl3)

My synthesized compound is 3,4-dihydropyrimidone derivative, which has 2 nitrogen in the ring. The $\ce{NH}$ protons are not appearing in the H NMR spectrum and the solvent used was deuterated ...
joe 's user avatar
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2 votes
1 answer
169 views

How to interpret this pair of IR and 1H NMR spectra?

I need to figure out the structure of a $C_{8}H_{14}O_{2}$ molecule with this IR spectrum: and these $^{1}$H NMR spectrum signals: m means 4 or more spikes. I worked out that the degree of ...
Zyxl's user avatar
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0 votes
2 answers
238 views

Which Hydrogen in this structure is more deshielded/shielded?

Looking at the 2 hydrogens connected to the Carbon-carbon double bond, which hydrogen is more deshielded or shielded?
user307640's user avatar
7 votes
1 answer
989 views

Why has acetaminophen only two different NMR chemical shifts related to phenyl?

I learned that, by using NMR, you could tell how many different hydrogen environments an molecule has. For example, benzene has only one. Since acetaminophen has an amide bond, and the bond has ...
satoru kurita's user avatar
1 vote
1 answer
401 views

Why are the protons of ethene magnetically equivalent?

According to this website, For two protons to be magnetically equivalent they not only have to have the same chemical shift, but they must also each have the same J coupling to other magnetic nuclei ...
Akash's user avatar
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2 votes
0 answers
68 views

Fermi Contact Interactions and resultant coupling contants

I am currently learning about spin-spin coupling mechanisms and have become very confused about the mechanisms by which spin-spin coupling happens in NMR. I understand how we can draw diagrams where ...
FFerreira's user avatar
0 votes
0 answers
131 views

NMR Assignment of cinnamaldehyde

I'm struggling to understand the assignment of the aromatic protons in this compound. Based on the simulated spectra (and lit spectra), the three protons on the left are all overlapping. To the best ...
Peter's user avatar
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5 votes
1 answer
135 views

Why is a ring carbon C-R of a substituted ferrocene more downshifted on 13C-NMR?

Upon assigning $\ce{^{13}C}$-NMR for 1,1'-bis(α-methylmethanol)ferrocene, we discovered the substituted FcC-CH peak (95.14 ppm) was more downshifted than the CH-OH peak (65.59 ppm) as was confirmed by ...
Kld952's user avatar
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12 votes
3 answers
717 views

Reconstruction of NMR spectrum by entropy maximization (MaxEnt)

Currently NMR spectra are generated by Fourier transformation of free induction decay curves from time domain to frequency domain. In the late 60 s-80s some researchers proposed reconstruction of NMR ...
AChem's user avatar
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2 votes
1 answer
608 views

Why does population difference matter in NMR

I know that population difference matters in NMR for sensitivity, that the splitting is dependent upon the gyromagnetic ratio of the nucleus, and that the population of the spin states is almost ...
CasualChemist96's user avatar
3 votes
0 answers
80 views

Regioselectivity in oxo-Diels-Alder reaction

I have one doubt about the dimerization of methacryloyl chloride into the product 3: The dimerized product was observerd around 10-15mol% in different commercial samples of methacryloyl chloride, as ...
Elnani's user avatar
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0 answers
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Tips on understanding one-bond J couplings in NMR

I have just started a spectroscopy course in nuclear magnetic resonance, which I have loved thus far, but have been extremely puzzled regarding 1J coupling constants. I was wondering if any of you had ...
nking1390's user avatar
3 votes
0 answers
140 views

Can proton NMR be used to study transition metal complexes?

I prepared metal complexes with a Schiff base ligand L using cobalt(II) chloride hexahydrate, iron(III) chloride hexahydrate, and nickel(II) nitrate hexahydrate. I used 1H NMR to study the difference ...
Sunita's user avatar
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1 vote
0 answers
333 views

Phenol's resonance structure doesn't match NMR

I've asked a question before and quickly realised that the resonance/mesometric effects played a large role in determining the C-13 NMR spectrum of phenol, shown below. This is the resonance ...
John Hon's user avatar
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How many hydrogen environments are there in phenyl acetic acid? [duplicate]

How does the molecule below have only three hydrogen environments? Should it not have 5 different hydrogen environments according to the labelled diagram?
jack Morgan's user avatar
1 vote
0 answers
19 views

Can two S=1/2 centers have J and D parameters simultaneously?

I am new to EPR/ESR and need some help in connecting theory with a published experimental data. Following is my query. What I understood from EPR theory is that two active EPR centers with S=1/2 ...
user49535's user avatar
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3 votes
0 answers
491 views

Why does heavy water have two different solvent peaks with DSS and TSP?

I was going through the NMR solvent peaks chart of Cambridge isotope laboratories (PDF) and I noticed that $\ce{D2O}$ had two solvent peaks: one at 4.8 with sodium trimethylsilylpropanesulfonate (DSS) ...
carbon12's user avatar
4 votes
0 answers
86 views

What is it about nuclei with low gyromagnetic ratios that make them unreceptive in NMR?

I'm having some trouble rationalizing why nuclei with low gyromagnetic ratios are considered unreceptive in NMR. I know it's because it will take a higher magnetic field to "hit" its Larmor ...
CasualChemist96's user avatar
5 votes
0 answers
332 views

Considering the odd mass number rule, how does $\ce{^{14}{N}}$ NMR work?

In my high school chemistry class, we learned that NMR only works for nuclei with odd mass number. Hence, we often use the $\ce{^1{H}}$ and $\ce{^{13}{C}}$ spectra. However, on this page about NMR I ...
MaplePanda's user avatar
2 votes
1 answer
164 views

NMR spectroscopy nomenclature: induced vs local vs effective magnetic field (B)

This is a simple question but I can't seem to find a place where they use the same nomenclature... I was wondering whether these are all the same thing: $B_\mathrm{induced}$, $B_\mathrm{local}$, $B_\...
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