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.
529 questions
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Double bonds in Ergocalciferol (coupling constant, NMR)
I have measured Ergocalciferol (below) and want to know how to interpret the coupling constant of 11 Hz between H9 and H10.
A rule of thumb is ca. 10 Hz = cis and ca. 15 Hz = trans for DB.
Between H21 ...
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Mysterious NMR Peak
I've tried to synthesize 7,7-Dichlorobicyclo[4.1.0]heptane via the cycloaddition of dichlorocarbene and cyclohexene. The dichlorocarbene was prepared in situ with chloroform, an aqueous NaOH solution, ...
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Proton NMR of Propanolol Hydrochloride
I noticed in previous references that the 3H region often appears as a multiplet in many propranolol hydrochloride $\ce{^1H}$-NMR spectra (most of them in DMSO-$d_6$ solvent). However, in this ...
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NMR water peak at 4.79 ppm in chloroform?
So I am teaching an organic chemistry lab right now, part of which is that the students measure their own H-NMR spectra and report on purity, impurities etc.
Now some of the students ask me about some ...
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Chemical shift of 29Si NMR in silicate species
In silicate species, the value Qn with n = BO/T is used to described a particular tetrahedral {SiO4} in which oxygen could form Si-O-Si bridge (BO) or Si-OH (NBO). 29Si NMR is used to determine the ...
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How far does an electron withdrawing group reach with respect to affecting proton NMR peaks?
Above is the proton NMR stretch for 1-nitropropane. There are three peaks, one at 1.0 ppm, one at 2.0 ppm, and another at 4.4 ppm.
The peak at 1.0 ppm can be attributed to methyl hydrogens and the ...
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Structure of an unknown compound
In my organic lab, I analyzed an unknown compound using ¹H-NMR, IR, ¹³C-NMR, and mass spectrometry. I selected the only colored compound in the batch—a yellow liquid, if I recall correctly. Although I ...
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Intramolecular H-bonding plausible in PCE derivative?
In $\ce{^1H}$-NMR (DMSO) I see two broad peaks at 9-10 ppm. The compound is the HCl salt of the first image, so the 2-fluoro (NMR structure wrong). Since I expected the protons to be identical I ...
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Why do Alkynes have Shielded Protons?
I have recently started reading NMR spectrometry, and just finished reading $\ce{^{1}H}$-NMR and $\ce{^{13}C}$-NMR.
I stumbled upon the varying chemical shifts of the three $\pi$ ring systems: 1) ...
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Nitrobenzene HNMR splitting (simple explanation for a HS student in Gr 12)
So, I am currently studying spectroscopy in school and I came across this question: "How many chemical signals would be expected to be seen in an HNMR spectrum of nitrobenzene".
I saw that ...
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Purification of thiols
I have synthesized various esters with a free thiol group from the corresponding alcohol and acyl chloride in DCM. For NMR, I need the substances to be very pure. How can I purify the compounds ...
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Proton shielding Proton NMR
In proton NMR, why does $\ce{COCH2}$ have a higher chemical shift than $\ce{CH3CO}$ in 2-butanone ($\ce{CH3COCH2CH3}$) despite both being next to C=O? Shouldn’t $\ce{COCH2}$ have a lower chemical ...
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(Why) Is TMS really needed to reference NMR spectra?
In NMR textbooks it is oftentimes stated that referencing NMR spectra to an internal standard such as tetramethylsilane (TMS) is necessary to make spectra comparable as the absolute resonance ...
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How to understand the contour plot of NMR data of peptide reconsituited into mechanical oriented DMPC membrane?
I need help understanding the contour plot I mentioned. I have two questions:
How do the authors relate the topological restraints to the theoretical model? As I understand it, the tilt vs. pitch ...
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Impurity in H-NMR spectrum of Hantzsch ester after synthetic procedure
In the $\ce{^1H}$-NMR spectrum of synthesized Hantzsch ester (a dihydropyridine derivative), there are some impurity peaks I cannot explain: a singlet at $\pu{8.81 ppm}$, a quartet at $\pu{4.4 ppm}$, ...
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