scholarly journals Carbon-13 NMR Chemical Shift of Methyl Group: A Useful Parameter for Structural Analysis of C-Methylated Flavonoids

2006 ◽  
Vol 1 (11) ◽  
pp. 1934578X0600101
Author(s):  
Pawan K. Agrawal ◽  
Chandan Agrawal ◽  
Shravan Agrawal
Keyword(s):  
Structural Analysis ◽  
Chemical Shift ◽  
Chemical Shifts ◽  
Nmr Chemical Shift ◽  
Methyl Group ◽  
Nmr Chemical Shifts ◽  
Nmr Study ◽  
Pterocarpus Santalinus ◽  
Group A ◽  
C Nmr

The 13C NMR resonances corresponding to the C-Me group of C-6 and/or C-8 C-methylated-flavonoids absorb between 6.7–10.0 ppm and typically between 6.7–8.7 ppm. A comparative 13C NMR study reflects that the 13C NMR chemical shifts reported for 6-hydroxy-5-methyl-3′,4′,5′-trimethoxyaurone-4-O-α-L-rhamnoside from Pterocarpus santalinus and 8-C-methyl-5,7,2′,4′- tetramethoxyflavanone from Terminalia alata are inconsistent with the assigned structures, and therefore need reconsideration.

The halogen effect on the 13C NMR chemical shift in substituted benzenes

2018 ◽  
Vol 20 (16) ◽  
pp. 11247-11259 ◽  
Author(s):  
Renan V. Viesser ◽  
Lucas C. Ducati ◽  
Cláudio F. Tormena ◽  
Jochen Autschbach
Keyword(s):  
Chemical Shift ◽  
13C Nmr ◽  
Chemical Shifts ◽  
Nmr Chemical Shift ◽  
Substituted Benzenes ◽  
Nmr Chemical Shifts ◽  
Halogen Effect ◽  
C Nmr ◽  
Group Effects

X (F, Cl, Br, I) and R (NH2, NO2) group effects on 13C NMR chemical shifts are explained by π and σ orbitals, respectively.

Origin of the 29Si NMR chemical shift in R3Si–X and relationship to the formation of silylium (R3Si+) ions

2020 ◽  
Vol 49 (45) ◽  
pp. 16453-16463 ◽  
Author(s):  
Winn Huynh ◽  
Matthew P. Conley
Keyword(s):  
Chemical Shift ◽  
Chemical Shifts ◽  
29Si Nmr ◽  
Surface Oxygen ◽  
Nmr Chemical Shift ◽  
Dft Methods ◽  
Nmr Chemical Shifts

The origin in deshielding of 29Si NMR chemical shifts in R3Si–X, where X = H, OMe, Cl, OTf, [CH6B11X6], toluene, and OX (OX = surface oxygen), as well as iPr3Si+ and Mes3Si+ were studied using DFT methods.

Synthesis, X-ray crystal structure, and solid-state 13C NMR study of tris(9-crown-3)triphenylene

2001 ◽  
Vol 79 (2) ◽  
pp. 195-200 ◽  
Author(s):  
Gerald W Buchanan ◽  
Majid F Rastegar ◽  
Glenn PA Yap
Keyword(s):  
Crystal Structure ◽  
Solid State ◽  
Crown Ether ◽  
Chemical Shifts ◽  
Aromatic Rings ◽  
X Ray ◽  
Nmr Study ◽  
Group A ◽  
C Nmr ◽  
Solid State 13C Nmr

Benzo-9-crown-3 ether trimerizes in the presence of FeCl3 and aqueous H2SO4 to produce tris(9-crown-3)triphenylene in 25.4% yield. This compound crystallizes in the monoclinic P21/c space group: a = 13.759(2) Å, b = 13.318(2) Å, c = 13.399(2) Å, β = 96.883(2)°, with Z = 4. The three 9-crown-3 ether units of the trimer possess different geometries and there is substantial deviation from coplanarity in the three aromatic rings. 13C NMR chemical shifts in the solid state are consistent with this lack of symmetry and are discussed in terms of the X-ray crystal-structure data.Key words: crown ether, trimerization, stereochemistry.

Carbon-13 nuclear magnetic resonance studies of organotellurium compounds. II. Chemical shift trends

1982 ◽  
Vol 60 (5) ◽  
pp. 596-600 ◽  
Author(s):  
Raj. K. Chadha ◽  
Jack M. Miller
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Chemical Shift ◽  
Chemical Shifts ◽  
Magnetic Resonance Studies ◽  
Nmr Chemical Shifts ◽  
Organic Group ◽  
Opposite Trend ◽  
Organotellurium Compounds ◽  
C Nmr

13C nmr chemical shifts are reported for some aromatic and aliphatic tellurium compounds. For a given organic group, the shift of the C1 atom varies in the order [Formula: see text], as expected from electronegative considerations. The C2 atom experiences an opposite trend while the C3 and C4 atoms of the ring experience smaller changes. The chemical shifts of para-substituted aromatic tellurium compounds do not show additivity of contributions from the substituents.

Accurate and cost-effective NMR chemical shift predictions for proteins using a molecules-in-molecules fragmentation-based method

2020 ◽  
Vol 22 (47) ◽  
pp. 27781-27799
Author(s):  
Sruthy K. Chandy ◽  
Bishnu Thapa ◽  
Krishnan Raghavachari
Keyword(s):  
Chemical Shift ◽  
Quantum Chemical ◽  
Chemical Method ◽  
Chemical Shifts ◽  
Cost Effective ◽  
Quantum Chemical Method ◽  
Solvation Model ◽  
Nmr Chemical Shift ◽  
Nmr Chemical Shifts

We have developed a two-layer Molecules-in-Molecules (MIM2) fragmentation-based quantum chemical method including an efficient solvation model for the prediction of NMR chemical shifts with a target accuracy of ∼0.30 ppm for 1H and ∼2–3 ppm for 13C.

scholarly journals NMR spectroscopic properties of furo[2′,3′:4,5]pyrrolo[1,2-d][1,2,4]triazine derivatives

2017 ◽  
Vol 16 (2) ◽  
pp. 147-151 ◽  
Author(s):  
Ivana Zemanová ◽  
Renata Gašparová
Keyword(s):  
Chemical Shift ◽  
Carbonyl Group ◽  
Chemical Shifts ◽  
Spectroscopic Properties ◽  
Chloromethyl Group ◽  
Nmr Chemical Shifts ◽  
H Nmr ◽  
Triazine Derivatives ◽  
C Nmr ◽  
Electron Withdrawing Substituents

Abstract The 1H and 13C NMR spectroscopic properties of a series of furo[2′,3′:4,5]pyrrolo[1,2-d][1,2,4]triazin-8(7H)-ones and -thiones were investigated. The influence of various electron donating as well as electron withdrawing substituents at C-5 or N-7 on 1H NMR chemical shifts as well as 13C chemical shifts at C8 were observed. The 5-chloromethyl group had a little influence on the chemical shift of H-7 proton and the 8-thione group causes deshielding of H-7 as well as H-5 protons in comparison with the C-8 carbonyl group.

NMR effective radius of hydrogen in XIV group hydrides evaluated by NMR spectroscopy

2017 ◽  
Vol 46 (41) ◽  
pp. 14094-14097 ◽  
Author(s):  
M. Benedetti ◽  
F. De Castro ◽  
A. Ciccarese ◽  
F. P. Fanizzi
Keyword(s):  
Nmr Spectroscopy ◽  
Chemical Shift ◽  
Chemical Shifts ◽  
Effective Radius ◽  
Nmr Chemical Shift ◽  
Ionic Radii ◽  
Nmr Chemical Shifts

In the [ABrnIm] (A = C, Si, Ge, Sn; n + m = 4) compounds, with the heavier halido ligands bonded to the central IV group elements, the 13C, 29Si, 73Ge and 119Sn NMR chemical shifts were found to be linearly related to the bonded halides ionic radii overall sum, ∑(rh). The 207Pb NMR chemical shift of the unstable [PbH4] hydride could be calculated.

Identification of acyl groups occurring in sesquiterpene lactones: Proton and carbon-13 NMR study

1987 ◽  
Vol 52 (2) ◽  
pp. 453-475 ◽  
Author(s):  
Miloš Buděšínský ◽  
David Šaman
Keyword(s):  
Chemical Shifts ◽  
Sesquiterpene Lactones ◽  
Nmr Chemical Shifts ◽  
H Nmr ◽  
Nmr Parameters ◽  
Nmr Data ◽  
Nmr Study ◽  
C Nmr

Characteristic 1H NMR parameters of 88 acyl groups, hitherto found as ester substituents in natural sesquiterpenic lactones, were determined from the measured spectra as well as literature data. Characteristic 13C NMR chemical shifts for 45 acyl groups were obtained in the same way; for the remaining acyls with hitherto unknown 13C NMR data the values were calculated on the basis of semiempirical relationships.

13C NMR study of 3-(X-benzal)phthalides and 2-(X-benzal)-1,3-indanediones

1980 ◽  
Vol 45 (10) ◽  
pp. 2772-2778 ◽  
Author(s):  
Eva Solčániová ◽  
Pavol Hrnčiar ◽  
Tibor Liptaj
Keyword(s):  
Chemical Shift ◽  
Nmr Spectra ◽  
Electronic Effect ◽  
Chemical Shifts ◽  
Substituent Effects ◽  
Carbonyl Groups ◽  
Aryl Group ◽  
Nmr Study ◽  
Derivatives Of ◽  
C Nmr

13C NMR spectra of 14 derivatives of 3-(X-benzal)phthalides (I) and 10 derivatives of 2-(X-benzal)-1,3-indanediones (II) were investigated. The correlation of 13C chemical shifts of carbon atoms of the phthalide ring with σ-constants showed that the electronic effect of substituents was transmitted from the benzylidene group of 3-(X-benzal)phthalides on the chemical shift of the carbonyl group not only through oxygen, but also through the aromatic ring of the phthalide moiety. The transmission of substituent effects in 2-(X-benzal)-1,3-indanediones on the chemical shift of the carbonyl groups was more pronounced on the carbonyl, which is in the trans-arrangement with respect to the aryl group. This phenomenon was also observed at carbon atoms of the benzene ring of the indanedione moiety closer to the trans-CO group.

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