Analyse par résonance magnétique nucléaire 13C de la stabilité relative des spirochromènes et des mérocyanines dérivant du méthoxy-3 nitro-5 salicylaldéhyde

1982 ◽  
Vol 60 (21) ◽  
pp. 2644-2653 ◽  
Author(s):  
Michel Maguet ◽  
Michel Le Baccon ◽  
Yves Poirier ◽  
Robert Guglielmetti
Keyword(s):  
Chemical Shift ◽  
Carbon Atom ◽  
Intermediate Position ◽  
Nmr Study ◽  
Résonance Magnétique ◽  
Limiting Value ◽  
C Nmr

Heterocycloimmonium salts generally react with 3-methoxy 5-nitro salicylaldéhyde to give spirochromenes or merocyanines. Only the latter compounds are obtained in the thiazolinic and the benzimidazolinic series. The linking of a paraffinic ring to the merocyanines allows their 13C nmr study. The comparison of their spectra with those of heterocycloimmonium salts stresses a hyperconjugative effect in the thiazolinic and the benzimidazolinic series. The benzoxazolinic series appears to be in an intermediate position: the thermodynamic stabilities of spirochromenes and merocyanines are quite similar. The limiting value of the chemical shift of the carbon atom involved in the spiroannellation of merocyanines, can be approximately determined.

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.

Déplacements chimiques de la résonance magnétique nucléaire 13C dans les complexes carbonylés octaédriques des métaux de transition du groupe VIB. Effet écran produit par les électrons d non-liants du métal

1977 ◽  
Vol 55 (23) ◽  
pp. 4056-4060 ◽  
Author(s):  
Daniel Cozak ◽  
Ian S. Butler
Keyword(s):  
Electronic Structure ◽  
Chemical Shift ◽  
Metal Carbonyl ◽  
Shielding Effect ◽  
Chemical Shielding ◽  
Carbonyl Ligands ◽  
Résonance Magnétique ◽  
Carbonyl Bond ◽  
D Orbitals ◽  
C Nmr

The 13C nmr shielding effect at the carbonyl ligands due to the paramagnetic current in the non-bonding d orbitals of the metal in the group VIB M(CO)6 complexes has been evaluated. For these complexes, the only contribution of significant importance to the chemical shielding calculated for the carbonyl ligands is opposite to that observed experimentally. The carbonyl chemical shift produced by substitution of one of the carbonyl ligands is discussed in terms of electronic structure of the metal and the metal–carbonyl bond lengths in the M(CO)5L complexes.

Résonance magnétique nucléaire 13C des dérivés allyliques de la colonne IV-A, de type (C6H5)3ECH2CH=CH—CH3. Effets électroniques du substituant du noyau aromatique

1984 ◽  
Vol 62 (1) ◽  
pp. 133-135 ◽  
Author(s):  
E. Matarasso-Tchiroukhine
Keyword(s):  
Excitation Energy ◽  
Electronic Excitation ◽  
Inductive Effect ◽  
Chemical Shifts ◽  
Aromatic Nucleus ◽  
Electronic Excitation Energy ◽  
Nmr Study ◽  
Résonance Magnétique ◽  
The Mean ◽  
C Nmr

The 13C nmr study of the series (C6H5)3ECH2CH=CH—CH31E shows, for the aromatic nucleus, a polarization consistent with a mesomeric electron withdrawing effect of the substituent in the case of E = Si, Ge, Sn; inversely, a mesomeric donating effect, in the case E = Pb, involving a higher electronegativity for Pb; and a donating π inductive effect, in the case E = C. The mean electronic excitation energy seems to dominate the chemical shifts of the aromatic carbons Cipso and Cortho, as well as the coupling 0J(13C—207Pb).

scholarly journals Use of13C-NMR as complementar identification tool in essential oil analysis

1997 ◽  
Vol 13 (4) ◽  
pp. 265-273 ◽  
Author(s):  
José Wilson Alencar ◽  
Maria Goretti de Vasconcelos Silva ◽  
Maria Iracema Lacerda Machado ◽  
Afrânio Aragão Craveiro ◽  
Francisco José de Abreu Matos ◽  
...  
Keyword(s):  
Chemical Shift ◽  
Carbon Atom ◽  
Essential Oil ◽  
Chemical Shifts ◽  
Chemical Constituents ◽  
Structural Features ◽  
Oil Analysis ◽  
Nmr Data ◽  
C Nmr ◽  
Identification Tool

A program using13C-NMR data was developed to improve GC/MS identifications of chemical constituents in essential oils. Compiled data uses 2290 and 2370 chemical shifts of 229 monoterpenes and 158 sesquiterpenes, respectively, stored into two reference libraries. Each carbon atom was codified using rules that correlates its chemical shift with structural features of the carbon hybridization and vicinity.

Fluorescence Reagents for Labelling of Biomolecules. Part I. Synthesis and Spectral Characterization of 2- and 4-Substituted 9-Isothiocyanatoacridines

1994 ◽  
Vol 59 (1) ◽  
pp. 203-212 ◽  
Author(s):  
Dana Mazagová ◽  
Danica Sabolová ◽  
Pavol Kristian ◽  
Ján Imrich ◽  
Marián Antalík ◽  
...  
Keyword(s):  
Chemical Shift ◽  
Carbon Atom ◽  
Fluorescence Intensity ◽  
Fluorescence Spectra ◽  
Chemical Shifts ◽  
H Nmr ◽  
Hammett Constants ◽  
Hydrolysis Of ◽  
C Nmr

9-Isothiocyanatoacridines VIII - XIV were prepared from the corresponding 9-chloroacridines I - VII. The IR, 1H NMR, 13C NMR and fluorescence spectra of the products are given. The 13C NMR chemical shifts of the C-9 ipso carbon atom exhibit a trend that is in accord with the Hammett constants of substituents bonded to the C-2 carbon. Effect of these substituents on the chemical shift of C-NCS was only small. The dependence of hydrolysis of isothiocyanates VIII - XIV on pH of the medium was studied. It was found that 9-isothiocyanatoacridines do not undergo hydrolysis at pH 7 - 10. The relative fluorescence intensities (F/F0) of compounds VIII - XIV at pH 7.4 have been determined in comparison with that of 9-aminoacridine. No direct dependence between the fluorescence intensity and the polar character of substituents has been found.

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.

Dérivés allyliques de la colonne IV-A, de type R3ECH2CH=CH—CH3 et R3ECH(CH3)CH=CH2. Approche des effets électroniques par résonance magnétique nucléaire 13C et 1H

1983 ◽  
Vol 61 (11) ◽  
pp. 2476-2485 ◽  
Author(s):  
E. Matarasso-Tchiroukhine ◽  
P. Cadiot
Keyword(s):  
Chemical Shifts ◽  
Main Group ◽  
Group Element ◽  
Appreciable Change ◽  
Spectroscopic Parameters ◽  
Group Electronegativity ◽  
Nmr Study ◽  
Résonance Magnétique ◽  
Derivatives Of ◽  
C Nmr

A comparative 1H and 13C nmr study of allylic derivatives of the IV-A group elements, of the type R3ECH2CH=CH—CH31E, Z and R3ECH(CH3)CH=CH2, 2, was performed (R = —C6H5, —CH3, E = C, Si, Ge, Sn, Pb). The present paper dealing with the allylic moiety concerns both the chemical shifts, δ1H and δ13C, and the homonuclear J(H—H) and heteronuclear couplings 1J(13C—H), nJ(13C—E), n = 1 to 4, nJ(E—C—H), n = 2 and 5. The spectra are consistent with a σ-allylic structure. In order to obtain an inductive order for the groups G(E) = —E(C6H5)3 a coherent group electronegativity scale was established. The intrinsic group electronegativities, without appreciable change, obey the following sequence:[Formula: see text]Both the changes along the series, in spectroscopic parameters, δ1H, δ13C, and the unusually large heteronuclear couplings, 2J(E—C—H), 5J(E—C—H), 4J(E—13C) (E = Sn, Pb), are interpreted in terms of an electronic mesomeric donating effect for the substituent σ, R3ECH2— and R3ECH(CH3)—, by σ–π hyperconjugation. Factors intrinsic to the main-group element control the chemical shifts δ1Hα and δ13Cα. The s-character of the bond Cα—Hα appears to control the 1J(13Cα—Hα) couplings; no correlation with a σ → π hyperconjugation could be established.

Crystal and solution structure of (E)-1,2-bis(ethylsulphonyl)cyclobutane-1,2-dicarbonitrile

1989 ◽  
Vol 54 (12) ◽  
pp. 3253-3259
Author(s):  
Jaroslav Podlaha ◽  
Miloš Buděšínský ◽  
Jana Podlahová ◽  
Jindřich Hašek
Keyword(s):  
Hydrogen Peroxide ◽  
Solution Structure ◽  
Peroxide Oxidation ◽  
X Ray ◽  
X Ray Crystallography ◽  
Nmr Study ◽  
Hydrogen Peroxide Oxidation ◽  
Unusual Product ◽  
C Nmr

The unusual product of the reaction of 2-chloroacrylonitrile with ethane thiol and following hydrogen peroxide oxidation was found to be (E)-1,2-bis(ethylsulphonyl)cyclobutane-1,2-dicarbonitrile by means of X-ray crystallography. 1H and 13C NMR study of this compound has proven the same conformation of the molecule in solution.

scholarly journals Brain energy metabolism in intracerebroventricularly administered streptozotocin mouse model of Alzheimer’s disease: A 1H-[13C]-NMR study

2021 ◽  
pp. 0271678X2199617
Author(s):  
Narayan D Soni ◽  
Akila Ramesh ◽  
Dipak Roy ◽  
Anant B Patel
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Glucose Oxidation ◽  
Neurodegenerative Disorder ◽  
Nmr Spectrum ◽  
Tissue Extracts ◽  
Model Of Alzheimer’S Disease ◽  
Nmr Study ◽  
Synaptic Neurotransmission ◽  
C Nmr

Alzheimer’s disease (AD) is a very common neurodegenerative disorder. Although a majority of the AD cases are sporadic, most of the studies are conducted using transgenic models. Intracerebroventricular (ICV) administered streptozotocin (STZ) animals have been used to explore mechanisms in sporadic AD. In this study, we have investigated memory and neurometabolism of ICV-STZ-administered C57BL6/J mice. The neuronal and astroglial metabolic activity was measured in 1H-[13C]-NMR spectrum of cortical and hippocampal tissue extracts of mice infused with [1,6-13C2]glucose and [2-13C]acetate, respectively. STZ-administered mice exhibited reduced (p = 0.00002) recognition index for memory. The levels of creatine, GABA, glutamate and NAA were reduced (p ≤ 0.04), while that of myo-inositol was increased (p < 0.05) in STZ-treated mice. There was a significant (p ≤ 0.014) reduction in aspartate-C3, glutamate-C4/C3, GABA-C2 and glutamine-C4 labeling from [1,6-13C2]glucose. This resulted in decreased rate of glucose oxidation in the cerebral cortex (0.64 ± 0.05 vs. 0.77 ± 0.05 µmol/g/min, p = 0.0008) and hippocampus (0.60 ± 0.04 vs. 0.73 ± 0.07 µmol/g/min, p = 0.001) of STZ-treated mice, due to similar reductions of glucose oxidation in glutamatergic and GABAergic neurons. Additionally, reduced glutamine-C4 labeling points towards compromised synaptic neurotransmission in STZ-treated mice. These data suggest that the ICV-STZ model exhibits neurometabolic deficits typically observed in AD, and its utility in understanding the mechanism of sporadic AD.

The biosynthesis of ephedrine

1989 ◽  
Vol 67 (6) ◽  
pp. 998-1009 ◽  
Author(s):  
Gunnar Grue-Sørensen ◽  
Ian D. Spenser
Keyword(s):  
Carbon Atom ◽  
Benzoic Acid ◽  
Pyruvic Acid ◽  
Nmr Spectra ◽  
Carbon Skeleton ◽  
Resonance Spectroscopy ◽  
Methyl Group ◽  
Acid Incorporation ◽  
Group A ◽  
C Nmr

It is shown by 13C nuclear magnetic resonance spectroscopy that the labelled C2 fragment of [2,3-13C2]pyruvic acid is transferred intact into the C-methyl group and the adjacent carbon atom of the Ephedra alkaloids, norephedrine, ephedrine, norpseudoephedrine, and pseudoephedrine, in growing plants of Ephedragerardiana. This finding serves to identify pyruvate as the elusive precursor of the aliphatic C2 terminus of the skeleton of the alkaloids. In earlier experiments with C-labelled substrates, label from [3-14C]pyruvic acid was incorporated mainly, but not exclusively, into the C-methyl group of ephedrine, and label from [2-14C]pyruvate was incorporated similarly into the carbon atom adjacent to the C-methyl group. A C6–C1 unit related to benzaldehyde or benzoic acid has long been known to generate the benzylic fragment of the carbon skeleton of the Ephedra alkaloids. It is likely that the carbon skeleton of ephedrine is generated from pyruvate and either benzaldehyde or benzoic acid, by a reaction analogous to the formation of acetoin or diacetyl from pyruvate and acetaldehyde or acetic acid, respectively. Keywords: biosynthesis of ephedrine, Ephedra alkaloids, 13C NMR spectra, ephedrine, biosynthesis of pyruvic acid, incorporation into ephedrine13C NMR spectra.

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