A structural reinvestigation of 4,6-dinitrobenzofuroxan by 1H, 13C, and 15N nuclear magnetic resonance

1989 ◽  
Vol 67 (3) ◽  
pp. 503-507 ◽  
Author(s):  
F. Terrier ◽  
J. C. Halle ◽  
P. MacCormack ◽  
M. J. Pouet
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Chemical Shifts ◽  
Nuclear Magnetic Resonance Study ◽  
H Nmr ◽  
Oxide Group ◽  
Proton Chemical Shifts ◽  
C Nmr ◽  
Nuclear Magnetic

A detailed nuclear magnetic resonance study of 4,6-dinitro-2,1,3-benzoxadiazole N-oxide (DNBF), which includes a 2D INADEQUATE analysis and experiments with samples 15N-labelled at the NO2 groups, is described. The results lead to an unambiguous assignment of the carbon and proton chemical shifts in various solvents. Some 1H and 13C data pertaining to 4,6-dinitro-2,1,3-benzoxadiazole (DNBZ), the deoxygenated analog of DNBF, are also reported, allowing the influence of the N-oxide group on the proton and carbon chemical shifts to be discussed. It is shown that all of the 1H nmr evidence so far reported for the characterization of DNBF σ adducts as arising from nucleophilic addition to the 7-position, i.e., as structure 2a, has no significance. That complexation actually occurs at this position is, however, convincingly demonstrated by 15N data. These also allow us to establish that this process is both kinetically and thermodynamically favored. Keywords: nitrobenzofuroxans, Meisenheimer complexes, 13C nmr of benzofuroxans, 2,1,3-benzoxadiazole N-oxides, nitrobenzofuroxan σ-adducts.

scholarly journals Structural Characterization of Amadori Rearrangement Product of Glucosylated Nα-Acetyl-Lysine by Nuclear Magnetic Resonance Spectroscopy

2014 ◽  
Vol 2014 ◽  
pp. 1-6 ◽  
Author(s):  
Chuanjiang Li ◽  
Hui Wang ◽  
Manuel Juárez ◽  
Eric Dongliang Ruan
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Maillard Reaction ◽  
Structural Characterization ◽  
Resonance Spectroscopy ◽  
H Nmr ◽  
Amadori Rearrangement ◽  
C Nmr ◽  
Nuclear Magnetic

Maillard reaction is a nonenzymatic reaction between reducing sugars and free amino acid moieties, which is known as one of the most important modifications in food science. It is essential to characterize the structure of Amadori rearrangement products (ARPs) formed in the early stage of Maillard reaction. In the present study, the Nα-acetyl-lysine-glucose model had been successfully set up to produce ARP, Nα-acetyl-lysine-glucose. After HPLC purification, ARP had been identified by ESI-MS with intense [M+H]+ ion at 351 m/z and the purity of ARP was confirmed to be over 90% by the relative intensity of [M+H]+ ion. Further structural characterization of the ARP was accomplished by using nuclear magnetic resonance (NMR) spectroscopy, including 1D 1H NMR and 13C NMR, the distortionless enhancement by polarization transfer (DEPT-135) and 2D 1H-1H and 13C-1H correlation spectroscopy (COSY) and 2D nuclear overhauser enhancement spectroscopy (NOESY). The complexity of 1D 1H NMR and 13C NMR was observed due to the presence of isomers in glucose moiety of ARP. However, DEPT-135 and 2D NMR techniques provided more structural information to assign the 1H and 13C resonances of ARP. 2D NOESY had successfully confirmed the glycosylated site between 10-N in Nα-acetyl-lysine and 7′-C in glucose.

A nuclear magnetic resonance study of the conformations of triribonucleoside diphosphates, diribonucleoside phosphates, 5′-ribonucleoside phosphates, and ribonucleosides of uracil and cytosine; temperature dependence of the base proton chemical shifts

1969 ◽  
Vol 47 (3) ◽  
pp. 513-515 ◽  
Author(s):  
Ian C. P. Smith ◽  
B. J. Blackburn ◽  
Tetsuo Yamane
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Temperature Dependence ◽  
Chemical Shifts ◽  
Nuclear Magnetic Resonance Study ◽  
Magnetic Resonance Study ◽  
Nuclear Magnetic Resonance Spectra ◽  
Anti Conformation ◽  
Proton Chemical Shifts ◽  
Nuclear Magnetic

The temperature dependence of the nuclear magnetic resonance spectra of U, C, 5′-UMP, 5′-CMP, UpU, and CpU indicates a specific deshielding of the base proton at position-6 by an hydroxyl, phosphodiester, or phosphate group at position-5′, and demonstrates that in these compounds the bases exist in the anti conformation. Similar experiments on the wobble pair UpUpU and UpUpC suggest that the spatial arrangements of both trinucleoside diphosphates are identical, and that in these arrangements the bases are predominantly in the anti conformation.

Nuclear Magnetic Resonance Chemical Shifts of some Monosubstituted Isothiazoles

1975 ◽  
Vol 53 (4) ◽  
pp. 596-603 ◽  
Author(s):  
Roderick E. Wasylishen ◽  
Thomas R. Clem ◽  
Edwin D. Becker
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Chemical Shifts ◽  
Substituent Effects ◽  
Charge Densities ◽  
Monosubstituted Benzenes ◽  
Proton Chemical Shifts ◽  
Nuclear Magnetic

Carbon-13 and proton chemical shifts have been measured for several monosubstituted isothiazoles. Substituent effects upon these chemical shifts are compared with those observed for monosubstituted benzenes, pyridines, and thiophenes. In general the observed substituent effects in the isothiazoles and thiophenes closely parallel one another. Correlations between the observed carbon-13 Chemical shifts and CNDO/2 calculated charge densities are examined.

Anesthetic-membrane interaction: A 2H nuclear magnetic resonance study of the binding of specifically deuterated tetracaine and procaine to phosphatidylcholine

1984 ◽  
Vol 62 (2-3) ◽  
pp. 178-184 ◽  
Author(s):  
Eric C. Kelusky ◽  
Ian C. P. Smith
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Local Anesthetics ◽  
Nuclear Magnetic Resonance Study ◽  
Weakly Bound ◽  
Slow Exchange ◽  
H Nmr ◽  
Line Shapes ◽  
Acyl Chains ◽  
Nuclear Magnetic

The binding of the local anesthetics tetracaine and procaine with multilamellar dispersions of egg phosphatidylcholine has been studied by 2H nuclear magnetic resonance (NMR). The 2H-NMR line shapes of specifically deuterated local anesthetics are found to be very dependent on the attainment of a true equilibrium. The equilibrium could be most properly reached by the use of repeated freeze–thaw–vortex cycles. The data for tetracaine are consistent with the three-site exchange model proposed earlier. Tetracaine is in slow exchange between a strongly bound site and a weakly bound site and in fast exchange between the weakly bound site and free in solution. The slow exchange rate is estimated, from temperature and dilution studies, to be approximately 1.5 × 103 s−1 at pH 5.5 and slightly faster at pH 9.5. Comparisons of the quadrupole splittings with those seen for our earlier work in egg phosphatidylethanolamine suggest that the location of the strongly bound site in phosphatidylcholine is dependent on the anesthetic charge. This is in contrast to egg phosphatidylethanolamine, where molecular shapes appear to be the determining factor for the location of the anesthetic. Procaine bound very weakly to the model membranes, to yield only a broad resonance and no quadrupole splitting. It appears that procaine, unlike tetracaine, is not bound by the ordered acyl chains.

A carbon-13 CP/MAS nuclear magnetic resonance study of several 1,4-disubstituted benzenes in the solid state

1989 ◽  
Vol 67 (3) ◽  
pp. 525-534 ◽  
Author(s):  
Glenn H. Penner ◽  
Roderick E. Wasylishen
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Solid State ◽  
Magnetic Resonance ◽  
Chemical Shifts ◽  
Substituent Effects ◽  
Nuclear Magnetic Resonance Study ◽  
Solution Studies ◽  
Temperature Solution ◽  
Cp Mas Nmr ◽  
Nuclear Magnetic

The carbon-13 chemical shifts of several 1,4-disubstituted benzenes in the solid state are reported. At least one of the substituents is unsymmetrical and in most cases this leads to different 13C chemical shifts of C-2 and C-6 and in some cases to different shifts for C-3 and C-5. The 13C chemical shifts observed in the solid state are compared with those measured in solution and, where possible, with those obtained in low temperature solution studies where internal rotation of the unsymmetrical substituent is slow on the 13C chemical shift time scale. Agreement between the chemical shifts observed in the solid state and solution is excellent. The potential application of CP/MAS nuclear magnetic resonance in deducing the conformation of benzene derivatives with two unsymmetrical substituents is discussed. Keywords: carbon-13 CP/MAS NMR, 13C NMR chemical shifts, substituent effects.

scholarly journals Kernresonanz-Untersuchunghen von 1.2.3-Selenadiazolen/ Nuclear Magnetic Resonance of 1,2,3-Selenadiazoles

1981 ◽  
Vol 36 (8) ◽  
pp. 1017-1022 ◽  
Author(s):  
Herbert Meier ◽  
Johannes Zountsas ◽  
Oswald Zimmer
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Chemical Shifts ◽  
Coupling Constants ◽  
Spectroscopical Study ◽  
C Nmr ◽  
Nuclear Magnetic

Abstract A 1H and 13C NMR spectroscopical study is performed on the basis of 37 1,2,3-selena-diazoles. Besides the discussion of chemical shifts and coupling constants of 1H and 13C, selenium satellites were measured providing 1H77 Se and 13C77 Se coupling constants.

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