scholarly journals Conformations in Solution and in Solid-State Polymorphs: Correlating Experimental and Calculated Nuclear Magnetic Resonance Chemical Shifts for Tolfenamic Acid

2020 ◽  
Vol 124 (43) ◽  
pp. 8959-8977
Author(s):  
Helen Blade ◽  
Charles D. Blundell ◽  
Steven P. Brown ◽  
Jake Carson ◽  
Hugh R. W. Dannatt ◽  
...  
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Solid State ◽  
Magnetic Resonance ◽  
Chemical Shifts ◽  
Tolfenamic Acid ◽  
Nuclear Magnetic

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 In-situ Nitrous Acid Generation over Silica Imidazole Catalyst for Dyes Production

2019 ◽  
Vol 14 (2) ◽  
pp. 247
Author(s):  
Kasim Mohammed Hello ◽  
Nahla Ghaze Fahad
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Solid State ◽  
Magnetic Resonance ◽  
Nitrous Acid ◽  
Diazonium Salt ◽  
Chemical Shifts ◽  
Imidazolium Chloride ◽  
Acid Generation ◽  
Nuclear Magnetic

The objective of this research is to prepare a new type of heterogeneous catalyst and to study its usage for in-situ nitrous acid generation to form a diazonium salt. The high pure silica (> 95%) was produced by burning the clean rice husk at 800 °C. After that, the silica was transferred to sodium silicate using 1.0 M of NaOH, followed by immobilizing with 3-(chloropropyl)triethoxysilane in a simple one-pot synthesis. Finally, the material was refluxed with (0.015 mol) of p-xylyl di-imidazolium chloride. The silicon solid-state nuclear magnetic resonance shows the Q4, Q3, T3, and T2 chemical shifts at expected position. Carbon solid-state nuclear magnetic resonance spectrum shows different peaks at different chemical shifts related to the carbon structures of the organic moieties. The catalyst is stable up to 277 ºC according to the thermal analysis. TEM images show smooth and porous regularly shaped particles with an estimation size of ca. 5 nm. Coupling reaction of aromatic compounds was carried out with a diazonium salt of aniline to yield a monoazo dye. All dyes were showed matching the elemental analysis with the theoretical calculation. Besides this, the spectrum of FT-IR and UV-Visible were recorded. The catalyst was stable, easy separation from the reaction mixture, and reusable by a simple experimental procedure. The catalyst could be used successfully for the nitrous acid generation. Copyright © 2019 BCREC Group. All rights reserved 

A carbon-13 nuclear magnetic resonance study of solid tetracyclines

1987 ◽  
Vol 65 (2) ◽  
pp. 357-362 ◽  
Author(s):  
Sandra Mooibroek ◽  
Roderick E. Wasylishen
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Solid State ◽  
Magnetic Resonance ◽  
Pulse Sequence ◽  
Chemical Shifts ◽  
Nuclear Magnetic Resonance Study ◽  
Magic Angle ◽  
X Ray Diffraction ◽  
Magic Angle Sample Spinning ◽  
Nuclear Magnetic

Magic angle sample spinning and proton/carbon-13 cross-polarization techniques have been used to obtain high resolution solid state 13C nuclear magnetic resonance spectra of several tetracycline antibiotics. Carbon-13 resonances in the solid state are assigned by measuring the extent of dipolar broadening due to neighbouring quadrupolar nuclei and by using a pulse sequence that suppresses non-quaternary carbon resonances. The observed 13C chemical shifts are discussed in light of the known solid state structures derived from X-ray diffraction, and are compared with those in solution. It is shown that the solid state nuclear magnetic reosnance technique is capable of clearly distinguishing between the neutral and zwitterionic forms of the tetracycline free bases.

Analysis of Lead Carboxylates and Lead-Containing Pigments in Oil Paintings by Solid- State Nuclear Magnetic Resonance

2014 ◽  
Vol 1656 ◽  
pp. 149-156 ◽  
Author(s):  
Jaclyn Catalano ◽  
Yao Yao ◽  
Anna Murphy ◽  
Nicholas Zumbulyadis ◽  
Silvia A. Centeno ◽  
...  
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Solid State ◽  
Magnetic Resonance ◽  
Structural Information ◽  
Chemical Shifts ◽  
Paint Film ◽  
Type I ◽  
Oil Paintings ◽  
Lead Stearate ◽  
Nuclear Magnetic

ABSTRACTSoap formation in traditional oil paintings occurs when heavy-metal-containing pigments, such as lead white, 2Pb(CO3)2·Pb(OH)2, and lead-tin yellow type I, Pb2SnO4, react with fatty acids in the binding medium. These soaps may form aggregates that can be 100-200 μm in diameter, which swell and protrude through the paint surface, resulting in the degradation of the paint film and damage to the integrity of the artwork. In addition, soap formation has been reported to play a role in the increased transparency of paint films that allows the painting support, the preparatory drawing, and the artists’ alterations to become visible to the naked eye. The factors that trigger soap formation and the mechanism(s) of the process are not yet well understood. To elucidate these issues, chemical and structural information is necessary which can be obtained by solid-state 207Pb, 119Sn, and 13C nuclear magnetic resonance (NMR). In the present study, a combination of 207Pb NMR pulse sequences was used to determine accurately the NMR parameters of lead-containing pigments and lead carboxylates known to be involved in soap formation, such as lead palmitate, lead stearate, and lead azelate. These results show that the local coordination environment of lead azelate is different from lead palmitate or lead stearate and therefore it is unlikely that lead azelate would be incorporated into an ordered structure containing lead palmitate and lead stearate. In addition, the chemical shifts of the pigments obtained are different from those of the soaps, demonstrating that 207Pb NMR is useful in characterizing the components when present in a mixture, such as a paint film. The NMR methods discussed can also be applied to other Pb-containing cultural heritage materials, electronic and optoelectronic materials, superconducting materials, and environmentally contaminated materials.

Improving the accuracy of solid-state nuclear magnetic resonance chemical shift prediction with a simple molecular correction

2019 ◽  
Vol 21 (27) ◽  
pp. 14992-15000 ◽  
Author(s):  
Martin Dračínský ◽  
Pablo Unzueta ◽  
Gregory J. O. Beran
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Solid State ◽  
Magnetic Resonance ◽  
Chemical Shift ◽  
Solid State Nmr ◽  
Chemical Shifts ◽  
Chemical Shift Prediction ◽  
Nmr Chemical Shifts ◽  
Nuclear Magnetic

A simple molecular correction improves significantly the accuracy of predictions of solid-state NMR chemical shifts.

Solid-state nuclear magnetic resonance study of the structure of lanthanum phosphate crystals and glasses

2000 ◽  
Vol 15 (11) ◽  
pp. 2463-2467 ◽  
Author(s):  
Nancy E. Rashid ◽  
Brian L. Phillips ◽  
Subhash H. Risbud
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Solid State ◽  
Magnetic Resonance ◽  
Chemical Shifts ◽  
Nuclear Magnetic Resonance Study ◽  
Phosphate Glasses ◽  
Resonance Spectroscopy ◽  
X Ray Diffraction ◽  
Lanthanum Phosphate ◽  
Nuclear Magnetic

Lanthanum phosphate glasses were synthesized by melt quenching and characterized by x-ray diffraction, electron microprobe analysis, and solid-state nuclear magnetic resonance spectroscopy. A range of compositions near the metaphosphate composition (75 mol% P2O5) was examined. Comparison of 31P chemical shifts and shielding anisotropies of glasses with those of the crystalline phases of La(PO3)3 (metaphosphate) and LaP5O14 (pentaphosphate) were consistent with the presence of primarily chainlike Q2 phosphate groups.

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