A Comparative CP/MAS 13C-NMR Study of the Supermolecular Structure of Polysaccharides in Sulphite and Kraft Pulps

Holzforschung ◽  
2002 ◽  
Vol 56 (2) ◽  
pp. 179-184 ◽  
Author(s):  
Eva-Lena Hult ◽  
Per Tomas Larsson ◽  
Tommy Iversen
Keyword(s):  
Supermolecular Structure ◽  
Kraft Pulping ◽  
Magic Angle ◽  
Kraft Pulps ◽  
General Observation ◽  
Spectral Fitting ◽  
Nmr Study ◽  
Cellulose Iβ ◽  
Cp Mas 13C Nmr ◽  
C Nmr

Summary The supermolecular structure of polysaccharides in unbleached sulphite pulps and kraft pulps was investigated by CP/MAS 13C-NMR (Cross Polarisation Magic Angle Carbon-13 Nuclear Magnetic Resonance) in combination with spectral fitting. The cellulose crystallinity was found to be higher in the kraft pulps than in the sulphite pulps. Acellulose Iα to cellulose Iβ conversion was observed during kraft pulping but not during sulphite pulping. The sulphite pulps exhibited smaller lateral fibril aggregate dimensions than the kraft pulps. The spectral behaviour of the hemicelluloses in the sulphite pulps was different from that in the kraft pulps. The general observation is that the supermolecular structure of the polysaccharides in the investigated sulphite pulps is very similar to the structure observed in wood.

Eucalyptus globulus Kraft Pulp Residual Lignin. Part 2. Modification of Residual Lignin Structure in Oxygen Bleaching

Holzforschung ◽  
2001 ◽  
Vol 55 (6) ◽  
pp. 645-651 ◽  
Author(s):  
A.P. Duarte ◽  
D. Robert ◽  
D. Lachenal
Keyword(s):  
Acid Hydrolysis ◽  
Structural Changes ◽  
Kraft Pulping ◽  
Kraft Pulps ◽  
Residual Lignin ◽  
Qualitative And Quantitative ◽  
Methylene Groups ◽  
Hydrolysis Conditions ◽  
C Nmr ◽  
Oxygen Bleaching

Summary Residual lignins were isolated from unbleached and oxygen-bleached Eucalyptus kraft pulps by acid hydrolysis. The structural changes and degradation of residual lignin occurring during kraft pulping and oxygen bleaching were followed and identified by elemental analysis, residual carbohydrate analysis, molecular mass distribution, as well as qualitative and quantitative solution 13C NMR. The dissolved lignins in the kraft cooked and oxygen bleached liquors were also studied and compared with the corresponding residual lignins. Milled wood lignin treated under acid hydrolysis conditions served as a reference for the structural comparison. The results show that etherified syringyl structures were quite resistant towards degradation in the oxygen bleaching, causing little depolymerisation in residual lignin and a small increase in carboxylic acid content, but producing appreciable amounts of saturated aliphatic methylene groups.

An Nmr Study of the Occupation of C60 Interstitial Sites by Oxygen Molecules

1992 ◽  
Vol 270 ◽  
Author(s):  
Roger A. Assink ◽  
Douglas A. Loy ◽  
James E. Schirber ◽  
Bruno Morosin
Keyword(s):  
Ambient Pressure ◽  
Primary Resonance ◽  
Magic Angle Spinning ◽  
Magic Angle ◽  
Nmr Study ◽  
Minor Peak ◽  
Fermi Contact ◽  
Angle Spinning ◽  
A Minor ◽  
C Nmr

ABSTRACTThe 13C NMR of FCC C60 under magic angle spinning (MAS) conditionsyields linewidths on the order of 1 Hz at fields of 4.7 T. The spectrum consists of a primary resonance at 143.7 ppm and a minor peak shifted 0.7 ppm downfield. The intensity of the minor resonance relative to the primary resonance was found to vary from 0.6 to 5.5 % depending on the sample history. The downfield shift obeys Curie's law and isattributed to the Fermi contact coupling interaction between paramagnetic oxygen molecules and all 60 carbon atoms of rapidly rotating adjacent C60 molecules. Exposure of the sample to 1 kbar oxygen for 1 3/4 hours resulted in a spectrum of 7 evenly spaced resonances corresponding to 0 to 6 of the adjacent octahedral interstitial sites being filled with oxygen molecules. At ambient pressure, the oxygen diffused out of the lattice on time scales ranging from hours to days.

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.

Magic Angle Spinning NMR Study on Inversion Behavior and Vacancy Disorder in Alumina-Rich Spinel

2018 ◽  
Vol 57 (14) ◽  
pp. 8390-8395 ◽  
Author(s):  
Bingtian Tu ◽  
He Zhang ◽  
Hao Wang ◽  
Weimin Wang ◽  
Zhengyi Fu
Keyword(s):  
Magic Angle Spinning ◽  
Magic Angle ◽  
Nmr Study ◽  
Angle Spinning

Phosphorus-31 chemical shieldings in a fused cis-1,2,3-benzothiadiphosphole: a dipolar NMR study

1992 ◽  
Vol 70 (4) ◽  
pp. 1229-1235 ◽  
Author(s):  
Gang Wu ◽  
Roderick E. Wasylishen ◽  
William P. Power ◽  
Graziano Baccolini
Keyword(s):  
Line Shape ◽  
Magic Angle Spinning ◽  
Pair Approximation ◽  
Magic Angle ◽  
Single Bond ◽  
Chemical Shielding ◽  
Spin Pair ◽  
Nmr Study ◽  
Shielding Tensors ◽  
Angle Spinning

Phosphorus-31 NMR static powder spectra and high-resolution magic angle spinning spectra have been obtained for a new heterocyclic compound, cis-2,10-dimethyl[1,2,3]benzothiadiphospholo[2,3b][1,2,3]benzothiadiphosphole (1), which contains a P(III)—P(III) single bond. The homonuclear 31P–31P dipolar interaction manifests itself in both the magic angle spinning spectra and the non-spinning line shape. Under the AX spin pair approximation, analysis of the spinning sidebands in the MAS experiment yields a full characterization of the two 31P chemical shielding tensors. This approximation is confirmed by the exact powder line shape simulation for a homonuclear spin pair. Analysis of the dipolar subspectra also yields the absolute sign of 1J(P,P), which is found to be negative. Keywords: phosphorus–phosphorus single bond, chemical shielding tensors, dipolar NMR, MAS, static line shape.

MAGIC-ANGLE-SPINNING29Si-NMR STUDY OF THE STRUCTURE OF ZSM-5 AND ZSM-11 ZEOLITES

1982 ◽  
Vol 11 (12) ◽  
pp. 2003-2006 ◽  
Author(s):  
J. B. Nagy ◽  
Z. Gabelica ◽  
E. G. Derouane ◽  
P. A. Jacobs
Keyword(s):  
Magic Angle ◽  
Nmr Study

A 13C and 15N nuclear magnetic resonance study of solid ammonium thiocyanate

1987 ◽  
Vol 65 (5) ◽  
pp. 941-946 ◽  
Author(s):  
Ross M. Dickson ◽  
Michael S. McKinnon ◽  
James F. Britten ◽  
Roderick E. Wasylishen
Keyword(s):  
Ammonium Thiocyanate ◽  
Nuclear Magnetic Resonance Study ◽  
Magic Angle Spinning ◽  
Magic Angle ◽  
Chemical Shielding ◽  
X Ray ◽  
Shielding Constants ◽  
Angle Spinning ◽  
Good Agreement ◽  
C Nmr

The static 13C nmr powder pattern for solid ammonium thiocyanate is analyzed to obtain the 13C chemical shielding anisotropy, 321 ± 7 ppm, and the 13C–14N dipolar splitting, 1295 ± 25 Hz. Slow magic angle spinning 15N nmr experiments are analyzed to obtain a nitrogen chemical shielding anisotropy of 415 ± 15 ppm. The 13C–14N dipolar splitting leads to an effective C—N bond length of 1.19 ± 0.01 Å, in good agreement with the value of 1.176 Å reported from accurate X-ray and neutron crystallographic studies. In solid NH4NCS absolute values of the average shielding constants [Formula: see text] and ct[Formula: see text] are 52 and 34 ppm, respectively. Comparison of calculated and observed [Formula: see text] values indicates that intermolecular interactions decrease the 13C and 15N shielding constants by approximately 10 and 30 ppm, respectively.

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