scholarly journals Using 13C nuclear magnetic resonance spectroscopy for the study of northern hardwood tissues

2005 ◽  
Vol 35 (8) ◽  
pp. 1821-1831 ◽  
Author(s):  
Chris E Johnson ◽  
Ronald J Smernik ◽  
Thomas G Siccama ◽  
David K Kiemle ◽  
Zhihong Xu ◽  
...  
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Structural Chemistry ◽  
Resonance Spectroscopy ◽  
Magic Angle ◽  
Betula Alleghaniensis ◽  
13C Nuclear Magnetic Resonance ◽  
Bark Chemistry ◽  
C Nmr ◽  
Nuclear Magnetic

Nuclear magnetic resonance (NMR) spectroscopy is a useful tool for examining the structural chemistry of natural organic matter. The use of cross-polarization and magic-angle spinning to study 13C functionality (CPMAS 13C NMR) is convenient, but not always quantitative. We used various 13C NMR techniques to examine the structural chemistry of bark and wood of sugar maple (Acer saccharum Marsh.), American beech (Fagus grandifolia Ehrh.), and yellow birch (Betula alleghaniensis Britt.). Spin counting experiments showed that 87%–97% of the 13C in the samples was observable by CPMAS 13C NMR. A comparison of CPMAS and Bloch decay experiments revealed few differences in spectral properties. Together, these results suggest that CPMAS 13C NMR is quantitative for these tissues. We observed little variation in the structural chemistry of wood, either among samples of the same species or among species. Within-species variations in bark chemistry were greater than in wood, probably because of variations in environmental conditions. However, we observed no significant differences in bark chemistry among the species. Bark and wood chemistry differed significantly, with the bark spectra displaying greater contributions from lignin, suberin, waxes, and resins. Hardwood spectra differ from softwood spectra in the aromatic C regions because of the contribution of syringyl units to hardwood lignin. Hardwood bark appears to contain less tannins than softwood bark. Together, the quantitative and qualitative features of CPMAS 13C NMR spectra are useful for studying the ecology of living and detrital wood and bark.

13C nuclear magnetic resonance spectroscopy with cross-polarization and magic-angle spinning investigation of the proximate-analysis fractions used to assess litter quality in decomposition studies

1997 ◽  
Vol 75 (9) ◽  
pp. 1601-1613 ◽  
Author(s):  
Caroline M. Preston ◽  
J. A. (Tony) Trofymow ◽  
Junning Niu ◽  
Brian G. Sayer
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Litter Quality ◽  
Proximate Analysis ◽  
Magic Angle Spinning ◽  
Resonance Spectroscopy ◽  
Magic Angle ◽  
Klason Lignin ◽  
13C Nuclear Magnetic Resonance ◽  
Nuclear Magnetic

Proximate analysis is often used in decomposition studies to characterize the organic components of foliar litter. The percent weight residue remaining after extraction by nonpolar and polar solvents and H3SO4 hydrolysis (Klason lignin, KL) is commonly used as a measure of litter quality and a modelling parameter. While KL is associated with resistance to decay, its nature is not well understood and it has long been suspected that it incorporates nonlignin components. We used solid-state 13C nuclear magnetic resonance (NMR) spectroscopy to characterize litter, extracted residue, and the KL fraction of five species. NMR shows that cutin and condensed tannin are both significant components of litter and its extraction residues, in addition to lignin and carbohydrate. Hydrolysis with H2SO4 removes carbohydrates and amino acids, leaving the KL fraction derived from cutin, tannin, and lignin. Tannin retention in KL was also demonstrated by a hydrolysis study of purified tannins and a brown-rot lignin, using both NMR and the proanthocyanidin assay for condensed tannins. Although the NMR results are qualitative at this stage, it is clear that KL has limited use as a parameter controlling litter decomposition, and that other biopolymers should not be ignored in conceptual models, chemical analysis, and experimental design. Key words: Klason lignin, 13C CPMAS NMR, proximate analysis, litter quality, decomposition, tannin.

13C Nuclear magnetic resonance spectroscopy in the elucidation of structures of diterpenoid alkaloids

1987 ◽  
Vol 65 (1) ◽  
pp. 99-103 ◽  
Author(s):  
Balawant S. Joshi ◽  
John K. Wunderlich ◽  
S. William Pelletier
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Magnetic Resonance Spectroscopy ◽  
Nuclear Magnetic Resonance Spectroscopy ◽  
Resonance Spectroscopy ◽  
Diterpenoid Alkaloids ◽  
Chemical Examination ◽  
13C Nuclear Magnetic Resonance ◽  
C Nmr ◽  
Nuclear Magnetic

13C Nuclear magnetic resonance spectroscopy is an exceptionally useful tool for the structure determination of diterpenoid alkaloids. A detailed study of the 1H and 13C nmr spectra of aconitine and 3-deoxyaconitine has permitted definite assignments to all the carbon atoms of the molecule. Chemical shift revisions have been suggested for certain carbon atoms of the C19-diterpenoid alkaloids. Chemical examination of Aconitumcolumbianum Nutt. ssp. columbianum, A. forrestii Stapf, Delphiniumtatsienense Franch., and D. vestitum Wall, resulted in the isolation of several new C19-diterpenoid alkaloids. The structure derivation of those alkaloids was based mainly on 13C nmr spectroscopic evidence.

High resolution 13C nuclear magnetic resonance spectra of solid pyrazoles. Application to annular tautomerism

1988 ◽  
Vol 66 (5) ◽  
pp. 1141-1146 ◽  
Author(s):  
Robert Faure ◽  
Émile-Jean Vincent ◽  
André Rousseau ◽  
Rose Maria Claramunt ◽  
José Elguero
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Solid State ◽  
Magnetic Resonance ◽  
Magic Angle Spinning ◽  
Resonance Spectroscopy ◽  
Magic Angle ◽  
13C Nuclear Magnetic Resonance ◽  
Annular Tautomerism ◽  
Angle Spinning ◽  
Nuclear Magnetic

Carbon-13 nuclear magnetic resonance spectroscopy in the solid state (cross polarization/magic angle spinning technique) is a very suitable method for studying the annular tautomerism of pyrazoles. In all the compounds studied, the tautomerism is frozen and the signals are well resolved except for 3,5-dimethyl-4-nitro pyrazole, which shows broad signals. In the case of 4-substituted derivatives of 3(5)-methylpyrazoles, the tautomer present in the solid state is a 4-X-5 methylpyrazole. 3-Phenyl-5-methylpyrazole (4H or 4-methyl) is favoured over the 3-methyl-5-phenyl tautomer.

Nuphar thiaspirane sulfoxides. 13C nuclear magnetic resonance determined configuration and utilization in the interconversion of thiaspirane stereochemical types

1978 ◽  
Vol 56 (1) ◽  
pp. 56-61 ◽  
Author(s):  
R. T. LaLonde ◽  
C. F. Wong
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Subsequent Reduction ◽  
13C Nuclear Magnetic Resonance ◽  
Sodium Borodeuteride ◽  
C Nmr ◽  
Nuclear Magnetic

The configuration of the sulfoxide oxygen in syn- and anti-thiobinupharidine sulfoxide was determined by employing the 13C nmr sulfoxidation increments of C-6. Establishment of the 13C nmr line assignments for C-6 included the study of the C-6 and C-6′ deuterated thiobinupharidine and the corresponding sulfoxides. Thermolysis of syn-thiobinupharidine sulfoxide in DMSO and subsequent reduction with sodium borodeuteride in methanol yielded thiobinupharidine, labelled with deuterium only at C-6, and thionuphlutine B, labelled with deuterium at both C-6 and C-6′. Treatment of the anti sulfoxide in xylene or DMSO resulted in no thiobinupharidine or thionuphlutine B. Similarly, syn-neothiobinupharidine sulfoxide gave neothiobinupharidine and a new thiaspirane, thionuphlutine C. These two compounds were not produced from anti-neothiobinupharidine sulfoxide heated in xylene.

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