Lignins, nuclear magnetic resonance

In an attempt to delineate the degree of preservation of lignin in pre-Tertiary coal, we examined numerous coalified wood samples ranging in age from Carboniferous to Cretaceous. The samples were initially screened by solid-state l C nuclear magnetic resonance to detect the possible presence of methoxyl carbon. Once such carbons were detected, the samples were subjected to analytical pyrolysis to determine the relative yields of methoxyphenols which would provide an indication of the state of preservation of the lignin-derived structu units. We report here on the identification of lignin-derived methoxyphenols in the coalified wood samples selected for analytical pyrolysis. 

In an attempt to relate calculated results to experimental findings for monomeric, lignin model compounds, preliminary work has compared theoretically determined electron densities and chemical shifts reported from carbon-13 nuclear magnetic resonance spectroscopy (62). Although chemical shifts are a function of numerous factors, of which electron density is only one, both theoretical and empirical relationships of this nature have been explored for a variety of compound classes, and are reviewed by Ebra-heem and Webb (63), Martin et al. (64), Nelson and Williams (65), and Farnum (66). 

Nimz, H. H., and Ludemann, H. D., 1976, Carbon 13 nuclear magnetic resonance spectra of lignins 6. Lignin and DHP acetates. Holzforsch. 30 33-40. 

Hatcher, P.H. (1987) Chemical structural studies of natural lignin by dipolar dephasing solid state 13C nuclear magnetic resonance. Org. Geochem. 11, 31-39. 

Gerstein BC, Dybowski CR (1985) Transient techniques in NMR of solids an introduction to theory and practice Academic Press, Orlando, 295 pp Hatcher PG (1987) Chemical structural studies of natural lignin by dipolar dephased solid-state nC nuclear magnetic resonance Org Geochem 11 31-39 Hatfield GR, Maciel GE, Erbatur O, Erbatur G (1987) Qualitative and quantitative analysis of solid lignin samples by carbon-13 nuclear magnetic resonance spectrometry Anal Chem 59 172-179... 

Morgan KR, Newman RH (1987) Estimation of the tannin content of eucalypts and other hardwoods by carbon-13 nuclear magnetic resonance Appita 40 450-454 Newman RH (1987) Effects of finite preparation pulse power on carbon-13 cross-polarization NMR spectra of heterogeneous samples J Magn Reson 72 337-340 Newman RH (1989) Carbon 13 NMR studies of lignin in solid samples - a review Chemistry Division Report, DSIR, New Zealand... 

Lenz BL (1968) Application of nuclear magnetic resonance spectroscopy to characterization of lignin Tappi 51 511-519... 

For the further study of the structural heterogeneity of lignin, mild and selective cleavage of bonds, pyrolysis gas chromatography-mass spectrometry (GC-MS), and solid state nuclear magnetic resonance are particularly important. 

Cabannes factor 500 carbohydrate content of lignin pepara-tions 73, 306, 307, 343, 413, 421 carbon-13 nuclear magnetic resonance spectroscopy, C NMR 43, 146, 250-273,... 

HNMR, see proton nuclear magnetic resonance spectroscopy hardwood (guaiacyl-syringyl) lignins 3, 4, 6, 7, 47, 67, 68, 142, 143, 224, 293, 294,... 

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