scholarly journals Structural Characterization of Wheat Straw Lignin as Revealed by Analytical Pyrolysis, 2D-NMR, and Reductive Cleavage Methods

2012 ◽  
Vol 60 (23) ◽  
pp. 5922-5935 ◽  
Author(s):  
José C. del Río ◽  
Jorge Rencoret ◽  
Pepijn Prinsen ◽  
Ángel T. Martínez ◽  
John Ralph ◽  
...  
Keyword(s):  
Wheat Straw ◽  
Structural Characterization ◽  
2D Nmr ◽  
Reductive Cleavage ◽  
Analytical Pyrolysis

Structural characterization of milled wood lignins from different eucalypt species

Holzforschung ◽  
2008 ◽  
Vol 62 (5) ◽  
Author(s):  
Jorge Rencoret ◽  
Gisela Marques ◽  
Ana Gutiérrez ◽  
David Ibarra ◽  
Jiebing Li ◽  
...  
Keyword(s):  
Eucalyptus Globulus ◽  
Chemical Structure ◽  
2D Nmr ◽  
Analytical Pyrolysis ◽  
Additional Information ◽  
Diaryl Ether ◽  
Heteronuclear Single Quantum Correlation ◽  
Relative Abundances ◽  
Type 3

Abstract The chemical structure of milled-wood lignins from Eucalyptus globulus, E. nitens, E. maidenii, E. grandis, and E. dunnii was investigated. The lignins were characterized by analytical pyrolysis, thioacidolysis, and 2D-NMR that confirmed the predominance of syringyl over guaiacyl units and only showed traces of p-hydroxyphenyl units. E. globulus lignin had the highest syringyl content. The heteronuclear single quantum correlation (HSQC) NMR spectra yielded information about relative abundances of inter-unit linkages in the whole polymer. All the lignins showed a predominance of β-O-4′ ether linkages (66–72% of total side-chains), followed by β-β′ resinol-type linkages (16–19%) and lower amounts of β-5′ phenylcoumaran-type (3–7%) and β-1′ spirodienone-type linkages (1–4%). The analysis of desulfurated thioacidolysis dimers provided additional information on the relative abundances of the various carbon-carbon and diaryl ether bonds, and the type of units (syringyl or guaiacyl) involved in each of the above linkage types. Interestingly, 93–94% of the total β-β′ dimers included two syringyl units indicating that most of the β-β′ substructures identified in the HSQC spectra were of the syringaresinol type. Moreover, three isomers of a major trimeric compound were found which were tentatively identified as arising from a β-β′ syringaresinol substructure attached to a guaiacyl unit through a 4-O-5′ linkage.

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