Henry I. Bolker

Polymeric Structure of Spruce Lignin

From the Flory-Stockmayer theory and molecular weights of successive fractions of lignin obtained by extraction of spruce wood with a mixture of water, dioxane, and hydrochloric acid and by sulfonation, the average length of the primary chains was estimated to be 18 phenylpropane units. From data on the acid-catalyzed cleavage of model compounds in various solvents the degrees of cross-linking in four extraction processes were calculated. The average degree of cross-linking of intact lignin was found to be 0.277; that is, 5 out of every 18 phenylpropane units bear cross-linking benzyl ether groups. Of the five, three are also etherified at their phenolic ends (B groups), and two are not (X groups).

31P NMR Spectroscopy in Wood Chemistry Part V. Qualitative Analysis of Lignin Functional Groups

Abstract Dioxane lignin isolated from a hardwood (birch, betula verrucosa) and milled wood lignin isolated from a softwood (black spruce, picea mariana) were subjected to a variety of selective reactions to modify some of their functional groups. All the lignins were then treated with 1, 3, 2-dioxaphospholanyl chloride (I) and the 31P NMR spectra of the derivatives were recorded. Most of the 31P NMR signals were assigned from the chemical shifts previously obtained from model compounds. The signals arising from derivatizing me labile protons in carbohydrates, erythro and threo forms in β-O-4 structures, primary hydroxyls in a variety of lignin structures, syringyl and guaiacyl phenolic hydroxyls and those of carboxylic acids were assigned. The alpha benzylic hydroxyls in β-O-4 structures within birch lignin were less reactive toward alkylation than those in spruce lignin, consistent with the findings of previous workers; a difference attributable to the aryl part of the β-O-4 ether. The 31P NMR spectrosco...

Condensation of Lignin in Dioxane-Water-HCl

Abstract Black spruce sawdust, when treated batchwise, in accordance with the principles of the gel degradation theory, with dioxane: H2O:HCl (90:8:1.8 by volume) at various extents of lignin solubilization, gave a series of lignin fractions. The undialyzed lignin preparations, characterized by Klason lignin, methoxy contents, microanalysis, and U.V. absorptivity, were found to be reasonably uniform in composition. Gel permeation chromatography with a combination of refractive index (RI) and Low Angle Laser Light Scattering (LALLS) detection gave fractions that qualitatively resembled those obtained by the degradation of synthetic model polymer gels. In efforts to quantitatively correlate molecular weights (M w) of these lignins with the existing gel degradation models, however, the problems of lignin fluorescence, association and recondensation were encountered. During the batchwise dioxane:H2O:HCl extraction of wood, irreversible recondensation of the lignin fragments took place, limiting analysis of th...

The Gel Degradation Theory. Part III. An Experimental Kinetic Verification

Abstract Yan and Johnsons kinetic model, which has been developed for the purpose of describing wood delignification, recognizes the polymer network structure of lignin. Their model is experimentally examined with a synthetic network polymer. The starting material was functionalized monodisperse polystyrene crosslinked to yield networks in which the parameters of the theoretical equations were known. By the hydrolytic random cleavage of the crosslinks, kinetic data for this model network degradation experiment was obtained. Thus, the kinetics of this model degradation were found to be adequately described by the Yan and Johnson expressions, which furnish additional support for the gel degradation theory and the model examined herein.

Keto groups in cellulose and mannan oxidized by dinitrogen tetroxide

Abstract Mannan B and cellulose were oxidized with nitrogen tetroxide to transform the C-6 hydroxyls into carboxyl groups. In both products keto groups had formed on secondary carbons in side-reactions. After reduction of the oxidized polysaccharides with sodium borohydride- t 4 , determination of the radioactivity indicated that the ratio of keto groups in oxycellulose to those in oxymannan was 2:1. Comparison of the count of radioactivity with that of diphenylmethanol- t 2 prepared from a similarly reduced sample of diphenyl ketone showed that the oxymannan contained one keto group for every 10 anhydro- d -mannose units.