Some pertinent results and views from the earlier history of lignin chemistry, pointing to the importance of the arylpropane skeleton, are outlined. Later development, beginning with the dehydrogenation theory and experimental studies on the dehydrogenative polymerization of p-hydroxycinnamyl alcohols, is then reviewed. Finally, recent degradative work resulting in a detailed picture of lignin structure is discussed.

Lignin chemistry—past, present and future

Methods in Lignin Chemistry

It is a privilege to be able to contribute to this volume in which Professor Zervas’ friends, students, and colleagues have joined together to honor him and his remarkable contributions to peptide chemistry. Although I did not know him until after his days in the Bergmann Laboratory at the Rockefeller Institute, I can claim the distinction of now working in those very same rooms that they occupied back in the mid-1930s. Like all peptide chemists, I am greatly indebted to Professor Zervas, having depended so heavily on the carbobenzoxy group and on the various modified urethan protecting groups which have been direct extensions of the revolutionary advance that Bergmann and Zervas made.

Solid-phase peptide synthesis.

Acid catalysis has long been used to depolymerize plant cell wall polysaccharides, and the mechanisms by which acid affects carbohydrates have been extensively studied. Lignin depolymerization, however, is not as well understood, primarily due to the heterogeneity and reactivity of lignin. We present an experimental and theoretical study of acid-catalyzed cleavage of two non-phenolic and two phenolic dimers that exhibit the β-O-4 ether linkage, the most common intermonomer bond in lignin. This work demonstrates that the rate of acid-catalyzed β-O-4 cleavage in dimers exhibiting a phenolic hydroxyl group is 2 orders of magnitude faster than in non-phenolic dimers. The experiments suggest that the major product distribution is similar for all model compounds, but a stable phenyl-dihydrobenzofuran species is observed in the acidolysis of two of the γ-carbinol containing model compounds. The presence of a methoxy substituent, commonly found in native lignin, prevents the formation of this intermediate. Reacti...

A Mechanistic Investigation of Acid-Catalyzed Cleavage of Aryl-Ether Linkages: Implications for Lignin Depolymerization in Acidic Environments

The decomposition of lignin was examined in supercritical water with and without phenol at 673 K. In the absence of phenol, the yield of tetrahydrofuran (THF)-insoluble (TIS) products decreased and the molecular weight distribution of THF-soluble (TS) products shifted toward lower molecular weights as the water density increased. The increase in water density enhanced the lignin conversion. In the presence of phenol, the yield of TIS products was lower and the molecular weight distribution of TS products shifted toward lower molecular weights than those in the absence of phenol. Some alkylphenols were obtained only in the presence of phenols, because of the reaction of phenol with the decomposition products. These results show that the reaction of phenol with reactive sites occurred in supercritical water and suppressed cross-linking reactions among reactive sites of large fragments. This promoted the decomposition of lignin to lower-molecular-weight compounds.

Conversion of Lignin with Supercritical Water−Phenol Mixtures

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Acid Degradation of Lignin. III. Formation of Formaldehyde.

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Organic Selenium Compounds. XVII. Reactions of Carbon Diselenide with Active Methylene Compounds.

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Studies on Orchidaceae Alkaloids. XX. The Constitution and Relative Configuration of Crepidine, an Alkaloid from Dendrobium crepidatum Lindl.

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Studies of Polarized Ethylenes. Part II. Preparation of 1,1-Bis-dimethylaminoethylenes and 1,3-Dimethyl-2-methylene-imidazolidines.

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F. Solymosy

Papers

Acid Degradation of Lignin. III. Formation of Formaldehyde.

Organic Selenium Compounds. XVII. Reactions of Carbon Diselenide with Active Methylene Compounds.

Studies on Orchidaceae Alkaloids. XX. The Constitution and Relative Configuration of Crepidine, an Alkaloid from Dendrobium crepidatum Lindl.

Studies of Polarized Ethylenes. Part II. Preparation of 1,1-Bis-dimethylaminoethylenes and 1,3-Dimethyl-2-methylene-imidazolidines.

Monte-Carlo Investigation of Nearest-neighbour Auto-inhibitory Effects in the Oxidation of Amylose by Periodate Ion.