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University of Helsinki Laboratory of Organic Chemistry
 

Laboratory of Organic Chemistry

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Laboratory of Organic Chemistry
Department of Chemistry
University of Helsinki
P.O. Box 55
FI-00014 UNIVERSITY OF HELSINKI

Wood chemistry

Kuva

 

Project leader: University Lecturer Jussi Sipilä
Members: Paula Nousiainen

Wood as a primary source of renewable biomaterials forms the basis of chemical energy flow on earth. Present chemical interest in the wood science consists, for example, elucidation of the biochemistry of wood formation, studies exploiting the wood as a pool of chiral auxiliarity and suppressing the environmental concerns connected to technical wood biomass applications by means of “green chemistry” approaches. At the Laboratory of Organic Chemistry at the Department of Chemistry, University of Helsinki , the main topics in wood science are:

Lignin biosynthesis

Mechanistic studies on the biosynthesis of wood lignins. The role of oxidative enzymes during plant cell wall biosynthesis is presently studied. Oxidative cross-coupling experiments on lignin model compounds yield new facts about the formation of lignins in plant cell walls. Particular attention is paid on the chemistry of 5,5-biphenyl structures that constitute the most important branching structures in lignins.

Transition metal complexes as mimics for oxidative enzymes in lignin biochemistry. As a reference for oxidative enzymes in vivo, the chemistry of lignin oxidation is studied using transition metal complexes, such as Salen type Schiff bases, porphyrins, phthalocyanine and bimetallic catalysts. Typical metals in the catalysts are Mn, Fe, Cu and Co.

Application of 2D and 3D NMR spectroscopy to lignin structure determination. The use of multidimensional NMR has provided unambiguous assignments of side chain structures in lignins. The work is carried out by comparing the NMR information of natural preparates to those given by synthetic oligomeric lignin samples. These studies are carried out using 2D and 3D on 500 and 800 MHz NMR techniques.

Synthesis of oligomeric lignin model compounds. Procedures for new, convenient large scale preparation of arylglycerol b -ether and biphenyl type oligomeric (trimers, tetramers, hexamers) lignin model compounds are under continuous study in the laboratory.

Pulping and bleaching chemistry

Modern NMR techniques and model studies in analysis of changes in lignin chemical structure during pulping . So called “Kraft”-process using NaOH and NaHS as active cooking chemicals forms the basis of modern chemical wood pulping procedures. At present, several modifications to the process have been introduced. To elucidate the effects of different process variables on the chemistry of the cook, laboratory cooks with oligomeric lignin models of defined structures are performed and the results compared with the information obtained from “technical” lignins isolated from industrial processes. The work includes modern 1D and 2D NMR analysis methods as well as LC-MS studies.

Transition metal complexes as pulp bleaching catalysts. The modern pulping procedure involves either one or two-stage oxygen-treatment of the pulp. In this procedure approximately half of the lignin remaining in the pulp can be removed without significant loss in pulp properties. The effect of different transition metal complexes on pulp residual lignin oxidative degradation is studied on model compounds and technical lignins.

Selective oxidative coupling of phenols

Oxidative reactions using peroxidases and metal-centered catalysts on chiral coupling of phenols are studied. Recent themes in this project include the mechanism of formation of dimeric products and oxygenated products from phenolic cinnamyl alcohols and esters, and the attachment of chiral auxiliaries to phenolic cinnamyl alcohols and esters to study the induction of enantioselectivity.