The basic mechanistic aspects of the photo- and radiation chemistry of lignin model compounds (LMCs) are discussed with respect to important processes related to lignin degradation. Several reactions occur after direct irradiation, photosensitized or radiation chemically induced oxidation of LMCs. Direct irradiation studies on LMCs have provided supportive evidence for the involvement of hydrogen abstraction reactions from phenols, β-cleavage of substituted α-aryloxyacetophenones and cleavage of ketyl radicals (formed by photoreduction of aromatic ketones or hydrogen abstraction from arylglycerol β-aryl ethers) in the photoyellowing of lignin rich pulps. Photosensitized and radiation chemically induced generation of reactive oxygen species and their reaction with LMCs are reviewed. The side-chain reactivity of LMC radical cations, generated by radiation chemical means, is also discussed in relation with the enzymatic degradation of lignin.

Photo- and radiation chemical induced degradation of lignin model compounds.

The invention is a method for improving the efficiency of aqueous cationic wet strength additives by pretreating cellulose surfaces with reactive anionic compounds, thus providing the cellulose surface with additional anionic sites suitable for retaining a high proportion of said cationic wet strength additives on the cellulose. The wet strength additives on the cellulose surface are cured or reacted with the cellulose surface. The resulting fibrous material has unusually high wet strength with unusually low doses of cationic wet strength additive. The preferred reactive anionic compounds comprise compounds having a reactive group suitable for covalent bonding to hydroxyl groups on cellulose, and further having sulfonic or other anionic end groups capable of attracting cationic wet strength compounds in aqueous solution. The invention also includes means of preventing photoyellowing of high-yield fibers while simultaneously improving wet strength performance.

Method for improved wet strength paper

One- and two-electron transfer reactions of 3,5-di-tert-butylcatechol and the corresponding quinone were studied by fast kinetic spectroscopy coupled with laser photolysis and pulse radiolysis, and...

Redox reactions of 3,5-di-tert-butyl-1,2-benzoquinone. Implications for reversal of paper yellowing

A semiquantitative analytical method has been developed for the determination of the total quinonoid content (o-benzoquinones and p-benzoquinones) of soluble lignins. The method is based on detailed measurements and observations made with model o- and p-quinones, which in dry organic solvents were shown to form adducts with trimethyl phosphite in quantitative yield. These adducts gave 31P NMR signals for o- and p-quinones at around −46 and −2 ppm, respectively. In the presence of moisture and lignin the adducts from o-quinones were shown to be hydrolyzed to the open ring product, dimethylphenyl phosphate (−2 ppm), at an overall yield of ∼70%. Similarly, the hydrolysis yields of p-quinone adducts with trimethyl phosphite were ∼70%. Consequently, a number of important issues in relation to the use of trimethyl phosphite toward the quantitative analysis of quinonoid groups in lignins have been investigated, which permitted the development of an experimental semiquantitative protocol recommended for spectral ...

Semiquantitative Determination of Quinonoid Structures in Isolated Lignins by 31P Nuclear Magnetic Resonance

The reactions of three hydroxy- and/or methoxy-substituted stilbenes with hydroxyl radicals (HO.) or with hydroxyl radicals and superoxide radicals (HO. + O 2 ?/HO 2 .) under alkaline and acidic conditions have been studied. In this part, the course of cleavage of the conjugated double bond in the stilbenes is described. The preparation of the starting stilbenes and of a suggested intermediate using previously published methods with some modifications is also given.

https://www.degruyter.com/view/j/hfsg.1996.50.issue-4/hfsg.1996.50.4.342/hfsg.1996.50.4.342.pdf

The reactions of chromophores of the stilbene type with hydroxyl radical (HO.) and superoxide radical (O2.-/HO2.). Part I. The cleavage of the conjugated double bond

/pdf/reactive-structures-in-wood-and-high-yield-pulps-iv-daylight-eo9h6zq652.pdf

A. J. Kondow

Papers

Reactive Structures in Wood and High-yield Pulps. IV. Daylight-induced Oxidation of Stilbene Structures in the Solid State.