Chromophores in cellulosics, VI. First isolation and identification of residual chromophores from aged cotton linters

Hexeneuronic acids (HexA) are a major cause of discoloration (yellowing/brightness reversion) in pulps from xylan-containing wood, being generated from the xylan's 4-O-methylglucuronic acid residues. The HexA-derived chromophores, whose identification and structure confirmation have been described in the previous part of this series (Rosenau et al. in Cellulose, 2017), were subject to conditions of peroxide bleaching, i.e. treatment with hydrogen peroxide in alkaline medium. These chromophores, ladder-type oligomers of mixed aromatic-quinoid and mixed furanoid-benzoid character, are degraded relatively quickly to one major product, 2,5-dihydroxy-[1,4]-benzoquinone (DHBQ), and a minor component, 2,5-dihydroxyacetophenone (DHA). These two compounds, which have already been identified as two of the three key chromophores (besides 5,8-dihydroxy-[1,4]-naphthoquinone, DHNQ) in aged cellulosics, are potent chromophores themselves and are subsequently more slowly degraded to non-colored degradation products, according to pathways already described in previous parts of this series. The occurrence of DHBQ and DHA in the bleaching treatment of the HexAderived chromophores establishes the link between HexA chemistry and the key chromophore classes of residual chromophores found in aged cellulosic materials.

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“…The data agree very well with previously published data of the respective compounds (Rosenau et al 2007(Rosenau et al , 2011 …”

Section: Pulp Bleachingsupporting

confidence: 92%

Chromophores from hexeneuronic acids: chemical behavior under peroxide bleaching conditions

et al. 2017

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“…These to a high extent leave the environment of the sample. Other heavier products of simultaneous oxidation and glucopyranose breakage include oligomers are also supposed to be formed in paper [25] but their contribution to the overall oxidation is rather low [26]. We will address this topic in future works.…”

Section: Resultsmentioning

confidence: 99%

Experimental and Theoretical Study of the Yellowing of Ancient Paper

Conte

Pulci

Sole

et al. 2012

e-J. Surf. Sci. Nanotechnol.

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Paper is the most widely used writing support due to the remarkable properties of its principal componentcellulose -one of the most abundant biomaterials present on Earth. However, due to the complexity of the material, an exhaustive picture of its degradation pathways is still missing. In this paper, we will present recent results and progresses obtained in the comprehension of the role of cellulose oxidation in the yellowing of ancient paper. Visible and ultraviolet spectra of cellulose in ancient paper samples and reference modern samples artificially aged have been interpreted with the aid of ab-initio Time-Dependent Density Functional Theory calculations. Through the comparison of measured and calculated absorption spectra, several oxidized forms of cellulose polymers, acting as chromophores, and responsible for ancient paper yellowing were identified. The relative concentration of ketones and aldehydic groups depends on the environmental conditions in which samples were stored along their life.

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“…This stabilization effect is especially important when bleaching at alkaline pH, as in a peroxide stage (P stage). Traditional industrial bleaching agents T. Elder USDA Forest Service, Southern Research Station, 521 Devall Dr., Auburn, AL 36849, USA T. Rosenau Johan Gadolin Process Chemistry Centre, Å bo Akademi University, Porthansgatan 3, Å bo, Turku 20500, Finland attack localized double bonds, a reaction that is hindered in these chromophores due to precisely these attributes, delocalization of electrons and high symmetry (Rosenau et al 2011).…”

Section: Introductionmentioning

confidence: 99%

Degradation of the cellulosic key chromophores 2,5- and 2,6-dihydroxyacetophenone by hydrogen peroxide under alkaline conditions. Chromophores in cellulosics, XVII

et al. 2018

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The dihydroxyacetophenones 2,5-dihydroxyacetophenone (2,5-DHAP) and 2,6-dihydroxyacetophenone (2,6-DHAP) belong to the key chromophores in cellulosic materials. The pulp and paper industry targets these key chromophores in their bleaching sequences to obtain brighter products. 2,5-DHAP and 2,6-DHAP were degraded with hydrogen peroxide in alkaline media, similar to conditions of peroxide bleaching (P stage) in industrial pulp bleaching. Degradation product analyses were performed by GC-MS and NMR. The degradation reaction starts by loss of acetic acid originating from the acetyl moiety of the dihydroxyacetophenones (Baeyer-Villiger rearrangement). Further reaction steps involve introduction of another hydroxyl group at C-1 (previously acetyl bearing), and further oxidation of the resulting trihydroxybenzene to quinone intermediates which are ultimately degraded to a mixture of low-molecular weight carboxylic acids.Electronic supplementary material The online version of this article (https://doi.org/10.1007/s10570-018-1817-0) contains supplementary material, which is available to authorized users.

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Chromophores in cellulosics, VI. First isolation and identification of residual chromophores from aged cotton linters

Cited by 51 publications

References 23 publications

Chromophores from hexeneuronic acids: chemical behavior under peroxide bleaching conditions

Chromophores from hexeneuronic acids: chemical behavior under peroxide bleaching conditions

Experimental and Theoretical Study of the Yellowing of Ancient Paper

Degradation of the cellulosic key chromophores 2,5- and 2,6-dihydroxyacetophenone by hydrogen peroxide under alkaline conditions. Chromophores in cellulosics, XVII

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