Pitfalls in the chemistry of cellulosic key chromophores

Amer, Hassan; Zwirchmayr, Nele Sophie; Bacher, Markus; Hosoya, Takashi; Potthast, Antje; Rosenau, Thomas

doi:10.1007/s10570-018-2131-6

Cited by 8 publications

(5 citation statements)

References 37 publications

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“…Follow-up studies to our investigations on DHBQ in the chromophore chemistry of cellulosic fibers [17,18] showed that DHBQ and urea formed 1H-benzo[d]imidazole-2,5,6(3H)-trione (9) with the two quinone-carbonyls remaining non-derivatized. Thus, the formation of an aromatic or conjugated system could not be the decisive factor, otherwise urea would rather have formed the corresponding -hypothetical -ortho-quinone diimine structure.…”

Section: Resultsmentioning

confidence: 91%

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Strain-induced Reactivity Effects in the Reaction of 2,5-Dihydroxy-[1,4]- benzoquinone with Diamines

Hofinger

Rosenau

2021

COC

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: The regioselectivity of the reaction of 2,5-dihydroxy-[1,4]-benzoquinone (DHBQ) with diamines could not be explained satisfactorily so far. In general, the reaction products can be derived from the tautomeric ortho-quinoid structure of a hypothetical 4,5-dihydroxy-[1,2]-benzoquinone. However, both aromatic and aliphatic 1,2-diamines form in some cases phenazines, formally by diimine formation on the quinoid carbonyl groups, and in other cases the corresponding 1,2- diamino-[1,2]-benzoquinones, by nucleophilic substitution of the OH groups, the regioselectivity apparently not following any discernible pattern. The reactivity was now explained by an adapted theory of strain-induced bond localization (SIBL). Here, the preservation of the "natural" geometry of the two quinoid C–C double bonds (C3=C4 and C5=C6) as well as the N–N distance of the co-reacting diamine are crucial. A decrease of the annulation angle sum (N–C4–C5 + C4–C5–N) is tolerated well and the 4,5-diamino-ortho-quinones, having relatively short N–N spacings are formed. An increase in the angular sum is energetically unfavorable, so that diamines with a larger N–N distance afford the corresponding ortho-quinone imines. Thus, for the reaction of DHBQ with diamines, exact predictions of the regioselectivity, and the resulting product structure, can be made on the basis of simple computations of bond spacings and product geometries.

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Section: Resultsmentioning

confidence: 91%

“…Benzo[c][1,2,5]thiadiazole-5,6(1H,3H)-dione 2,2-dioxide (18), orange crystals, m.p. = 180-181°C, yield 99.3%, purity (GCMS): 99.8%.…”

Section: Reaction With Sulfamidementioning

confidence: 99%

Strain-induced Reactivity Effects in the Reaction of 2,5-Dihydroxy-[1,4]- benzoquinone with Diamines

Hofinger

Rosenau

2021

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“…Sample coloration derives from the acid degradation of the xanthan and cellulose polymers 35,36 and chromophore formation in the presence of glyoxal. 37 During preparation before the cross-linking step at 140°C and after drying over-night the samples are uncoloured.…”

Section: Discussionmentioning

confidence: 99%

Imperfect cross-linking of xanthan for pH-responsive bio-based composite moist wound dressings by stencil printing

Wurm,

Lenninger,

Mayr

et al. 2023

J Biomater Appl

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The work addresses the use of bio-based and –degradable materials for the production of a moist, adaptive and anti-microbial wound dressing. The dressing is targeted to exhibit a pH-dependent active agent release. Xanthan hydrogel structures are coated on cellulose fabrics via stencil printing and subsequently cross-linked using glyoxal. By alteration of the cross-linker content from 1 to 6% by mass, the hydrogel elasticity can be tuned within a range of 2–16 kPa storage modulus. Increasing initial glyoxal concentrations also result in higher amounts of glyoxal release. Glyoxal, an anti-microbial agent with approval in veterinary medicine, is mostly released upon wound application supporting infection management. As wound simulation, normal saline, as pH 5 and pH 8 buffer solutions, were used. The release profile and magnitude of approx. 65%–90% glyoxal is pH-dependent. Increased release rates of glyoxal are present in pH 8 fluids, which mostly base on faster hydrogel swelling. Higher total glyoxal release is present in pH 5 fluid and normal saline after 3 days. Accordingly, a pH-dependent release profile was encountered. As glyoxal attacks any cell unselectively, it is expected to be effective against antibiotic resistant bacteria. By stencil printing the dressing size can be adjusted to minimize healthy glyoxal tissue exposure.

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“…In addition, RhA salts are virtually insoluble and tend to precipitate on the walls and bottom of the cuvette, even at concentrations as low as 1 lM. GC-MS was not an option either: the reaction had to be stopped reliably, and the sample had to be dried and derivatized, which did not work quantitatively for either compound (Hettegger et al 2019). The rapid neutralization with excess sodium sulfite solution and subsequent UV/Vis measurement of the resulting alkaline solution at 310 nm worked very well and was the method of choice.…”

Section: Model Compound Experimentsmentioning

confidence: 99%

Degradation of the cellulosic key chromophore 2,5-dihydroxy-[1,4]-benzoquinone (DHBQ) under conditions of chlorine dioxide pulp bleaching: formation of rhodizonate as secondary chromophore—a combined experimental and theoretical study

et al. 2020

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2,5-Dihydroxy-[1,4]-benzoquinone (DHBQ, 1) is the most prominent representative of cellulosic key chromophores, which occur almost ubiquitously in all types of aged cellulosics. The degradation of DHBQ by chlorine dioxide under conditions of industrial pulp bleaching (''D stage'') was studied, i.e. in moderately acidic medium (pH 3) at temperatures between 50 and 90°C. The degradation in the presence of excess ClO 2 generates rhodizonic acid (RhA, 5,6-dihydroxycyclohex-5-ene-1,2,3,4-tetrone, 2) as a secondary chromophore which is even more stable and more potent as a chromophore than the starting DHBQ, especially in the form of its salts. At least a threefold ClO 2 excess is needed for complete DHBQ consumption. The reaction from DHBQ to RhA involves pentahydroxybenzene (PHB, I) as an intermediate which is either readily further oxidized to RhA by excess ClO 2 or slowly reconverted to DHBQ in the absence of ClO 2. The RhA yield after 30 min reaction time had a maximum of 83% at a DHBQ/ ClO 2 molar ratio of 1:5, and decreased with increasing ClO 2 charge, reaching 38% at a DHBQ/ClO 2 ratio of

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Pitfalls in the chemistry of cellulosic key chromophores

Cited by 8 publications

References 37 publications

Strain-induced Reactivity Effects in the Reaction of 2,5-Dihydroxy-[1,4]- benzoquinone with Diamines

Strain-induced Reactivity Effects in the Reaction of 2,5-Dihydroxy-[1,4]- benzoquinone with Diamines

Imperfect cross-linking of xanthan for pH-responsive bio-based composite moist wound dressings by stencil printing

Degradation of the cellulosic key chromophore 2,5-dihydroxy-[1,4]-benzoquinone (DHBQ) under conditions of chlorine dioxide pulp bleaching: formation of rhodizonate as secondary chromophore—a combined experimental and theoretical study

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