Formation of free radicals in photoirradiated cellulose and related compounds

The processes of radical formation in N-methylmorpholine-N-oxide monohydrate (NMMO) and cellulose/NMMO solutions were studied by ESR at 77 K under high-power UV (lambda = 248 nm) excimer laser flash photolysis. Radicals mainly generated were attributed to the nitroxide type radicals -CH2-NO*-CH2- and -CH2-NO*-CH3 at the first step and methyl *CH3 and formyl *CHO radicals at the second step of the photoreaction. Kinetic studies of these radicals revealed that formation and recombination rates of the radicals depend on the cellulose concentration in cellulose/NMMO solutions and the concentration of additional ingredients, e.g. Fe(II) and propyl gallate. Even at frozen state temperature, acceleration or quenching of radical reaction processes was found. The proposed scheme of UV light-induced NMMO degradation during irradiation based on ESR data correlates well with independently obtained results based on high-performance liquid chromatography (HPLC). The analysis of degradation products by HPLC, e.g. aminoethanol and acetaldehyde, supports the assumption concerning a radical-initiated ring opening of NMMO.

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“…24). A comparison with previous investigations 25 indicated only some obvious differences in experimental spectra recorded at 77 K (Fig. 7).…”

Section: Cellulosementioning

confidence: 56%

Electron spin resonance study of radicals generated in cellulose/N‐methylmorpholine solutions after flash photolysis at 77 K

Konkin

Wendler

Roth

et al. 2006

Magnetic Reson in Chemistry

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“…New linkages in the 50 and 100 kGy irradiated wood samples can be observed, the bands at around 1740 and 1715 cm −1 demonstrate new formation of carbonyl groups such as aldehydes and ketones. Moreover, EBI can create free radicals in wood (e.g., lignin); detailed information about the formation of free radicals in wood was given by Fengel and Wegener [5] and Hon [37,38]. Free radicals in wood can be formed mainly be the cleavage of ether bonds leading to phenoxy radicals in lignin, however, also alkoxy radicals can be produced when polysaccharide were irradiated.…”

Section: Chemical and Structural Analysismentioning

confidence: 99%

Changes in mechanical and chemical wood properties by electron beam irradiation

Schnabel

Huber

Grünewald

et al. 2015

Applied Surface Science

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“…Presumably, some chromophore that absorbs at longer wavelengths and that can initiate C-O bond cleavage is removed in the bleaching process. The D N values at 270 nm for unbleached and bleached samples were very close to each other, presumably because 270 nm light has enough energy to break the C-O bonds directly (Hon 1976). At 500 nm, destruction of the C-O bonds and of aromatic rings was only observed for the unbleached samples.…”

Section: Carbohydrate Peaks (1) C-o Bondsmentioning

confidence: 77%

FT-IR Study of the Effect of Irradiation Wavelength on the Colour Reversion of Thermomechanical Pulps

Kimura¹,

Kimura²,

Gray³

1994

HFSG

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The effect of irradiation by light of wavelengths 270, 320, 390 and 500nm on the colour reversion of unbleached and bleached thermomechanical pulp was monitored by FT-IR transmission spectroscopy. The aromatic ring structure in lignin and the C-O and C-H bonds in the wood carbohydrates decreased much more rapidly at shorter irradiation wavelengths for bolh unbleached and bleached pulp samples. The rate of decrease of aromatic ring and guaiacyl structures is the same at all wavelengths for the unbleached pulp, whereas for the bleached pulp, the rate of decrease of the guaiacyl structure is much larger than that of the total aromatic ring structure for irradiation at 270 and 320 nm. New bands at 1719 and 1684 cm' 1 were generated by all wavelengths but the increase in the 1684 cm" 1 band caused by 390nm radiation is especially large, compared with the 1719cm"" 1 band. The increase in non-conjugated carbonyl group content is strongly related to the disappearance of aromatic rings for 270 and 320nm radiation, but not for 390 nm radiation, indicating that colour reversion reactions at 270 and 320 nm are different from those at 390 nm. A band at 1584cm" 1 also increases with irradiation at 390 nm. The increasing bands at 1684 and 1584cm" 1 may be due to the formation of quinone structures.

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Formation of free radicals in photoirradiated cellulose and related compounds

Cited by 32 publications

References 16 publications

Electron spin resonance study of radicals generated in cellulose/N‐methylmorpholine solutions after flash photolysis at 77 K

Electron spin resonance study of radicals generated in cellulose/N‐methylmorpholine solutions after flash photolysis at 77 K

Changes in mechanical and chemical wood properties by electron beam irradiation

FT-IR Study of the Effect of Irradiation Wavelength on the Colour Reversion of Thermomechanical Pulps

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