Photodegradation of lignin model compounds: part 2—substituted stilbenes

Weir, N.A.; Arct, J.; Ceccarelli, Alfredo

doi:10.1016/0141-3910(94)00115-o

Cited by 11 publications

(11 citation statements)

References 22 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…According to Weir et al, compounds 4 and 5 displayed significant UV absorption at 320 nm upon irradiation, concomitant with the coloration of the samples. As noted above, one explanation for this observation could be the formation, through photoinduced isomerization, of the corresponding (nondegraded) cis -stilbenes.…”

Section: Resultsmentioning

confidence: 97%

“…Excitation Spectra of Substituted Stilbenes and their o -Quinones. In the experimental study by Weir et al, UV/vis absorption and emission spectra were recorded for the methoxylated stilbenes ( 3 − 5 ) of Figure , as a function of time during up to 5 min irradiation at λ ≥ 300 nm. It was concluded that the absorption maxima of the nondegraded stilbenes lie at 340, 342, and 350 nm, respectively, with the corresponding extinction coefficients equal to 4 × 10 4 , 3.1 × 10 4 , and 3.4 × 10 4 dm 3 mol -1 cm -1 .…”

Section: Resultsmentioning

confidence: 99%

“…The latter type of reactions is believed to proceed by way of photoinduced formation of singlet oxygen. For an overview of photoinduced degradation of lignin model compounds, we refer to ref 11. From anaerobic (thus eliminating the possibility of singlet oxygen mediated reactions) photochemical studies of β-O-4 aryl ether analogues and polyalkoxylated stilbenes, a mechanism underlying the photoinduced yellowing based on the observed formation of low-molecular-weight products methane and ethane has been put forth, 12,13 as outlined in Figure 1.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Photodegradation of Substituted Stilbene Compounds: What Colors Aging Paper Yellow?

Durbeej

Eriksson

2005

J. Phys. Chem. A

View full text Add to dashboard Cite

Photodegradation of lignin is one of the major postprocessing problems in paper production, as this renders yellowing of the paper and reduced paper quality. In this study, we have explored the photochemical properties of substituted stilbene derivatives believed to be key chromophores in the photodegradation of lignin derived from cinnamyl alcohol. In particular, the present work focuses on the computation of UV/vis electronic absorption spectra for different methoxylated stilbenes and their proposed photodegradation products. All calculations were performed using the time-dependent formalism of density functional theory (TD-DFT) and the B3LYP hybrid functional. It is concluded that the methodology employed is capable of reproducing not only the overall spectra, but also subtle features owing to the effects of different substitution patterns. For the strongly absorbing first excited singlet state (HOMO --> LUMO excitation) of the methoxylated stilbenes, the calculated transition energies are, albeit somewhat fortuitously, in excellent agreement with experimental data. The light-induced yellowing indirectly caused by the presence of stilbenes can be rationalized in terms of the absorption spectra of the resulting photodegraded o-quinones, for which distinct transitions in the 420-500 nm region of the visible spectrum lacking prior to degradation are observed.

show abstract

Section: Resultsmentioning

confidence: 97%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Photodegradation of Substituted Stilbene Compounds: What Colors Aging Paper Yellow?

Durbeej

Eriksson

2005

J. Phys. Chem. A

View full text Add to dashboard Cite

show abstract

“…However, they do not primarily lead to the formation of color. Fast color formation upon irradiation of stilbene model compounds was also reported by Weir et al (1995b). On the other hand, Ruffin et al (1998) concluded that the para-stilbene phenols formed from -1 structures are scarce in hydrogen peroxide-bleached pulp and that they could not explain the rapid yellowing of bleached mechanical pulps.…”

Section: Other Reactionsmentioning

confidence: 92%

Review: Light-Induced Yellowing of Lignocellulosic Pulps – Mechanisms and Preventive Methods

Paulsson¹,

Parkås²

2012

BioResources

View full text Add to dashboard Cite

This review will focus on recent progress regarding the mechanisms of light-induced discoloration of mechanical and chemimechanical pulps and on the proposed preventive treatments. It is evident that the mechanisms behind photoyellowing of lignin-rich pulps are complex and that several types of reaction pathways may coexist. Photoyellowing proceeds via one initial fast phase and a slower following phase. The fast phase has been ascribed to oxidation of free phenolic groups and/or hydroquinones and catechols to photoproducts of mainly quinonoid character. A multitude of reactions involving several lignin subunits are possible. Important intermediates are phenoxyl radicals, and to some extent ketyl radicals. The importance of the phenacyl aryl ether pathway might be more important than previously thought, even though the original content of such groups is low in lignin. Even though many preventive methods against photoyellowing have been suggested, no cost-efficient treatment is available to hinder photoreversion of lignincontaining paper permanently. Suggested methods for stabilization include chemical modification (etherification and esterification), coating the paper product, addition of radical scavengers, excited state quenchers, or ultraviolet absorbing compounds.

show abstract

“…Stilbene FWAs may form oxygenated products, such as hydroxystilbenes and p ‐hydroxyquinone structures via reactions of the FWA with ROS, which can then undergo further oxidation to form highly coloured p ‐quinonoid compounds. These reactions are known to occur in bleached, lignin‐rich woodpulps [82] and it has been suggested that stilbene–hydroquinone derivatives are the major chromophores responsible for colour reversion in bleached pulps [83].…”

Section: Photoyellowing Of Wool Treated With Fluorescent Whitening Agmentioning

confidence: 99%

Photoyellowing of wool. Part 2: Photoyellowing mechanisms and methods of prevention^†

Millington

2006

Coloration Technology

View full text Add to dashboard Cite

Part 1 of this review discussed the effects of light on wool keratin and the factors that affect the rate of photoyellowing. Part 2 describes the various photochemical mechanisms that have been proposed to account for photoyellowing of wool by sunlight, and focuses in particular on their strengths and weaknesses. The mechanisms involved in the rapid photoyellowing of wool treated with a fluorescent whitening agent are described in some detail since this remains a serious commercial problem. Existing methods for reducing the rate of wool photoyellowing are reviewed, together with a discussion of the remaining scientific and technical challenges to achieve bright, white wool fabrics and garments of high photostability.Scheme 1

show abstract

Photodegradation of lignin model compounds: part 2—substituted stilbenes

Cited by 11 publications

References 22 publications

Photodegradation of Substituted Stilbene Compounds: What Colors Aging Paper Yellow?

Photodegradation of Substituted Stilbene Compounds: What Colors Aging Paper Yellow?

Review: Light-Induced Yellowing of Lignocellulosic Pulps – Mechanisms and Preventive Methods

Photoyellowing of wool. Part 2: Photoyellowing mechanisms and methods of prevention^†

Contact Info

Product

Resources

About

Photodegradation of lignin model compounds: part 2—substituted stilbenes

Cited by 11 publications

References 22 publications

Photodegradation of Substituted Stilbene Compounds: What Colors Aging Paper Yellow?

Photodegradation of Substituted Stilbene Compounds: What Colors Aging Paper Yellow?

Review: Light-Induced Yellowing of Lignocellulosic Pulps – Mechanisms and Preventive Methods

Photoyellowing of wool. Part 2: Photoyellowing mechanisms and methods of prevention†

Contact Info

Product

Resources

About

Photoyellowing of wool. Part 2: Photoyellowing mechanisms and methods of prevention^†