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A selectivity study of reaction of the carbonate radical anion with methyl beta- D-cellobioside and methyl beta-D-glucoside in oxygenated aqueous solutions
KTH, Skolan för kemivetenskap (CHE), Kemi, Kärnkemi.
KTH, Skolan för kemivetenskap (CHE), Kemi, Kärnkemi.
KTH, Skolan för kemivetenskap (CHE), Kemi, Kärnkemi.
2006 (engelsk)Inngår i: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 60, nr 2, s. 130-136Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

In the presence of oxygen, radiolytically generated carbonate radical anions, CO3.-, were reacted with methyl beta-D-cellobioside and methyl beta-D-glucoside. From the ensuing product pattern, it was concluded that CO3 center dot- abstracts hydrogen atoms predominantly from glucosidic C1 - H bonds. This high intramolecular selectivity was rationalised mainly in terms of a polar effect on the transition state of the hydrogen abstraction reaction. The present findings are in sharp contrast to the relative inertness of CO3(center dot-) towards glucosidic C1 - H bonds previously observed in cotton linters. The reasons for this discrepancy are discussed in light of a possible future role of CO3 center dot- as a bleaching agent for pulp.

sted, utgiver, år, opplag, sider
2006. Vol. 60, nr 2, s. 130-136
Emneord [en]
carbohydrate, carbonate radical, glucosidic cleavage, hydrogen abstraction, intramolecular, model compounds, selectivity
HSV kategori
Identifikatorer
URN: urn:nbn:se:kth:diva-5268DOI: 10.1515/HF.2006.021ISI: 000236203100003Scopus ID: 2-s2.0-33644925334OAI: oai:DiVA.org:kth-5268DiVA, id: diva2:8207
Merknad
QC 20101001. Uppdaterad från manuskript till artikel (20101001). Tidigare titel: A Selectivity Study of the Carbonate Radical Anion Reacting with Methyl-β-D-cellobioside and Methyl-β-D-glucoside in Oxygenated Aqueous Solutions Tilgjengelig fra: 2005-06-02 Laget: 2005-06-02 Sist oppdatert: 2017-12-04bibliografisk kontrollert
Inngår i avhandling
1. The inter-and intramolecular selectivity of the carbonate radical anion in its reactions with lignin and carbohydrates
Åpne denne publikasjonen i ny fane eller vindu >>The inter-and intramolecular selectivity of the carbonate radical anion in its reactions with lignin and carbohydrates
2005 (engelsk)Doktoravhandling, med artikler (Annet vitenskapelig)
Abstract [en]

In the present thesis, the effects of the carbonate radical anion on lignin and cellulose were investigated.

The carbonate radical has a rather high reactivity towards aromatic lignin constituents. It reacts especially fast with phenolates. All these reactions occur by way of electron transfer. Small carbohydrates react with CO3 •- much slower than aromatics. These reactions are hydrogen transfer reactions. However, in very basic media, where the carbohydrates deprotonate to some extent, their anions react with CO3 •- by way of electron transfer and the rates approach those of non-phenolic aromatics. These findings suggest that in neutral or slightly alkaline media CO3 •- might serve as an excellent delignifying agent of pulp down to very low lignin contents. With small carbohydrates possessing one or two glucosidic bonds, CO3 •- abstracts hydrogen predominantly from C1 – H bonds, which results in rupture of the glucosidic linkage. Interestingly, however, the glucosidic bonds in cotton linters are rather resistent towards CO3 •-. This has probably morphological reasons. These results imply that, even at very low lignin contents, where CO3 •- is bound to react with cellulose, the reactions will not lead to substantial decrease in pulp viscosity.

At present the cheapest and most practical way of producing CO3 •- radicals in the presence of pulp is to mix the latter with peroxynitrite and CO2. We have performed such experiments on pulp with very promising results. The Kappa number decreased substantially, brightness increased, while the viscosity remained high. This confirms the predicted excellent properties of the carbonate radical.

However, before the peroxynitrite method can be implemented in the pulp industry, a number of technical problems has to be solved. Chief among them is a slow and steady dosage of peroxynitrite to minimise side reactions of the radicals with peroxynitrite and the nitrite impurity. The fate of the NO2 radical, the coproduct of CO3 •-, has also to be assessed. NO2 will probably have to be removed by vigorous degassing in order to block the possible nitration of cellulose.

sted, utgiver, år, opplag, sider
Stockholm: KTH, 2005. s. 62
Serie
Trita-KKE, ISSN 0349-6465 ; 0501
Emneord
Chemistry, nuclear chemistry, Kemi
HSV kategori
Identifikatorer
urn:nbn:se:kth:diva-257 (URN)91-7178-098-X (ISBN)
Disputas
2005-06-15, Sal E3, Lindstedtsvägen 3, Stockholm, 14:00 (engelsk)
Opponent
Veileder
Merknad
QC 20101001Tilgjengelig fra: 2005-06-02 Laget: 2005-06-02 Sist oppdatert: 2010-10-01bibliografisk kontrollert

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