Investigation on the Hydrogen Abstraction from Methyl Glucoside by Active Oxygen Species Under Oxygen Delignification Conditions. Part 5: Comprehensive Results on Experiments Using Deuterium-Labeled Methyl Glucosides

Abstract

A pair of carbohydrate model compounds, methyl β-d-glucopyranoside (MGP) and a deuterated MGP labeled at each C-H bond, was reacted with active oxygen species (AOS) generated from reactions between O₂ and a co-existing phenolic compound, 2,4,6-trimethylphenol (TMPh) or 4-hydroxy-3-methoxybenzyl alcohol (vanillyl alcohol, Valc), under O₂ delignification conditions. The pair were also reacted with O• generated in the alkaline H₂O₂ treatment with the addition of FeCl₃. Clear kinetic isotope effects were observed only in the reactions of two pairs using the deuterated MGPs labeled at the anomeric and C-2 positions in this system. These results suggest that at least a specific AOS is generated only in this system and that a major AOS in the O₂-Valc system is highly reactive O•. It is also suggested that the AOS specifically generated only in this system is a peroxyl radical derived by the combination reaction between the TMPh phenoxyl radical and O₂.

KEYWORDS:

• Bleaching
• cellulose
• lignin
• oxidation
• pulp