Generation and Reactivity of Ketyl Radicals with Lignin Related Structures. On the Importance of the Ketyl Pathway in the Photoyellowing of Lignin Containing Pulps and Papers
作者:Claudia Fabbri、Massimo Bietti、Osvaldo Lanzalunga
DOI:10.1021/jo047826u
日期:2005.4.1
the photochemical studies ketyl radicals have been produced by charge-transfer (CT) photoactivation of the electron donor−acceptor salts of methyl viologen (MV2+) with α-hydroxy-α-phenoxymethyl-aryl acetates. This process leads to the instantaneous formation of the reduced acceptor (methyl viologen radical cation, MV+•), as is clearly shown in a laser flash photolysis experiment by the two absorption
通过辐射化学和光化学技术已经产生了具有木质素相关结构的酮基。在以前的研究中,酮基是通过α-羰基-β-芳基醚木质素模型与pH值为6.0的水溶液的脉冲辐射分解产生的溶剂化电子反应生成的。酮基的紫外-可见光谱的特征在于三个主要吸收带。当在碱性溶液(pH 11.0)中记录光谱时,这些谱带的形状和位置略有变化,现在将它们分配给了酮基自由基阴离子,并确定了1-(3,4,5-三甲氧基苯基)的ap K a = 9.5。 -2-苯氧基乙醇-1-基。发现酮基的衰变速率与剂量有关,在低剂量时,其范围为(1.7-2.7)×10 3 s- 1。在存在氧气的情况下,观察到酮基的快速衰变(k 2 = 1.8-2.7×10 9 M - 1 s - 1),伴随而来的是形成稳定的产物,即起始酮。在光化学研究中,已经通过α-羟基-α-苯氧基甲基-芳基乙酸酯的甲基紫精(MV 2+)的电子给体-受体盐的电荷转移(CT)光活化产生了