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タイトル: | Radical chain reactions in pyrolytic cleavage of the ether linkages of lignin model dimers and a trimer |
著者: | Watanabe, Toshihiro Kawamoto, Haruo https://orcid.org/0000-0002-4934-8054 (unconfirmed) Saka, Shiro |
著者名の別形: | 渡辺, 敏弘 河本, 晴雄 坂, 志朗 |
キーワード: | α-ether β-ether hydrogen abstraction lignin pyrolysis radical chain reaction |
発行日: | 1-Jul-2009 |
出版者: | De Gruyter |
誌名: | Holzforschung |
巻: | 63 |
号: | 4 |
開始ページ: | 424 |
終了ページ: | 430 |
抄録: | β-Ether-type dimers, [1-(4-hydroxy-3-methoxyphenyl)-2-(2-methoxyphenoxy)-1-propanol and 1-(3, 4-dimethoxyphenyl)-2-(2-methoxyphenoxy)-1-propanol], and an α, β-diether-type trimer [1-(4-(3, 4-dimethoxybenzyloxy)-3-methoxyphenyl) -2- (2-methoxyphenoxy) -1-propanol] were pyrolyzed in a closed ampoule reactor (N₂/250–400°C/2 min). 1-Phenylpropenes (Cα=Cβ) and 1-phenylpropanones (Cα=O) were obtained as the major β-ether-cleaved products. Radical chain mechanisms are proposed in which hydrogen abstraction at the phenolic O-H and Cα-Hs occurs, respectively. The former reaction which gives rise to three radical species was much more effective than the latter. As the effective reaction increases the radical concentration, cleavage of the β-ether linkage in the phenolic dimer is achieved at a much lower temperature (260°C) than that of the non-phenolic type (360°C). Radical chain reactions are initiated in the case of the trimer with a weak Cα-O bond at lower temperature (320°C) than those of the non-phenolic (methylated) dimer, since homolysis of the Cα-O bond produces the phenoxy type dimer and 3, 4-dimethoxybenzyl radicals as initiators. However, some of the dimer phenoxyl radical was stabilized by H-abstraction (to form dimer) or by recombination with a 3, 4-dimethoxybenzyl radical (to form C-benzylated products) so that the chain depolymerization via quinone methide intermediate was suppressed. |
著作権等: | © by Walter de Gruyter • Berlin • New York. The full-text file will be made open to the public on 1 July 2010 in accordance with publisher's 'Terms and Conditions for Self-Archiving'. |
URI: | http://hdl.handle.net/2433/240652 |
DOI(出版社版): | 10.1515/HF.2009.076 |
出現コレクション: | 学術雑誌掲載論文等 |
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