Ozonolysis of Lignin Models in Aqueous Solution: Anisole, 1,2-Dimethoxybenzene, 1,4-Dimethoxybenzene, and 1,3,5-Trimethoxybenzene
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- 作者：Eino Mvula ; Sergej Naumov ; Clemens von Sonntag
- 刊名：Environmental Science & Technology
- 出版年：2009
- 出版时间：August 15, 2009
- 年：2009
- 卷：43
- 期：16
- 页码：6275-6282
- 全文大小：269K
- 年卷期：v.43,no.16(August 15, 2009)
- ISSN：1520-5851
文摘
The lignin models anisole, 1,2-dimethoxybenzene, 1,4-dimethoxybenzene, and 1,3,5-trimethoxybenzene were reacted with ozone in aqueous solution, and major products were identified and quantified with respect to ozone consumption when reference material was available. Hydroxylation products in yields equivalent to those of singlet oxygen and muconic products (in analogy to the Criegee mechanism) dominate. The formation of quinones points to the release of methanol. Hydroxyl radicals (•OH, quantified, main precursor: O3•−), singlet oxygen (quantified), O2•− radicals (quantified), and as counterparts of the •OH radicals radical cations of these methoxybenzenes must each play an important role as intermediates. In the case of 1,4-dimethoxybenzene, for example, the following products were identified (yields in parentheses when quantified): methyl(2Z,4E)-4-methoxy-6-oxo-hexa-2,4-dienoate 5 (52%), hydroquinone 6 (2%), 1,4-benzoquinone 7 (8%), 2,5-dimethoxyhydroquinone 8, 2,5-dimethoxy-1,4-benzoquinone 9, singlet oxygen (6%), hydrogen peroxide (56%), •OH (17%), O2•− (≤9%). Gibbs energies for the various potential reaction pathways were calculated with the help of the Jaguar 7.5 program.