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首页> 外文学位 >Determination of phenolic hydroxyl content in lignin and lignin model compounds by the periodate oxidation method.
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Determination of phenolic hydroxyl content in lignin and lignin model compounds by the periodate oxidation method.

机译：用高碘酸盐氧化法测定木质素和木质素模型化合物中的酚羟基含量。

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摘要

Free phenolic hydroxyl groups are important functional groups in lignin. Determination of the number of phenolic groups in lignin would be of great value for the understanding of lignin structure and lignin reactivity. The phenolic hydroxyl group is one of the most important functional groups affecting the physical and chemical properties of lignin polymers. It has been the goal of many researchers to investigate and determine the role of free phenolic hydroxyl groups in lignin structure.; In this research, we investigated the use of the periodate oxidation method for the determination of the free phenolic hydroxyl content in lignin and lignin model compounds. Simple model compounds, including vanillin, acetovanillone, o-vanillin, creosol, and guaiacol, and dimer and trimer lignin model compounds were used to study the periodate oxidation method.; We found that solubility problems exist in some lignin dimer and all lignin trimer model compounds prior to the reaction with aqueous sodium periodate. Using the periodate oxidation method, lignin model compounds that are soluble in the aqueous periodate mixture and which contain a phenolic hydroxyl group adjacent to a methoxy group liberate methanol. Similar compounds which are insoluble do not react to produce methanol. The results demonstrate that when the substrate is insoluble, no methanol is released in lignin model compounds.; Because isolated lignins and lignins in pulp are largely insoluble, they presumably cannot react to liberate methanol. Interestingly, lignin does release some methanol during periodate oxidation despite the very low solubility in aqueous solution. It was concluded that the lignin must be cleaved during the process, generating soluble fractions which can then react with the periodate to produce methanol which is subsequently quantified.; The aminolysis method, another method used for the determination of phenolic hydroxyl content was carried out and compared to the periodate oxidation method. The results show comparable data obtained using these two methods.; Also, High Performance Exclusion Size Chromatography (HPSEC) was performed to examine the change of the size of the lignin molecule during periodate oxidation. The chromatogram of HPSEC shows an increase in the small molecular fractions following periodate oxidation.
机译：游离酚羟基是木质素中重要的官能团。确定木质素中酚基的数目对于理解木质素结构和木质素反应性具有重要价值。酚羟基是影响木质素聚合物的物理和化学性质的最重要的官能团之一。研究和确定游离酚羟基在木质素结构中的作用是许多研究者的目标。在这项研究中，我们调查了高碘酸盐氧化法用于测定木质素和木质素模型化合物中游离酚羟基含量的方法。使用简单的模型化合物，包括香兰素，乙酰香草醛，邻香兰素，甲酚和愈创木酚，以及二聚和三聚木质素模型化合物来研究高碘酸盐的氧化方法。我们发现在与高碘酸钠水溶液反应之前，某些木质素二聚体和所有木质素三聚体模型化合物中存在溶解度问题。使用高碘酸盐氧化法，木质素模型化合物可溶于含水高碘酸盐混合物中并且含有与甲氧基相邻的酚羟基，从而释放出甲醇。不溶的相似化合物不反应产生甲醇。结果表明，当底物不溶时，木质素模型化合物中不会释放甲醇。由于分离出的木质素和纸浆中的木质素基本不溶，因此它们可能无法反应释放甲醇。有趣的是，尽管在水溶液中的溶解度非常低，木质素的确在高碘酸盐氧化过程中会释放出一些甲醇。结论是木质素必须在该过程中裂解，产生可溶级分，然后可与高碘酸盐反应生成甲醇，随后对其进行定量。进行了氨解法，这是另一种用于测定酚羟基含量的方法，并与高碘酸盐氧化法进行了比较。结果显示使用这两种方法获得的可比数据。另外，进行了高性能排阻色谱法（HPSEC），以检查高碘酸盐氧化过程中木质素分子大小的变化。 HPSEC的色谱图显示高碘酸盐氧化后小分子级分增加。

著录项

  • 作者

    Kwon, Heok Bum.;

  • 作者单位

    The University of Maine.;

  • 授予单位 The University of Maine.;
  • 学科 Chemistry Organic.
  • 学位 Ph.D.
  • 年度 1995
  • 页码 168 p.
  • 总页数 168
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 有机化学;
  • 关键词

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