Division of Applied Chemistry and Biochemistry, National Institute of Technology, Tomakomai College, Nishikioka 443, Tomakomai, Hokkaido 059 1275, Japan.
Division of Applied Chemistry and Biochemistry, National Institute of Technology, Tomakomai College, Nishikioka 443, Tomakomai, Hokkaido 059 1275, Japan.
Carbohydr Polym. 2017 Feb 10;157:728-738. doi: 10.1016/j.carbpol.2016.10.056. Epub 2016 Oct 20.
Methylcellulose samples with different degrees of substitution were prepared by a heterogeneous reaction of cellulose. Two-dimensional NMR spectroscopy provided complete assignment of the H and C chemical shifts of the un-, 2-mono-, 3-mono-, 6-mono-, 2,3-di-, 2,6-di-, 3,6-di-, and 2,3,6-tri-substituted anhydroglucose units (AGUs). Comparative analysis of the chemical shift data revealed the relationship between the methyl substituents at the 2-, 3-, and 6-positions and the H and C chemical shifts of the AGUs; additivity could be applied to the H and C chemical shifts of methylcellulose. Quantitative C NMR spectra of the samples determined the composition of the eight AGUs and the substituent distribution at the 2-, 3-, and 6-positions of cellulose. This provided estimations of the hydroxyl group reactivity toward methylation and the interactions between the substituent groups within the same AGU.
通过纤维素的多相反应制备了不同取代度的甲基纤维素样品。二维 NMR 光谱为未取代、2-单取代、3-单取代、6-单取代、2,3-二取代、2,6-二取代、3,6-二取代和 2,3,6-三取代的脱水葡萄糖单元 (AGU) 的 H 和 C 化学位移提供了完整的归属。对化学位移数据的比较分析揭示了 2-、3-和 6-位甲基取代基与 AGU 的 H 和 C 化学位移之间的关系；加和性可应用于甲基纤维素的 H 和 C 化学位移。样品的定量 C NMR 光谱确定了八个 AGU 的组成以及纤维素 2-、3-和 6-位的取代基分布。这提供了对羟基向甲基化反应性以及同一 AGU 内取代基基团之间相互作用的估计。
