NMR 对羧甲基纤维素钠的结构表征：聚合物链中取代基分布和单体的摩尔分数。
NMR characterization of sodium carboxymethyl cellulose: Substituent distribution and mole fraction of monomers in the polymer chains.
机构信息
Department of Science and Engineering for Materials, Tomakomai National College of Technology, Nishikioka 443, Tomakomai, Hokkaido 059 1275, Japan.
Department of Science and Engineering for Materials, Tomakomai National College of Technology, Nishikioka 443, Tomakomai, Hokkaido 059 1275, Japan.
出版信息
Carbohydr Polym. 2016 Aug 1;146:1-9. doi: 10.1016/j.carbpol.2016.03.021. Epub 2016 Mar 14.
A series of sodium carboxymethyl cellulose (CMC) samples with degrees of substitution (DS) from 0.68 to 2.84 were prepared from cellulose by multistep carboxymethylation. Two-dimensional NMR spectroscopic analyses allowed complete assignment of the (1)H and (13)C chemical shifts of the eight anhydroglucose units (AGUs) found in CMC: 2,3,6-tri-, 2,3-di-, 2,6-di-, 3,6-di-, 2-mono-, 3-mono-, 6-mono-, and unsubstituted AGUs. A comparative analysis of the chemical shift data revealed the substituent effects of the carboxymethyl groups at the 2-, 3-, and 6-positions on the (1)H and (13)C chemical shifts of the AGUs and that additivity could be applied to the (1)H and (13)C chemical shifts of CMC. Quantitative (13)C NMR spectra of the CMC samples allowed determination of the AGU composition, as well as the substituent distribution at the 2-, 3-, and 6-positions of cellulose, which allowed estimation of the reactivity of the hydroxyl groups toward the carboxymethylation.
一系列取代度（DS）从 0.68 到 2.84 的羧甲基纤维素（CMC）样品是由纤维素通过多步羧甲基化制备的。二维 NMR 光谱分析允许对 CMC 中发现的八个无水葡萄糖单元（AGU）的（1）H 和（13）C 化学位移进行完全分配：2,3,6-三，2,3-二，2,6-二，3,6-二，2-单，3-单，6-单和未取代的 AGU。对化学位移数据的比较分析揭示了羧甲基基团在 2-，3-和 6-位对 AGU 的（1）H 和（13）C 化学位移的取代基效应，并且可以将加和性应用于 CMC 的（1）H 和（13）C 化学位移。CMC 样品的定量（13）C NMR 光谱允许确定 AGU 组成以及纤维素 2-，3-和 6-位的取代基分布，这允许估计羟基对羧甲基化的反应性。
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