Liitiä Tiina M, Maunu Sirkka L, Hortling Bo, Toikka Merja, Kilpeläinen Ilkka
Laboratory of Polymer Chemistry, P.O. Box 55, FIN-00014 University of Helsinki, Finland.
J Agric Food Chem. 2003 Apr 9;51(8):2136-43. doi: 10.1021/jf0204349.
Modern multidimensional NMR spectroscopic methods were applied to investigate the effects of kraft pulping and oxygen delignification on lignin side-chain structures. In addition to the two-dimensional HSQC measurements, the three-dimensional HSQC-TOCSY technique was utilized to elucidate the (1)H-(1)H and (1)H-(13)C correlations of individual spin systems and thus indicate a certain lignin side-chain structure. Unlike earlier, nonlabeled samples were used for 3D measurements. According to 2D and 3D NMR spectra, most of the structures identified in milled wood lignin (MWL) are still present in technical lignins after kraft pulping and oxygen delignification. Although the main reaction during kraft pulping is the cleavage of beta-O-4 linkages, these structures are still left in spent liquor lignin as well as in residual lignin. The amount of coniferyl alcohol and dihydroconiferyl alcohol end groups, as well as some unidentified saturated end groups, is higher in technical lignins than in MWL. Contrary to our earlier observations, no diphenylmethane structures were observed in any technical lignins. Vinyl aryl ether structures could not be detected in technical lignins either.
采用现代多维核磁共振光谱法研究硫酸盐制浆和氧脱木素对木质素侧链结构的影响。除了二维异核单量子相干（HSQC）测量外，还利用三维HSQC-全相关谱（TOCSY）技术来阐明各个自旋系统的氢-氢（¹H-¹H）和氢-碳（¹H-¹³C）相关性，从而确定某种木质素侧链结构。与早期不同，此次三维测量使用的是未标记样品。根据二维和三维核磁共振光谱，磨木木素（MWL）中鉴定出的大多数结构在硫酸盐制浆和氧脱木素后的工业木质素中仍然存在。尽管硫酸盐制浆过程中的主要反应是β-O-4键的断裂，但这些结构仍保留在黑液木质素以及残余木质素中。工业木质素中松柏醇和二氢松柏醇端基以及一些未鉴定的饱和端基的含量高于磨木木素。与我们早期的观察结果相反，在任何工业木质素中均未观察到二苯基甲烷结构。在工业木质素中也未检测到乙烯基芳基醚结构。
