Permanganate, lignin degradation

Fig.6.3.1. Reaction sequence for the oxidative degradation of lignin with potassium permanganate...

The first evidence of the aromatic nature of lignin was provided at the beginning of the twentieth centnry by the recovery of veratric acid from methylated spruce wood subjected to permanganate oxidation, a method then developed by Frendenberg and, more comprehensively, by Miksche and coworkers in the seventies [40], Over the last 50 years, considerable efforts and creativity have been devoted to the conception and development of innovative degradation methods or to the improvement of already established methods. However, as repeatedly reported, no one method can answer all questions related to lignins, which, becanse of their complex polymeric structure, call for the combined and critical use of various methods provided with complementary performances. 

G Gellerstedt. Chemical degradation methods Permanganate oxidation. In SY Lin, CW Dence, eds. Methods in Lignin Chemistry. Berlin Heidelberg Springer-Verlag, 1992, pp. 322-333. 

Calculating from the yield of metahemipinic acid (38) on degradation of lignins by permanganate oxidation, Miksche and coworkers estimated that there are abont 3% nnits of types 36 or 37 in softwood lignin [17] and abont 2% snch units in hardwood lignins [18] [Note the 2- and 6-positions are equivalent in syringylpropane nnits (2)]. 

Evidence for the occurrence of a series of additional types of lignin units (for instance 60-64) have been obtained in studies of degradation products obtained on permanganate oxidation of lignins [4], On the basis of the yields of oxidation products, Adler [4] concluded that only small amounts of units such as 60-64 can be present in lignins. 

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