Thioacidolysis reaction products

In a later extension of the thioacidolysis reaction, a second step, a Raney nickel reduction, was introduced, thereby also permitting the analysis of dimeric and trimeric degradation products by gas chromatography [20,76]. By this method, more than 20 different dimeric and 16 trimeric structures, representing aU the various inter-unit linkages depicted in Fig. 9.5, except the 3-0-4 and dibenzodioxocin structures, have been qualitatively identified from spruce wood. Similar data from birch and aspen wood are also available [23]. 

The main syringyl (S) and guaiacyl (G) monomeric products from the thioacidolysis of lignins are isolated by preparative-scale experiments (Lapierre et al. 1986a,b). The only difference between these and the previously described analytical procedure is that the reaction mixture (500 ml of reagent and 3-6g of lignin sample) is refluxed. The product yields are identical for both analytical and preparative procedures. 

Note 5 A kinetic study of the recovery of main monomeric products in the thioacidolysis of soluble lignin and unsoluble wood or straw samples has revealed that, between 2 and 6h, the yields are remarkably constant when compared to those reported for acidolysis (Gellerstedt et al 1984, Lapierre 1986) With prolonged reaction time (24h), product yields decrease slightly... 

From wood, the reaction gives a high yield of low molecular mass degradation products (monomers to trimers, with traces of higher products) and, after treatment, no lignin can be detected in the remaining wood material. Thioacidolysis, when applied to kraft pulps, on the other hand, in addition to monomers-trimers also results in the presence of polymeric material formed as a consequence of pulping reactions [20]. 

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