Thioacidolysis product yields

In the case of saponification residues (Table V), these trends were even more pronounced for the upper internode. Total yields of thioacidolysis products, (S + G), were slightly higher for the case of PR (Table IV), than that of SR (Table V). However, the residual lignin from the SR of the lower internodes was relatively unchanged when compared with PR, with the difference between SR and PR being nearly negligible in the case of normal maize but significant in the case of the mutant. 

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... 

Table 6.4.4. Yields of main p-hydroxyphenyl (H), guaiacyl (G) and syringyl (S) C C, monomeric thioacidolysis products recovered from insoluble extractive-free lignocelluloses and soluble lignin fractions...

Fig. 6.4.5. Gas chromatrogram of tnmethylsilylated products from the thioacidolysis of a pine kraft lignin corresponding to 51% pulp yield (see Fig 6 4 "5 for description of notations and symbols)...

In Table 6 4 3 are shown the yields of monomeric products recovered from milled wood lignin (MWL) and enzymatically liberated lignin (EL) fractions successively isolated from poplar wood and subjected to various degradation procedures (Lapierre 1986) These values reveal that acidolysis, which should allow the characterization of the same lignin structures as thioacidolysis,... 

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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