Both Willstätter and Freudenberg lignins when treated with diazomethane give methylated products containing one additional methoxyl group, calculated on the basis of a molecular weight of about 850 for native lignin. When heated with phenol in the presence of a small amount of hydrogen chloride, both diazomethane-methylated lignin derivatives are converted into soluble phenol lignin derivatives containing one more methoxyl group than the corresponding phenol derivatives prepared from original, untreated Willstätter and Freudenberg lignins. This higher methoxyl value is also shown by the former phenol lignins on acetylation. The diazomethane-methylated phenol lignin derivatives prepared from diazomethane-methylated Willstätter and Freudenberg lignins correspond with the diazomethane-methylated phenol lignin derivatives prepared from original Willstätter and Freudenberg lignins. Also the fully methylated derivatives prepared from the phenol diazomethane-methylated Willstätter and Freudenberg lignins correspond with those described previously (2). The difference in methoxyl value between the phenol derivatives obtained from Willstätter lignin and the corresponding derivatives from Freudenberg lignin of 0.8–2.1% may be due possibly to the presence in the Freudenberg lignin of a methylene oxide ring which is removed in the isolation of Willstätter lignin, thus giving rise to the higher methoxyl content in the methylated derivatives of the latter. The action of methyl alcohol on original, on diazomethane-premethylated, and on fully methylated Willstätter and Freudenberg lignins was also investigated.
Role of methoxyl group in char formation from lignin-related compounds