Sulfonation of some lignin models

Conclusions

• 1. The sulfonation of some lignin model compounds has been performed: phenylmethylcarbinol, phenyl-ethylcarbinol, guaiacylmethylcarbinol, veratrylmethylcarbinol, p-hydroxyphenylethylcarbinol, and gualacyl-guaiacoxymethylcarbinol, under the conditions of acid bisulfite digestion. Models not substituted in the nucleus are sulfonated with difficulty even at pH 0.8, and are recovered to the extent of 80% in unchanged form. Arylalkylcarbinols with a guaiacyl structure in the aromatic nucleus are sulfonated easily at all pH; veratrylmethylcarbinol is not sulfonated at pH 7.0 and is recovered under these conditions almost entirely unchanged. Guaiacylguaiacoxymethylcarbinol was sulfonated at pH 1.5 and formed a sulfonated derivative in yield up to 40% of the theoretically possible.

• 2. Competing processes of acid condensation to form substances of a polymeric character take place along with sulfonation of lignin models which are substituted in the nucleus. In distinction from guaiacyl- and veratrylethylcarbinols, which form indane derivatives, in the case of p-hydroxyphenylethylcarbinol the formation of the corresponding dibenzyl ether was observed. Guaiacylguaiacoxymethylcarbinol forms guaiacol in a yield of about 1% of that theoretically possible, which indicates hydrolysis of theβ-alkyl-aryl ether bond under the conditions of sulfite digestion.