pK(a)-values of guaiacyl and syringyl phenols related to lignin

The literature relating to the pK(a)-values of guaiacyl- and syringyl-deriv ed phenols has been thoroughly surveyed and summarized. In addition, the pK (a)-values of a number of guaiacyl, syringyl and other phenols related to l ignin have been determined using a spectrophotometric method combined with multivariate evaluation. Differences and similarities between the acidities of a number of substances are extensively discussed. The pK(a)-value stron gly affects the delignification during pulping, bleaching and leaching of l ignin during pulp washing.