The bleaching and photostabilization of high-yield pulp by sulfur compounds. II. Reaction of glycol mercaptoesters with model quinones.

The reaction of ethylene glycol dimercaptoacetate and pentaerythritol tetra mercaptoacetate with p-benzoquinone have been investigated, both in solutio n and in the presence of cellulose fibers. In either system, Michael additi on is the predominant reaction, leading to decolorization of the quinone by converting it to a substituted hydroquinone. This reaction accounts for th e initial bleaching of high-yield pulp produced by these compounds. Handshe ets impregnated with these compounds have been irradiated for extended peri ods of time, and are found ultimately to become more discolored than untrea ted handsheets. The darkening may be the result of photoinitiated redox che mistry between the Michael adducts and quinones produced in the photodegrad ation of lignin.