Adducts of Anthrahydroquinone and Anthranol with Lignin Model Quinone Methides. 9,10-13C Labelled Anthranol-Lignin Aeducts; Examination of Adouct Formation and Stereochemistry in the Polymer

Abstract

Abstract Threo and erythro isomers of 3-acetoxy-1-(4-acetoxy-3-methoxyphenyl) -1- (9,10-dihydro-10-hydroxy-9-oxoanthracen-10-yl) -2-(2-tnethoxyphenoxy)-propane 8 have been synthesized. These compounds are appropriate model compounds for adducts between anthranol (9-hydroxyanthracene) and quinone raethides of β-aryl ether units in the lignin polymer. Adducts of this type are believed to result from side reactions during the anthraquinone-accelerated pulping of wood and may contribute to extensive losses of anthraquinone from the pulping system. The 13C NMR chemical shift3 of C-10 in the threo and erythro isomers of β are 44.1 and 47.5 ppm relative to tetramethylsilane. Peaks with corresponding chemical shifts appeared in a spectrum of an acetylated adduct prepared from lignin and 9,10- 3C labelled anthranol. As in model systems the threo isomer predominated.