Chemical Factors Underlying the More Rapid β-O-4 Bond Cleavage of Syringyl than Guaiacyl Lignin under Alkaline Delignification Conditions. (2nd November 2017)

• Record Type: Journal Article
• Authors: Shimizu, Satoko; Akiyama, Takuya; Yokoyama, Tomoya; Matsumoto, Yuji
• Is Part Of: Journal of wood chemistry and technology. Volume 37:Number 6(2017)
• Page Start: 451
• Page End: 466
• Publication Date: 2017-11-02
• Subjects: Alkyl-aryl ether -- cooking -- configuration -- p-hydroxyphenyl; Wood -- Chemistry -- Periodicals; Wood; Wood -- Chemistry; Periodicals; 674.13
• DOI: 10.1080/02773813.2017.1340957
• Languages: English
• ISSNs: 0277-3813

Abstract

Abstract : This study aimed to clarify why the β- O -4 bond cleavage of syringyl lignin is more rapid than that of guaiacyl lignin under alkaline pulping conditions. We examined whether or not three chemical factors, acidity of the α-hydroxy group, nucleophilicity of the generated α-alkoxide, and leaving ability of the leaving phenoxide, are different between syringyl and guaiacyl lignins and control the rate of the alkaline-induced β- O -4 bond cleavage, employing dimeric non-phenolic β- O -4-type lignin model compounds (LMCs) and novel methods for estimating these three factors. The results indicated that the α-hydroxy groups of syringyl-type LMCs are relatively more acidic than those of guaiacyl-type and that syringyl nucleus is a better leaving group than guaiacyl nucleus in the β- O -4 bond cleavage. These factors result in the β- O -4 bond of syringyl lignin being more prone to the alkaline-induced cleavage than that of guaiacyl lignin.