Revisiting the mechanism of <i>β</i>-<i>O</i>-4 bond cleavage during acidolysis of lignin. Part 9: Comprehensive results for guaiacyl-type compounds and the difference in participation mode of bromide and chloride anions between C₆-C₃-type and C₆-C₂-type compounds

A phenolic β-O-4-type lignin model compound with a C6-C3-type side-chain and two guaiacyl nuclei and its derivatives were individually acidolyzed in aqueous 82 vol% 1,4-dioxane containing 0.2 mol/L HBr, HCl, or H2SO4 at 85 °C in this study. The obtained results, combined with those in the series of this study in which phenolic and non-phenolic C6-C3- and C6-C2-type analogues were used, generated the following results and proposals. The H2O addition reproducing the original compound is preponderant as a reaction mode of the benzyl cation intermediate (BC) over the other modes leading to the β-O-4 bond cleavage, especially in the acidolyses using H2SO4 and those of C6-C3-type compounds. A well-known phenomenon whether formaldehyde is liberated from C6-C3-type compounds is regulated by acid types appears less clearly in phenolic than in non-phenolic compounds. Br¯ as well as Cl¯ nucleophilically assists the H¯ transfer from the β- to α-carbon of BC, especially in C6-C3-types, which accelerates and regulates the acidolyses using HBr as well as HCl. Furthermore, Br¯ is suggested to nucleophilically attack the β-carbon of non-phenolic C6-C3-type BC to cleave the β-O-4 bond, which explains the characteristically peculiar observation in the acidolysis of the non-phenolic C6-C3-type compound using HBr described in our previous report.</p

研究船「みらい」における洋上水蒸気のライダー観測

http://www.godac.jamstec.go.jp/darwin/cruise/mirai/mr15-04/

An attempt to retrieve continuous water vapor profiles in marine lower troposphere using shipboard Raman/Mie lidar system

http://www.godac.jamstec.go.jp/darwin/cruise/mirai/mr15-04/

Corrigendum: An attempt to retrieve continuous water vapor profiles in marine lower troposphere using shipboard Raman/Mie lidar system

http://www.godac.jamstec.go.jp/darwin/cruise/mirai/mr15-04/

「みらい」MR18-04レグ2における13N137E集中観測概要

http://www.godac.jamstec.go.jp/darwin/cruise/mirai/mr18-04_leg2/

Parsivel及びLPMを用いた雨滴粒径分布観測で見えたデータ特性

http://www.godac.jamstec.go.jp/darwin/cruise/mirai/mr15-04/ehttp://www.godac.jamstec.go.jp/darwin/cruise/mirai/mr14-01/ehttp://www.godac.jamstec.go.jp/darwin/cruise/mirai/mr14-02/ehttp://www.godac.jamstec.go.jp/darwin/cruise/mirai/mr16-08/

An attempt to examine oceanic drop size distribution and precipitating system characteristics using shipboard disdrometer and polarimetric radar

http://www.godac.jamstec.go.jp/darwin/cruise/mirai/mr15-04/ehttp://www.godac.jamstec.go.jp/darwin/cruise/mirai/mr14-06/ehttp://www.godac.jamstec.go.jp/darwin/cruise/mirai/mr14-01/ehttp://www.godac.jamstec.go.jp/darwin/cruise/mirai/mr14-02/ehttp://www.godac.jamstec.go.jp/darwin/cruise/mirai/mr13-03/