The Reactions of Lignin during Neutral Sulfite Pulping. Part VII. The Behavior of Structural Elements Containing Carbonyl Groups.

Abstract

Neutral sulfonation of coniferaldehyde (I) [458-36-6], 3-(3,4-dimethoxyphenyl)-2-propenaldehyde [4497-40-9], 2-(2-methoxyphenoxy)-2-(3,5-dimethoxybenzoyl)ethanol (II) [10548-77-3], and (2-methoxyphenoxy)acetaldehyde (III) [18167-91-4] as models for carbonyl-contg. units in lignin (IV) [9005-53-2] revealed that all carbonyl-contg. structural elements of IV undergo extensive sulfonation and suffer cleavage of aryl alkyl ether bonds when subjected to the conditions of neutral sulfite pulping. These reactions resulted in the removal of the aldehydic groups in end units (type I and III), in the sepn. of adjacent units (type II), and in the formation of potential chromophoric groups of the catechol type.