Acidolysis of Bamboo Lignin III : Estimation of Arylglycerol-β-aryl Ether Groups in Lignins

Abstract

The amounts of both uncondensed and condensed types of arylglycerol-α, β-diaryl ether groups in a bamboo, beech and a conifer (Thuja standishii) MWL's were estimated by gasliquid chromatography of arylacetones as acidolysis monomer and by spectral analysis of phenolic hydroxyl groups released after mild acidolysis and acidolysis of the MWL's, respectively. The experimental results showed that the amounts of α-aryl ethers were between 0.07 and 0.09 and those of β-aryl ethers were 0.56 (bamboo), 0.51 (beech) and 0.35 (Thuja)/C_6-C_3 of which uncondensed types amounted 0.25, 0.26 and 0.18, respectively. It was tentatively concluded that the polymeric system of the bamboo lignin is composed of about 10:68: 22 of ρ-coumaryl alcohol, coniferyl alcohol and sinapyl alcohol via similar linkages found in spruce lignin and ρ-coumaric acid (O.O7/C_6-C_3) is esterified at the terminal γ-carbons of the side chains of the polymeric system.