Tetramethylammonium hydroxide thermochemolysis of guaiacyl–syringyl and guaiacyl dehydrogenation polymers

Abstract Tetramethylammonium hydroxide thermochemolysis of lignin was investigated using guaiacyl–syringyl and guaiacyl dehydrogenation polymers. The guaiacyl–syringyl mixed polymer provided: (1) 1-(3,4-dimethoxyphenyl)-1,2,3-trimethoxypropane isomers ( 11 / 12 ) and 1-(3,4,5-trimethoxyphenyl)-1,2,3-trimethoxypropane isomers ( 15 / 16 ) as β-aryl ether subunit-derived products, (2) 2,3,3′,4′-tetramethoxy-5-(3-methoxyprop-1-enyl)stilbene ( 18 ) and 2,3,3′,4′,5′-pentamethoxy-5-(3-methoxyprop-1-enyl)stilbene ( 22 ) as β-5 subunit-derived products, (3) pinoresinol dimethyl ether ( 21 ), medioresinol dimethyl ether ( 23 ) and syringaresinol dimethyl ether ( 24 ) as β–β subunit-derived products, respectively, and (4) coniferyl alcohol dimethyl ether ( 8 ) and sinapyl alcohol dimethyl ether ( 14 ) from 4- O -linked coniferyl and sinapyl alcohols. The ratio of products stemming from β-aryl ether, β-5, β–β subunits was 23:13:64. The guaiacyl polymer provided 11 / 12 , 18 , 21 , and 8 , suggesting the same reactions occurring also in the guaiacyl polymer, although the ratio (31:32:37) of the products from β-aryl ether, β-5, β–β subunits differed.