Nitration of 1-(3?, 4?-dimethoxyphenyl)-2-(2?-methoxyphenoxy)-3-hydroxypropanone and 1-(3?,4?-dimethoxyphenyl)-2-(2?-methoxyphenoxy)-1,3-propanediol as model compounds in lignin

Abstract

1. When the model compounds of lignin: 1-(3′,4′-dimethoxyphenyl)-2-(2″-methoxypheaoxy)-3-hydroxy-propanone (III) and 1-(3′,4′-dimethoxyphenyl)-2-(2″-methoxyphenoxy)-1,3-propanediol (VII) are nitrated with 9 moles of conc. HNO3 in CCl4, at 18–20°, theβ-alkyl-arylether linkage in them is retained. This gives reason to believe that this type of bond in lignin is also resistant to the action of cone. HNO3 in anhydrous media. 2. In the nitration of 1-(3′,4′-dimethoxyphenyl)-2-(2″-methoxypheaoxy)-1,3-propanediol, together with entrance of the nitro group into the ring, there occurs electrophilic substitution of the side chain by the nitro group. 3. A large excess of HNO3, used in the nitration of compounds (III) and (VII), leads to the esterification of both the primary and secondary alcohol groups in these compounds, with the formation of the corresponding nitrates. 4. On the basis of the obtained results it is possible to assume that in the nitration of lignin the primary and secondary alcohol groups present in lignin are also responsible for the formation of the nitroester nitrogen. In this connection, the presence of the benzyl alcohol group in LMR facilitates its fragmentation, while the presence of a keto group, conjugated with the aromatic ring, in contrast, facilitates a stabilization of the lignin molecule during its nitration in anhydrous media.