Electrocatalytic hydrogenation of lignin models at Raney nickel and palladium-based electrodes
Electrocatalytic hydrogenation of lignin models at Raney nickel and palladium-based electrodes
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DOI：
10.1139/cjc-78-3-307
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发表时间：
2000-03-01
影响因子：
1.1
通讯作者：
Ménard, H
中科院分区：
文献类型：
--
作者：
Cyr, A;Chiltz, F;Ménard, H
在25 ~ 75%C的温度范围内，以氢氧化钠水溶液为介质，在Raney镍和钯基阴极上，对β-O-4木质素模型化合物进行了恒电流电催化氢化（ECH）。结果发现，在两种类型的电极上，具有一个β-O-4键的酚β-芳基乙基-芳基醚的氢解都发生，得到酚类化合物的混合物。1-（4-羟基-3-甲氧基苯基）-2-（2-甲氧基苯氧基）-1-乙醇（模型1）在阮内镍上的ECH得到愈创木酚（9）、乙酰香草酮（11b）、α-甲基香草醇（12 b）以及它们进一步氢化得到的产物。β-O-4键在1的亚甲基的一个氢被羟甲基取代后更难断裂（见2）。然而，通过在1的酚位置引入β-甲基香草基而获得的具有两个b-O-4键的模型4以与1相同的速率在阮内镍上氢解。只有连接到羟乙基苯酚部分的C-O芳基键被裂解。在钯下，1的氢解仅需要理论电量的一半，这是由于通过1的脱氢生成化学吸附的氢，然后氢解所得的酮。提出了模型1的ECH的一般反应方案。
The electrocatalytic hydrogenation (ECH) of beta-O-4 lignin model compounds has been carried out at constant current at Raney nickel and palladium-based cathodes in aqueous sodium hydroxide solution at temperatures ranging from 25 to 75%C. It was found that the hydrogenolysis of phenolic beta-arylethyl-aryl ethers with one beta-O-4 linkage takes place at both types of electrodes to give a mixture of phenolic compounds. The ECH of 1-(4-hydroxy-3-methoxyphenyl)-2-(2-methoxyphenoxy)-1-ethanol (model 1) at Raney nickel gives guaiacol (9), acetovanillone (11b), alpha-methylvanillyl alcohol (12b), and products derived from their further hydrogenation. The beta-O-4 bond is more difficult to cleave upon replacing one hydrogen of the methylene group of 1 by a hydroxymethyl group (see 2). However, model 4 with two b-O-4 linkages obtained by the introduction of an beta-methylvanillyl group at the phenolic position of 1 is hydrogenolysed at the same rate as 1 at Raney nickel. Only the C-O aryl bond attached to the hydroxyethylphenol moiety is cleaved. At palladium, the hydrogenolysis of 1 requires only half of the theoretical amount of electricity due to the generation of chemisorbed hydrogen by dehydrogenation of 1 followed by hydrogenolysis of the resulting ketone. A general reaction scheme is proposed for the ECH of model 1.