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首页> 美国卫生研究院文献>Polymers >Mechanism of Base-Catalyzed Resorcinol-Formaldehyde and Phenol-Resorcinol-Formaldehyde Condensation Reactions: A Theoretical Study
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Mechanism of Base-Catalyzed Resorcinol-Formaldehyde and Phenol-Resorcinol-Formaldehyde Condensation Reactions: A Theoretical Study

机译：碱催化间苯二酚-甲醛与苯酚-间苯二酚-甲醛缩合反应机理的理论研究

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The base-catalyzed resorcinol-formaldehyde condensation reactions were theoretically investigated in this study by employing a quantum chemistry method. The condensation reaction includes two steps: (1) formation of the quinonemethide (QM) intermediate from hydroxymethylresorcinol; (2) Michael addition between the quinonemethide and resorcinol anion. The first step is the rate-determining step. Two mechanisms, unimolecular elimination of the conjugate base (E1cb) and water-aided elimination (WAE), were identified for the formation of QM. The hydroxymethylresorcinol anion produces neutral QM while the dianion produces a quinonemethide anion (QMA). The calculated potential energy barriers suggested that the QMA formation is much more favorable. Although resorcinol-formaldehyde and phenol-formaldehyde condensations share a common mechanism, the former would be faster if the QMA participates in condensations. The potential energy barriers for formation of 2-QM, 4-QM, 6-QM, 2-QMA, and 4-QMA were calculated. The results show that the formations of 6-QM and 4-QMA have relatively lower energy barriers. This rationalized previous experimental observations that the 2,4-(2,6-) and 6,6′-(4,4′-) methylene linkages were dominant, whereas the 2,2′-linkage was almost absent. The resorcinol-phenol-formaldehyde co-condensations were also calculated. The cold-setting characteristic of phenol-resorcinol-formaldehyde co-condensed resin can be attributed to participation of resorcinol quinonemethides in condensations.
机译：本研究采用量子化学方法对碱催化的间苯二酚-甲醛缩合反应进行了理论研究。缩合反应包括两个步骤：（1）由羟甲基间苯二酚形成醌甲基（QM）中间体； （2）在醌甲基化物和间苯二酚阴离子之间的迈克尔加成。第一步是速率确定步骤。两种机制，共轭碱的单分子消除（E1cb）和水助消除（WAE），被确定为形成QM。羟甲基间苯二酚阴离子产生中性QM，而二价阴离子产生醌甲基阴离子（QMA）。计算出的势能垒表明QMA的形成更为有利。尽管间苯二酚-甲醛和苯酚-甲醛缩合具有共同的机理，但是如果QMA参与缩合，前者会更快。计算了形成2-QM，4-QM，6-QM，2-QMA和4-QMA的势能垒。结果表明6-QM和4-QMA的形成具有相对较低的能垒。这使先前的实验观察合理化，即2,4-（2,6-）和6,6'-（4,4'-）亚甲基键占主导地位，而2,2'-键几乎不存在。还计算了间苯二酚-苯酚-甲醛的共缩合率。苯酚-间苯二酚-甲醛共缩合树脂的冷固特性可归因于间苯二酚醌甲基化物参与缩合。

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