Cleavage and (re)formation of oxymethylene moieties are essential steps during the build-up of polyoxymethylene (POM), a technically relevant high-performance polymer. To reveal how the catalyst accomplishes the cleavage of oxymethylene moieties, the kinetics of the ring-opening of trioxane was studied. Thereby insights into the initial phase of the growth of oxymethylene chains were obtained. The chain length of short oligomers was controlled with acetic anhydride as transfer agent. With a high ratio of acetic anhydride to trioxane, the first homologues of the series, trioxymethylene diacetate, dioxymethylene diacetate and monooxymethylene diacetate were obtained in excellent yield. The homologues show distinct features in the NMR and IR spectra that were related to their reactivity during chain propagation. Formation of intermediate hemi-acetal oxonium moieties is suggested to be a key step in the reaction pathway. Such molecular level insight may be a crucial factor for further tailoring production and properties of polyoxymethylene as well as introducing oligomeric oxymethylene diacetates to new application fields.

中文翻译：

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三恶烷聚合初期的反应路径†

甲醛部分的裂解和（重新）形成是聚甲醛（POM）（一种技术上相关的高性能聚合物）的建立过程中的重要步骤。为了揭示催化剂如何完成甲醛部分的裂解，对三恶烷的开环动力学进行了研究。从而获得对甲醛链生长的初始阶段的见识。用乙酸酐作为转移剂控制短低聚物的链长。在乙酸酐与三恶烷的比例高的情况下，以优异的收率获得了该系列的第一同系物，即三乙酸二甲醛，二乙酸二甲醛和一乙酸二甲醛。同源物在NMR和IR光谱中显示出不同的特征，这些特征与其在链增长期间的反应性有关。中间半缩醛氧鎓部分的形成被认为是反应途径中的关键步骤。这种分子水平的了解可能是进一步调整聚甲醛的生产和性能以及将低聚甲醛二乙酸酯引入新的应用领域的关键因素。