Quantitative and qualitative 1H, 13C, and 15N NMR spectroscopic investigation of the urea-formaldehyde resin synthesis
Quantitative and qualitative 1H, 13C, and 15N NMR spectroscopic investigation of the urea-formaldehyde resin synthesis
复制标题
DOI：
10.1002/mrc.4044
复制
发表时间：
2014-04-01
影响因子：
2
通讯作者：
Hasse, Hans
中科院分区：
文献类型：
--
作者：
Steinhof, Oliver;Kibrik, Eleonore J.;Hasse, Hans
脲醛树脂是化学工业的大宗产品。它们的合成涉及复杂的反应网络。目前的工作有助于它的说明，提出了详细的NMR光谱研究结果与不同的方法。除了（1）H NMR和（13）C NMR外，还应用了N-15 NMR谱，并使用了富含N-15的尿素。给出了详细的核磁共振信号分配和合成羟甲基化步骤的反应网络模型。由于其较高的光谱色散和所有关键反应直接涉及氮中心的事实，N-15 NMR提供了比（1）H和（13）C NMR光谱更多的细节。对称和不对称的二羟甲基脲可以从单羟甲基脲、三羟甲基脲和亚甲基桥连脲中清楚地区分和分离。证实了羟甲基脲半缩甲醛的存在。1，3，5-恶二嗪烷-4-酮（脲）及其衍生物在本文研究的反应混合物中未发现，但通过替代途径制备。甲醛与尿素的摩尔比为1、2和4，pH值为7.5和8.5，反应温度为60 ℃。版权所有（c）2014约翰威利父子有限公司
Urea-formaldehyde resins are bulk products of the chemical industry. Their synthesis involves a complex reaction network. The present work contributes to its elucidation by presenting results from detailed NMR spectroscopic studies with different methods. Besides(1)H NMR and(13)C NMR,N-15 NMR spectroscopy is also applied.N-15-enriched urea was used for the investigations. A detailed NMR signal assignment and a model of the reaction network of the hydroxymethylation step of the synthesis are presented. Because of its higher spectral dispersion and the fact that all key reactions directly involve the nitrogen centers,N-15 NMR provides a much larger amount of detail than do(1)H and(13)C NMR spectroscopy. Symmetric and asymmetric dimethylol urea can be clearly distinguished and separated from monomethylol urea, trimethylol urea, and methylene-bridged urea. The existence of hemiformals of methylol urea is confirmed. 1,3,5-Oxadiazinan-4-on (uron) and its derivatives were not found in the reaction mixtures investigated here but were prepared via alternative routes. The molar ratios of formaldehyde to urea were 1, 2, and 4, the pH values 7.5 and 8.5, and the reaction temperature 60 degrees C. Copyright (c) 2014 John Wiley & Sons, Ltd.