Mechanism of Isocyanate Reactions with Ethanol1
Mechanism of Isocyanate Reactions with Ethanol1
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DOI：
10.1021/ja01527a022
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发表时间：
1959-09
影响因子：
15
通讯作者：
L. Ferstandig;R. Scherrer
中科院分区：
文献类型：
--
作者：
L. Ferstandig;R. Scherrer
测定并比较了一组苯基取代异氰酸酯(苯基异氰酸酯、间甲苯二异氰酸酯和国标二异氰酸酯)和一组苄基取代异氰酸酯(苯基异氰酸酯、1，3-二甲基二异氰酸酯、1，4-二甲基二异氰酸酯和5-丁基-L，3-二甲基二异氰酸酯)与乙醇的反应速率。用Arrhenius方程计算了活化能。苄基型的反应速度比苯型慢，但它们的速率在较高的温度下收敛，因为前者具有明显更高的活化能量。异氰酸酯和乙醇的反应机理相同，均为一级反应。从反应的精细机理讨论了吸电子取代基加快反应速度的观察结果。近年来，开发了一种需要使用二异氰酸酯的新型聚酯橡胶2。在这种合成中，羟基与异氰酸酯的反应是相当重要的。我们选择这个反应进行研究，是为了比较几种新的二异氰酸酯和以前可用的二异氰酸酯。
The rates of reaction with ethanol of a group of phenyl-substituted isocyanates (phenyl isocyanate, m-tolylene diisocyanate and£,¿>'-diisocyanatodiphenylmethane) and a group of benzyl-substituted isocyanates (benzyl isocyanate, 1, 3-xylylene diisocyanate, 1, 4-xylylene diisocyanate and 5-/-butyl-l, 3-xylyiene diisocyanate) were measured and compared. The energies of activation were calculated using the Arrhenius equation. The benzyl type reacts more slowly than the phenyl type, but their rates converge at higher temperatures because the former have significantly higher energies ofactivation. The reaction mechanism, which is the same for both classes, is first order in isocyanate and in alcohol concentration. The observation that electron-withdrawing substituents accelerate the rate of reaction is discussed with respectto the fine mechanism of the reaction.In recent years, a new type of polyester rubber2 has been developed which requires the use of di-isocyanates. In this synthesis, the reaction of hydroxyl groups with isocyanate groups is quite important. We chose this reaction for study in order to compare several new diisocyanates with previously available diisocyanates.