electrophilicity parameter (E = 9.6) of the 1-phenylethyl cation, 1+, has been determined and combined with the nucleophilicity parameter (N = 0.78, s = 0.95) of styrene (St) to predict diffusion-limited propagation in the cationic polymerization of St by the linear free energy relationship log k = s(N + E). This prediction has been experimentally verified using two different diffusion clock methods, which
1-苯基乙基阳离子的亲电子参数(E = 9.6)1 +已确定,并与
苯乙烯(St)的亲核参数(N = 0.78,s = 0.95)结合,通过线性自由能关系log k = s(N + E)。该预测已通过两种不同的扩散时钟方法进行了实验验证,它们提供了k p ± ≈2×10 9 L mol -1 s -1的值,比先前接受的值高了6个数量级,用于传播的绝对速率常数TiCl 4的-80°C下在
甲基环己烷/
氯甲烷60/40(v / v)中诱导St聚合。所述ķ p ±值的温度范围内保持不变-50至-80℃,这表明传播不具有焓屏障; 但是,它随着溶剂极性的增加而适度增加。
路易斯酸的性质对k p ±影响很小,因为用TiCl 4或SnCl 4获得了相似的值。电离的表观速率常数, ,失活速率常数,ķ -我,和电离的表观平衡常数, 也已被确定为温度的函数。这随温度的 升高略有增加,k - i适度增加;因此, 总聚合速率随温度升高而适度降低。