【摘要】 研究了以可溶住钼为催化剂,叔丁基过氧化氢环氧化1,5-顺,顺-环辛二烯的反应动力学。主要产物为单环氧和双环氧化合物,按照一组动力学公式使用计算机模拟分析处理了实验数据,得出环氧化反应是分步进行的,首先产生单环氧产物然后进行第二步环氧化。从40—90℃温度范围内的速度常数求出两步反应的活化焓基本相同,使第二步反应明显减慢的原因在于两步的活化熵上的差别,这可归结于由于环氧基团的导人引起空间阻碍致使六价钼络合物难于与烯烃进一步配位。这是因为双烯是取顺,顺构型,从而使两个双键之间的空间更为拥挤,用体积较大的氧化剂过氧化羟基异丙苯溶液代替叔丁基过氧化氢不能得到双环氧产物也证实了这个推论。更多还原

【Abstract】 In the presence of soluble molybdenum (1), the kinetics of the epoxidation of 1, 5-cis, cis-cyclooctadiene with t-butyl hydroperoxide was studied. The main products are monoepoxide and diepoxide, their compositions vary with the temperature. At giving time interval, the data of individual concentration of diene raw material, peroxide, monoepoxide, diepoxide and further oxidation products were treated according to a set of kinetic equations with computer simulation technique. It is concluded that the epoxidation takes place step-wisely. The monoepoxide appears first and then the second epoxidation step goes on. The second epoxidation step is at least 5 times slower than that of the first one. From the rate constants at temperature ranged from 40 to 90℃,the activation parameters were cal culated and the enthalpies for the two steps are almost the same, they are 16.6 atnd 16.4Kcal/mol respectively. The slowdown of the second step is due to the difference in the entropy term, which can be attributed to the steric hindrance caused by the introduction of epoxide group that inhibits the further coordination of Mo (Ⅵ)-complex to the substrate, since the diene takes a cis-cis conformation, which caused the space between two olefin bonds much crowded. This deduction is also confirmed by the result that no diepoxide product is found, even at higher temperature when the t-butyl hydroperoxide is replaced with a more bulky oxidant such as dimethylbenzyl hydroperoxide.更多还原