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N-烯基硝酮的分子内环加成反应可能得到氧桥和碳桥的两种产物,但N-3-丁烯基硝酮却只有单一的氧桥产物,已被用来合成一系列新的区域专一性化合物.弄清此反应机理是很有意义的.本文用过渡状态理论和AM1方法进行研究,结果表明,虽然存在得到两种产物的平行反应,但由于这两个反应的速率常数之比很大,基本上只得到单一的氧桥产物.生成氧桥产物的反应活化焓比较小,活化熵比较大.活化熵对反应速率常数比值的贡献是不可忽略的.
The intramolecular cycloaddition reaction of N-enyl nitrones may yield two products of oxygen bridges and carbon bridges, but N-3-butenyl nitrones have only a single oxygen bridge product and have been used to synthesize a series of It is of great significance to clarify the mechanism of this reaction.In this paper, the transition state theory and the AM1 method are used to study the results. The results show that although there are parallel reactions of the two products, The ratio of rate constants is very large and basically only a single oxygen bridge product is obtained.The enthalpy of activation of oxygen bridge products is relatively small and the activation entropy is relatively large.The contribution of activation entropy to the reaction rate constant ratio can not be neglected.