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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >An Extension of the Hammond Postulate. Structural Effects on the Classification of Chemical Reactions
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An Extension of the Hammond Postulate. Structural Effects on the Classification of Chemical Reactions

机译:哈蒙德假设的扩展。结构对化学反应分类的影响

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Combination of the reaction energy, a thermodynamic index, with structural descriptors, such as the force constants associated with the reactant and products potential wells, allows us to define a new index that quantifies the position of the transition state and classifies reactions in terms of their Hammond or anti-Hammond character. Switching from the classical restricted Hammond behavior to a general behavior, in which the position of the transition state is not only conditioned by energy comparisons, occurs through adding a new term accounting for the structural effects in the potential-energy function. It is shown that these effects strongly influence the position of transition states but leave the barrier height practically unchanged. Analysis of 27 chemical reactions of different types, such as rotational isomerizations, SN2, and intramolecular reordering reactions, provides strong support to the model presented here.
机译:反应能,热力学指标与结构描述符(例如与反应物和产物势阱相关的力常数)的组合,使我们能够定义一个新的指标,该指标可量化过渡态的位置并根据反应的状态对其进行分类Hammond或反Hammond字符。从经典的受限哈蒙德行为转换为一般行为,在这种行为中,过渡状态的位置不仅受能量比较的限制,还可以通过添加一个新的术语来解释势能函数中的结构效应,从而实现这一转变。结果表明,这些效应强烈影响过渡态的位置,但势垒高度实际上保持不变。分析27种不同类型的化学反应,例如旋转异构化,SN2和分子内重排反应,为此处介绍的模型提供了有力的支持。

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