Carbenium and carbonium ions in liquid- and solid-superacid-catalyzed activation of small alkanes
Carbenium and carbonium ions in liquid- and solid-superacid-catalyzed activation of small alkanes
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DOI：
10.1351/pac200072122309
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发表时间：
2000-01
影响因子：
1.8
通讯作者：
J. Sommer;R. Jost
中科院分区：
文献类型：
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作者：
J. Sommer;R. Jost
酸催化烃类反应是目前炼油化工中催化剂用量最大、转化量最大的反应。然而，尽管对反应中间体的碳阳离子性质的普遍协议，初始步骤和表面上的阳离子的真实性质仍然是开放的辩论。在这些方面，我们的基础知识已经从物理有机化学中具有里程碑意义的实验中获得了巨大的收获，这些实验使用液体超强酸作为溶剂进行光谱观察。当超强酸的范围超过哈米特酸度标度的11个对数单位时，小烷烃的机械行为相应地变化。这允许与强固体酸如沸石或工业中使用的其他固体酸进行比较。烷烃和酸的同位素标记是用于理解中间体的性质以及碳正离子和碳正离子干预的反应机制的有力工具。
Abstract Acid-catalyzed hydrocarbon reactions involve by far the largest amount of catalyst and the largest volume of transformation in oil refinery and chemical industry. However, despite the general agreement on the carbocationic nature of the reaction intermediates, the initial steps and the true nature of the cations on the surface are still open to debate. On these points our basic knowledge has gained enormously from landmark experiments in physical organic chemistry with spectroscopic observations using liquid superacids as solvents. As the range of superacidity covers over 11 logarithmic units of the Hammett acidity scale, the mechanistic behavior of small alkanes vary accordingly. This allows for comparison with strong solid acids such as zeolite or others used in industry. Isotopic labeling of the alkane and the acids is a powerful tool used to understand the nature of the intermediates, as well as the reaction mechanism in which carbenium and carbonium ions intervene.