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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Substituent Effects in the Unimolecular Fragmentation of Anisole Dication Derivatives
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Substituent Effects in the Unimolecular Fragmentation of Anisole Dication Derivatives

机译：茴香醚阳离子衍生物单分子裂解中的取代基作用

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摘要

The unimolecular fragmentation of metastable anisole dications is studied by tandem-mass spectrometry. Permutations of OH, OCH_3, and NH_2 substituents as well as extensive labeling experiments are used as probes to unravel the mechanisms of the various fragmentation pathways observed. The main channel corresponds to methyl ion elimination, which leads to an energetically favorable charge separation ("Coulomb explosion"). Loss of a neutral CO molecule forms another important branch, and the expelled CO has incorporated a carbon atom from the phenyl ring of anisole. Substitution of the anisole dication with OH, OCH_3, and NH_2 groups results in more specific fragmentations. Ortho- and para-substitutions lead to preferential methyl ion elimination, whereas meta-substitution favors CO loss. The substituent effects are also reflected in pronounced changes in the apparent kinetic isotope effects upon substitution of OCH_3 by OCD_3. On the basis of the various experimental findings and some explorative DFT calculations, possible mechanisms for the skeletal rearrangements prior to CO elimination are proposed.
机译：通过串联质谱研究亚稳苯甲醚的单分子裂解。 OH，OCH_3和NH_2取代基的排列以及广泛的标记实验被用作揭示所观察到的各种断裂途径机理的探针。主通道对应于甲基离子的消除，这导致了能量上有利的电荷分离（“库仑爆炸”）。中性CO分子的损失形成了另一个重要的分支，被排出的CO已经结合了来自苯甲醚苯环的碳原子。用OH，OCH_3和NH_2基团取代茴香醚指示剂会导致更具体的碎裂。邻位和对位取代可优先消除甲基离子，而间位取代则有利于CO的损失。取代基效应还反映在OCD_3取代OCH_3后，表观动力学同位素效应的明显变化。基于各种实验结果和一些探索性的DFT计算，提出了消除CO之前骨骼重排的可能机制。

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