Roaming-Mediated CH₂NH Elimination from the Ionization of Aromatic Ethylamines

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• 作者：Mengxing Zhang ; Huijun Guo and Prof. Dr. Lidong Zhang
• 刊名：ChemistryOpen
• 出版年：2017
• 出版时间：February 2017
• 年：2017
• 卷：6
• 期：1
• 页码：40-45
• 全文大小：1045K
• ISSN：2191-1363

文摘

The ionization of aromatic ethylamines by photons or electrons leads to elimination of CH₂NH fragments, supposedly deriving from the McLafferty rearrangement involving intramolecular γ-hydrogen transfer. Using tryptamine and phenethylamine as examples, the results reported here suggest that the McLafferty mechanism is inadequate for interpreting the observations of CH₂NH elimination due to much higher calculated appearance energy than experimentally measured values. Furthermore, by considering the roaming-mediated effect, the calculated appearance energy for the elimination of CH₂NH fragments is reduced and matches well with the experimental results and verifies the existence of roaming-mediated effect. This effect could potentially be extended to explain the general CH₂NH elimination of aromatic ethylamines. Due to the similar hydrogen transfer to that of the McLafferty mechanism, the roaming-mediated effect was taken into account to suggest a novel mechanism, termed the “roaming-modified McLafferty rearrangement”, that explains the observations of CH₂NH elimination in the ionization of aromatic ethylamines. This is a reasonable modification of the McLafferty rearrangement mechanism.