IR spectroscopy of protonated toluene: Probing ring hydrogen shifts in gaseous arenium ions

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• 作者：Otto Dopfer ; Joel Lemaire ; Philippe Maî ; tre ; Barbara Chiavarino ; Maria Elisa Crestoni and Simonetta Fornarini
• 关键词：Photodissociation ; FT-ICR mass spectrometry ; IR spectroscopy ; Reactive intermediates ; Structure elucidation
• 刊名：International Journal of Mass Spectrometry
• 出版年：2006
• 出版时间：1 March 2006
• 年：2006
• 卷：249-250
• 期：Complete
• 页码：149-154
• 全文大小：252 K

文摘

Toluenium ions [CH₃C₆H₆]⁺, formed by protonation of toluene by C₂H₅⁺ ions in the cell of a Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometer, have been assayed by IR multiphoton dissociation (IRMPD) spectroscopy. Their IRMPD spectrum compares well with the calculated IR absorption spectra for the ortho-, meta-, and para-toluenium isomers, suggesting a mixture rich in the ortho/para isomers. When the protonation is effected on perdeuterated toluene, the so-formed ions present IRMPD features characteristic for both CD₂ and CHD groups in the arenium ring. This finding is spectroscopic evidence for the occurrence of ring hydrogen shifts and provides the first example of differentiation of families of isotopomers (bearing either two D-atoms or one D-atom and one H-atom on the tetrahedral ring carbon) by the powerful tool of IRMPD using the tunable IR radiation of a free electron laser.