کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
1193791 1492320 2010 8 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Infrared spectra and structures of diamantyl and triamantyl carbocations
موضوعات مرتبط
مهندسی و علوم پایه شیمی شیمی آنالیزی یا شیمی تجزیه
پیش نمایش صفحه اول مقاله
Infrared spectra and structures of diamantyl and triamantyl carbocations
چکیده انگلیسی

Gas-phase infrared spectra have been recorded for the diamantyl and triamantyl carbocations by infrared multiple photon dissociation (IRMPD) spectroscopy using the free electron laser FELIX. Chemical ionization of the neutral parent diamondoid molecule in an rf ion trap is accompanied by H-atom loss, forming a stable closed-shell carbocation. Comparing the IRMPD spectra with harmonic DFT calculations permits to determine the structures of the species trapped in our set-up. Comparison of experimental and calculated spectra suggests that H-atom abstraction occurs on a tertiary carbon (CH group) rather than on a secondary carbon (CH2 group), as also indicated by the calculated relative energies of the various isomers. Combining experimental results and DFT calculations, we compare the spectra of neutral and carbocationic forms of adamantane, diamantane and triamantane. Substantial differences are observed between the IR spectra of neutral and ionic species. In the ions, the 3 μm CH stretching modes become much weaker, while the other mid-IR modes strongly gain in intensity. An intense band centered at 1200 cm−1 due to a CH/CH2 bending mode appears to be characteristic of the dehydrogenated cationic species. Finally, the intensities of the low frequency modes (≤900≤900 cm−1) associated with carbon cage deformations appear to be most sensitive to the ionization and dehydrogenation state of the molecules.

The gas-phase IR spectra of the diamantyl and triamantyl carbocations are presented and discussed in the context of their astro-chemical relevance.Figure optionsDownload high-quality image (59 K)Download as PowerPoint slide

ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: International Journal of Mass Spectrometry - Volume 297, Issues 1–3, 1 November 2010, Pages 55–62
نویسندگان
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