Intracluster reaction, fragmentation, and structure of monomethylamine, dimethylamine, and trimethylamine cluster ions

W. B. Tzeng, K. Narayanan, G. C. Chang, W. C. Tsai, J. J. Ho

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Ammonia, monomethylamine (MMA), dimethylamine (DMA), and trimethylamine (TMA) clusters, formed in a supersonic expansion, were investigated using a multiphoton ionization time-of-flight mass spectrometer. The observed major product ions resulting from prompt fragmentation following ionization are (NH3)nH+, (CH3NH2)nH+, [(CH3)2NH]nH+, and [(CH3)3N]nH+. Detection of stable CH2=NH2+ and (CH2=NH-CH3)+ immonium ions and other fragments provides evidence for molecular rearrangement and fragmentation within our observable time windows. Anomalously large relative intensities observed for (NH3)5H+, (CH3NH2)4H+, [(CH3)2NH]3H+, and [(CH3)3N]2H+ are attributed to enhanced stability of the cluster ions, due to the complete filling of hydrogen-bonding sites on the "central ions". Fully optimized geometries and stabilization energies of these cluster ions have been predicted using ab initio molecular orbital methods. The experimental findings are in very good agreement with the calculated results.

Original languageEnglish
Pages (from-to)15340-15345
Number of pages6
JournalJournal of physical chemistry
Issue number38
Publication statusPublished - 1996 Sep 19


ASJC Scopus subject areas

  • Engineering(all)
  • Physical and Theoretical Chemistry

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