The (Dimethylamino)methyl Radical. A Neutralization-Reionization and ab Initio Study

Scott A. Shaffer, František Tureček, Ronald L. Cerny

Research output: Contribution to journalArticlepeer-review

43 Scopus citations

Abstract

The (dimethylamino)methyl radical (1) is generated in the gas phase by collisional neutralization of (CH3)2N+=CH2(1+) with Xe, (CH3)3N, and CH3SSCH3 and by collisionally activated dissociation of ionized 1,2- bis(dimethylamino)ethane (2) at 8 keV and characterized by neutralization-reionization mass spectrometry. Vertical neutralization of 1+ involves large Franck-Condon effects and produces 1 with ≥76 kJ mol−1 excess internal energy. Neutral 1 dissociates by loss of methyl to give CH3N==CH2 which undergoes further dissociation upon reionization. In contrast to vacuum pyrolysis, a significant fraction of 1 survives for 3.6 μs to yield 0.6–2.5% 1+ after collisional reionization with O2, ICl, NO2, and TiCl4, whereas >25% of 1 survives after collisionally activated dissociation of 2•+. Equilibrium geometries of 1 and 1+ from ab initio calculations with the 6-31G* basis set substantially differ in the C-N bond lengths and pyramidization at N and CH2. Calculations using the Møller-Plesset theory at the MP4- (SDTQ)/6-31G* and MP4(SDQ)/6-311G** levels with zero-point vibrational energy corrections are used to estimate the relative stabilities of 1, 1+, and their ionic and neutral dissociation products. The vertical ionization energies of 1 and C2H5N isomers are calculated and evaluated at the MP2 and MP4/6-311G** levels of theory. Large Franck- Condon effects are predicted by theory and found by experiment in the vertical neutralization of CH3N==CH2•+ and aziridine•+. Stable H2CNHCH2 biradical is prepared by neutralization of +CH2NHCH2 and predicted to be the (1A1) singlet electronic state.

Original languageEnglish (US)
Pages (from-to)12117-12124
Number of pages8
JournalJournal of the American Chemical Society
Volume115
Issue number25
DOIs
StatePublished - Dec 1 1993

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

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