THE (DIMETHYLAMINO)METHYL RADICAL - A NEUTRALIZATION-REIONIZATION ANDAB-INITIO STUDY

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-b is(dimethylamino)ethane (2) at 8 keV and characterized by neutralizati on-reionization mass spectrometry. Vertical neutralization of 1+ invol ves large Franck-Condon effects and produces 1 with greater-than-or-eq ual-to 76 kJ mol-1 excess internal energy. Neutral 1 dissociates by lo ss of methyl to give CH3N=CH2 which undergoes further dissociation upo n reionization. In contrast to vacuum pyrolysis, a significant fractio n of 1 survives for 3.6 mus to yield 0.6-2.5% 1+ after collisional rei onization with O2, ICl, NO2, and TiCl4, whereas >25% of 1 survives aft er collisionally activated dissociation of 2.+. Equilibrium geometries of 1 and 1+ from ab initio calculations with the 6-31G basis set sub stantially differ in the C-N bond lengths and pyramidization at N and CH2. Calculations using the Moller-Plesset theory at the MP4-(SDTQ)/6- 31G and MP4(SDQ)/6-311G** levels with zero-point vibrational energy c orrections are used to estimate the relative stabilities of 1, 1+, and their ionic and neutral dissociation products. The vertical ionizatio n 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 neutraliz ation of CH3N=CH2.+ and aziridine.+. Stable .H2CNHCH2. biradical is pr epared by neutralization of +CH2NHCH2. and predicted to be the (1A1) s inglet electronic state.