THE (DIMETHYLAMINO)METHYL RADICAL - A NEUTRALIZATION-REIONIZATION AND AB-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-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 greater-than-or-equal-to 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 mus 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 Moller-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.