Journal of Physical Chemistry A vol:102 issue:5 pages:861-869
date:Univ Mons, Chim Organ Lab, B-7000 Mons, Belgium; Univ Louvain, Dept Chem, B-3001 Louvain, Belgium; Ecole Polytech, Dept Chim, Lab Mecan React, URA CNRS 1307, F-91128 Palaiseau, France
Acetonitrile N-methylide radical cations [CH3CNCH2](.+), a(.+), and N-methylketeneimine [CH3NCCH2](.+), b(.+) have been prepared by ion-molecule reactions between ionized cyclobutanone or ionized ketene and acetonitrile or methyl isocyanide. Ion structures have been identified using different experimental conditions including Fourier transform ion-cyclotron resonance experiments, high-and low-energy collisional processes, and reactions within a quadrupole (rf-only) collision cell installed in a large-scale tandem mass spectrometer. All experiments demonstate that a(.+) and b(.+) are stable distonic species that do not easily interconvert. Ab initio molecular-orbital calculations at the QCISD(T)//UMP2 level with a 6-31G(d,p) basis set show that ions a(.+) and b(.+) are of comparable stability, and a heat of formation of 970 kJ/mol is proposed for both species.