Definitive characterization of some C_5H_5N~(·+) and C_6H_7N~(·+) radical cations by associative ion-molecule reactions

摘要

Isomeric C_5H_5N~(·+) and C_6H_7N~(·+) radical cations were allowed to interact with various neutral reagents in the quadrupole collision chamber of a six sector magnetic deflection type tandem mass spectrometer. Using CH_3SSCH_3, CH_3OH, or H_2O, iso-C_3H_7I, and tert-C_4H_9NC as substrates, specific associative ion-molecule reactions occur whose products were analyzed in a subsequent high energy collision induced dissociation experiment. Differentiation between ionized pyridine and its 1,2-H shift isomer is readily achieved with each of the four substrates as the latter C_5H_5N~_(·+) ion exhibits a radical-type reactivity characteristic of its distonic character. An unambiguous structure characterization of the C_6H_7N~(·+) ions, namely ionized 2-methylpyridine, the N-methylene pyridinium ylide ion, the 2-methylene-1-hydropyridine ion, and the N-methyl-2-dehydropyridine radical cation, is realized when all of the above substrates are used in the analysis.