DIFFERENTIATION OF N-PROTONATED FROM C-PROTONATED ANILINE BY NEUTRALIZATION-REIONIZATION

Amino- and ring-protonated aniline are distinguished in the gas phase by neutralization-reionization mass spectrometry. This method takes ad vantage of the dramatically different stabilities and reactivities of the neutralized forms of N- and C-protonated aniline, to ascertain the reby the specific protonation site(s). Fast atom bombardment ionizatio n of aniline is found to yield primarily the anilinium cation (N-proto nated tautomer). In contrast, chemical ionization with a variety of re agent gases is shown to generate mixtures in which the ring-protonated species predominates.