Chemical ionization mass spectrometry of bifunctional compounds. The behaviour of bifunctional compounds on protonation

Positive‐ion chemical ionization mass spectra were measured for simple bifunctional aromatic compounds of the type p‐XCH2C6H4CH2Y, where X = NH2, NH(CH3) and N(CH3)2 and Y = OH and OCH3. For each compound, essentially only three peaks of ions, [MH]+, [ MH ‐ XH] + and [MH ‐ YH] +, appeared. The B/E con stant linked‐scan spectra showed that the stable non‐decomposing [MH]+ had the proton only on the nitrogen‐containing functional group. From these data, the relative amounts of total protonation, the ratio of N‐and O‐protonation and the fraction of fragmenting [MH]+ can be calculated. The ease of protonation (protonation susceptibility) and the reactivity (fragmentation capability) of the respective functional groups are discussed.