Structure determination of some C4H5N+˙ Ions from substituted pyridines by collisionally activated dissociation mass spectrometry

A standard procedure for recording and correcting collisionally activated dissociation mass spectra is proposed, and used to distinguish between the C₄H₅N^+˙ ions formed from hydroxy- and amino-pyridines after loss of CO and HCN, respectively. It is concluded that these ions are cyclic. From the 4-isomers the 3H-pyrrole ion is formed whereas from 2-hydroxypyridine the 1H-pyrrole ion is formed. In the other cases, mixtures of 2H- and either 1H- or 3H-pyrrole ions are generated, depending on the nature of the precursor.