Thermal decompositions of N‐methylpyridinium, quinolinium, isoquinolinium and phenanthridinium salts in a mass spectrometer. Evidence for a specific HI elimination and for an oxidation to amides

The mass spectra of some N ‐methylpyridinium, quinolinium, isoquinolinium and phenanthridinium salts (R + X − ) The salt will be represented by R + X − or RX, R + being the organic moiety, with its associated mass and X‐ the inorganic anion. are analyzed (X − = I − or ClO 4 − ). For X − = I − , thermal decomposition gives rise mainly to the superimposed spectra of CH 3 I and the free base. Hence, iodide salts cannot be determined specifically by their mass spectra. When an α‐methyl group is present, e.g. 2‐methylpyridinium methiodide, elimination of HI becomes an important thermal process. For X − = ClO 4 − , the same pattern is observed, but in addition a generally important peak at [R + 15] is present. This peak is due to the oxidation, mainly α to the nitrogen of the organic moiety by the ClO 4 − ion, giving rise to the corresponding amide. In some cases, chlorination of the organic moiety has been observed as well as double oxidation. The thermal processes for the perchlorate salts are characteristic and are useful in the elucidation of the quaternary structure.