Reaction of cyclohexanone with [NH₄]⁺ under chemical ionization conditions. 1—formation of protonated unsubstituted imines

High resolution and metastable decomposition spectra of the ions [M + NH 4 ] + (and [M + ND 4 ] + ) formed by reaction of [NH 4 ] + (and [ND 4 ] + ) with cyclohexanone have been measured. The results provide evidence that the m / z 98 ion, which is abundant in the chemical ionization (NH 3 ) spectrum of cyclohexanone, is in fact composed of two isobaric ions: a protonated imine ion and the molecular ion of cyclohexanone. The former is formed by a mechanism analogous to that occurring in solution.