Studies of reactions of a series of ions with nitrogen containing heterocyclic molecules using a selected ion flow tube

A series of reactions between NH3+, O2+, O+, Kr+, N+, N2+, Ar+, Ne+, NH4+ and H3O+ and three heterocyclic molecules (pyridine, pyrimidine and piperidine) were studied using a selected ion flow tube (SIFT) at 298 K. The stability of each ring was investigated through reactivity and the rate coefficients and ion product distributions were determined for each reaction. Most of the reactions proceed by charge transfer or proton transfer when energetically possible, with varying degrees of fragmentation. Based on microreversibility, gas phase formation routes are suggested for the production of ionized pyridine and pyrimidine. If these reverse reactions proceed with no or small activation energy barriers, this would be of interest for formation of heterocyclic rings in the interstellar medium and in the Titan atmosphere. Dissociation mechanisms leading to the major fragment product ions in both the pyridine and pyrimidine reactions have been studied and provide information about the site of interaction between the ions and molecules.