Equilibrium studies of gas phase ion-molecule reactions. Ion cyclotron resonance results for the reaction CO_2H+ + CH_4 ⇄ CH+_5 + CO_2

The recent application of mass spectrometric techniques to the determination of equilibria in gas phase ion-molecule reactions has provided an abundance of thermochemical data relating to the intrinsic (gas phase) stability and solvation energetics of ionic species. Ion cyclotron resonance (ICR) flowing afterglow (FA) high pressure mass spectroscopy (HPMS), and trapping of ions in the space charge of an electron beam of standard mass spectrometers (TIMS) have all been applied in the investigation of reversible ion-molecule reactions under conditions where equilibrium may be attained. Not surprisingly, a healthy skepticism has developed regarding the validity of the assumption that equilibrium is truly established in these experiments, which are performed under vastly different conditions of gas density, ion residence times, and applied electric fields. A comparison of results using different techniques is particularly valuable, and for this reason we wish to report ICR results for the reversible proton transfer Reaction (1)