Thermal ion—molecule reactions in oxygen-containing molecules. Ion—molecule clustering reactions in trioxane

Abstract

The ion—molecule clustering reactions in trioxane have been studied with a time-of-flight mass spectrometer. The cluster ions, (CH 2O) n H + ( n = 3—9), were formed at long delay times. The first steps of the clustering reactions initiated by CH 2OH + and (CH 2O) 2H + were third-order reaction mechanisms and the second steps were second order. Similarly, the first step of the clustering reaction initiated by the protonated molecular ion, (CH 2O) 3H +, was a third-order reaction mechanism and the second step was second-order. However, the reaction order of the first step of the reaction with CH 2OH + changed with increasing delay time. The rate constants of the third-order clustering reactions observed in trioxane were very much arger than those reported in other simple molecules, and agreed with the values calculated theoretically using an empirical rate constant equation. It was found that the cluster ions formed in the clustering reactions of a polyatomic oxygen-containing molecule, such as trioxane, have a long life-time and are relatively stable owing to the large number of degrees of freedom of these ions. In addition, it was shown that the stability and reactivity of the cluster ion correlates with the structure of the ion.