Studies of the ion—molecule reactions in (CH 3) 2S, (CH 3S) 2, CH 3SH and C 2H 5 at 298 K by photoionization mass spectrometry

Abstract

The ion—molecule reactions occurring in the photoionized gases, (CH 3) 2S, (CH 3S) 2, CH 3SH and C 2H 5SH at 298 K have been studied using the pressure variation techniquo at pressures up to 0.600 torr. Profiles of product-ion formation with pressure have been obtained as have the rate constants for the disappearance of the primary molecular ion, M +. For (CH 3) 2S and (CH 3S) 2, the major product in the dimer ion (2 M) +. The proton transfer reactions to form an (M + 1) + ion are endothermic and occur only in the case of (CH 3) 2S when an electronically excited M + ion is generated. At very high pressures, minor amounts of trimer ions are observed for both (CH 3) 2S and (CH 3S) 2. It is suggested that the polymeric ion structures involve SS bonding. In CH 3SH and C 2H 5SH, proton transfer occurs readily at low pressures. At higher pressures, the formation of several dimeric and trimeric ions is observed in each case. The proton bound clusters are not as stable as those of the analogous oxygen compounds. There is no H 2S elimination from the clusters but loss of hydrogen atoms or molecules readily occurs.