Journal of Physical Chemistry A, Vol.104, No.4, 801-810, 2000
Selected ion flow tube studies of S+(S-4) reactions with small oxygenated and sulfurated organic molecules
The reactions of ground-state S+(S-4) with CH3OH, CH3SH, C2H5OH, C2H5SH, CH3OCH3, CH3SCH3, CH2O, CH3CHO, C2H5CHO, CH3C(O)CH3, C2H5C(O)CH3, HCO2H, CH3CO2H, C2H5CO2H, HCO2CH3, HCO2C2H5, CH3CO2CH3, CH3CO2C2H5, C2H5CO2CH3, and C2H5CO2C2H5 have been studied with a selected ion flow tube (SIFT) at 296 +/- 4 K. All of these reactions proceed rapidly, with binary rate coefficients greater than or equal to 2/3k(th)((2)) where k(th)((2)), is the theoretical binary collisional rate coefficient. A strong correlation between the exothermicity of charge (i.e., electron) transfer and the prominence of the charge-transfer channel is observed. Extensive branching into numerous product channels occurs in many of these reactions, with channels such as charge transfer, hydride (H-) abstraction, hydroxide (OH-) abstraction, and insertion being common, although several other modes of reaction are observed. The overall reactivity of Si(S-4) is similar in many respects to that of SO+((2)Pi(r)), a closely related ion that is abundant in interstellar molecular clouds (ISC). The rate coefficients and product distributions for the reactions of S+(S-4) with the 20 molecules listed above are presented and discussed in terms of reaction mechanisms and product formation. Reactions of S+(4S) and the corresponding reactions of SO+((2)Pi(r)) are compared, where possible, and discussed in terms of reaction mechanisms and significance to the chemistry of sulfur in ISC.
Keywords:DENSE INTERSTELLAR CLOUDS;RATE COEFFICIENTS;ASTRONOMICALIDENTIFICATION;LABORATORY DETECTION;NEUTRAL REACTIONS;COMPACT RIDGE;AB-INITIO;CHEMISTRY;ISOMERS;ENERGY