title: Distonic ion .CH2CH2SCH2+ and the isomeric trimethylene and propylene sulfide radical cations. Assessment of structures and reactivities via decomposition and redox reactions.
abstract: The distonic radical ion .CH2CH2SCH2+ (1+.), generated by dissociative electron ionization of 1,4-dithiane or 1,4-thioxane, is identified in the gas phase by its collisionally activated dissociation (CAD), neutralization -reionization (+NR+) and charge-reversal (+CR-) mass spectra. The unimolecular chemistry of 1+. is shown to be substantially different from that of the isomeric, ring-closed, trimethylene sulfide ion (2+.). Hence, a substantial isomerization barrier must separate 1+. from the thermodynamically more stable 2+.. Charge permutation (i.e. charge-stripping, +NR+ and +CR-) are far superior, compared to collision-induced fragmentation, for distinguishing 1+. from 2+., mainly because the oxidized (1++ and 2++) and reduced forms (1 and 2 as well as 1-. and 2-.) of these cations have much lower tendencies for isomerization that 1+. and 2+. themselves. The diradical .CH2CH2SCH2. (1), formed by neutralization of 1+., is found to exist as a bound species, requiring appreciable activation energies for both decomposition to CH2CH2 plus SCH2 and ring-closure to 2. The dissociations and redox reactions of the propylene sulfide ion (3+.) are also assessed in this study and clearly indicate that 3+. is a stable C3H6S+. isomer. Further, the C3H6S+. ions from thiane, 1,3-dithiane and 2-methyl-1,3-dithiane are characterized based on their combined CAD, +NR+ and +CR- spectra. The two 1,3-dithianes produce ionized trimethylene sulfide, 2+.. In contrast, thiane gives rise to a C3H6S+. isomer other than 1+.(-3t); the data strongly suggest that this isomer is the 1-propene-1-thiol radical cation, namely CH3CH = CH-SH+..
authors.affiliation: Department of Chemistry, University of Akron, Ohio 44325-3601, USA.
authors.forename: M J
authors.initials: MJ
authors.lastname: Polce
authors.forename: C
authors.initials: C
authors.lastname: Wesdemiotis
mesh_terms: D002412:Cations / Q000737:chemistry; D005609:Free Radicals; D013058:Mass Spectrometry; D010084:Oxidation-Reduction; D013440:Sulfides / Q000737:chemistry*
chemical_list: D002412:Cations; D005609:Free Radicals; D013440:Sulfides