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Distonic Ion · CH 2 CH 2 SCH + 2 and the Isomeric Trimethylene and Propylene Sulfide Radical Cations. Assessment of Structures and Reactivities via Decomposition and Redox Reactions
Author(s) -
Polce Michael J.,
Wesdemiotis Chrys
Publication year - 1996
Publication title -
rapid communications in mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.528
H-Index - 136
eISSN - 1097-0231
pISSN - 0951-4198
DOI - 10.1002/(sici)1097-0231(19960131)10:2<235::aid-rcm472>3.0.co;2-1
Subject(s) - chemistry , dissociation (chemistry) , photochemistry , radical ion , diradical , fragmentation (computing) , isomerization , dithiane , propene , sulfide , redox , ion , medicinal chemistry , inorganic chemistry , organic chemistry , catalysis , singlet state , physics , computer science , nuclear physics , excited state , operating system
The distonic radical ion · CH 2 CH 2 SCH + 2 (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 than 1 +· and 2 +· themselves. The diradical · CH 2 CH 2 SCH · 2(1), formed by neutralization of 1 +· , is found to exist as a bound species, requiring appreciable activation energies for both decomposition to CH 2 CH 2plus SCH 2and 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 C 3 H 6 S +·isomer. Further, the C 3 H 6 S +·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 C 3 H 6 S +·isomer other than 1 +· –3 +· ; the data strongly suggest that this isomer is the 1‐propene‐1‐thiol radical cation, namely CH 3 CH=CH–SH +· .