17302-63-5Relevant articles and documents
Anion structure determination in the gas phase: Chemical reactivity as a probe
Lee, Jeehiun K.,Grabowski, Joseph J.
, p. 9422 - 9429 (2007/10/03)
In the gas phase, the discrimination between two isomeric anion structures is a challenge that requires different solutions for different applications. The anionic oxy-Cope rearrangement involves the rearrangement of an alkoxide to an isomeric enolate; the mechanistic study of such a process in the gas phase requires a simple and selective probe process. Using a flowing afterglow mass spectrometer, we have examined the utility and limitations of using chemical reactivity to discriminate between alkoxides and enolates in the gas phase. A series of alkoxides and enolates were allowed to react with three chemical probe reagents: methanol-O-d, methyl nitrite, and dimethyl disulfide. Quantitative and qualitative characterization of each probe reagent reveals the especially broad and flexible utility of dimethyl disulfide as a chemical probe. Dimethyl disulfide is a selective reagent with ambident behavior that reacts efficiently with all anions studied and fully capitalizes on the structure/reactivity differences between alkoxides and enolates. Alkoxides behave as classical "hard bases" when allowed to react with dimethyl disulfide, effecting elimination across the C-S bond, whereas enolates, "soft bases", attack at sulfur. Methyl nitrite is also a selective ambident probe reagent but, due to its particularly slow reaction with enolates, is useful only in conjunction with a more reliable probe such as dimethyl disulfide. Methanol-O-d, for a variety of reasons detailed in the paper, is unsuitable as a chemical probe reagent for the unequivocal discernment between alkoxides and enolates.
Dimethyl Disulfide: Anion-Molecule Reactions in the Gas Phase at 300 K
Grabowski, Joseph J.,Zhang, Lijian
, p. 1193 - 1203 (2007/10/02)
The thermally equilibrated gas-phase anion-molecule reactions of dimethyl disulfide were examined in a helium bath gas at 0.3 Torr at 300 K by the flowing afterglow technique.All anions more basic than methanethiolate were observed to undergo reaction, but anions less basic than HS(1-) reacted too slowly to form observable products.Sulfur-centered nucleophiles slightly less basic than methanethiolate were found to undergo thiolate/disulfide interchange.Two bimolecular reaction pathways are proposed to account for the primary reaction products: substitution at sulfurand elimination across the carbon-sulfur bond.The elimination pathway involves initial formation of an ion-dipole complex containing thioformaldehyde and methanethiolate, which subsequently undergoes either addition to give a rearranged thiolate product or dissociation.The primary factor in determining whether an anion gives sulfur substitution or elimination products is the structure of the anion and not the nucleophile base strength.Anions at least as basic as methoxide and in which the charge is localized preferred to react by elimination across the carbon-sulfur bond, while all delocalized carbanion bases strongly preferred substitution at sulfur.
