Abstract
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.
| Original language | American English |
|---|---|
| Pages (from-to) | 9422-9429 |
| Number of pages | 8 |
| Journal | Journal of Organic Chemistry |
| Volume | 61 |
| Issue number | 26 |
| DOIs | |
| State | Published - Dec 27 1996 |
| Externally published | Yes |
ASJC Scopus subject areas
- Organic Chemistry