Abstract
The gas-phase ion chemistry of sterically crowded keto/enol pairs has been probed by using several experimental techniques in order to shed light on some highly remarkable mechanistic features of these systems. Labelling experiments prove that propene loss from ionized isopropyl trimesitylvinyl ether is a site-specific process by which, via a four-membered transition state, the ionized enol and not its tautomeric ketone is generated. Kinetic energy release measurements support earlier conclusions that enol cation radicals in a rate-determining step isomerize to (excited) ketones from which dissociations of the C(α)C(β) bond takes place. A correlation of the kinetic energy release, associated with this reaction, with the effects of substituents attached to the α-aryl group is not possible. Further, kinetic energy release measurements do not reflect the different behaviour of keto/enol tautomers in the reciprocal methyl/hydrogen migration. Similarly, the analysis of metastable ion spectra is not a means of distinguishing keto/enol forms; in contrast, for most pairs, a straightforward characterization is possible based on the analysis of collision-induced reactions.
| Original language | English |
|---|---|
| Pages (from-to) | 287-302 |
| Number of pages | 16 |
| Journal | International Journal of Mass Spectrometry and Ion Processes |
| Volume | 71 |
| Issue number | 3 |
| DOIs | |
| State | Published - 30 Sep 1986 |
Bibliographical note
Funding Information:Financial support of our work by the Fonds der Chemischen Industrie and the Deutsche Forschungsgemeinschaft( Projekt Schw 221/7-2) is gratefully acknowledged. The work in Jerusalem was supported by a grant from the United States-Israel Binational Science Foundation (BSF), Jerusalem to which we are grateful. E.U. wishes to thank the Deutscher Akademischer Austauschdienst (DAAD) and Norges Teknisk Naturvitenskaplige For-skningsrad and DEMINEX (Norge) for a scholarship in connection with his stay in Berlin.