The electron-ionisation-induced amide-bond cleavage of some 2'-methyl- and 2'-ethyl-substitute 2- and 3-thiophenecarboxanilides, which yields formally anilylium ions having relative intensities apparently in contrast with the Stevenson-Audier rule, has been investigated by mass-analysed ion kinetic energy (MIKE) spectrometry and compared to that of the 3'- and 4'-isomers. It has been shown that, in the case of the 2'-methyl and 2'-ethyl derivatives, the amide-bond cleavage is anchimerically assisted through the hidden migration of a benzyl hydrogen to the nitrogen, Analysis of the MIKE and collision-induced decomposition (CID) MIKE spectra of model compounds indicates that this cryptic ortho effect produces a stable ortho quinoide or aminotropylium structure.
|Titolo:||Studies in organic mass spectrometry.20. A hidden ortho effect in the electron ionisation mass spectra of some 2'-alkyl substituted 2- and 3-thiophenecarboxanilides|
|Data di pubblicazione:||1996|
|Appare nelle tipologie:||1.1 Articolo in rivista|