Fragmention behaviour of ω-functionalized allenes and their isomeric acetylenes under electron impact. Study on the isomerization of molecular ions and structural assignment of heteroatom migration related to a McLafferty-type rearrangement by CAD-MIKE spectrometry

Abstract

CAD-MIKE Spectra of ions (1)–(6) are discussed. The main fragmentation pathway, loss of an ethylenic fragment leading to C₄H₅X⁺˙ ion, has been confirmed to proceed via a McLafferty-type rearrangement by comparison of the CAD-MIKE spectra of this ion to those of model structures. It is further shown, by means of kinetic-energy-release measurements (T values), that the investigated isomeric species do not interconvert after electron impact to an appreciable extent.