title: Electron ionization (EI) mass spectra of exo-endo double-bond isomers of polycyano "push-pull" pentadienes derived from cycloalkylidene malonic acid derivatives.
abstract: The title compounds, which exist in solutions as mixtures of exo/endo double bond isomers due to the "push-pull" effect of the electron-donating and electron-withdrawing substituents, were studied by mass-spectrometric methods. Their fragmentation routes under electron impact were established and confirmed by metastable ion analysis and accurate mass measurements. The results demonstrated that the relative amounts of exo/endo isomeric molecular ions are in close agreement with the isomeric ratios observed in solutions by the NMR, although the mass spectra of the tetracyano derivatives indicated a small fraction of molecular ions existing in the endo form, which could not be detected in solution by the NMR methods.
authors.affiliation: Department of Chemistry, University of Turku, Turku, Finland. kpihlaja@utu.fi
authors.forename: Kalevi
authors.initials: K
authors.lastname: Pihlaja
authors.forename: Vladimir V
authors.initials: VV
authors.lastname: Ovcharenko
authors.forename: Pentti
authors.initials: P
authors.lastname: Oksman
authors.forename: Erich
authors.initials: E
authors.lastname: Kleinpeter
authors.forename: Jochen
authors.initials: J
authors.lastname: Woller