Effect of Geometrical Isomerism on the Behaviour of cis and trans Hexahydroindanes under Electron Impact

Abstract

RECENTLY1 I reported observations on the behaviour of cis and trans decalines under electron impact. It was shown that in these ionized stereoisomers an effect due to geometrical isomerism appears in two different ways. First, mass spectra, although qualitatively identical, show important differences between relative abundances of several main fragment ions. Relative abundances of molecular ions also differ and indicate a greater stability of ionized trans isomer. Secondly, from the point of view of energetics two results were obtained: (a) Ionization potentials measured for both isomers are the same, 9.61 ± 0.02 eV, within experimental uncertainties. (b) Appearance potentials of the two fragment ions first produced indicate that a lower energy is required to dissociate ionized cis isomer into fragments.