Ionization and appearance potentials in organic chemistry. I—energetic aspects of the mass spectra of stereoisomeric 4‐substituted N‐alkyl‐2‐methyldecahydroquinol‐4‐ols

Abstract

AbstractThe ionization potentials for the stereoisomers of trans‐fused 1,2‐dimethyl‐ and 1‐ethyl‐2‐methyl‐4‐R‐decahydroquinol‐4‐ols (RCCH, CHCH2 or C2H5) and the appearance potentials for the [M–CH3]+ and [M–C2H5]+ ions (loss of 2‐CH3 and 4‐C2H5 groups potential, respectively) were measured by using the electron impact method. The ionization and appearance potential for [M–CH3]+ are always lower for the isomers with the axial 2‐CH3 group. For the C‐2 epimers, the difference between the appearance potentials for the [M–CH3]+ ion values is likely to be equal to the enthalpy differences between the ground states of the epimers and the dissociation energy differences between the axial and equatorial C2–CH3 bonds. The appearance potentials for [M–C2H5]+ for the C‐4 epimers possessing the 4‐C2H5 group were very similar. At the same time, the appearance potentials for the [M–CH3]+ ions were lower for less stable epimers which had an axial 4‐C2H5 group.