Mass spectrometry in stereochemical problems. 6 — The case of mono and di‐substituted norbornanes

The mass spectrometric behaviour of pairs of stereoisomeric mono‐ and di‐substituted norbornanes, namely bicyclo[2.2.1]heptane‐2‐ endo ‐ and ‐ exo ‐carboxylic acid, methyl bicyclo[2.2.1]heptane‐2‐ endo ‐ and ‐ exo ‐carboxylate, 2‐ exo ‐acetamidobicyclo[2.2.1]heptane‐2‐ endo ‐ and 2‐ endo ‐acetamidobicyclo[2.2.1]heptane‐2‐ exo ‐carboxylic acid and methyl 2‐ exo ‐acetamidobicyclo[2.2.1]heptane‐2‐ endo ‐ and 2‐ endo ‐acetamido‐bicyclo[2.2.1]heptane‐2‐ exo ‐carboxylate was studied in detail with particular emphasis on characterization of the stereoisomers. The fragmentation patterns, studied with the aid of mass‐analysed ion kinetic energy spectrometry, were supported by semi‐empirical MO–SFC calculations, performed using the AM1 method included in the AMPAC program.