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Electronic effects in the electron ionization fragmentations of 2‐aryl substituted octahydro‐1,3‐ and ‐3,1‐benzoxazines
Author(s) -
Vainiotalo Pirjo,
Lehtelä PirjoLiisa,
Fülöp Ferenc,
Bernáth Gábor,
Vuorilehto Lauri,
Pihlaja Kalevi
Publication year - 1993
Publication title -
rapid communications in mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.528
H-Index - 136
eISSN - 1097-0231
pISSN - 0951-4198
DOI - 10.1002/rcm.1290070613
Subject(s) - chemistry , fragmentation (computing) , substituent , electron ionization , ring (chemistry) , aryl , ionization , mass spectrum , ion , polyatomic ion , spectral line , chemical ionization , ionization energy , medicinal chemistry , stereochemistry , computational chemistry , organic chemistry , alkyl , physics , astronomy , computer science , operating system
The 70 eV electron ionization mass spectra of 27 2‐aryl substituted octahydro‐1,3‐ and ‐3,1‐benzoxazines have been recorded in order to find out how the site and stereochemistry of the ring fusion and especially the nature of the substitutent X on the 2‐phenyl group affect their fragmentation patterns. The structural isomers showed clearly different spectra; however, stereoisomeric differentiation was possible only with 1,3‐derivatives. The fragment‐ion peaks connected with the ionized ring and open chain forms of the compounds studied were clearly present in all the spectra. Analogously to the results obtained in solution, the electron‐withdrawing ability of X increased the abundance of the fragments originating from the ring form. Also, the relative importance of different fragmentation channels varied according to the electron donating or withdrawing ability of the substituent X.