Solvolyses were carried out with 6.0 mM doubly labeled 1,2-dianisyl-2-p-(2H3)methoxyphenyl[2-13C]vinyl bromide in 70% HOAc – 30% H2O in the presence of 0, 1, 5, 10, or 400 molar equivalents of added NaOAc. The distributions of products derived from the 4 possible isotopomeric trianisylvinyl cationic intermediates were determined from the mass spectra of the isotopomeric dianisyl ketones obtained from degradation of the reaction products, the spectra being obtained by the chemical ionization technique in order to minimize possible complications by multiple fragmentations. The mass spectrometrie results obtained showed agreement with previously obtained 14C scrambling data and with the 13C scramblings obtained in the present study using 13C nmr. Increasing amounts of added NaOAc had the effect of decreasing the extents of scrambling from 1,2-anisyl shifts as previously observed. However, the formation of products from all 4 possible doubly labeled isotopomeric trianisylvinyl cations definitely demonstrated the occurrence of successive 1,2-anisyl shifts in the trianisylvinyl cation, and the detection of such successive shifts was not possible in previous work using a singly labeled substrate. The observed distribution of products derived from the 4 isotopomeric cations could be calculated assuming various contributions from equilibrations among these isotopomeric cations, and the mechanistic implications of the results are discussed.
Mass spectrometric analysis of additives in polymer extracts by desorption chemical ionization and collisional induced dissociation with B/E linked scanning