Generation of gas-phase sodiated arenes such as [(Na-3(C6H4)(+)] from benzene dicarboxylate salts

摘要

Upon collision-induced activation, gaseous sodium adducts generated by electrospray ionization of disodium salts of 1,2- 1,3-, and 1,4-benzene dicarboxylic acids (m/z 233) undergo an unprecedented expulsion Of CO2 by a rearrangement process to produce an ion of m/z 189 in which all three sodium atoms are retained. When isolated in a collision cell of a tandem-in-space mass spectrometer, and subjected to collision-induced dissociation (CID), only the m/z 189 ions derived from the meta and para isomers underwent a further CO2 loss to produce a peak at m/z 145 for a sodiated arene of formula (Na3C6H4)(+). This previously unreported m/z 145 ion, which is useful to differentiate meta and para benzene dicarboxylates from their ortho isomer, is in fact the sodium adduct of phenelenedisodium. Moreover, the m/z 189 ion from all three isomers readily expelled a sodium radical to produce a peak at m/z 166 for a radical cation [((C6H4CO2Na2)-C-center dot)(+)], which then eliminated CO2 to produce a peak at m/z 122 for the distonic cation ((C6H4Na2)-C-center dot)(+).