Structural characterization of nitrated 2′-hydroxychalcones by electrospray ionization tandem mass spectrometry

Isomeric 2′-hydroxychalcones bearing nitro and methoxy groups in different positions of their skeleton were analyzed by tandem mass spectrometry (MS/MS) with electrospray ionization (ESI), in positive mode. Collision-induced dissociation of the protonated molecules, [M + H]+, formed under electrospray conditions were studied and it was found that the product ion spectra of these chalcones presented different fragmentation patterns depending on the position of the substituents on the molecule. The product ion spectra (ESI-MS/MS) of the B ring ortho-nitro substituted 2′-hydroxychalcone and of the 4′-methoxychalcones showed loss of OH•, 2OH• and combined losses of OH• and H2O. These fragment ions were absent in the spectra of the respective meta- and para isomers. The observed differences in the product ion spectra of these nitrochalcones allowed identification of the o-nitro derivatives. Distinction between the meta- and para-derivatives was not achieved. Chalcones bearing 6′-methoxy substituents showed dis...