Dehalogenation reactions in chemical ionization mass spectrometry

Abstract

The dehalogenation reactions occurring in certain halogenated chalcones and α-phenylcinnamonitriles under chemical ionization conditions have been studied. Reductive dehalogenation in halogenated chalcones leads to the formation of the MH⁺ ion of the parent unsubstituted chalcone, while a similar reaction in halogenated α-phenyl cinnamonitriles leads to a radical-induced cyclization product, 3-phenylquinoline, in the 2′-chloro and 2′-bromo derivatives and mostly to the parent nitrile in the case of 3′- and 4′-chloro derivatives. The abundance of the dehalogenation ion increases in the order F < Cl < Br. The operation of a radical mechanism for this process is confirmed by experiments with radical traps such as tetracyanoquinodimethane.