Studies in organic mass spectrometry—XII: Mass spectra of chalcones and flavanones. The isomerisation of 2′-hydroxy-chalcone and flavanone

The mass spectra of isomeric 2′-hydroxy-chalcones and flavanones (i.e. 2-phenyl-chroman-4-ones) are essentially identical. Thermal isomerisation prior to ionisation was ruled out. A study of metastable transitions (first and second field free region of a double focusing instrument), as well as low energy spectra of both isomers, pointed towards completely identical fragmentation pathways for the two compounds. Five deuterated compounds were then investigated. The heats of formation of the most important ions were determined. It was concluded that an intramolecular equilibrium exists between a chalcone type and a flavanone type molecular ion.