ELECTRON IONISATION MASS SPECTRA OF SOME 
SUBSTITUTED CHALCONES

N. Palibroda1, Z. Moldovan1, A. Pamula1, V. Zaharia2

		1National Institute for Research and Development of 
		Izotopic and Molecular Technologies Cluj-Napoca
		2“Iuliu Hatieganu” University of Medicine and Pharmacy
		Cluj-Napoca

Electron ionisation mass spectra of some substituted chalcones were investigated with the intention to characterise newly synthesized compounds, having biologic potential as antibacterial and antiinflamatory products.
The chalcones under investigation were based on aryl-thiazolo[3,2-b][1,2,4]triazole or aryl-thiazole heterocycles that were condensed with ortho or para hydroxyacetophenone. The aryl group had the following substituents in the para position: R1 = H, Cl and CH3.
Mass spectra were recorded on a MAT 311 mass spectrometer with EI ion source, using the direct inlet probe under temperature programming of the sample crucible from room temperature to 300 oC. All substituted chalcones showed intense molecular ions, supporting the structure of the synthesized compounds. In fact, for all three substituents R1, the molecular ion was the base peak of the spectrum.
Fragmentations of the molecules under electron impact, common to all substituted chalcones investigated, could be observed. Fragmentation of the single bond between the triazole ring and the adiacent phenyl ring produces very few ions, if any. Fragmentation of the single bond between the thiazole ring and the ethylene group is also weak, producing the ion m/z 199 + R1 +H of low intensity. Abundant fragment ions appear at the carbonyl group on the phenyl side, with ion m/z = 93. Very important are the fragment ions on the bond between the carbonyl and ethylene groups,  m/z = 225 + R1 and m/z = 121, and these ions are much more intense for the structures having the hydroxy group of the acetophenone ring in the para position. For the ortho substituent the fragment m/z = 225 + R1 is less intense and is accompanied by a m/z = 225 + R1 + H ion.
A very important fragmentation appears by breaking two bonds of the thiazole ring accompanied by proton transfers. Ions m/z 174 + R1 +2H and m/z 172 -H are very intense for the ortho substituent, but significantly less intense for the para substituent and permit therefore to distinguish between the ortho and para hydroxy substitution of acetophenone.
Chalcones based on the thiazole heterocycle show similar fragmentation.
Ion compositions were verified by exact mass determinations under high resolution and fragmentation pathways were also investigated by metastable ion transitions in the field free regions of the mass spectrometer.