Mass Spectrometry Study of Coumarins: Correlation Between Charges of Atoms and Fragmentation Processes

Abstract

The mass spectrometry of a number of 6-substituted coumarins was studied in the context of correlating fragmentation pathways and electronic charges of atoms performed by AM1 semiempirical method. The atomic charges of atoms are found to be good predictors of the fragmentation pathways.

<b>Analysis of fragmentations of coumarins in mass spectrometry using the electronic charges of atoms</b>

“…The cleavage of the lactone ring take place at O 1 and then looses the CO after breaking the C 2 -C 3 bond, to give fragment A as indicated in the Schemes 2 and 3. When X = OH or NH 2 , fragment A (M-28) is the most abundant fragment as previously observed [11][12]14] and can lead to many other fragments as illustrated in the Schemes 2 and 3: Whether X = OH or NH 2 , the same fragmentation processes were practically obtained and good correlation with the electronic charges of atoms were observed. In this case, most of important fragmentations took place at the level of atom which exhibited a significative negative charge.…”

“…The presence of odd molecular ions in mass spectra is indicative of the identity of the nitrogenated compounds. In previous papers [11][12], fragmentations of coumarins have been found to occur near the atoms bearing high negative charges. When X = OH or halogen, O 11 is known to be the site of the electronic beam impact, but when X is nitrogen moiety, the high negative charge of nitrogen suggests that N 13 could also be a site of the electronic beam impact, particulary in the case of dialkyl substituted nitrogen.…”

“…They have been reported for antifungal and anti-inflammatory [8], antimicrobial and antibacterial [9], and on top, anti-HIV [10] activities. Recently, we found a good correlation between the fragmentation processes in mass spectrometry of two series of coumarins and the electronic charges of their atoms [11][12]. We found that the fragmentation took place at the level of atoms bearing high negative charges.…”

AM1 and electron impact mass spectrometry study of the fragmentation of 4-acyl isochroman-1,3-diones

“…They have been identified by their melting points and by their 1 H, 13 C and 17 O NMR spectra [3,5]. Mass spectra.…”

“…Their crystal structures have also been investigated [10][11][12]. Recently a new approach of analysis of fragmentation processes of coumarins in electron impact mass spectrometry has been described to give a good correlation with the electronic charges of their atoms [13][14][15]. It has been found that fragmentation processes in electron impact mass spectrometry (EIMS) takes place mainly at the level of atoms bearing high negative charge.…”