Mass spectrometric fragmentation pathways of isotope labeled 2,5-disubstituted-1,3,4-oxadiazoles and thiadiazoles

Mass spectrometric decomposition of N-arylbenzonitrilium ions

“…Our findings based on accurate masses have to be considered a complement of previous papers concerning HNCO loss from protonated 1,3,4-oxadiazoles [8][9][10][11] and the reactions between nitrobenzenes and benzonitrile radical cations [7].…”

“…On the basis of the mass spectra recorded for isotope labeled compound, it has been shown previously that the fragment ion formed by HNCO loss from protonated 1 (under ESI condition) contains exclusively C(5) carbon atom of oxadiazole ring [10]. In addition, theoretical calculations performed for various 2,5-diaryl-1,3,4-oxadiazoles have shown that such groups like methoxy or amino (electron-donor groups) at 4 -position favor the protonation of N(3) atom of oxadiazole ring [9,11].…”

“…Recently, a number of solution properties of these ions have been reported by Ruane et al [6]. As for the gas phase, Narylbenzonitrilium ions are formed by ion-molecule reaction between nitrobenzenes and benzonitrile radical cations (detection of nitroaromatic compounds) [7], and they are products of mass spectrometric decomposition of protonated 2,5-diaryl-1,3,4-oxadiazoles (unusual skeletal rearrangement) [8][9][10][11]. In order to determine the structure of these ions, we report the mass spectrometric decomposition of benzonitrilium ion derived from 2-(4 -methoxy)phenyl-5-phenyl-1,3,4-oxadiazole and from N-(4 -methoxyphenyl)-benzamide and 4-methoxy-N-phenyl-benzamide (compounds 1, 2 and 3, respectively).…”

Synthesis and antifungal activity of novel 5‐substituted 4‐(1,3,4‐thiadiazol‐2‐yl)benzene‐1,3‐diols

“…The major fragmentation pathway in most derivatives involved the cleavage of the S C 2 and N-N bonds of 1,3,4-thiadiazole ring with formation of (HO) 2 [29]. The cleavage of C 2 -N 3 and S C 5 bonds directed toward (HO) 2 C 6 H 3 CS + (m/z 153) fragmentation is also observed.…”

Differentiation of isomeric para‐ and meta‐substituted 2,5‐diphenyl‐1,3,4‐oxadiazole derivatives of anthracene by electrospray ionization tandem mass spectrometry

“…[11] A literature survey showed that few reports are available on mass spectral fragmentation of oxadiazole derivatives. [12][13][14][15][16][17][18][19] As these compounds belong to the category of organic light-emitting diodes (OLEDs) containing an oxadiazole group, the fragmentation behavior of these compounds under mass spectrometric conditions assumes importance and is desirable. These mass spectral studies may help in understanding the degradation process of these materials and in turn their stability and life.…”