Negative charge induced dissociation: fragmentation of deprotonated N‐benzylidene‐2‐hydroxylanilines in electrospray ionization mass spectrometry

Abstract

Unimolecular reactivities of different N-benzylidene-2-hydroxylaniline anions were investigated in gas phase by electrospray ionization tandem mass spectrometry. All the collision-induced dissociation spectra of N-benzylidene-2-hydroxylaniline anions show similar ions at phenyl anions, neutral loss of benzonitrile and benzoxazole anions, respectively. The possible fragmentation pathway was probed through deuterium labeling and various group substituents experiments. Computational results were applied to shed light on the mechanism of fragmentation patterns. The proton in the CH=N is reactive in the formation of the concerned ions. Its direct transfer to the oxygen results in 2-hydroxyphenyl anion. Proton abstraction between benzoxazole and phenyl anion leads to the formation of benzene and benzoxazole anion.

Analysis of the Total Biflavonoids Extract from Selaginella doederleinii by HPLC-QTOF-MS and Its In Vitro and In Vivo Anticancer Effects

“…High-resolution tandem mass spectrometry can provide elemental composition information of both the precursor and product ions, which is very helpful in fragmentation pattern deduction [ 12 , 13 , 14 , 15 , 16 , 17 ] and structural characterization for natural products, such as polyphenols [ 18 , 19 ], flavonoids [ 19 , 20 , 21 ], alkaloids [ 22 ], and terpenes [ 18 , 21 ]. Using this technique, the fragmentation behaviors in the positive ion mode of biflavonoids in the Selaginella genus have been studied [ 23 , 24 ], which will aid in the elucidation of unknown compounds of this kind.…”

Ortho‐hydroxyl effect and proton transfer via ion–neutral complex: the fragmentation study of protonated imine resveratrol analogues in mass spectrometry

“…The substituted groups at different sites may also lead to significant differences in the unimolecular reactions . It is well known that the odd‐electron ions of ortho ‐compounds can be distinguished from those of related meta ‐ or para ‐isomers in electron impact ionization mass spectra .…”

“…The substituted groups at different sites may also lead to significant differences in the unimolecular reactions. [50][51][52][53][54][55][56][57][58][59][60][61][62] It is well known that the odd-electron ions of ortho-compounds can be distinguished from those of related meta-or para-isomers in electron impact ionization mass spectra. [50,55,57,58,60] Gas-phase unimolecular reactions of ortho-substitued compounds in ESI mass spectrometry have been recently studied, and they were found to give unique CID mass spectra as compared with those of the corresponding meta-or para-isomers.…”

“…[50,55,57,58,60] Gas-phase unimolecular reactions of ortho-substitued compounds in ESI mass spectrometry have been recently studied, and they were found to give unique CID mass spectra as compared with those of the corresponding meta-or para-isomers. [51][52][53][54][55][56]62] Imine resveratrol analogues are fundamental structures that contain a carbonnitrogen double bond with the nitrogen atom connected to an aryl or alkyl group, and the presence of the hydroxyl group on the aryl group is very important for their radical scavenging and biochemistry activities. [63][64][65][66][67][68][69][70][71] Insights into unimolecule dissociation and ortho-effect are indispensable for illustrating the detailed mechanisms of gas-phase chemistry.…”

“…It is well known that the odd‐electron ions of ortho ‐compounds can be distinguished from those of related meta ‐ or para ‐isomers in electron impact ionization mass spectra . Gas‐phase unimolecular reactions of ortho ‐substitued compounds in ESI mass spectrometry have been recently studied, and they were found to give unique CID mass spectra as compared with those of the corresponding meta ‐ or para ‐isomers . Imine resveratrol analogues are fundamental structures that contain a carbon‐nitrogen double bond with the nitrogen atom connected to an aryl or alkyl group, and the presence of the hydroxyl group on the aryl group is very important for their radical scavenging and biochemistry activities …”