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Studying On The Gas Phase Reactions Of Three Kinds Of Sulfur Heteroatomic Compounds

Posted on:2015-05-08Degree:MasterType:Thesis
Country:ChinaCandidate:F F ZhangFull Text:PDF
GTID:2181330467451253Subject:Analytical Chemistry
Abstract/Summary:PDF Full Text Request
Firstly, the kinetic method and the theoretical calculation were applied to evaluate the fragmentation of the protonated Esomeprazole analogs in this paper. All collision-induced dissociation (CID) mass spectrometry experiments were carried out using electrospray ionization ion trap mass spectrometry in positive ion mode. In the fragmentation of the protonated Esomeprazole analogs, the C-S bond breakage is observed, which gives rise to protonated2-(sulfinlymethylene)pyridines and protonated benzimidazoles. Density functional theory calculations demonstrate that the nitrogen atom of pyridine part is the thermodynamically most favorable protonation site, and the C-S bond cleavage is triggered by the transfer of this ionizing proton from the nitrogen atom of pyridine part to the carbon atom of benzimidazole part. Moreover, with the kinetic plot, the intensity ratios of two protonated product ions yield a linear relationship with the differences in proton affinities of the corresponding neutral molecules, which provides strong experimental evidence that the reaction proceeds via proton-bound2-(sulfinlymethylene)pyridines/benzimidazoles complex intermediates. Secondly, the fragmentation mechanisms of the deprotonated rhodanime derivatives were investigated by the negative ESI-MS". The neutral loss C8H5NO2S and the simultaneous loss of CO2, CO and S small molecule were observed. In addition, the electron-withdrawing groups at phenyl ring facilitated the neutral loss C8H5NO2S, whereas the electron-donating groups strongly favored losing the CO2, CO and S at the same time.Finally, the atmospheric pressure chemical ionization technology (APCI) was applied to study the fragmentation of the phenyl (3-iodine) phenyl thioether compounds. The neutral loss of iodine radical from the molecular ion yielded the characteristic product ion M-127. For the compounds with an electron-donating group on the benzene ring, the neutral loss of HS radical from fragmentation ion M-127was observed with the continuous1,3-H migration and benzene alkynyl migration; In contrast, for the compounds with an electron-withdrawing group such as Cl and Br, the neutral loss of S took place after the neutral loss of Cl or Br radical accompanied with the1,5-H migration and benzene alkynyl cation migration. On the other hand, the neutral loss of the CS molecule from the product ion M-127was also observed with the migration of benzene radical. Finally, it is demonstrated that the neutral loss of HS radical, S and CS was in the control of the product ion stability and transition state energy by the quantum chemistry calculation.
Keywords/Search Tags:mass spectrometry, collision induced dissociation, density functional theory, the kinetic method
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