2 - (4,6 - Dimethoxy-pyrimidin-2 - Thio)-n-benzamide And Its Derivatives Mass Spectrometry

Mass spectrometry is an ideal tool for studying the gas-phase chemistry of organic compounds because it is performed under vacuum conditions.With the development of electrospray and matrix assist laser desorption ionization in recent years,the use of mass spectrometry analysis has been extended to a much larger realm,and as such, can better simulate chemical transformation in the solution phase.In this thesis, ESI-IT/FTICR-MS~n is used to investigate the gas-phase behavior of a series of organic compounds.The deprotonated 2-(4,6-dimethoxypyrimidin-2-ylsulfanyl)-N-phenylbenzamide and its derivatives were studied,wherein two competitive gas-phase Smiles rearrangement reactions were observed.High resolution mass spectrometry and N-cyclohexyl-2-(4,6-dimethoxypyrimidin-2-ylsulfanyl)benzamide were used to verify the fragmentation pathway.Theoretical computations were performed to determine the reaction mechanisms of the representative compound 1 using the semi-empirical PM3 method.The substituent effect was studied and three positional isomers were successfully distinguished.The same compounds exhibited different fragmentation pathways in the positive mode.The possible mechanism was proposed and high resolution mass spectrometry was used to confirm the elemental composition of the product ions.Interestingly, upon studying the fragmentation of[M+Li]~+,LiOH loss was observed aside from the Smiles rearrangement.The deuterium experiment was performed to demonstrate the mechanism.The substituent effect was likewise studied.To further investigate the mechanism of LiOH neutral loss,a series of N-phenylbenzamide derivatives were synthesized and their lithium ion-induced fragmentation patterns were studied.