Studying On The Gas Phase Fragmentation Mechanism About Two Types Of 3-substituted Indole Derivatives In Mass Spectrometry

In this thesis,a combination of high-resolution electospray ionization high-energy collisional dissociation mass spectrometry(ESI-HCD-MS/MS),hydrogen-deuterium exchange experiments and density functional theory(DFT)calculation was applied to investigate the gas phase fragmentation reaction for two kinds of organic compounds,including 3-phenylsulfonyl-indole compounds and 3-(phenylthio)-1H-indole derivatives.It was found that the protonated ions of these two compounds produced indole radical cations in electrospray ionization secondary mass spectrometry,but the mechanism was completely different.In addition,the H/D scrambling phenomenon was observed durning the H/D exchange experiment of 3-benzenesulfonyl indole derivatives,and an H/D scrambling proton transfer reaction model was established.Firstly,a combination of ESI-HCD-MS/MS,hydrogen-deuterium exchange experiments and DFT calculation was applied to study the fragmentation mechanisms of protonated 3-phenylsulfonyl-indole compounds.In the high-energy collisional dissociation(HCD)mass spectrometry,there were four kinds of product ions,the product ion a(indole sulfonyl cation derivatives)was formed by 1,5-hydrogen transfer followed by 1,5-hydrogen transfer or 1,2-hydrogen transfer to benzene ring C7 atoms when 1,4-hydrogen transfer occurs,while ion a lose a SO neutral to form the ion d(3-oxindole cation derivatives).When the proton transfer to the C3 atom,the INC-1 was formed,and the derict separation gave rise to the ion b(3-phenylsulfonyl cation derivatives),otherwise the INC-1 have a charge transfer reaction to generate the INC-2,in the complex INC-2 gave rise to the product ion e(indole radical cation derivatives).Moreover,kinetic method showed that the ln([b]/[e])against the ionization energy of indole neutral with different groups was a straight line,which further verified that the progress of generating product ions e and b was mediated by a ion/neutral complex.With the hydrogen-deuterium exchange experiments improved that the H/D Scrambling on the indole ring and the H/D Scrambling phenomenon on the benzene ring prior to fragmentation.Secondly,the gas phase fragmentation mechanisms of protonated 3-(phenylthio)-1H-indoles were studied by high-resolution electrospray ionization high-energy collisional dissociation mass spectrometry,combined with the density functional theory(DFT)calculations and H/D exchange experiments.As a result,three characteristic product ions including 3-(substitued phenyl)indole radical cation,substitued indole radical cation and 3-thioxo-substitued indole cation were observed in their HCD-MS/MS spectra,which were resulted from neutral losses of thiol radical,phenylthio radical and substituted benzene,respectively.The neutral elimination of thiol radical was triggered by a phenyl nucleophilic substitution on the C3 position of indole ring,followed by homolysis of C-S bond.On the other hand,neutral losses of phenylthio radical and substituted benzene were induced by a 1,2-hydride shift followed a homolytic cleavage of C-S bond and a 1,4-proton shift accompanied with a heterolytic cleavage of C-S bond,respectively.And the H/D exchange experiment was used to further verify the direction of proton migration,indicating that the hydrogen at the C2 ring of the indole ring was involved in the 1,5-proton migration and the 1,4-proton migration reaction,but H/D Scrambling phenomenon haven't been observed.This work is potential for exploring the gas phase behavior of even-electron ions.