Studying On The Cleavage Reactions Of C-S Bond Under Atmospheric Pressure Ionization Mass Spectrometry

In this work,fragmentation reaction induced by cleavage of C-S bond of 3-iodophenyl phenyl sulfides was studied by atmospheric pressure chemical ionization(APCI)combined with ion trap mass spectrometry and verified by the density functional theory(DFT)method.It was showed that under APCI condition,all compounds generated molecular ions,and after collisonal induced dissociation(CID),there was loss of iodine radical at first,leading to the formation of positively charged diphenyl sulfides biradicals.Loss of HS radical was proposed from spin multiplicity transformation from a triplet ground state to a singlet excited state,followed by electrophilic cycloaddition and a series of rearrangements.While elimination of CS was induced by direct substituted phenyl radical shift in triplet ground state,mediated by cyclization and ring opening as well.Moreover,experiments of substituent effect demonstrated that neutral loss of HS radical was always on primary position regardless of electron-withdrawing or electron-donating groups,and this superiority was enlarged with increase of electron-donating capability of the substituent groups.In additon,when benzene was substituented with CH3,Cl,Br or without substituent group,neutral losses of S and CS were obtained after continuous eliminating of iodine radical,substituent groups or H radical and mediated by dibenzothiophene.Systematical discussion for C-S bond cleavage induced neutral losses in gas phase fragmentation reaction for 3-iodophenyl phenyl sulfides would provide support for further relevant scientific study.Then fragmentation reactions mediated by C-S bond cleavage of three kinds of bis(phenylthio)benzene isomers were studied by atmospheric pressure chemical ionization(APCI)assisted with theoratical calculations tools.All compounds produced molecular ions mainly in positive ion mode,which furtherly resulting in the neutral loss of benzenesulfur radical with direct charge-induced heterolytic cleavage of C-S bond after collisonal activitation.When induced by radical delocalization,followed by cycloaddition and a series of rearrangements,loss of HS radical was observed.What's more,continuous loss of HS radical was only detected in o-bis(phenylthio)benzenes while characteristic eliminations of S2 were detected in m and p-bis(phenylthio)benzenes.Furthermore,loss of substituted benzenethiol was obtained in o and m-bis(phenylthio)benzenes and there was substituted benzene elimination existing in the latter.Difference in fragmentation behaviors of three kinds of bis(phenylthio)benzene isomers under APCI-MS/MS was discussed,and the defferentiation of these isomers could be realized according to the loss of HS radical,S2,substituted benzenethiol and substituted benzene.Finally,researches for 3-dimethylamino-1-phenyl-2-p-tolylsulfanyl-propenone derivatives were carried out using electrospray ionization ion trap mass spectrometry and theoretical calculations.The results showed that all compounds were pronotated under electrospray ionization ion trap mass spectrometry in positive mode and after collision induced dissociation(CID),there were competitive cleavage reactions between C-S and C-C bond.Results derived from quantum chemistry density functional theory showed that O atom of carbonay was the thermodynamically most favorable protonation site.1,5-Proton shif to ipso-carbon of phenyl sulfides leaded to the neutral loss of toluene,while 1,4-H shift followed by 1,2-H shift to ipso-carbon phenyl carbonyl contributed to the cleavage of C-C bond,leading to the elimination of substituted benzene.In addition,experiments for substituent effects indicated that electron-donating groups tended to the cleavage of C-C bond to loss susbtituted benzene,which was controlled thermodynamically,whereas C-S bond cleavage leading to the elimination of toluene was favored with the control of dynamical factors.This chapter discussed competitive cleavage of C-S and C-C bond reactions,making relevant bond cleavage studies complete and supporting theoretical basis for further work.