Fragmentation pathways of n-substituted phthalimide derivatives using electrospray ionization quadrupole time-of-flight mass spectrometry

N-substituted phthalimide derivatives were studied by electrospray ionization mass spectrometry (ESI-MS) in positive mode in conjunction with high-resolution quadrupole time-of-flight mass spectrometry (Q-TOF-MS), in order to study its' fragmetation pathways. Based on mass spectrum behaviors of the fragmentation pathways, all the five compounds showed a similar cleavage progress. Classical losses of CO and methanol owing to the presence of ester were observed in all these compounds; in addition, the loss of moth-er nucleus N-hydroxy phthalimide was observed in the five compounds. The characteristic ions of compounds 1-4 were the ions which lost methanol and N-hydroxy phthalimide. However, the characteristic ion of compound 5 was the ion of losing N-hydroxy phthalimide, whoses structure was similar to tropylium ion, then continuously lost a molecular C2H2 after losing methanol and CO in a row.