Fast atom bombardment (FAB) mass spectrometry of piperidine N-oxide derivatives and free radical quenching under FAB conditions

✍ Scribed by Lin Yan; Yiwei Fang; Min Fang; Lizhi Zhu; Dekang Shen; Xiyun Liang

• Publisher: John Wiley and Sons
• Year: 1989
• Tongue: English
• Weight: 527 KB
• Volume: 24
• Category: Article
• ISSN: 1076-5174
• DOI: 10.1002/oms.1210240503

✦ Synopsis

100080, Peoples' Republic of China Mechanisms are proposed for the formation of M+, [M + 2H]+ and [M + 3 H 1 ' ions in the fast atom bomhardment (FAB) mass spectra of 4-(2,2,6,6tetramethyl-l-oxyl)-piperidol and its carboxylates. Free radical quenching induced by the fast atom beam has been observed. The effects of temperature on the radical quenching and of acid on the FAB mass spectra are discussed. The experiment showed that the volatile liquid samples with vapour pressures higher than that for glycerol produced M' even-electron molecular ions, and the FAB mass spectra were similar to the corresponding electron ionization mass spectra. For the solid samples, it was found that the free radicals were quenched during the FAB process so that the mononitroxide and dinitroxide compounds produced [M + 2 w ' and [M + 3H]+ ions, respectively. Further experiments showed that the intensities and stabilities of [M + 2H]+ and [M + 3Hj+ ions could be improved by addition of acids. R 1 CH,(CH,),CO 2 CH,(CH,),CO Mea/: 4 3 H C,H,CO M e I 5 CH,CH=CHCO 0 6 CH,=CCO I CH, 7 CH,=CHCO X 8 OC(CH,),CO 9 OC(CH,),CO 10 OCC,H,CO

EXPERIMENTAL

Compounds 1-10 were synthesized by the methods previously reported.28 EI mass spectra were obtained with an AEI (Kratos) MS 50 double-focusing mass spectrometer and DS-30 data system. The electron energy was 70 eV and the accelerating voltage was 8 kV. The ion source was kept at 200°C and the inlet probe temperature ranged from room temperature to 390°C depending on the volatility of the compound examined.

FAB experiments were performed on a KYKY