Application of Mass Spectra Isotope to Interpret the Derivatives of the Benzoxazolone

The fragmentation mechanism of five derivatives is discussed in this arti-cle. Four of them(Ⅰ): R_1=R_2=H; (Ⅱ) R_1=Cl, R_2=H; (Ⅲ):R_1=Cl, R_2=CH_2OH; (Ⅳ): R_1=Cl, R_2=CH_2S? (OC_2H_5)_ contain the benzoxazolone skele- ton (R_1R_2C_7H_3NO_2). The isotopic peaks show that the fragmentation mechanism M~+→M-CO_2 of (Ⅰ) and (Ⅱ) occurs. The isotopic peaks, the accurate mass and the metastable scau (B/E link-ed scan) demonstrated the following fragmentation mechanism: M~+, m/z_(201(2.5%))~(199(10.5%)) (-CH_2O/*)m/z_(171(33.1%)~(169(100%)-CO_2/m/z_(127(7.8%))~(125(23.9%)) (Ⅲ)The structural factors of stabilizing M~+and base peak are discussed.