The mass spectra of six derivatives of 2-pyrimidinoxal aniline were reported. The characteristics and operational principles of the ion trap MS were introduced. The fragmentation pathways were studied using the ion trap MS^n technology. It has been found that there exist two complex but characteristic rearrangements and fragmentation patterns for these compounds. The base peaks of all the derivatives were [M-17]^+. And they all yielded the peak of [M-17-90] ^+. In addition, they had the same fragments such as m/z: 246 and so on. HRMS of compound c and the MS of the acetylation product of compound c proved the fragmentation pathways.

Key words: PYRIMIDINE P, BENZAMINE P, REARRANGEMENT REACTION, PYROLYSIS, MASS SPECTROGRAPHY