The mass spectra of several structurally related ring B seco 5‐keto compounds (I to VII) have been examined. The mass spectra of I, II, III and IV are conspicuous by an intense peak at m/e112(C7H12O) and those of V (highest mass peak at [M CH3COOH]), VI and VII by a prominent peak at m/e 100 (C7H10O), which apparently results from McLafferty rearrangement involving 5‐keto function and an appropriate γ‐hydrogen at C‐8 and C‐11. This rearrangement, leading to the aforementioned ions, is of diagnostic value in the characterisation of such compounds. The mass spectrum of VIII exhibits a prominent ion peak at m/e 332 (C23H40O) resulting from McLafferty rearrangement involving the 5‐keto function and C2H. This offers an excellent means of differentiating between the isomeric acids (III and VIII). The fragmentation pathways suggested are supported by accurate mass measurement of the salient fragment ions and in some cases by appropriate metastable peaks.
ASJC Scopus subject areas
- Molecular Medicine