Electron impact mass spectra of 1-methyl-oestra-1,3,5(10)-trienes having intact and 13,17-seco-D-ring structures

Electron impact mass spectra of 1-methyl-oestra-1,3,5(10)-trien-17-one, its oxime, the homologous 18-norketone, 1-methyl-oestra-1,3,5(10),13(18)-tetraene-17-carbonitrile and the corresponding 13,17-seco epoxide are described. The major fragmentation pathways of these compounds are reported and discussed in relation to their structures, and the structures of the ions m/e 144, 157, 170 and 183 characteristic of the 1-methyl-oestratriene skeleton are described. The relative abundances of these characteristic ions were shown to relat to the presence or absence of a 13,17-seco-D-ring in these compounds.