title: The electron impact induced cleavage of the C-17--C-20 bond and D-ring in trimethylsilyl derivatives of C21 steroids. Reciprocal exchange of trimethylsilyl groups.
abstract: The cleavage of the C-17--C-20 bond in the trimethylsilyl derivatives of C21 steroids has been investigated with the aid of isotopic labelling. A significant amount of reciprocal exchange was observed between trimethylsilyl groups or hydrogen atoms on the 20-O- and 17-O-positions. The loss of positional identity of these groups was found to influence the specificity of fragmentation reactions associated with the 17 beta-sidechain and the D-ring. It is supposed that the interchange of these silyl groups is facilitated by donation of the non-bonding electrons on oxygen to the empty d orbitals of silicon.
mesh_terms: D055598:Chemical Phenomena; D002621:Chemistry; D008401:Gas Chromatography-Mass Spectrometry; D012825:Silicon / Q000032:analysis*; D013256:Steroids / Q000032:analysis*; D014297:Trimethylsilyl Compounds / Q000032:analysis*
chemical_list: D013256:Steroids; D014297:Trimethylsilyl Compounds; D012825:Silicon