Abstract The electron impact mass spectra of six 5, 5-dimethyl and eleven 3, 5, 5-trimethyl- perhydro-1, 3, 2-oxazaphosphorine 2-oxides and 2-sulphides are reported and compared with those of analogous 5, 5-dimethyl-1, 3, 2-dioxaphosph (v) orinans. Compounds of the 3, 5, 5-trimethyl series produce an important ion at m/z 44 which clearly distinguishes them from the 5, 5-dimethyl series. The 2-sulphides are characterized by loss of thiol radical ...
