Mass spectra of some substituted methylcyclosiloxanes

Abstract

The mass spectra of the substituted methylcyclosiloxanes [Formula: see text] where X = H (n = 4, 5 and 6), X = C6H5 (n = 3 and 4), X = Br (n = 3 and 4), X = Co(CO)4 (n = 4 and 5) have been measured. The compounds X = H fragment by the same kinds of substituent loss and ring contraction mechanisms as previously reported for the compounds X = CH3 but also by the loss of methylhydrogensilanone. The compounds X = Ph fragment by loss of benzene from an intramolecularly bridging benzenonium ion, formed from [M − CH3]+• and by losses of the phenylmethylsilanone fragments. The compounds X = Br only undergo substituent loss without ring fragmentation. The compounds X = Co(CO)4 show stepwise loss of all CO groups from [M]+•, [M − Co(CO)4]+, and [M]++.