Chapter one provides a brief history and current state of knowledge of the chemistry of organosilicon reactive intermediates relevant to this thesis. Chapter two outlines the experimental techniques used in the majority of work carried out in this thesis. Chapter three describes an experimental investigation of the pyrolysis of 4-dimethylsilylbut-l-ene and 5-dimethylsilylpent-l-ene, with and without excess methylchloride as a silyl radical trap. The results of computer modelling of the pyrolysis of 4-dimethylsilylbut-1-ene with excess methylchloride are described, in which information concerning the isomerisation of an alpha-silyl radical to a silyl radical via a hydrogen shift is obtained. Chapter four describes the results of an experimental investigation of the reactions of dimethylsilene and dimethylsilylene with anions. Chapters five and six contain the results of computer modelling of three related pyrolysis mechanisms composed of complex series of unimolecular rearrangements of silylenes, silenes, disilenes and disilacyclopropanes. Chapter seven describes an experimental determination of Arrhenius parameters for the trapping of dimethylsilene by butadiene, together with the results of pyrolysis of butadiene adducts of methylsilene, dimethylsilene and dimethylsilylene. Chapter eight is an experimental investigation of the pyrolysis of cis and trans dimethy1(1-propenyl)vinylsilane with excess 2,3-dimethylbutadiene as a silylene trap. Interpretation of the results as a cis-trans isomerisation and decomposition of the cis isomer via a silacyclopropane intermediate are reinforced by the results of computer modelling of both systems. Chapter nine describes an experimental investigation of the pyrolysis of 1, 2-dimethyldisilane with and without butadiene as a silylene trap. Computer modelling of the pyrolysis with the absence of butadiene is used to clarify the pyrolysis mechanism. Chapter ten is an experimental investigation of the pyrolysis of silacyclobutane and methylsilacyclobutane with excess butadiene to trap silylene intermediates and thus suppress secondary decomposition. Arrhenius parameters for the primary decomposition pathways are determined.