Date of Award
Doctor of Philosophy
Thomas J. Barton
The flash vacuum pyrolysis (FVP) of bis(trimethylsilyl)ketene led to 1-trimethylsilylpropyne and a trace of cyclotrisiloxane. The products were accounted for by postulating a retro-Wolff process. The decomposition kinetics of dimethylsilyl(trimethylsilyl)ketene were followed in a stirred-flow reactor (SFR) and the activation parameters (Ea = 51.7 Kcal/mol, log A = 12.97) were obtained. FVP of several alkyl(trimethylsilyl)ketenes were also examined. These ketenes have been observed to decompose by three different routes viz., a retro-Wolff process, a homolytic cleavage process and a retro-ene process. When the alkyl group was t-butyl, the retro-Wolff product was not observed. From decomposition kinetics of t-butyl(trimethylsilyl)ketene to form trimethylsilyketene, the evaluated activation parameters (Ea = 54.6 Kcal/mol, log A = 13.0) were found to be consistent with a retro-ene process;The FVP studies were extended to dimethylsilyl(trimethylsilyl)thioketene and bis(trimethylsilyl)thioketene. The former produced trimethylsilylacetylene in a remarkable 92% yield with extrusion of dimethylsilanethione (Me[subscript]2Si = S). The latter thioketene gave a complex mixture of products, all of which are economically accounted for by postulating a 1,2-silyl shift (a retro-thio Wolff process) to give an [alpha]-thioketocarbene. Rearrangements of this thioketocarbene led to products. From the decomposition kinetics of hydridosilylthioketene the activation parameters (Ea = 44.8 Kcal/mol, log A = 13.3) were determined;Tris(dimethylsilyl)ketenimine on FVP afforded dimethylsilylacetylene and cyclodisilazane. The products were accounted for by a retro-Wolff type rearrangement;In an effort to study the structure of a silylketene, several bulky silyketenes were synthesized;Thermally generated silylenes were observed to react with certain silylketene and -thioketene with the formation of silylacetylenes;Alkyl radicals stabilization due to [alpha]- and [beta]-trimethylsilyl groups were evaluated and both were found to be the same (2.6 ± 1 Kcal/mol).
Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/
Gitendra Chandra Paul
Paul, Gitendra Chandra, "Kinetic and mechanistic aspects of the thermal decomposition of silyketenes, -thioketenes and -ketenimines " (1988). Retrospective Theses and Dissertations. 9713.