FTIR study of thermally induced transformations of trimethylsilylmethyl acetate in the temperature range 623–813 K

The chemistry of trimethylsilylmethyl acetate in the gas phase in the temperature range 623–813 K has been investigated under static conditions using Fourier transform IR spectroscopy. Little change occurs at temperatures lower than 623 K, at which temperature a thermally induced isomerization to form ethyldimethylsilyl acetate occurs. Some ethanoic acid is also produced at this temperature. The ethyldimethylsilyl acetate produced undergoes thermolysis at temperatures >723 K giving methane, ethene, carbon monoxide, carbon dioxide, ethanoic acid, 1,3-diethyl-1,1,3,3-tetramethyldisiloxane, cyclohexamethyltrisiloxane, and cyclooctamethyltetrasiloxane as products. Loss of ethyldimethylsilyl acetate is first order over the whole temperature range, and first-order rate constants vary from 4.87×10−5 s−1 at 723 K to 33.5×10−5 s−1 at 813 K, respectively, leading to an activation energy, Ea, of 110(4) kJ mol−1. An intramolecular five-centre process is proposed for the isomerization reaction. The thermolysis is interpreted in terms of principally radical reactions involving initial homolytic dissociation of the EtMe2SiOC(O)CH3 bond.