The pyrolysis of 2-chloroethylsilanes.

Kinetic runs were carried out on 2-chloroethyltrinethyl- -silane in both greased and grease-free systems. It was found that to obtain a possible homogeneous decomposition in the greased system the surface of the reaction vessel had to be coated with carbon by decomposing allyl bromide in the reaction vessel. The products were then found to be 96% ethylene and trimethylchloro- -silane, 2% hydrogen chloride and vinyltrimethylsilane and 2% vinyl chloride and trimethylsilane. The reactions were:- Me3SiCH2CH2Cl ? C2H4 + Me3SiCl Me3SiCH2CH2Cl ? HCl + Me3SiCH=CH2 Me3SiCH2CH2Cl ? CH2=CHCl + Me3SiH When runs were carried out in the grease-free reaction vessel the only products found were ethylene and trimethylchloro-silane, the sole reaction appearring to be:- Me3SiCH2CH2Cl ? C2H4 + Me3SiCl A short series of runs were carried out on 2-hydroxy- -ethyltrimethylsilane. A heterogeneous dehydration appeared to be the major reaction as the major products wore water and vinylteimethylsilane i.e. Me3SiCH2CH2OH ? Me3SiCH=CH2 + H2O Some preliminary runs were done on 1,2-dichloroethyl-trimethylsilane which was found to be even more sensitive to surface than 2-chloroethyltrimethylsilane and to be more complex in its decomposition. The main products were found to be vinyl chloride and trimethylchlorosilane but there was also an appreciable amount of hydrogen chloride and a chlorovinyltrimethylsilane. This compound thus appears to decompose by two reaction paths i.e. Me3SiCHClCH2Cl ? CH2=CHCl + Me3SiCl Me3SiCHClCH2Cl ? HCl + Me3SiCH=CHCl.