Hexamethyldisilane, pyrolysis

Similar values have been obtained for AHffMesSi ) from two independent studies. The bond dissociation enthalpy DHfMeaSi-SiMea) = 332 +12 kJ moC was obtained from a kinetic study on the very low pressure pyrolysis of hexamethyldisilane and the enthalpy of formation of trimethylsilyl ion, AHf (MeaSi ) = 617.3 + 2.3kJmor, was determined using threshold photoelectron-photoion coincidence spectroscopy (TPEPICO). Both data are related to AHf°(Me3Si ). 

A similar value has been obtained for A/ff (MesSi ) from an independent kinetic study on the very low pressure pyrolysis of hexamethyldisilane (Reaction 2.5) [6]. A bond dissociation enthalpy D/f(Me3Si—SiMes) = 332 12kJ/mol was obtained which is related to A/ff (MesSi ) by Equation (2.6). 

Most details about the pyrolysis of hexamethyldisilane are known, including some estimations of the Si-Si bond energy23 90> 91>101 > 102> (see also p. 52). At atmospheric pressure, decomposition starts at about 600 °C and yields mainly me3SiCH2Sime2H513 and me3SiH494 ... 

Similar intramolecular isomerizations have been observed upon high-temperature pyrolysis of hexamethyldisilane 130) in a quartz tube, or by treatment of isopropenylpentamethyldisilane 82), 1,2-diisopropenyl-tetramethyldisilane 82), and 1,3-diisopropenylhexamethyltrisilane 82) with concentrated sulfuric acid. 

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