In this study the effects of the nature of metal alkoxides on their vapour pressures and thermal decomposition chemistry are reported. The vapour pressure and the volatility of a metal alkoxide strongly depends on the steric effect of its alkoxy group. The thermal decomposition chemistry of one metal alkoxide (di-acetoxy-di-t-butoxy-silane, DADBS) has been studied by mass spectrometry at temperatures between 423 and 923 K. The pyrolytic products were acetic acid anhydride and 2-methyl propene. The acetic acid anhydride is formed at temperatures above 473 K and 2-methyl propene is formed above 673 K by a ß -hydride elimination mechanism. In these steps, a 6-ring intermediate is supposed to be formed. The silicon acid finally remaining is proposed to react by poly-condensation to SiO2 coatings or powder.