FT-IR STUDY OF THE GAS-PHASE AUTOXIDATION OF TRIMETHYLGERMANE

The kinetics and mechanism of the autoxidation of trimethylgermane in the gas phase has been investigated in the temperature range 493-533 K using Fourier transform infrared spectroscopy. Over a wide molar rati o of reactants (Me3GeH:O2 ratio in the range (1:1)-(1:31)) the loss of Me3GeH follows second-order kinetics but is independent of oxygen abu ndance. The products of the reaction are heyamethyldigermoxane, Me3GeO GeMe3, and water. No other products are apparent. For a 1:10 Me3GeH:02 molar ratio, second-order rate constants vary from 2.46 mol-1 de s-1 at 493 K to 64.1 mol-1 dm3 s-1 at 533 K. The activation energy for the process -is determined to be 190 +/- 19 kJ mol-1. The proposed mechan ism involves an initial abstraction of the hydridic hydrogen atom from germanium followed by the reaction of the trimethylgermyl radical thu s formed with oxygen, giving the (trimethylgermyl)peroxyl radical. Thi s radical is converted into trimethylgermyl hydroperoxide, Me3GeOOH, b y further H-abstraction from Me3GeH and undergoes O-O bond fission to form (trimethylgermyl)oxyl and hydroxyl radicals. The radicals thus pr oduced propagate the reaction by H-abstraction from Me3GeH, forming th e intermediate Me3GeOH and water. Hexamethyldigermoxane is subsequentl y formed by self-condensation of two Me3GeOH molecules.