Ab initio investigation of ethane dissociation using generalized transition state theory

The simple carbon-carbon scission of ethane is investigated by performing q uantum mechanical calculations. The approach described in this paper was de veloped to determine dissociation rate constants for both small and large o rganic molecules, such as n-alkanes or alkyl-benzenes, for reasonable range s of computation time and accuracy. The methodology that we propose is base d on generalized transition state theory, where transition states are defin ed along rate constant profiles and not along potential energy curves. Simu lations reported in this paper aim to validate this methodology by examinin g the dissociation of ethane. Calculations, performed at the DFT B3:LYP 6-3 1G** theory level, correctly account for the looseness of the transition st ate as a function of temperature. Dissociation activation parameters obtain ed by this method are in good agreement with data available in the literatu re. Despite the assumptions made, the order of magnitude and the specific t emperature dependence of rate constants for methyl recombination are also f airly predicted.