Correlations Based on Mechanical Similarity

The concept of mechanical similarity has been discussed in Chapter 5. This can be divided into two major subclasses (1) dynamic similarity and (2) kin atic similarity. The correlations based on these two subclasses are discussed separately. 

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The above discussion demonstrates that the activation barrier for the silane Si-H bond is relatively small compared to that for an alkane C-H bond. This is surprising in that one might have expected comparable energy barriers for activation of both the Si-H and C-H bonds based on the similar enthalpy of activation AH from macroscopic kinetic measurements (41-44). Clearly other mechanisms are at work to make up the energy barrier in the case of Si-H bond activation. To investigate if more intermediates are involved, which may provide an explanation for the reported apparent AH values, the reaction is followed extending into the nano- and microsecond regime. The experiments show that only the previously discussed ethyl-solvate appears on these time-resolved IR spectra. Its decay correlates very well with the product rise as displayed in Fig. 15. 

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