A note on rate constants of “unimolecular” reactions

1948 ◽  
Vol 44 (0) ◽  
pp. 399-412 ◽  
Author(s):  
R. M. Barrer
Keyword(s):  
Rate Constants ◽  
Unimolecular Reactions

The kinetics of internal energy randomisation in thermal unimolecular reactions

1980 ◽  
Vol 58 (21) ◽  
pp. 2236-2245 ◽  
Author(s):  
Huw Owen Pritchard
Keyword(s):  
Internal Energy ◽  
Lower Limit ◽  
Rate Constant ◽  
Rate Constants ◽  
Rate Function ◽  
Second Order ◽  
Specific Rate ◽  
Unimolecular Reactions ◽  
Methyl Isocyanide ◽  
Kinetics Of

The aim of this paper is to present a minimal theory of thermal unimolecular reactions, including explicitly the kinetics of intramolecular randomisation processes. A quasi-diatomic model is formulated and, within the framework of the model, both first-and second-order randomisation processes among reactant and product states are examined.It is concluded that a vital mechanism for the intramolecular energy randomisation in thermal unimolecular reactions is a collisional one. On this assumption, a straightforward derivation of the Polanyi–Wigner specific rate function, as we have reinterpreted it, becomes possible.At the same time, anomalies in the fall-off curves for the thermal isomerisations of methyl isocyanide and ethyl isocyanide can be accounted for very simply: in the former case, values for both the first- and second-order randomisation rate constants can be derived, but in the latter case it is only possible to establish a lower limit for the second-order randomisation rate constant.

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