| Some of the Basic Aspects of Transition State Theory (TST) of Bimolecular Reaction Rates Revisited with an Input From Nonequilibrium Thermodynamics Anil A. Bhalekar1; Bjarne Andresen2; 1DEPARTMENT OF CHEMISTRY, R. T. M. NAGPUR UNIVERSITY, NAGPUR, India; 2UNIVERSITY OF COPENHAGEN, COPENHAGEN, Denmark; PAPER: 133/Energy/Regular (Oral) SCHEDULED: 17:10/Mon. 28 Nov. 2022/Game ABSTRACT: In view of the prevailing over skepticism about the sound thermodynamic base of the expression of the rate constant given by the traditional transition state theory (TST) of bimolecular reactions, its foundational ingredients are revisited in this paper. The inference drawn earlier of the existence of <i><i>quasiequilibrium</i></i> between the reactants and activated complexes has been properly amended. The need for this has been elucidated by showing that the use of <i>quasiequilibrium</i> amounts to use it as a pre-equilibrium step hence it implies that the conversion of activated complexes to the product molecules must be a slow step according to the basic principles of chemical kinetics. However, it has been demonstrated that the existence time of an activated complex is less than the time required to complete half of the molecular vibration of the activated complex. Which means they are highly reactive ones. Therefore, it is not the case of <i>pre-equilibrium </i>but, indeed, is the case of a steady state for the forward moving activated complexes, which is what Arnot had advocated earlier. However, we have demonstrated that the said steady state for the concentration of the forward moving activated complexes is a case of <i>dynamic chemical equilibrium</i> between the reactants and the forward moving activated complexes whose sound thermodynamic base has been elucidated by describing the corresponding nonequilibrium thermodynamics. Thus, the much-needed description of the thermodynamic base of TST given expression of the rate constant has been accomplished. References: <b>Bibliography</b><br />1. A. A. Bhalekar, Nonequilibrium thermodynamics of dynamic chemical equilibria, (Preceding Paper) (2020)<br />2. H. Eyring, Activated Complex in Chemical Reactions, <i>J. Chem. Phys.</i>, 3, 107-115 (1935).<br />3. M. G. Evans and M. Polanyi, Some applications of the transition state method to the calculation of reaction velocities, especially in solution, <i>Trans. Faraday Soc.</i>, 31, 875-894 (1935)<br />4. S. Glasstone, K. J. Laidler, and H. Eyring, <i>Theory of Rate Processes</i>, McGraw-Hill, New York, 1941<br />5. K. J. Laidler and J. C. Polanyi, <i>Theories of the Kinetics of Bimolecular Reactions</i>, Vol 3, of <i>Progress in Reaction Kinetics</i>, ch. 1, Pergomon Press, London, 1965<br />6. K. J. Laidler and M. C. King, The development of transition-state theory, <i>J. Phys. Chem.</i>, 87, 2657-2664 (1983)<br />7. C. L. Arnot, Activated complex theory of bimolecular gas reactions, <i>J. Chem. Educ.</i>, 49, 480-482 (1972)<br />8. I. Prigogine and R. Defay, <i>Chemical Thermodynamics</i>, D. H. Everett, Transl., Longmans-Green, London, 1954<br />9. A. A. Bhalekar, The transition state theory of bimolecular reaction rates via the Bodenstein steady state for activated complexes, <i>CACAA</i>, 4, 309-340 (2015) |
