ChemInform Abstract: ACCURACY OF TRANSITION STATE THEORY FOR THE THRESHOLD OF CHEMICAL REACTIONS WITH ACTIVATION ENERGY, COLLINEAR AND THREE-DIMENSIONAL H+H2

This chapter reviews the microscopic interpretation of the pre-exponential factor and the activation energy in rate constant expressions of the Arrhenius form. The pre-exponential factor of apparent unimolecular reactions is, roughly, expected to be of the order of a vibrational frequency, whereas the pre-exponential factor of bimolecular reactions, roughly, is related to the number of collisions per unit time and per unit volume. The activation energy of an elementary reaction can be interpreted as the average energy of the molecules that react minus the average energy of the reactants. Specializing to conventional transition-state theory, the activation energy is related to the classical barrier height of the potential energy surface plus the difference in zero-point energies and average internal energies between the activated complex and the reactants. When quantum tunnelling is included in transition-state theory, the activation energy is reduced, compared to the interpretation given in conventional transition-state theory.

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On the Calculation of Transition State Activity Coefficient and Solvent Effects on Chemical Reactions

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19981969 ◽

1998 ◽

Vol 63 (12) ◽

pp. 1969-1976 ◽

Cited By ~ 3

Author(s):

Alvaro Domínguez ◽

Rafael Jimenez ◽

Pilar López-Cornejo ◽

Pilar Pérez ◽

Francisco Sánchez

Keyword(s):

Activity Coefficient ◽

Transition State ◽

Chemical Reactions ◽

Solvent Effects ◽

Transition State Theory ◽

Reaction Medium ◽

State Theory ◽

Precursor Complex ◽

State Activity ◽

Classical Transition

Solvent effects, when the classical transition state theory (TST) holds, can be interpreted following the Brønsted equation. However, when calculating the activity coefficient of the transition state, γ# it is important to take into account that this coefficient is different from that of the precursor complex, γPC. The activity coefficient of the latter is, in fact, that calculated in classical treatments of salt and solvent effects. In this paper it is shown how the quotients γ#/γPC change when the reaction medium changes. Therefore, the conclusions taken on the basis of classical treatments may be erroneous.

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Kinetic Analysis of the Effect of Poliovirus Receptor on Viral Uncoating: the Receptor as a Catalyst

Journal of Virology ◽

10.1128/jvi.75.11.4984-4989.2001 ◽

2001 ◽

Vol 75 (11) ◽

pp. 4984-4989 ◽

Cited By ~ 55

Author(s):

Simon K. Tsang ◽

Brian M. McDermott ◽

Vincent R. Racaniello ◽

James M. Hogle

Keyword(s):

Activation Energy ◽

Transition State ◽

Kinetic Analysis ◽

Transition State Theory ◽

State Theory ◽

Viral Receptor ◽

Poliovirus Receptor ◽

Entropic Stabilization ◽

Entropic Effects

ABSTRACT We examined the role of soluble poliovirus receptor on the transition of native poliovirus (160S or N particle) to an infectious intermediate (135S or A particle). The viral receptor behaves as a classic transition state theory catalyst, facilitating the N-to-A conversion by lowering the activation energy for the process by 50 kcal/mol. In contrast to earlier studies which demonstrated that capsid-binding drugs inhibit thermally mediated N-to-A conversion through entropic stabilization alone, capsid-binding drugs are shown to inhibit receptor-mediated N-to-A conversion through a combination of enthalpic and entropic effects.

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