Mathematical Models Based on Transition State Theory for the Microbial Safety of Foods by High Pressure

2016 ◽  
pp. 331-349 ◽  
Author(s):  
Christopher J. Doona ◽  
Kenneth Kustin ◽  
Florence E. Feeherry ◽  
Edward W. Ross
Keyword(s):  
High Pressure ◽  
Transition State ◽  
Mathematical Models ◽  
Transition State Theory ◽  
State Theory ◽  
Microbial Safety

scholarly journals Association of Cl with C2H2by unified variable-reaction-coordinate and reaction-path variational transition-state theory

2020 ◽  
Vol 117 (11) ◽  
pp. 5610-5616
Author(s):  
Linyao Zhang ◽  
Donald G. Truhlar ◽  
Shaozeng Sun
Keyword(s):  
High Pressure ◽  
Transition State ◽  
Transition State Theory ◽  
Reaction Path ◽  
State Theory ◽  
Reaction Coordinate ◽  
Acetylene Molecule ◽  
Variational Transition State Theory ◽  
Pressure Limit ◽  
Variational Transition State

Barrierless unimolecular association reactions are prominent in atmospheric and combustion mechanisms but are challenging for both experiment and kinetics theory. A key datum for understanding the pressure dependence of association and dissociation reactions is the high-pressure limit, but this is often available experimentally only by extrapolation. Here we calculate the high-pressure limit for the addition of a chlorine atom to acetylene molecule (Cl + C2H2→C2H2Cl). This reaction has outer and inner transition states in series; the outer transition state is barrierless, and it is necessary to use different theoretical frameworks to treat the two kinds of transition state. Here we study the reaction in the high-pressure limit using multifaceted variable-reaction-coordinate variational transition-state theory (VRC-VTST) at the outer transition state and reaction-path variational transition state theory (RP-VTST) at the inner turning point; then we combine the results with the canonical unified statistical (CUS) theory. The calculations are based on a density functional validated against the W3X-L method, which is based on coupled cluster theory with single, double, and triple excitations and a quasiperturbative treatment of connected quadruple excitations [CCSDT(Q)], and the computed rate constants are in good agreement with some of the experimental results. The chlorovinyl (C2H2Cl) adduct has two isomers that are equilibrium structures of a double-well C≡C–H bending potential. Two procedures are used to calculate the vibrational partition function of chlorovinyl; one treats the two isomers separately and the other solves the anharmonic energy levels of the double well. We use these results to calculate the standard-state free energy and equilibrium constant of the reaction.

Dynamic Solvent Effects in the Degenerate Isomerization of a Hexafluoroacetone Anil Studied by High-Pressure 19 F NMR

1999 ◽  
Vol 54 (6-7) ◽  
pp. 417-421
Author(s):  
Yasushi Ohga ◽  
Tsutomu Asano ◽  
Norbert Karger ◽  
Thomas Gross ◽  
Hans-Dietrich Lüdemann
Keyword(s):  
High Pressure ◽  
Nmr Spectroscopy ◽  
Transition State ◽  
Solvent Effects ◽  
Transition State Theory ◽  
State Theory ◽  
Nonequilibrium Conditions ◽  
19 F Nmr

Abstract The rate of the degenerate isomerization of N-hexafluoroisopropylidene-N’,N’-dimethyl-ρ-phe-nylenediamine was measured by high-pressure 19F NMR spectroscopy in a viscous hydrocar-bon, 2,4-dicyclohexyl-2-methylpentane. Pressure-induced retardations that cannot be rationalized within the framework of the transition state theory (TST) were observed, and it was concluded that the reaction was cast into the TST-invalid nonequilibrium conditions by high pressure.

Microscopic Interpretation of Arrhenius Parameters

2018 ◽  
Author(s):  
Niels Engholm Henriksen ◽  
Flemming Yssing Hansen
Keyword(s):  
Activation Energy ◽  
Transition State ◽  
Transition State Theory ◽  
Average Energy ◽  
Zero Point ◽  
State Theory ◽  
Exponential Factor ◽  
Quantum Tunnelling ◽  
Microscopic Interpretation ◽  
The Difference

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.

Bimolecular Reactions, Transition-State Theory

2018 ◽  
Author(s):  
Niels Engholm Henriksen ◽  
Flemming Yssing Hansen
Keyword(s):  
Transition State ◽  
Saddle Point ◽  
Transition State Theory ◽  
Classical Mechanics ◽  
Small Degree ◽  
State Theory ◽  
Reaction Coordinate ◽  
Partition Functions ◽  
Bimolecular Reactions ◽  
Activated Complex

This chapter discusses an approximate approach—transition-state theory—to the calculation of rate constants for bimolecular reactions. A reaction coordinate is identified from a normal-mode coordinate analysis of the activated complex, that is, the supermolecule on the saddle-point of the potential energy surface. Motion along this coordinate is treated by classical mechanics and recrossings of the saddle point from the product to the reactant side are neglected, leading to the result of conventional transition-state theory expressed in terms of relevant partition functions. Various alternative derivations are presented. Corrections that incorporate quantum mechanical tunnelling along the reaction coordinate are described. Tunnelling through an Eckart barrier is discussed and the approximate Wigner tunnelling correction factor is derived in the limit of a small degree of tunnelling. It concludes with applications of transition-state theory to, for example, the F + H2 reaction, and comparisons with results based on quasi-classical mechanics as well as exact quantum mechanics.

Quasiclassical Trajectory and Transition State Theory Studies of the N(4S) + H2↔ NH(X3Σ-) + H Reaction

2002 ◽  
Vol 106 (16) ◽  
pp. 4125-4136 ◽  
Author(s):  
Ronald Z. Pascual ◽  
George C. Schatz ◽  
Gÿorgÿ Lendvay ◽  
Diego Troya
Keyword(s):  
Transition State ◽  
Transition State Theory ◽  
State Theory
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