On the Mechanism of Reversible Unimolecular Reactions and the Canonical (“High Pressure”) Limit of the Rate Coefficient at Low Pressures*)

1984 ◽  
Vol 88 (2) ◽  
pp. 94-100 ◽  
Author(s):  
Martin Quack
Keyword(s):  
High Pressure ◽  
Rate Coefficient ◽  
Unimolecular Reactions ◽  
Pressure Limit ◽  
Low Pressures

THE HIGH PRESSURE LIMIT OF UNIMOLECULAR REACTIONS

1961 ◽  
Vol 65 (2) ◽  
pp. 373-373 ◽  
Author(s):  
M. C. Flowers ◽  
H. M. Frey
Keyword(s):  
High Pressure ◽  
Unimolecular Reactions ◽  
Pressure Limit

Prediction of the Rate Coefficient for the F+SOF3 Recombination Reaction

1990 ◽  
Vol 43 (1) ◽  
pp. 169 ◽  
Author(s):  
IG Pitt ◽  
RG Gilbert ◽  
KR Ryan
Keyword(s):  
Experimental Study ◽  
High Pressure ◽  
Pressure Dependence ◽  
Variational Approach ◽  
Potential Surface ◽  
Rate Coefficient ◽  
Recombination Reaction ◽  
Pressure Limit ◽  
Association Reaction ◽  
Recombination Rate Coefficient

The pressure dependence of the rate coefficient for the recombination reaction SOF3+F → SOF4 has been calculated by utilizing an RRKM canonical variational approach with a hindered-rotor Gorin potential surface. With no adjustable parameters, the high-pressure recombination rate coefficient is predicted to be c. 1×10-10cm3s-1. It was further established that this rate coefficient is close to its high-pressure limit above c. 100 Pa. These results support the conclusions of an experimental study in which this rate coefficient was measured relative to that of the association reaction between SOF3 and O.

A COMPARISON OF SLATER'S THEORY OF UNIMOLECULAR REACTIONS WITH EXPERIMENTAL DATA

1959 ◽  
Vol 37 (6) ◽  
pp. 1035-1037 ◽  
Author(s):  
Everett Thiele ◽  
David J. Wilson
Keyword(s):  
Experimental Data ◽  
High Pressure ◽  
Lower Bounds ◽  
Rate Constant ◽  
Unimolecular Reactions ◽  
Pressure Limit ◽  
Nitrogen Pentoxide ◽  
Simplified Method ◽  
Experimental Values

Slater's theory of unimolecular reactions is tested by comparing theoretical and experimental values of the pressure at which the rate constant has fallen off from the high-pressure limit by 5%. A simplified method is used for calculating lower bounds to the theoretical value of this pressure. Agreement with experimental data on cyclobutane, cyclobutene, and nitrogen pentoxide is rather poor; experimental values are lower than the calculated lower bounds.

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.

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