High-Pressure-Limit and Pressure-Dependent Rate Rules for Unimolecular Reactions Related to Hydroperoxy Alkyl Radicals in Normal Alkyl Cyclohexane Combustion. 1. Concerted HO2 Elimination Reaction Class and β-Scission Reaction Class

2021 ◽  
Author(s):  
Xiaoxia Yao ◽  
Weiqiang Pang ◽  
Tao Li ◽  
Jiangtao Shentu ◽  
Zerong Li ◽  
...  
Keyword(s):  
High Pressure ◽  
Elimination Reaction ◽  
Unimolecular Reactions ◽  
Alkyl Radicals ◽  
Pressure Limit ◽  
Dependent Rate

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

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.

High-Pressure Rate Rules for Alkyl + O2 Reactions. 2. The Isomerization, Cyclic Ether Formation, and β-Scission Reactions of Hydroperoxy Alkyl Radicals

2012 ◽  
Vol 116 (21) ◽  
pp. 5068-5089 ◽  
Author(s):  
Stephanie M. Villano ◽  
Lam K. Huynh ◽  
Hans-Heinrich Carstensen ◽  
Anthony M. Dean
Keyword(s):  
High Pressure ◽  
Cyclic Ether ◽  
Alkyl Radicals

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.

scholarly journals High-Pressure Limit of Equilibrium in Axisymmetric Open Traps

2019 ◽  
Vol 14 (0) ◽  
pp. 2403007-2403007 ◽  
Author(s):  
Mikhail S. KHRISTO ◽  
Alexey D. BEKLEMISHEV
Keyword(s):  
High Pressure ◽  
Pressure Limit

Theoretical Studies on the Effect of the Medium on Tautomeric Phenomena in Neutral and Protonated Acridin-9-amine. Mechanism of Tautomerization in Neutral Entities

1997 ◽  
Vol 50 (2) ◽  
pp. 97 ◽  
Author(s):  
Janusz Rak ◽  
Piotr Skurski ◽  
Ludwika Jozwiak ◽  
Jerzy Blazejowski
Keyword(s):  
High Pressure ◽  
Liquid Phase ◽  
Gaseous Phase ◽  
Dipole Moments ◽  
State Level ◽  
Theoretical Studies ◽  
Pressure Limit ◽  
Energy Gaps ◽  
Tautomeric Forms ◽  
Physicochemical Features

Semiempirical AM1 and PM3 (gaseous phase) and AM1-COSMO, PM3-COSMO and PM3-AQ (liquid phase) methods were used to examine the structure, as well as the thermodynamic and physicochemical features (dipole moments and LUMO and HOMO energies), of tautomeric forms of neutral, mono- and di-protonated acridin-9-amine. The energy gaps between possible tautomers are only insignificantly influenced by the medium and reveal the coexistence of neutral and diprotonated entities in two forms, and the monoprotonated entity in one form. Entropy and thermal energy, which can be evaluated only for gaseous systems on the basis of statistical mechanics, both increase with temperature and affect equilibria between tautomers. The mechanism of bimolecular tautomerization of neutral acridin-9-amine was examinated by the PM3 and PM3-AQ methods. The inclusion of entropy changes accompanying tautomerization in the gaseous phase enabled high-pressure-limit rate constants for well-defined steps of the process at the RRKM and transition state level of theory to be predicted. Thermodynamic and kinetic considerations indicate that neutral acridin-9-amine should coexist in amino and imino tautomeric forms, and that both these entities can convert into each other at moderate temperatures.

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