Thermal dissociation rate of ethane at the high pressure limit from 250 to 2500 K

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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High-Pressure Limit of Equilibrium in Axisymmetric Open Traps

Plasma and Fusion Research ◽

10.1585/pfr.14.2403007 ◽

2019 ◽

Vol 14 (0) ◽

pp. 2403007-2403007 ◽

Cited By ~ 4

Author(s):

Mikhail S. KHRISTO ◽

Alexey D. BEKLEMISHEV

Keyword(s):

High Pressure ◽

Pressure Limit

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Field Drift Of Plasma-Induced Defects In Phosphorus Doped Si By Reverse Bias Annealing (RBA)

MRS Proceedings ◽

10.1557/proc-442-81 ◽

1996 ◽

Vol 442 ◽

Cited By ~ 1

Author(s):

J. Takeuchi ◽

Y. Zaitsu ◽

T. Shimizu ◽

S. Matsumoto ◽

K. Wada

Keyword(s):

Reverse Bias ◽

Arrhenius Plot ◽

Thermal Dissociation ◽

Dissociation Rate ◽

Plasma Exposure ◽

Defect Complexes ◽

Induced Defects ◽

Phosphorus Doped ◽

Charged Defects ◽

Field Drift

AbstractThe property of plasma induced defects in phosphorus doped CZ silicon has been investigated by reverse bias annealing (RBA). After CF4 plasma exposure, charge density at the surface decreased since plasma induced negatively charged defects inactivated phosphorus. With the increase of annealing time, inactivated phosphorus area moved into the bulk with reverse bias of −3V. Thus it is clearly observed that negatively charged defects drifted from the surface into the bulk. The thermal dissociation energy for phosphorus-defect complexes is estimated to be 1.22eV from the Arrhenius plot of dissociation rate. These defects are likely to be Si self interstitials or vacancies.

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The Kinetic Activation Volumes for the Binding of Iodide to Cobalamin (Vitamin B12) Studied on a High Pressure Laser Temperature Jump Apparatus

Canadian Journal of Chemistry ◽

10.1139/v74-147 ◽

1974 ◽

Vol 52 (6) ◽

pp. 910-914 ◽

Cited By ~ 13

Author(s):

Brian B. Hasinoff

Keyword(s):

High Pressure ◽

Metal Ion ◽

Temperature Jump ◽

Outer Sphere ◽

Dissociation Rate ◽

Vitamin B ◽

Laser Temperature Jump ◽

Dissociation Rate Constants ◽

Kinetics Of ◽

Activated Complex

The relaxation kinetics of the reaction of iodide with cobalamin (vitamin B12) were studied on a high pressure laser temperature jump apparatus in aqueous solution at 25° and ionic strength 0.2 M. Analysis of the pressure dependence of the formation and dissociation rate constants gave their respective volumes of activation to be: ΔVf* = 5.50 ± 0.8 cm3 mol−1 and ΔVd* = 11.5 ± 1.6 cm3 mol−1 The positive activation volume for formation of the complex, ΔVf*, after appropriate correction for the volume change due to formation of an outer sphere complex, is consistent with a dissociative type mechanism in which the metal ion – water bond is stretched in the activated complex.

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

Australian Journal of Chemistry ◽

10.1071/c96184 ◽

1997 ◽

Vol 50 (2) ◽

pp. 97 ◽

Cited By ~ 10

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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