A quantitative approximation for the quantum dynamics of hydrogen transfer: Transition state dynamics and decay in ClHCl−

1994 ◽  
Vol 101 (3) ◽  
pp. 1975-1987 ◽  
Author(s):  
Anne B. McCoy ◽  
R. Benny Gerber ◽  
Mark A. Ratner
Keyword(s):  
Transition State ◽  
Quantum Dynamics ◽  
Hydrogen Transfer

Model Calculations of Isotope Effects. III. Isotope Effects in Hydrogen Transfer Reactions, and Transition State Force Fields

1979 ◽  
Vol 32 (9) ◽  
pp. 1869
Author(s):  
DJ McLennan
Keyword(s):  
Transition State ◽  
Hydrogen Transfer ◽  
Force Fields ◽  
Isotope Effects ◽  
Semiempirical Method ◽  
Model Calculations ◽  
Surface Hydrogen ◽  
Kinetic Isotope ◽  
State Force ◽  
Better Than

Model calculations of kinetic isotope effects for the reactions: C2H6+·CH3 → ·C2H5+CH4 CH4 + ·CF3 → ·CH3+CHF3 are reported. Transition state geometries were those calculated by Dewar and coworkers using the MNDO semiempirical method. Transition state force fields were formulated from empirical expressions for stretching, bending, linear bending and interaction valence force constants by using bond orders as disposable parameters. Although it proved impossible to assign a best force field to either reaction, the calculated isotope effects generally were in satisfactory agreement with experiment, and were better than those calculated from the MNDO potential energy surface. Hydrogen tunnelling is apparently implicated in the CH4+ CF3 reaction.

COMPARATIVE STUDY OF REACTION RATE CONSTANTS FOR THE NH3 + H → NH2 + H2 REACTION WITH GLOBE DYNAMICS AND TRANSITION STATE THEORIES

2009 ◽  
Vol 08 (06) ◽  
pp. 1227-1233 ◽  
Author(s):  
JU LIPING ◽  
LU RUIFENG
Keyword(s):  
Transition State ◽  
Cross Sections ◽  
Rate Constants ◽  
Quantum Dynamics ◽  
Classical Trajectory ◽  
State Theory ◽  
Title Reaction ◽  
Reaction Rate Constants ◽  
Barrier Type ◽  
Good Agreement

The nine-dimension quasi-classical trajectory (QCT) calculations have been carried out for the title reaction with a global potential energy surface (PES) constructed by Corchado and Espinosa-García (J Chem Phys106:4013, 1997). The detailed dynamics calculations cover the specific collision energies falling in the range of 0.62–3.04 eV, which are sufficient to fit the calculated reactive cross-sections into a barrier-type excitation function and to obtain the thermal rate constants. The present QCT rate constants are in good agreement with the recent quantum dynamics (QD) results, both of which are much lower than that of the previous variational transition state theory (VTST).

scholarly journals Mechanistic Molecular Motion of Transition-Metal Mediated Beta-Hydride Transfer: Quasiclassical Trajectories Reveal Dynamically Ballistic, Dynamically Unrelaxed, Two Step, and Concerted Mechanisms

2020 ◽  
Author(s):  
Josh Wheeler ◽  
Ryan Carlsen ◽  
Daniel Ess
Keyword(s):  
Transition State ◽  
Density Functional ◽  
Hydrogen Transfer ◽  
Transition States ◽  
Surface Shape ◽  
Concerted Mechanism ◽  
Hydrogen Elimination ◽  
Migratory Insertion ◽  
One Step ◽  
Quasiclassical Trajectories

<div>The transfer of a -hydrogen from a metal-alkyl group to ethylene is a fundamental</div><div>organometallic transformation. Previously proposed mechanisms for this transformation involve either a</div><div>two-step -hydrogen elimination and migratory insertion sequence with a metal hydride intermediate</div><div>or a one-step concerted pathway. Here, we report density functional theory (DFT) quasiclassical direct</div><div>dynamics trajectories that reveal new dynamical mechanisms for the -hydrogen transfer of</div><div>[Cp*RhIII(Et)(ethylene)]</div><div>Despite the DFT energy landscape showing a two-step mechanism with a Rh-H</div><div>intermediate, quasiclassical trajectories commencing from the -hydrogen elimination transition state</div><div>revealed complete dynamical skipping of this intermediate. The skipping occurred either extremely fast</div><div>(typically <100 femtoseconds (fs)) through a dynamically ballistic mechanism or slower through a</div><div>dynamically unrelaxed mechanism. Consistent with trajectories begun at the transition state, all</div><div>trajectories initiated at the Rh-H intermediate show continuation along the reaction coordinate. All of</div><div>these trajectory outcomes are consistent with the Rh-H intermediate <1 kcal/mol stabilized relative to</div><div>the -hydrogen elimination and migratory insertion transition states. For Co, which on the energy</div><div>landscape is a one-step concerted mechanism, trajectories showed extremely fast traversing of the</div><div>transition-state zone (<50 fs), and this concerted mechanism is dynamically different than the Rh</div><div>ballistic mechanism. In contrast to Rh, for Ir, in addition to dynamically ballistic and unrelaxed</div><div>mechanisms, trajectories also stopped at the Ir-H intermediate. This is consistent with an Ir-H</div><div>intermediate that is stabilized by ~3 kcal/mol relative to the -hydrogen elimination and migratory</div><div>insertion transition states. Overall, comparison of Rh to Co and Ir provides understanding of the</div><div>relationship between the energy surface shape and resulting dynamical mechanisms of an</div><div>organometallic transformation.</div>

Quantum dynamics of the F+H2 reaction: Resonance models, and energy and flux distributions in the transition state

1978 ◽  
Vol 69 (8) ◽  
pp. 3746-3755 ◽  
Author(s):  
Susan L. Latham ◽  
Joe F. McNutt ◽  
Robert E. Wyatt ◽  
Michael J. Redmon
Keyword(s):  
Transition State ◽  
Quantum Dynamics ◽  
Reaction Resonance
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