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States and transitions

For analysing equilibrium solvent effects on reaction rates it is connnon to use the thennodynamic fomuilation of TST and to relate observed solvent-mduced changes in the rate coefficient to variations in Gibbs free-energy differences between solvated reactant and transition states with respect to some reference state. Starting from the simple one-dimensional expression for the TST rate coefficient of a unimolecular reaction a— r... [Pg.833]

Considering equation (A3.6.3). if activity coefficients of reactant and transition state are approximately equal, for a imimolecular reaction one should observe This in fact is observed for many unimolecular... [Pg.834]

If reliable quantum mechanical calcnlations of reactant and transition state stnictures in vacnnm are feasible, treating electrostatic solvent effects on the basis of SRCF-PCM rising cavity shapes derived from methods... [Pg.838]

The transition from k to on the low-pressure side ean be eonstnieted using iiiidtidimensional unimoleeular rate theory [1, 44], if one knows the barrier height for the reaetion and the vibrational frequeneies of the reaetant and transition state. The transition from to k y ean be deseribed in temis of Kramers theory [45]... [Pg.847]

Bennett C H 1977 Molecular dynamics and transition state theory the simulation of infrequent events Algorithms for Chemical Computation (ACS Symposium Series No 46) ed R E Christofferson (Washington, DC American Chemical Society)... [Pg.896]

The first two of these we can readily approach with the knowledge gained from the studies of trappmg and sticking of rare-gas atoms, but the long timescales involved in the third process may perhaps more usefiilly be addressed by kinetics and transition state theory [35]. [Pg.906]

This is connnonly known as the transition state theory approximation to the rate constant. Note that all one needs to do to evaluate (A3.11.187) is to detennine the partition function of the reagents and transition state, which is a problem in statistical mechanics rather than dynamics. This makes transition state theory a very usefiil approach for many applications. However, what is left out are two potentially important effects, tiiimelling and barrier recrossing, bodi of which lead to CRTs that differ from the sum of step frmctions assumed in (A3.11.1831. [Pg.993]

The classical mechanical RRKM k(E) takes a very simple fonn, if the internal degrees of freedom for the reactant and transition state are assumed to be hamionic oscillators. The classical sum of states for s harmonic oscillators is [16]... [Pg.1017]

Only in the high-energy limit does classical statistical mechanics give accurate values for the sum and density of states tenns in equation (A3.12.15) [3,14]. Thus, to detennine an accurate RRKM lc(E) for the general case, quantum statistical mechanics must be used. Since it is difficult to make anliannonic corrections, both the molecule and transition state are often assumed to be a collection of hannonic oscillators for calculating the... [Pg.1018]

For a RRKM calculation without any approximations, the complete vibrational/rotational Flamiltonian for the imimolecular system is used to calculate the reactant density and transition state s sum of states. No approximations are made regarding the coupling between vibration and rotation. Flowever, for many molecules the exact nature of the coupling between vibration and rotation is uncertain, particularly at high energies, and a model in which rotation and vibration are assumed separable is widely used to calculate the quantum RRKM k(E,J) [4,16]. To illustrate this model, first consider a linear polyatomic molecule which decomposes via a linear transition state. The rotational energy for tire reactant is assumed to be that for a rigid rotor, i.e. [Pg.1019]

In these models the treatment of K is the same for the molecule and transition state. It is worthwhile noting that mixed mode RRKM models are possible in which K is treated differently in the molecule and transition state [39],... [Pg.1020]

At any geometry g.], the gradient vector having components d EjJd Q. provides the forces (F. = -d Ej l d 2.) along each of the coordinates Q-. These forces are used in molecular dynamics simulations which solve the Newton F = ma equations and in molecular mechanics studies which are aimed at locating those geometries where the F vector vanishes (i.e. tire stable isomers and transition states discussed above). [Pg.2157]

Schlegel H B 1982 Optimization of equilibrium geometries and transition states J. Comput. Chem. 3 214... [Pg.2356]

Valtazanos P and Ruedenberg K 1986 Bifurcations and transition states Theor. Chim. Acta 69 281... [Pg.2359]

Given that a sequence folds to a known native stmcture, what are the mechanisms in the transition from the unfolded confonnation to the folded state This is a kinetics problem, the solution of which requires elucidation of the pathways and transition states in the folding process. [Pg.2642]

Figure C2.12.10. Different manifestations of shape-selectivity in zeolite catalysis. Reactant selectivity (top), product selectivity (middle) and transition state selectivity (bottom). Figure C2.12.10. Different manifestations of shape-selectivity in zeolite catalysis. Reactant selectivity (top), product selectivity (middle) and transition state selectivity (bottom).
Aj ala P Y and H B Schlegel 1997. A Combined Method for Determining Reaction Paths, Minima and Transition State Geometries. Journal of Chemical Physics 107 375-384. [Pg.315]

C, P Y Ayala, H B Schlegel and M J Erisch 1996. Using Redundant Internal Coordinates to Optimise Equilibrium Geometries and Transition States, journal of Computational Chemistry 17 49-56. [Pg.316]

J. Simons. A discussion of how local minima and transition states are loeated on eleetronie energy surfaees is provided in Chapter 20 of the present text. [Pg.350]


See other pages where States and transitions is mentioned: [Pg.833]    [Pg.834]    [Pg.834]    [Pg.835]    [Pg.835]    [Pg.837]    [Pg.841]    [Pg.841]    [Pg.841]    [Pg.841]    [Pg.841]    [Pg.842]    [Pg.879]    [Pg.1013]    [Pg.1019]    [Pg.1021]    [Pg.1023]    [Pg.2156]    [Pg.2421]    [Pg.11]    [Pg.220]    [Pg.349]    [Pg.568]    [Pg.57]    [Pg.305]    [Pg.652]    [Pg.513]    [Pg.518]    [Pg.129]    [Pg.149]   
See also in sourсe #XX -- [ Pg.279 ]




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Absolute Rate (Transition State) Theory and the Activated Complex

Activated complex, and transition states

And the transition state

And transition state geometry

And transition state theory

Aromatic and Antiaromatic Transition States

Assumptions and Derivation of the Basic Transition-State Method Expressions

Biological chemistry of phosphate esters cyclic substrates and transition states

Calculated vs. Experimental Isotope Effects and Transition State Structure

Colloid dynamics and transitions to dynamically arrested states

Cross-interaction constants and transition-state structure in solution

Cyclodextrins and other catalysts, the stabilisation of transition states

Cyclodextrins and other catalysts, the stabilization of transition states

Describing a Reaction Energy Diagrams and Transition States

Determining rate parameters using quantum chemical calculations and transition state theory

Deuterium kinetic isotope effects secondary, and transition state

Deuterium kinetic isotope effects, secondary, and transition state structure

EM and transition state structure

Effective charge and transition-state

Effective charge and transition-state structure in solution

Electronic Transitions and Lifetime of Excited States in Porphyrin-Based Compounds

Energies and Transition States

Energy Exchange and Transition-State Theory

Energy Transitions and Mixed States

Energy of intermediates and transition state

Enthalpy differences of starting alkenes and transition states in bromination

Entropies and Heat Capacities of Transition State Structures

Geometry Optimizations and Transition State Searching

Glass transition and the glassy state

Kinetic Isotope Effects Continued Variational Transition State Theory and Tunneling

Minima and Transition State Optimization

Minimum and transition state

Noncrystalline state and the glass transition

Potential Energy Surface Molecular Structure, Transition States, and Reaction Paths

Potential Surface and Transition State

Quantitative antihydrophobic effects in water and the geometries of transition states

Reaction Paths and Transition States

Reaction in Solution and the Transition-State Theory

Reaction mechanisms and transition-state shifts

Reactions and Transition State Theory

Reactivity and development of the transition state

Relative Importance of Initial- and Transition-state Effects

Secondary a-deuterium kinetic isotope effect and the structure of ferrocenylmethyl carbocation type transition state

Separation of Initial and Transition State Solvent Effects

Solid-State Chemistry of Thio-, Seleno and Transition Elements

State and Phase Transitions

Substrate and Transition State Binding

Syndiospecific Transition State Structure and Syndio-Insertion Catalytic Cycle

Temperature Effects and Transition State Theory

The Active Site and Transition States

The Aldol Addition of Preformed Enolates - Stereoselectivity and Transition-state Models

The Reaction Path Hamiltonian and Variational Transition State Theory

Thermodynamics and transition state

Transition Dipoles for Excitations to Singlet and Triplet States

Transition State Analogues and Adventitious Tight-binding Inhibitors

Transition State Species and Chemical Reactions

Transition State Theory and Microscopic Reversibility

Transition State Theory and Related Methods

Transition metals oxidation states and

Transition state and activation energy

Transition state and reactants

Transition state and recombination rate theories

Transition state conformation and

Transition state structure, secondary deuterium isotope effects and

Transition state theory and gas isotopic fractionation

Transition state theory and statistical mechanics

Transition state theory and supercritical fluids

Transition state theory, configuration and potential energy

Transition states and calculations

Transition states and energy barriers

Transition states and intermediates

Transition states and reaction rates

Transition states stabilization, and

Transition states, the stabilization of by cyclodextrins and other catalysts

Transition-State Theory and Enthalpy Diagrams

Transition-state Theory and Minimum Density of States

Transition-state theory and rate constants

Transition-state theory and the potential of mean force

Wide Angle Scattering During Crystallization and Solid State Phase Transitions

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